Co-reporter:Carles Felip-León, Francisco Galindo, and Juan F. Miravet, Valeria Castelletto and Ian W. Hamley
The Journal of Physical Chemistry B August 10, 2017 Volume 121(Issue 31) pp:7443-7443
Publication Date(Web):July 18, 2017
DOI:10.1021/acs.jpcb.7b06167
Peptides composed of hexaproline and glutamic acid (P6E) or lysine (P6K) as C-terminal units show thermally promoted aggregation, affording vesicle-like assemblies upon heating to 80 °C. The aggregation is analyzed by dynamic light scattering (DLS), with number-averaged diameters of ca. 600 and 300 nm, respectively, for P6E and P6K. NMR studies reveal that upon heating the amount of NMR-visible species is reduced to ca. 50% and that an important conformational change is experienced by the molecules in solution. Circular dichroism (CD) shows that at 20 °C the peptides present a polyproline II (PP-II) conformation which is disorganized upon heating. Scanning electron microscopy for samples which were fast frozen at 80 °C reveals vesicle-like assemblies. Using pyrene as a fluorescence probe, a critical aggregation concentration of ca. 30 μM was estimated for P6E, while that of P6K was above 0.6 mM. The aggregation process is found to be fully reversible and could serve as a basis for development of stimuli responsive carriers.
Co-reporter:Cuiyun Zhang, You Fan, Yunyi Zhang, Cong Yu, Hongfei Li, Yu ChenIan W. Hamley, Shichun Jiang
Macromolecules 2017 Volume 50(Issue 4) pp:
Publication Date(Web):February 10, 2017
DOI:10.1021/acs.macromol.6b02331
The self-assembly process of amphiphilic dendritic copolymers (ADPs) with a hydrophilic core and a hydrophobic shell was investigated via laser light scattering. The self-assembly occurs via a fast step and a slow step with different relaxation times. At the critical micelle concentration (CMC), the fusion of small micelles results in the rapid increase of the micelle size in the fast step. The slow step is associated with equilibrium through the fission and fusion of the micelles. The micelle size increases with the unimer concentration, which leads to a lower micelle concentration. The lower micelle concentration makes the relaxation time of the fast step increase with increasing unimer concentration. However, the fusion of larger micelles at higher concentration is more efficient to increase micelle size. The fusion of small micelles with large micelles at higher concentration accelerates the approaching equilibrium of the micelles except for the fission and fusion of micelles. With the increasing degree of amidation (DA), the relaxation time in the fast step increases and in the slow step it decreases.
Co-reporter:King Hang Aaron Lau;Valeria Castelletto;Thomas Kendall;Jan Sefcik;Ian W. Hamley;Mehedi Reza;Janne Ruokolainen
Chemical Communications 2017 vol. 53(Issue 13) pp:2178-2181
Publication Date(Web):2017/02/09
DOI:10.1039/C6CC09888F
Poly(N-substituted glycine) “peptoids” constitute a promising class of peptide-mimetic materials. We introduce the self-assembly of lipopeptoids into spherical micelles ca. 5 nm in diameter as well as larger assemblies by varying the peptoid sequence design. Our results point to design rules for the self-assembly of peptoid nanostructures, enabling the creation of stable, ultra-small peptidomimetic nanospheres.
Co-reporter:Charlotte J. C. Edwards-Gayle;Ian W. Hamley
Organic & Biomolecular Chemistry 2017 vol. 15(Issue 28) pp:5867-5876
Publication Date(Web):2017/07/19
DOI:10.1039/C7OB01092C
Molecular self-assembly is a multi-disciplinary field of research, with potential chemical and biological applications. One of the main driving forces of self-assembly is molecular amphiphilicity, which can drive formation of complex and stable nanostructures. Self-assembling peptide and peptide conjugates have attracted great attention due to their biocompatibility, biodegradability and biofunctionality. Understanding assembly enables the better design of peptide amphiphiles which may form useful and functional nanostructures. This review covers self-assembly of amphiphilic peptides and peptide mimetic materials, as well as their potential applications.
Co-reporter:V. Castelletto;A. Kaur;I. W. Hamley;R. H. Barnes;K.-A. Karatzas;D. Hermida-Merino;S. Swioklo;C. J. Connon;J. Stasiak;M. Reza;J. Ruokolainen
RSC Advances (2011-Present) 2017 vol. 7(Issue 14) pp:8366-8375
Publication Date(Web):2017/01/23
DOI:10.1039/C6RA27244D
Macroscopic capsules, with tunable properties based on hierarchical self-assembly on multiple lengthscales, are prepared from the co-operative self-assembly of polysaccharide and peptide amphiphiles. Different formulations can be used to create flexible membrane sacs in solution, soft capsules or rigid free-standing capsules. Samples are prepared by injecting a solution containing sodium alginate, with or without graphene oxide (GO), into a matrix consisting of a solution containing the peptide amphiphile PA C16-KKFF (K: lysine, F: phenylalanine), with or without CaCl2. Graphene oxide is added to the hybrid materials to modulate the mechanical properties of the capsules. Injection of sodium alginate solution into a pure PA matrix provides a flexible membrane sac in solution, while injection of NaAlg/GO solution into a PA matrix gives a soft capsule. Alternatively, a rigid free-standing capsule is made by injecting a NaAlg/GO solution into a PA + CaCl2 matrix solution. A comprehensive insight into the hierarchical order within the capsules is provided through analysis of X-ray scattering data. A novel “Langmuir–Blodgett” mechanism is proposed to account for the formation of the sacs and capsules as the alginate solution is injected at the interface of the PA solution. The capsules show a unique antibacterial effect specific for the Gram positive bacterium Listeria monocytogenes, which is an important human pathogen. The hybrid nanostructured capsules thus have remarkable bioactivity and due to their tunable structural and functional properties are likely to have a diversity of other future applications.
Co-reporter:Ian William Hamley, Steven Kirkham, Radoslaw M. Kowalczyk, Valeria Castelletto, Mehedi Reza and Janne Ruokolainen
Chemical Communications 2016 vol. 52(Issue 5) pp:1052-1052
Publication Date(Web):21 Dec 2015
DOI:10.1039/C5CC90557E
Correction for ‘Self-assembly of the anti-fungal polyene amphotericin B into giant helically-twisted nanotapes’ by Ian William Hamley et al., Chem. Commun., 2015, 51, 17680–17683.
Co-reporter:Steven Kirkham;Dr. Valeria Castelletto; Ian William Hamley;Dr. Katsuaki Inoue;Dr. Robert Rambo;Mehedi Reza; Janne Ruokolainen
ChemPhysChem 2016 Volume 17( Issue 14) pp:2118-2122
Publication Date(Web):
DOI:10.1002/cphc.201600308
Abstract
The cyclic lipopeptide Daptomycin, used as a treatment for infections where antimicrobial resistance is observed, is shown to self-assemble into spherical micelles above a critical aggregation concentration. Micelles are observed either in the absence or presence of CaCl2, in contrast to claims in the literature that CaCl2 is required for micellization.
Co-reporter:Valeria Castelletto, Steven Kirkham, Ian W. Hamley, Radoslaw Kowalczyk, Martin Rabe, Mehedi Reza, and Janne Ruokolainen
Biomacromolecules 2016 Volume 17(Issue 2) pp:
Publication Date(Web):January 10, 2016
DOI:10.1021/acs.biomac.5b01573
The self-assembly of the macrophage-activating lipopeptide MALP-2 in aqueous solution has been investigated and is compared to that of the constituent peptide GNNDESNISFKEK. MALP-2 is a toll-like receptor agonist lipopeptide with diverse potential biomedical applications and its self-assembly has not previously been examined. It is found to self-assemble, above a critical aggregation concentration (cac), into remarkable “fibre raft” structures, based on lateral aggregation of β-sheet based bilayer tapes. Peptide GNNDESNISFKEK also forms β-sheet structures above a cac, although the morphology is distinct, comprising highly extended and twisted tape structures. A detailed insight into the molecular packing within the MALP-2 raft and GNNDESNISFKEK nanotape structures is obtained through X-ray diffraction and small-angle X-ray scattering. These results point to the significant influence of the attached lipid chains on the self-assembly motif, which lead to the raft structure for the lipopeptide assemblies.
Co-reporter:Steven Kirkham, Ian W. Hamley, Andrew M. Smith, Ricardo M. Gouveia, Che J. Connon, Mehedi Reza, Janne Ruokolainen
Colloids and Surfaces B: Biointerfaces 2016 Volume 137() pp:104-108
Publication Date(Web):1 January 2016
DOI:10.1016/j.colsurfb.2015.04.062
Derivatives of fluorophore FITC (fluorescein isothiocyanate) are widely used in bioassays to label proteins and cells. An N-terminal leucine dipeptide is attached to FITC, and we show that this simple conjugate molecule is cytocompatible and is uptaken by cells (human dermal and corneal fibroblasts) in contrast to FITC itself. Co-localisation shows that FITC-LL segregates in peri-nuclear and intracellular vesicle regions. Above a critical aggregation concentration, the conjugate is shown to self-assemble into beta-sheet nanostructures comprising molecular bilayers.Figure optionsDownload full-size imageDownload as PowerPoint slide
Co-reporter:V. Castelletto, I. W. Hamley, M. Reza and J. Ruokolainen
Nanoscale 2015 vol. 7(Issue 1) pp:171-178
Publication Date(Web):23 Oct 2014
DOI:10.1039/C4NR05072J
The interaction of a designed bioactive lipopeptide C16-GGGRGDS, comprising a hexadecyl lipid chain attached to a functional heptapeptide, with the lipid-free apoliprotein, Apo-AI, is examined. This apolipoprotein is a major component of high density lipoprotein and it is involved in lipid metabolism and may serve as a biomarker for cardiovascular disease and Alzheimers’ disease. We find via isothermal titration calorimetry that binding between the lipopeptide and Apo-AI occurs up to a saturation condition, just above equimolar for a 10.7 μM concentration of Apo-AI. A similar value is obtained from circular dichroism spectroscopy, which probes the reduction in α-helical secondary structure of Apo-AI upon addition of C16-GGGRGDS. Electron microscopy images show a persistence of fibrillar structures due to self-assembly of C16-GGGRGDS in mixtures with Apo-AI above the saturation binding condition. A small fraction of spheroidal or possibly “nanodisc” structures was observed. Small-angle X-ray scattering (SAXS) data for Apo-AI can be fitted using a published crystal structure of the Apo-AI dimer. The SAXS data for the lipopeptide/Apo-AI mixtures above the saturation binding conditions can be fitted to the contribution from fibrillar structures coexisting with flat discs corresponding to Apo-AI/lipopeptide aggregates.
Co-reporter:Ian W. Hamley
Chemical Communications 2015 vol. 51(Issue 41) pp:8574-8583
Publication Date(Web):18 Mar 2015
DOI:10.1039/C5CC01535A
This Feature Article discusses several classes of lipopeptide with important biomedical applications as antimicrobial and antifungal agents, in immune therapies and in personal care applications among others. Two main classes of lipopeptide are considered: (i) bacterially-expressed lipopeptides with a cyclic peptide headgroup and (ii) linear lipopeptides (with one or more lipid chains) based on bio-derived and bio-inspired amino acid sequences with current clinical applications. The applications are briefly summarized, and the biophysical characterization of the molecules is reviewed, with a particular focus on self-assembly. For several of these types of biomolecule, the formation of micelles above a critical micelle concentration has been observed while others form bilayer structures, depending on conditions of pH and temperature. As yet, there are few studies on the possible relationship between self-assembly into structures such as micelles and bioactivity of this class of molecule although this is likely to attract further attention.
Co-reporter:Emerson Rodrigo da Silva, Wendel Andrade Alves, Valeria Castelletto, Mehedi Reza, Janne Ruokolainen, Rohanah Hussain and Ian William Hamley
Chemical Communications 2015 vol. 51(Issue 58) pp:11634-11637
Publication Date(Web):15 Jun 2015
DOI:10.1039/C5CC03640B
The self-assembly of peptide nanotubes formed by an L-glutamic acid-based bolaamphiphile is shown to proceed via a remarkable mechanism where the peptide conformation changes from β-sheet to unordered. The kinetics of this process are elucidated via X-ray scattering and UV circular dichroism methods. The reverse transition from “unordered” to β-sheet structures is triggered by UV radiation.
Co-reporter:Ian William Hamley, Steven Kirkham, Radoslaw M. Kowalczyk, Valeria Castelletto, Mehedi Reza and Janne Ruokolainen
Chemical Communications 2015 vol. 51(Issue 100) pp:17680-17683
Publication Date(Web):20 Oct 2015
DOI:10.1039/C5CC08224B
The amphiphilic polyene amphotericin B, a powerful treatment for systemic fungal infections, is shown to exhibit a critical aggregation concentration, and to form giant helically-twisted nanostructures via self-assembly in basic aqueous solution.
Co-reporter:Daniel Hermida-Merino, Gemma E. Newby, Ian W. Hamley, Wayne Hayes and Andrew Slark
Soft Matter 2015 vol. 11(Issue 29) pp:5799-5803
Publication Date(Web):30 Jun 2015
DOI:10.1039/C5SM01461A
Blending with a hydrogen-bonding supramolecular polymer is shown to be a successful novel strategy to induce microphase-separation in the melt of a Pluronic polyether block copolymer. The supramolecular polymer is a polybutadiene derivative with urea–urethane end caps. Microphase separation is analysed using small-angle X-ray scattering and its influence on the macroscopic rheological properties is analysed. FTIR spectroscopy provides a detailed picture of the inter-molecular interactions between the polymer chains that induces conformational changes leading to microphase separation.
Co-reporter:Ashkan Dehsorkhi, Ricardo M. Gouveia, Andrew M. Smith, Ian W. Hamley, Valeria Castelletto, Che J. Connon, Mehedi Reza and Janne Ruokolainen
Soft Matter 2015 vol. 11(Issue 16) pp:3115-3124
Publication Date(Web):05 Mar 2015
DOI:10.1039/C5SM00459D
We describe a bioactive lipopeptide that combines the capacity to promote the adhesion and subsequent self-detachment of live cells, using template-cell-environment feedback interactions. This self-assembling peptide amphiphile comprises a diene-containing hexadecyl lipid chain (C16e) linked to a matrix metalloprotease-cleavable sequence, Thr-Pro-Gly-Pro-Gln-Gly-Ile-Ala-Gly-Gln, and contiguous with a cell-attachment and signalling motif, Arg-Gly-Asp-Ser. Biophysical characterisation revealed that the PA self-assembles into 3 nm diameter spherical micelles above a critical aggregation concentration (cac). In addition, when used in solution at 5–150 nM (well below the cac), the PA is capable of forming film coatings that provide a stable surface for human corneal fibroblasts to attach and grow. Furthermore, these coatings were demonstrated to be sensitive to metalloproteases expressed endogenously by the attached cells, and consequently to elicit the controlled detachment of cells without compromising their viability. As such, this material constitutes a novel class of multi-functional coating for both fundamental and clinical applications in tissue engineering.
Co-reporter:Emerson Rodrigo da Silva, Merlin Nathaniel Mark Walter, Mehedi Reza, Valeria Castelletto, Janne Ruokolainen, Che John Connon, Wendel Andrade Alves, and Ian William Hamley
Biomacromolecules 2015 Volume 16(Issue 10) pp:
Publication Date(Web):September 8, 2015
DOI:10.1021/acs.biomac.5b00820
The spontaneous assembly of a peptide bolaamphiphile in water, namely, RFL4FR (R, arginine; F, phenylalanine; L, leucine) is investigated, along with its novel properties in surface modification and usage as substrates for cell culture. RFL4FR self-assembles into nanosheets through lateral association of the peptide backbone. The L4 sequence is located within the core of the nanosheets, whereas the R moieties are exposed to the water at the surface of the nanosheets. Kinetic assays indicate that the self-assembly is driven by a remarkable two-step process, where a nucleation phase is followed by fast growth of nanosheets with an autocatalysis process. The internal structure of the nanosheets is formed from ultrathin bolaamphiphile monolayers with a crystalline orthorhombic symmetry with cross-β organization. We show that human corneal stromal fibroblast (hCSF) cells can grow on polystyrene films coated with films dried from RFL4FR solutions. For the first time, this type of amphiphilic peptide is used as a substrate to modulate the wettability of solid surfaces for cell culture applications.
Co-reporter:Ian W. Hamley, Steven Kirkham, Ashkan Dehsorkhi, Valeria Castelletto, Mehedi Reza and Janne Ruokolainen
Chemical Communications 2014 vol. 50(Issue 100) pp:15948-15951
Publication Date(Web):30 Oct 2014
DOI:10.1039/C4CC07511K
The self-assembled structure of toll-like receptor agonist lipopeptides containing the CSK4 peptide sequence is examined in aqueous solution. A remarkable dependence of morphology on the number of attached hexadecyl lipid chains is demonstrated, with spherical micelle structures for mono- and di-lipidated structures observed, but flexible wormlike micelles for the homologue containing three lipid chains. The distinct modes of assembly may have an important influence on the bioactivity of this class of lipopeptide.
Co-reporter:V. Castelletto, R. J. Gouveia, C. J. Connon, I. W. Hamley, J. Seitsonen, J. Ruokolainen, E. Longo and G. Siligardi
Biomaterials Science 2014 vol. 2(Issue 6) pp:867-874
Publication Date(Web):29 Jan 2014
DOI:10.1039/C4BM00001C
The self-assembly of the alanine-rich amphiphilic peptides Lys(Ala)6Lys (KA6K) and Lys(Ala)6Glu (KA6E) with homotelechelic or heterotelechelic charged termini respectively has been investigated in aqueous solution. These peptides contain hexa-alanine sequences designed to serve as substrates for the enzyme elastase. Electrostatic repulsion of the lysine termini in KA6K prevents self-assembly, whereas in contrast KA6E is observed, through electron microscopy, to form tape-like fibrils, which based on X-ray scattering contain layers of thickness equal to the molecular length. The alanine residues enable efficient packing of the side-chains in a beta-sheet structure, as revealed by circular dichroism, FTIR and X-ray diffraction experiments. In buffer, KA6E is able to form hydrogels at sufficiently high concentration. These were used as substrates for elastase, and enzyme-induced de-gelation was observed due to the disruption of the beta-sheet fibrillar network. We propose that hydrogels of the simple designed amphiphilic peptide KA6E may serve as model substrates for elastase and this could ultimately lead to applications in biomedicine and regenerative medicine.
Co-reporter: Ian W. Hamley
Angewandte Chemie 2014 Volume 126( Issue 27) pp:6984-7000
Publication Date(Web):
DOI:10.1002/ange.201310006
Abstract
In diesem Aufsatz wird die Selbstorganisation verschiedener Klassen von Peptiden, einschließlich cyclischer Peptide, Amyloidpeptide und tensidartiger Peptide, zu Nanoröhrenstrukturen besprochen. Außer den Modi der Selbstorganisation werden auch Anwendungen auf den Gebieten der Bionanotechnologie und der synthetischen Materialien diskutiert.
Co-reporter:Ian W. Hamley, Steven Kirkham, Ashkan Dehsorkhi, and Valeria Castelletto , Jozef Adamcik and Raffaele Mezzenga , Janne Ruokolainen , Claudia Mazzuca, Emanuela Gatto, and Mariano Venanzi , Ernesto Placidi , Panayiotis Bilalis and Hermis Iatrou
Biomacromolecules 2014 15(9) pp: 3412-3420
Publication Date(Web):August 8, 2014
DOI:10.1021/bm500950c
Amyloid fibrils are formed by a model surfactant-like peptide (Ala)10-(His)6 containing a hexa-histidine tag. This peptide undergoes a remarkable two-step self-assembly process with two distinct critical aggregation concentrations (cac’s), probed by fluorescence techniques. A micromolar range cac is ascribed to the formation of prefibrillar structures, whereas a millimolar range cac is associated with the formation of well-defined but more compact fibrils. We examine the labeling of these model tagged amyloid fibrils using Ni-NTA functionalized gold nanoparticles (Nanogold). Successful labeling is demonstrated via electron microscopy imaging. The specificity of tagging does not disrupt the β-sheet structure of the peptide fibrils. Binding of fibrils and Nanogold is found to influence the circular dichroism associated with the gold nanoparticle plasmon absorption band. These results highlight a new approach to the fabrication of functionalized amyloid fibrils and the creation of peptide/nanoparticle hybrid materials.
Co-reporter: Ian W. Hamley
Angewandte Chemie International Edition 2014 Volume 53( Issue 27) pp:6866-6881
Publication Date(Web):
DOI:10.1002/anie.201310006
Abstract
The self-assembly of different classes of peptide, including cyclic peptides, amyloid peptides and surfactant-like peptides into nanotube structures is reviewed. The modes of self-assembly are discussed. Additionally, applications in bionanotechnology and synthetic materials science are summarized.
Co-reporter:Ian W. Hamley, Ashkan Dehsorkhi and Valeria Castelletto
Chemical Communications 2013 vol. 49(Issue 18) pp:1850-1852
Publication Date(Web):23 Jan 2013
DOI:10.1039/C3CC39057H
The surfactant-like peptide (Ala)6(Arg) is found to self-assemble into 3 nm-thick sheets in aqueous solution. Scanning transmission electron microscopy measurements of mass per unit area indicate a layer structure based on antiparallel dimers. At higher concentration the sheets wrap into unprecedented ultrathin helical ribbon and nanotube architectures.
Co-reporter:Ian W. Hamley, Ashkan Dehsorkhi, Valeria Castelletto, Steve Furzeland, Derek Atkins, Jani Seitsonen and Janne Ruokolainen
Soft Matter 2013 vol. 9(Issue 39) pp:9290-9293
Publication Date(Web):19 Aug 2013
DOI:10.1039/C3SM51725J
A designed peptide amphiphile C16-KKFFVLK self-assembles into nanotubes and helical ribbons in aqueous solution at room temperature. A remarkable unwinding transition, leading to twisted tapes, is observed on heating. Nanotubes and ribbons re-form on cooling.
Co-reporter:Roanne R. Jones, Valeria Castelletto, Che J. Connon, and Ian W. Hamley
Molecular Pharmaceutics 2013 Volume 10(Issue 3) pp:1063-1069
Publication Date(Web):January 15, 2013
DOI:10.1021/mp300549d
The collagen production of human dermal and corneal fibroblasts in contact with solutions of the peptide amphiphile (PA) C16–KTTKS is investigated and related to its self-assembly into nanotape structures. This PA is used in antiwrinkle cosmeceutical applications (trade name Matrixyl). We prove that C16–KTTKS stimulates collagen production in a concentration-dependent manner close to the critical aggregation concentration determined from pyrene fluorescence spectroscopy. This suggests that self-assembly and the stimulation of collagen production are inter-related.Keywords: collagen; fibroblasts; Matrixyl; peptide amphiphile; skincare;
Co-reporter:Ian W. Hamley, Ashkan Dehsorkhi, Valeria Castelletto, Jani Seitsonen, Janne Ruokolainen and Hermis Iatrou
Soft Matter 2013 vol. 9(Issue 19) pp:4794-4801
Publication Date(Web):28 Mar 2013
DOI:10.1039/C3SM50303H
The self-assembly in aqueous solution of the alanine-rich peptide A12R2 containing twelve alanine residues and two arginine residues has been investigated. This oligomeric peptide was synthesized via NCA-polymerization methods. The surfactant-like peptide is found via FTIR to form antiparallel dimers which aggregate into twisted fibrils, as revealed by cryogenic-transmission electron microscopy. The fibril substructure is probed via detailed X-ray scattering experiments, and are uniquely comprised of twisted tapes only 5 nm wide, set by the width of the antiparallel A12R2 dimers. The packing of the alanine residues leads to distinct “β-sheet” spacings compared to those for amyloid-forming peptides. For this peptide, β-sheet structure coexists with some α-helical content. These ultrafine amyloid fibrils present arginine at high density on their surfaces, and this may lead to applications in nanobiotechnology.
Co-reporter:Juan F. Miravet, Beatriu Escuder, Maria Dolores Segarra-Maset, Marta Tena-Solsona, Ian W. Hamley, Ashkan Dehsorkhi and Valeria Castelletto
Soft Matter 2013 vol. 9(Issue 13) pp:3558-3564
Publication Date(Web):20 Feb 2013
DOI:10.1039/C3SM27899A
A thermal transition is observed in the peptide amphiphile C16-KTTKS (TFA salt) from nanotapes at 20 °C to micelles at higher temperature (the transition temperature depending on concentration). The formation of extended nanotapes by the acetate salt of this peptide amphiphile, which incorporates a pentapeptide from type I procollagen, has been studied previously [V. Castelletto et al., Chem. Commun., 2010, 46, 9185]. Here, proton NMR and SAXS provide evidence for the TFA salt spherical micelles at high temperature. The phase behavior, with a Krafft temperature separating insoluble aggregates (extended nanotapes) at low temperature from the high temperature micellar phase resembles that for conventional surfactants, however this has not previously been reported for peptide amphiphiles.
Co-reporter:Ian W. Hamley, Ashkan Dehsorkhi, Paula Jauregi, Jani Seitsonen, Janne Ruokolainen, François Coutte, Gabrielle Chataigné and Philippe Jacques
Soft Matter 2013 vol. 9(Issue 40) pp:9572-9578
Publication Date(Web):21 Aug 2013
DOI:10.1039/C3SM51514A
The self-assembly in aqueous solution of three lipopeptides obtained from Bacillus subtilis has been investigated. The lipopeptides surfactin, plipastatin and mycosubtilin contain distinct cyclic peptide headgroups as well as differences in alkyl chain length, branching and chain length distribution. Cryogenic transmission electron microscopy and X-ray scattering reveal that surfactin and plipastatin aggregate into 2 nm-radius spherical micelles, whereas in complete contrast mycosubtilin self-assembles into extended nanotapes based on bilayer ordering of the lipopeptides. Circular dichroism and FTIR spectroscopy indicate the presence of turn structures in the cyclic peptide headgroup. The unexpected distinct mode of self-assembly of mycosubtilin compared to the other two lipopeptides is ascribed to differences in the surfactant packing parameter. This in turn is due to specific features of the conformation of the peptide headgroup and alkyl chain branching.
Co-reporter:Valeria Castelletto, Ricardo J. Gouveia, Che J. Connon, Ian W. Hamley
European Polymer Journal 2013 Volume 49(Issue 10) pp:2961-2967
Publication Date(Web):October 2013
DOI:10.1016/j.eurpolymj.2013.02.016
The self-assembly and bioactivity of the peptide–polymer conjugate DGRFFF–PEG3000 containing the RGD cell adhesion motif has been examined, in aqueous solution. The conjugate is designed to be amphiphilic by incorporation of three hydrophobic phenylalanine residues as well as the RGD unit and a short poly(ethylene glycol) (PEG) chain of molar mass 3000 kg mol−1. Above a critical aggregation concentration, determined by fluorescence measurements, signals of β-sheet structure are revealed by spectroscopic measurements, as well as X-ray diffraction. At high concentration, a self-assembled fibril nanostructure is revealed by electron microscopy. The fibrils are observed despite PEG crystallization which occurs on drying. This suggests that DGRFFF has an aggregation tendency that is sufficiently strong not to be prevented by PEG crystallization. The adhesion, viability and proliferation of human corneal fibroblasts was examined for films of the conjugate on tissue culture plates (TCPs) as well as low attachment plates. On TCP, DGRFFF–PEG3000 films prepared at sufficiently low concentration are viable, and cell proliferation is observed. However, on low attachment surfaces, neither cell adhesion nor proliferation was observed, indicating that the RGD motif was not available to enhance cell adhesion. This was ascribed to the core–shell architecture of the self-assembled fibrils with a peptide core surrounded by a PEG shell which hinders access to the RGD unit.Graphical abstractHighlights► Self-assembly of the peptide–PEG conjugate DGRFFF–PEG is studied. ► The conjugate contains the RGD cell adhesion motif. ► Fibrils are observed, with β-sheet content. ► The PEG crystallizes on drying but the fibril structure is retained. ► Films of the conjugate at low concentration are biocompatible: cell adhesion and proliferation are observed.
Co-reporter:Valeria Castelletto and Ian W. Hamley, Conor Whitehouse and Paul J. Matts , Rosemarie Osborne and Ellen S. Baker
Langmuir 2013 Volume 29(Issue 29) pp:9149-9155
Publication Date(Web):July 3, 2013
DOI:10.1021/la401771j
The self-assembly of three cosmetically active peptide amphiphiles C16-GHK, C16-KT, and C16-KTTKS (C16 denotes a hexadecyl, palmitoyl chain) used in commercial skin care products is examined. A range of spectroscopic, microscopic, and X-ray scattering methods is used to probe the secondary structure, aggregate morphology, and the nanostructure. Peptide amphiphile (PA) C16-KTTKS forms flat tapes and extended fibrillar structures with high β-sheet content. In contrast, C16-KT and C16-GHK exhibit crystal-like aggregates with, in the case of the latter PA, lower β-sheet content. All three PA samples show spacings from bilayer structures in small-angle X-ray scattering profiles, and all three have similar critical aggregation concentrations, this being governed by the lipid chain length. However, only C16-KTTKS is stained by Congo red, a diagnostic dye used to detect amyloid formation, and this PA also shows a highly aligned cross-β X-ray diffraction pattern consistent with the high β-sheet content in the self-assembled aggregates. These findings may provide important insights relevant to the role of self-assembled aggregates on the reported collagen-stimulating properties of these PAs.
Co-reporter:I. W. Hamley
Chemical Reviews 2012 Volume 112(Issue 10) pp:5147
Publication Date(Web):July 19, 2012
DOI:10.1021/cr3000994
Co-reporter:Pasquale Palladino, Valeria Castelletto, Ashkan Dehsorkhi, Dmitry Stetsenko and Ian W. Hamley
Chemical Communications 2012 vol. 48(Issue 78) pp:9774-9776
Publication Date(Web):13 Aug 2012
DOI:10.1039/C2CC34665F
Here we explore the physico-chemical properties of a peptide amphiphile obtained by chemical conjugation of the collagen-stimulating peptide KTTKS with 10,12-pentacosadiynoic acid which photopolymerizes as a stable and extended polydiacetylene. We investigate the self-assembly of this new polymer and rationalize its peculiar behavior in terms of a thermal conformational transition. Surprisingly, this polymer shows a thermal transition associated with a non-cooperative increase in β-sheet content at high temperature.
Co-reporter:Ian W. Hamley, Ge Cheng, Valeria Castelletto, Stephan Handschin and Raffaele Mezzenga
Chemical Communications 2012 vol. 48(Issue 31) pp:3757-3759
Publication Date(Web):22 Feb 2012
DOI:10.1039/C2CC17583E
Ring-closing olefin metathesis reactions are used to create intra-molecularly ring closed peptides or inter-molecularly ring-closed peptide dimers based on a designed amyloid peptide sequence. The uncrosslinked peptide self-assembles into high aspect ratio nanotubes, however ring-closing leads to the formation of fibrillar and twisted/helical ribbon structures.
Co-reporter:A. Dehsorkhi, V. Castelletto, I. W. Hamley and P. Lindner
Soft Matter 2012 vol. 8(Issue 33) pp:8608-8615
Publication Date(Web):11 Jul 2012
DOI:10.1039/C2SM25990G
The influence of a non-ionic polymeric surfactant on the self-assembly of a peptide amphiphile (PA) that forms nanotapes is investigated using a combination of microscopic, scattering and spectroscopic techniques. Mixtures of Pluronic copolymer P123 with the PA C16-KTTKS in aqueous solution were studied at a fixed concentration of the PA at which it is known to self-assemble into extended nanotapes, but varying P123 concentration. We find that P123 can disrupt the formation of C16-KTTKS nanotapes, leading instead to cylindrical nanofibril structures. The spherical micelles formed by P123 at room temperature are disrupted in the presence of the PA. There is a loss of cloudiness in the solutions as the large nanotape aggregates formed by C16-KTTKS are broken up, by P123 solubilization. At least locally, β-sheet structure is retained, as confirmed by XRD and FTIR spectroscopy, even for solutions containing 20 wt% P123. This indicates, unexpectedly, that peptide secondary structure can be retained in solutions with high concentration of non-ionic surfactant. Self-assembly in this system exhibits slow kinetics towards equilibrium, the initial self-assembly being dependent on the order of mixing. Heating above the lipid chain melting temperature assists in disrupting trapped non-equilibrium states.
Co-reporter:Valeria Castelletto, Ge Cheng, Steve Furzeland, Derek Atkins and Ian W. Hamley
Soft Matter 2012 vol. 8(Issue 20) pp:5434-5438
Publication Date(Web):16 Apr 2012
DOI:10.1039/C2SM25546D
The self-assembly in aqueous solution of PEG-peptide conjugates comprising a model amyloid peptide sequence FFKLVFF that contains the Aβ(16–20) KLVFF motif is investigated. X-ray diffraction reveals different packing motifs dependent on PEG chain length. This is correlated to remarkable differences in self-assembled nanostructures. The control of strand registry points to a subtle interplay between aromatic stacking, electrostatic and amphiphilic interactions.
Co-reporter:Pasquale Palladino, Valeria Castelletto, Ashkan Dehsorkhi, Dmitry Stetsenko, and Ian W. Hamley
Langmuir 2012 Volume 28(Issue 33) pp:12209-12215
Publication Date(Web):July 26, 2012
DOI:10.1021/la302123h
Studying peptide amphiphiles (PAs), we investigate the influence of alkyl chain length on the aggregation behavior of the collagen-derived peptide KTTKS with applications ranging from antiwrinkle cosmetic creams to potential uses in regenerative medicine. We have studied synthetic peptides amphiphiles C14–KTTKS (myristoyl-Lys-Thr-Thr-Lys-Ser) and C18–KTTKS (stearoyl-Lys-Thr-Thr-Lys-Ser) to investigate in detail their physicochemical properties. It is presumed that the hydrophobic chain in these self-assembling peptide amphiphiles enhances peptide permeation across the skin compared to KTTKS alone. Subsequently Cn–KTTKS should act as a prodrug and release the peptide by enzymatic cleavage. Our results should be useful in the further development of molecules with collagen-stimulating activity.
Co-reporter:V. Castelletto, G. Cheng, C. Stain, C. J. Connon, and I. W. Hamley
Langmuir 2012 Volume 28(Issue 31) pp:11599-11608
Publication Date(Web):July 12, 2012
DOI:10.1021/la302210b
The self-assembly of the peptide amphiphile (PA) hexadecyl-(β-alanine-histidine) is examined in aqueous solution, along with its mixtures with multilamellar vesicles formed by DPPC (dipalmitoyl phosphatidylcholine). This PA, denoted C16-βAH, contains a dipeptide headgroup corresponding to the bioactive molecule l-carnosine. It is found to self-assemble into nanotapes based on stacked layers of molecules. Bilayers are found to coexist with monolayers in which the PA molecules pack with alternating up–down arrangement so that the headgroups decorate both surfaces. The bilayers become dehydrated as PA concentration increases and the number of layers in the stack decreases to produce ultrathin nanotapes comprised of 2–3 bilayers. Addition of the PA to DPPC multilamellar vesicles leads to a transition to well-defined unilamellar vesicles. The unique ability to modulate the stacking of this PA as a function of concentration, combined with its ability to induce a multilamellar to unilamellar thinning of DPPC vesicles, may be useful in biomaterials applications where the presentation of the peptide function at the surface of self-assembled nanostructures is crucial.
Co-reporter:G. Cheng, C. Krasel, H. G. Zhou, D. Chappell, and I. W. Hamley
Organic Letters 2011 Volume 13(Issue 10) pp:2572-2575
Publication Date(Web):April 19, 2011
DOI:10.1021/ol1028145
The model amyloid peptide AAKLVFF was expressed as a His-tagged fusion protein with the immunoglobulin-binding domain B1 of streptococcal protein G (GB1), a small (56 residues), stable, single-domain protein. It is shown that expression of this model amyloid peptide is possible and is not hindered by aggregation. Formylation side reactions during the CNBr cleavage are investigated via synthesis of selectively formylated peptides.
Co-reporter:Valeria Castelletto, Ge Cheng and Ian W. Hamley
Chemical Communications 2011 vol. 47(Issue 46) pp:12470-12472
Publication Date(Web):31 Oct 2011
DOI:10.1039/C1CC15493A
A series of heptapeptides comprising the core sequence Aβ(16–20), KLVFF, of the amyloid β peptide coupled with paired N-terminal γ-amino acids are investigated in terms of cytotoxicity reduction and binding to the full Aβ peptide, both pointing to inhibition of fibrillisation for selected compounds. This is related to the self-assembly capacity of the heptapeptides.
Co-reporter:G. Cheng, V. Castelletto, R. R. Jones, C. J. Connon and I. W. Hamley
Soft Matter 2011 vol. 7(Issue 4) pp:1326-1333
Publication Date(Web):26 Aug 2010
DOI:10.1039/C0SM00408A
The self-assembly of tripeptides based on the RGD cell adhesion motif is investigated. Two tripeptides containing the Fmoc [N-(fluorenyl)-9-methoxycarbonyl] aromatic unit were synthesized, Fmoc-RGD and a control peptide containing a scrambled sequence, Fmoc-GRD. The Fmoc is used to control self-assembly via aromatic stacking interactions. The self-assembly and hydrogelation properties of the two Fmoc-tripeptides are compared. Both form well defined amyloid fibrils (as shown by cryo-TEM and SAXS) with β-sheet features in their circular dichroism and FTIR spectra. Both peptides form self-supporting hydrogels, the dynamic shear modulus of which was measured. Preliminary cell culture experiments reveal that Fmoc-RGD can be used as a support for bovine fibroblasts, but not Fmoc-GRD, consistent with the incorporation of the cell adhesion motif in the former peptide.
Co-reporter:Ian W. Hamley;Ge Cheng;Valeria Castelletto
Macromolecular Bioscience 2011 Volume 11( Issue 8) pp:1068-1078
Publication Date(Web):
DOI:10.1002/mabi.201100022
Co-reporter:Dr. Jozef Adamcik;Dr. Valeria Castelletto;Dr. Sreenath Bolisetty; Ian W. Hamley; Raffaele Mezzenga
Angewandte Chemie International Edition 2011 Volume 50( Issue 24) pp:5495-5498
Publication Date(Web):
DOI:10.1002/anie.201100807
Co-reporter:Valeria Castelletto and Ian W. Hamley, Çelen Cenker and Ulf Olsson , Jozef Adamcik, Raffaele Mezzenga , Juan F. Miravet, Beatriu Escuder and Francisco Rodríguez-Llansola
The Journal of Physical Chemistry B 2011 Volume 115(Issue 9) pp:2107-2116
Publication Date(Web):February 10, 2011
DOI:10.1021/jp111168s
The influence of charge and aromatic stacking interactions on the self-assembly of a series of four model amyloid peptides has been examined. The four model peptides are based on the KLVFF motif from the amyloid β peptide, Aβ(16−20) extended at the N terminus with two β-alanine residues. We have studied NH2-βAβAKLVFF-COOH (FF), NH2-βAβAKLVF-COOH (F), CH3CONH-βAβAKLVFF-CONH2 (CapF), and CH3CONH-βAβAKLVFF-CONH2 (CapFF). The former two are uncapped (net charge +2) and differ by one hydrophobic phenylalanine residue; the latter two are the analogous capped peptides (net charge +1). The self-assembly characteristics of these peptides are remarkably different and strongly dependent on concentration. NMR shows a shift from carboxylate to carboxylic acid forms upon increasing concentration. Saturation transfer measurements of solvent molecules indicate selective involvement of phenylalanine residues in driving the self-assembly process of CapFF due presumably to the effect of aromatic stacking interactions. FTIR spectroscopy reveals β-sheet features for the two peptides containing two phenylalanine residues but not the single phenylalanine residue, pointing again to the driving force for self-assembly. Circular dichroism (CD) in dilute solution reveals the polyproline II conformation, except for F which is disordered. We discuss the relationship of this observation to the significant pH shift observed for this peptide when compared the calculated value. Atomic force microscopy and cryogenic-TEM reveals the formation of twisted fibrils for CapFF, as previously also observed for FF. The influence of salt on the self-assembly of the model β-sheet forming capped peptide CapFF was investigated by FTIR. Cryo-TEM reveals that the extent of twisting decreases with increased salt concentration, leading to the formation of flat ribbon structures. These results highlight the important role of aggregation-induced pKa shifts in the self-assembly of model β-sheet peptides.
Co-reporter:Dr. Jozef Adamcik;Dr. Valeria Castelletto;Dr. Sreenath Bolisetty; Ian W. Hamley; Raffaele Mezzenga
Angewandte Chemie 2011 Volume 123( Issue 24) pp:5609-5612
Publication Date(Web):
DOI:10.1002/ange.201100807
Co-reporter:Valeria Castelletto, Ian W Hamley, Javier Perez, Ludmila Abezgauz and Dganit Danino
Chemical Communications 2010 vol. 46(Issue 48) pp:9185-9187
Publication Date(Web):29 Oct 2010
DOI:10.1039/C0CC03793A
The nanostructure of a peptide amphiphile in commercial use in anti-wrinkle creams is investigated. The peptide contains a matrikine, collagen-stimulating, pentapeptide sequence. Self-assembly into giant nanotapes is observed and the internal structure was found to comprise bilayers parallel to the flat tape surfaces.
Co-reporter:Valeria Castelletto, David R. Nutt, Ian W. Hamley, Seyda Bucak, Çelen Cenker and Ulf Olsson
Chemical Communications 2010 vol. 46(Issue 34) pp:6270-6272
Publication Date(Web):29 Jul 2010
DOI:10.1039/C0CC00212G
The structure of single wall peptide nanotubes is presented for the model surfactant-like peptide A6K. Capillary flow alignment of a sample in the nematic phase at high concentration in water leads to oriented X-ray diffraction patterns. Analysis of these, accompanied by molecular dynamics simulations, suggests the favourable self-assembly of antiparallel peptide dimers into β-sheet ribbons that wrap helically to form the nanotube wall.
Co-reporter:V. Castelletto, G. E. Newby, D. Hermida Merino, I. W. Hamley, D. Liu and L. Noirez
Polymer Chemistry 2010 vol. 1(Issue 4) pp:453-459
Publication Date(Web):01 Feb 2010
DOI:10.1039/B9PY00349E
The self-assembly of PEGylated peptides containing a modified sequence from the amyloid β peptide, YYKLVFF, has been studied in aqueous solution. Two PEG molar masses, PEG1k and PEG3k, were used in the conjugates. It is shown that both YYKLVFF–PEG hybrids form fibrils comprising a peptide core and a PEG corona. The fibrils are much longer for YYKLVFF–PEG1k, pointing to an influence of PEG chain length. The β-sheet secondary structure of the peptide is retained in the conjugate. Lyotropic liquid crystal phases, specifically nematic and hexagonal columnar phases, are formed at sufficiently high concentration. Flow alignment of these mesophases was investigated by small-angle neutron scattering with in situ steady shearing in a Couette cell. On drying, PEG crystallization occurs leading to characteristic peaks in the X-ray diffraction pattern, and to lamellar structures imaged by atomic force microscopy. The X-ray diffraction pattern retains features of the cross-β pattern from the β-sheet structure, showing that this is not disrupted by PEG crystallization.
Co-reporter:Daniel Hermida Merino, Andrew T. Slark, Howard M. Colquhoun, Wayne Hayes and Ian W. Hamley
Polymer Chemistry 2010 vol. 1(Issue 8) pp:1263-1271
Publication Date(Web):05 Jul 2010
DOI:10.1039/C0PY00122H
The ability to generate very stable assemblies via non-covalent interactions has enabled materials to be constructed that were not feasible via ‘traditional’ covalent bond formation processes. A series of low molecular mass bisurethane and bisurea polymers have been developed that form stable self-assembled networks through hydrogen bonding interactions. Thermo-responsive polymers were generated by end-capping poly(ethylene-co-butylene) or polybutadiene chains with the bisurethane or bisurea motif. Microphase separation is observed via TEM and small-angle X-ray scattering (SAXS) for the modified pseudo polymers and significant differences in the temperature dependence of microphase separation are analysed via SAXS. The importance of the polarity of the end groups is manifested in distinct temperature-dependent microphase separation behaviour. Information on the local hydrogen bonding structure is provided by wide-angle X-ray scattering and variable temperature FTIR.
Co-reporter:Ian W. Hamley;Valeria Castelletto;Claire Moulton;Daniel Myatt;Giuliano Siligardi;Cristiano L. P. Oliveira;Jan Skov Pedersen;Inbal Abutbul;Dganit Danino
Macromolecular Bioscience 2010 Volume 10( Issue 1) pp:40-48
Publication Date(Web):
DOI:10.1002/mabi.200900217
Co-reporter:I. W. Hamley
Soft Matter 2010 vol. 6(Issue 9) pp:1863-1871
Publication Date(Web):24 Feb 2010
DOI:10.1039/B923942A
This review discusses liquid crystal phase formation by biopolymers in solution. Lyotropic mesophases have been observed for several classes of biopolymer including DNA, peptides, polymer/peptide conjugates, glycopolymers and proteoglycans. Nematic or chiral nematic (cholesteric) phases are the most commonly observed mesophases, in which the rod-like fibrils have only orientational order. Hexagonal columnar phases are observed for several systems (DNA, PBLG, polymer/peptide hybrids) at higher concentration. Lamellar (smectic) phases are reported less often, although there are examples such as the layer arrangement of amylopectin side chains in starch. Possible explanations for the observed structures are discussed. The biological role of liquid crystal phases for several of these systems is outlined. Commonly, they may serve as a template to align fibrils for defined structural roles when the biopolymer is extruded and dried, for instance in the production of silk by spiders or silkworms, or of chitin in arthropod shells. In other cases, liquid crystal phase formation may occur in vivo simply as a consequence of high concentration, for instance the high packing density of DNA within cell nuclei.
Co-reporter:G. Cheng, V. Castelletto, C. M. Moulton, G. E. Newby and I. W. Hamley
Langmuir 2010 Volume 26(Issue 7) pp:4990-4998
Publication Date(Web):January 14, 2010
DOI:10.1021/la903678e
The self-assembly and hydrogelation properties of two Fmoc-tripeptides [Fmoc = N-(fluorenyl-9-methoxycarbonyl)] are investigated, in borate buffer and other basic solutions. A remarkable difference in self-assembly properties is observed comparing Fmoc-VLK(Boc) with Fmoc-K(Boc)LV, both containing K protected by Nε-tert-butyloxycarbonate (Boc). In borate buffer, the former peptide forms highly anisotropic fibrils which show local alignment, and the hydrogels show flow-aligning properties. In contrast, Fmoc-K(Boc)LV forms highly branched fibrils that produce isotropic hydrogels with a much higher modulus (G′ > 104 Pa), and lower concentration for hydrogel formation. The distinct self-assembled structures are ascribed to conformational differences, as revealed by secondary structure probes (CD, FTIR, Raman spectroscopy) and X-ray diffraction. Fmoc-VLK(Boc) forms well-defined β-sheets with a cross-β X-ray diffraction pattern, whereas Fmoc-KLV(Boc) forms unoriented assemblies with multiple stacked sheets. Interchange of the K and V residues when inverting the tripeptide sequence thus leads to substantial differences in self-assembled structures, suggesting a promising approach to control hydrogel properties.
Co-reporter:V. Castelletto, J. E. McKendrick and I. W. Hamley, U. Olsson and C. Cenker
Langmuir 2010 Volume 26(Issue 14) pp:11624-11627
Publication Date(Web):June 15, 2010
DOI:10.1021/la101806z
A micellar nanocontainer delivery and release system is designed on the basis of a peptide−polymer conjugate. The hybrid molecules self-assemble into micelles comprising a modified amyloid peptide core surrounded by a PEG corona. The modified amyloid peptide previously studied in our group forms helical ribbons based on a β-sheet motif and contains β-amino acids that are excluded from the β-sheet structure, thus being potentially useful as fibrillization inhibitors. In the model peptide−PEG hybrid system studied, enzymatic degradation using α-chymotrypsin leads to selective cleavage close to the PEG−peptide linkage, break up of the micelles, and release of peptides in unassociated form. The release of monomeric peptide is useful because aggregation of the released peptide into β-sheet amyloid fibrils is not observed. This concept has considerable potential in the targeted delivery of peptides for therapeutic applications.
Co-reporter:I.W. Hamley
Progress in Polymer Science 2009 Volume 34(Issue 11) pp:1161-1210
Publication Date(Web):November 2009
DOI:10.1016/j.progpolymsci.2009.06.003
The ordering of block copolymers in thin films is reviewed, starting from the fundamental principles and extending to recent promising developments as templates for nanolithography which may find important applications in the semiconductor industry. Ordering in supported thin films of symmetric and asymmetric AB diblock and ABA triblock copolymers is discussed, along with that of more complex materials such as ABC triblocks and liquid crystalline block copolymers. Techniques to prepare thin films, and to characterise ordering within them, are summarized. Several methods to align block copolymer nanostructures, important in several applications are outlined. A number of potential applications in nanolithography, production of porous materials, templating, and patterning of organic and inorganic materials are then presented. The influence of crystallization on the morphology of a block copolymer film is briefly discussed, as are structures in grafted block copolymer films.
Co-reporter:Ian W. Hamley;Ben M. D. O'Driscoll;Gudrun Lotze;Claire Moulton;Jürgen Allgaier;Henrich Frielinghaus
Macromolecular Rapid Communications 2009 Volume 30( Issue 24) pp:2141-2146
Publication Date(Web):
DOI:10.1002/marc.200900474
Co-reporter:Gemma E. Newby, Ian W. Hamley, Stephen M. King, Christopher M. Martin, Nicholas J. Terrill
Journal of Colloid and Interface Science 2009 Volume 329(Issue 1) pp:54-61
Publication Date(Web):1 January 2009
DOI:10.1016/j.jcis.2008.09.054
The structure and flow behaviour of binary mixtures of Pluronic block copolymers P85 and P123 is investigated by small-angle scattering, rheometry and mobility tests. Micelle dimensions are probed by dynamic light scattering. The micelle hydrodynamic radius for the 50/50 mixture is larger than that for either P85 or P123 alone, due to the formation of mixed micelles with a higher association number. The phase diagram for 50/50 mixtures contains regions of cubic and hexagonal phases similar to those for the parent homopolymers, however the region of stability of the cubic phase is enhanced at low temperature and concentrations above 40 wt%. This is ascribed to favourable packing of the mixed micelles containing core blocks with two different chain lengths, but similar corona chain lengths. The shear flow alignment of face-centred cubic and hexagonal phases is probed by in situ small-angle X-ray or neutron scattering with simultaneous rheology. The hexagonal phase can be aligned using steady shear in a Couette geometry, however the high modulus cubic phase cannot be aligned well in this way. This requires the application of oscillatory shear or compression.The structure and flow behaviour of binary mixtures of Pluronics P85 and P123 is investigated by small-angle scattering, rheometry and mobility tests. A phase diagram was compiled on the basis of these measurements, and shear alignment of gel phases probed by in situ small-angle scattering and rheometry experiments.
Co-reporter:Valeria Castelletto, Ian W. Hamley
Biophysical Chemistry 2009 Volume 141(2–3) pp:169-174
Publication Date(Web):May 2009
DOI:10.1016/j.bpc.2009.01.008
There has been great interest recently in peptide amphiphiles and block copolymers containing biomimetic peptide sequences due to applications in bionanotechnology. We investigate the self-assembly of the peptide-PEG amphiphile FFFF-PEG5000 containing the hydrophobic sequence of four phenylalanine residues conjugated to PEG of molar mass 5000. This serves as a simple model peptide amphiphile. At very low concentration, association of hydrophobic aromatic phenylalanine residues occurs, as revealed by circular dichroism and UV/vis fluorescence experiments. A critical aggregation concentration associated with the formation of hydrophobic domains is determined through pyrene fluorescence assays. At higher concentration, defined β-sheets develop as revealed by FTIR spectroscopy and X-ray diffraction. Transmission electron microscopy reveals self-assembled straight fibril structures. These are much shorter than those observed for amyloid peptides, the finite length may be set by the end cap energy due to the hydrophobicity of phenylalanine. The combination of these techniques points to different aggregation processes depending on concentration. Hydrophobic association into irregular aggregates occurs at low concentration, well-developed β-sheets only developing at higher concentration. Drying of FFFF-PEG5000 solutions leads to crystallization of PEG, as confirmed by polarized optical microscopy (POM), FTIR and X-ray diffraction (XRD). PEG crystallization does not disrupt local β-sheet structure (as indicated by FTIR and XRD). However on longer lengthscales the β-sheet fibrillar structure is perturbed because spherulites from PEG crystallization are observed by POM.
Co-reporter:Valeria Castelletto Dr.;IanW. Hamley ;RohanA. Hule Dr.;Darrin Pochan
Angewandte Chemie International Edition 2009 Volume 48( Issue 13) pp:2317-2320
Publication Date(Web):
DOI:10.1002/anie.200805500
Co-reporter:V. Castelletto and I. W. Hamley, P. J. F. Harris, U. Olsson, N. Spencer
The Journal of Physical Chemistry B 2009 Volume 113(Issue 29) pp:9978-9987
Publication Date(Web):June 25, 2009
DOI:10.1021/jp902860a
The solvent-induced transition between self-assembled structures formed by the peptide AAKLVFF is studied via electron microscopy, light scattering, and spectroscopic techniques. The peptide is based on a core fragment of the amyloid β-peptide, KLVFF, extended by two alanine residues. AAKLVFF exhibits distinct structures of twisted fibrils in water or nanotubes in methanol. For intermediate water/methanol compositions, these structures are disrupted and replaced by wide filamentous tapes that appear to be lateral aggregates of thin protofilaments. The orientation of the β-strands in the twisted tapes or nanotubes can be deduced from X-ray diffraction on aligned stalks, as well as FT-IR experiments in transmission compared to attenuated total reflection. Strands are aligned perpendicular to the axis of the twisted fibrils or the nanotubes. The results are interpreted in light of recent results on the effect of competitive hydrogen bonding upon self-assembly in soft materials in water/methanol mixtures.
Co-reporter:Tian Tang, Ian W. Hamley
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2009 Volume 336(1–3) pp:1-7
Publication Date(Web):20 March 2009
DOI:10.1016/j.colsurfa.2008.11.008
High-temperature polyol methods were used to fabricate micro- or nano-sized gold plates. 1,2-propanediol served as both medium and reducing agent. Triangular plates and polygonal plate shapes derived from triangular prisms as well as pentagonal structured gold particles have been synthesized. Poly(vinylpyrrolidone) (PVP) plays an important role, but is not necessary, for the formation of these structures. These gold plates may have applications in the characterisation of adsorbed proteins or peptides.
Co-reporter:Valeria Castelletto Dr.;IanW. Hamley ;RohanA. Hule Dr.;Darrin Pochan
Angewandte Chemie 2009 Volume 121( Issue 13) pp:2353-2356
Publication Date(Web):
DOI:10.1002/ange.200805500
Co-reporter:Ian W. Hamley;Marta J. Krysmann;Valeria Castelletto;Laurence Noirez
Advanced Materials 2008 Volume 20( Issue 23) pp:4394-4397
Publication Date(Web):
DOI:10.1002/adma.200800266
Co-reporter:Antonios Kelarakis, Tian Tang, Vasiliki Havredaki, Kyriakos Viras, Ian W. Hamley
Journal of Colloid and Interface Science 2008 Volume 320(Issue 1) pp:70-73
Publication Date(Web):1 April 2008
DOI:10.1016/j.jcis.2007.12.030
Critical micelle concentrations (cmc) of aqueous solutions of poly(methyl methacrylate)–block–poly(N -isopropylacrylamide) were determined at several temperatures by surface tensiometry. Below the lower critical solution temperature (LCST), the low ΔmicH0ΔmicH0 determined can be assigned to the PMMA block being tightly coiled in the dispersed molecular state, so that the unfavorable interactions of hydrophobic entities with water are minimized. Above the LCST the cmc value was found to increase; an anomalous behavior that can be directly related to the micelle–globule transition of the hydrophilic block. Interestingly, above the LCST the surface tension of relatively concentrated solutions was found to depend weakly on temperature not following the usual strong decrease with temperature expected for aqueous solutions.At low temperatures, surface tensiometry in aqueous solutions of PMAA–b–PNIPAm copolymer reveals a case of almost athermal micellization.
Co-reporter:Marta J. Krysmann, Valeria Castelletto, Antonios Kelarakis, Ian W. Hamley, Rohan A. Hule and Darrin J. Pochan
Biochemistry 2008 Volume 47(Issue 16) pp:
Publication Date(Web):March 28, 2008
DOI:10.1021/bi8000616
The self-assembly of a fragment of the amyloid β peptide that has been shown to be critical in amyloid fibrillization has been studied in aqueous solution. There are conflicting reports in the literature on the fibrillization of Aβ (16–20), i.e., KLVFF, and our results shed light on this. In dilute solution, self-assembly of NH2−KLVFF−COOH is strongly influenced by aromatic interactions between phenylalanine units, as revealed by UV spectroscopy and circular dichroism. Fourier transform infrared (FTIR) spectroscopy reveals β-sheet features in spectra taken for more concentrated solutions and also dried films. X-ray diffraction and cryo-transmission electron microscopy (cryo-TEM) provide further support for β-sheet amyloid fibril formation. A comparison of cryo-TEM images with those from conventional dried and negatively stained TEM specimens highlights the pronounced effects of sample preparation on the morphology. A comparison of FTIR data for samples in solution and dried samples also highlights the strong effect of drying on the self-assembled structure. In more concentrated phosphate-buffered saline (PBS) solution, gelation of NH2−KLVFF−COOH is observed. This is believed to be caused by screening of the electrostatic charge on the peptide, which enables β sheets to aggregate into a fibrillar gel network. The rheology of the hydrogel is probed, and the structure is investigated by light scattering and small-angle X-ray scattering.
Co-reporter:V. Castelletto, I.W. Hamley, P.J.F. Harris
Biophysical Chemistry 2008 Volume 138(1–2) pp:29-35
Publication Date(Web):November 2008
DOI:10.1016/j.bpc.2008.08.007
The self-assembly in films dried from aqueous solutions of a modified amyloid beta peptide fragment is studied. We focus on sequence Aβ(16–20), KLVFF, extended by two alanines at the N-terminus to give AAKLVFF. Self-assembly into twisted ribbon fibrils is observed, as confirmed by transmission electron microscopy (TEM). Dynamic light scattering reveals the semi-flexible nature of the AAKLVFF fibrils, while polarized optical microscopy shows that the peptide fibrils crystallize after an aqueous solution of AAKLVFF is matured over 5 days.The secondary structure of the fibrils is studied by FT-IR, circular dichroism and X-ray diffraction (XRD), which provide evidence for β-sheet structure in the fibril. From high resolution TEM it is concluded that the average width of an AAKLVFF fibril is (63 ± 18) nm, indicating that these fibrils comprise beta-sheets with multiple repeats of the unit cell, determined by XRD to have b and c dimensions 1.9 and 4.4 nm with an a axis 0.96 nm, corresponding to twice the peptide backbone spacing in the antiparallel β-sheet.
Co-reporter:Marta J. Krysmann;Sérgio S. Funari;Elisabetta Canetta;Ian W. Hamley
Macromolecular Chemistry and Physics 2008 Volume 209( Issue 9) pp:883-889
Publication Date(Web):
DOI:10.1002/macp.200700605
Co-reporter:IanW. Hamley ;MartaJ. Krysmann;Antonios Kelarakis Dr.;Valeria Castelletto Dr.;Laurence Noirez Dr.;RohanA. Hule;DarrinJ. Pochan
Chemistry - A European Journal 2008 Volume 14( Issue 36) pp:11369-11375
Publication Date(Web):
DOI:10.1002/chem.200800817
Abstract
The self-assembly in aqueous solution of a PEG–peptide conjugate is studied by spectroscopy, electron microscopy, rheology and small-angle X-ray and neutron scattering (SAXS and SANS). The peptide fragment, FFKLVFF is based on fragment KLVFF of the amyloid β-peptide, Aβ(16–20), extended by two hydrophobic phenylalanine units. This is conjugated to PEG which confers water solubility and leads to distinct self-assembled structures. Small-angle scattering reveals the formation of cylindrical fibrils comprising a peptide core and PEG corona. This constrained structure leads to a model parallel β-sheet self-assembled structure with a radial arrangement of β sheets. On increasing concentration, successively nematic and hexagonal columnar phases are formed. The flow-induced alignment of both structures was studied in situ by SANS using a Couette cell. Shear-induced alignment is responsible for the shear thinning behaviour observed by dynamic shear rheometry. Incomplete recovery of moduli after cessation of shear is consistent with the observation from SANS of retained orientation in the sample.
Co-reporter:IanW. Hamley ;MartaJ. Krysmann;Antonios Kelarakis Dr.;Valeria Castelletto Dr.;Laurence Noirez Dr.;RohanA. Hule;DarrinJ. Pochan
Chemistry - A European Journal 2008 Volume 14( Issue 36) pp:
Publication Date(Web):
DOI:10.1002/chem.200890150
No abstract is available for this article.
Co-reporter:Ian W. Hamley and Marta J. Krysmann
Langmuir 2008 Volume 24(Issue 15) pp:8210-8214
Publication Date(Web):July 4, 2008
DOI:10.1021/la8005426
The effect of poly(ethylene glycol) PEG crystallization on β-sheet fibril formation is studied for a series of three peptide/PEG conjugates containing fragments modified from the amyloid β peptide, specifically KLVFF, FFKLVFF, and AAKLVFF. These are conjugated to PEG with Mn = 3300 g mol−1. It is found, via small-angle X-ray scattering, X-ray diffraction, atomic force microscopy, and polarized optical microscopy, that PEG crystallinity in dried samples can disturb fibrillization, in particular cross-β amyloid structure formation, for the conjugate containing the weak fibrillizer KLVFF, whereas this is retained for the conjugates containing the stronger fibrillizers AAKLVFF and FFKLVFF. For these two samples, the alignment of peptide fibrils also drives the orientation of the attached PEG chains. Our results highlight the importance of the antagonistic effects of PEG crystallization and peptide fibril formation in PEG/peptide conjugates.
Co-reporter:Antonios Kelarakis, Valeria Castelletto, Marta J. Krysmann, Vasiliki Havredaki, Kyriakos Viras and Ian W. Hamley
Biomacromolecules 2008 Volume 9(Issue 5) pp:
Publication Date(Web):April 8, 2008
DOI:10.1021/bm800046m
The interactions of bovine serum albumin (BSA) with three ethylene oxide/butylene oxide (E/B) copolymers having different block lengths and varying molecular architectures is examined in this study in aqueous solutions. Dynamic light scattering (DLS) indicates the absence of BSA−polymer binding in micellar systems of copolymers with lengthy hydrophilic blocks. On the contrary, stable protein−polymer aggregates were observed in the case of E18B10 block copolymer. Results from DLS and SAXS suggest the dissociation of E/B copolymer micelles in the presence of protein and the absorption of polymer chains to BSA surface. At high protein loadings, bound BSA adopts a more compact conformation in solution. The secondary structure of the protein remains essentially unaffected even at high polymer concentrations. Raman spectroscopy was used to give insight to the configurations of the bound molecules in concentrated solutions. In the vicinity of the critical gel concentration of E18B10 introduction of BSA can dramatically modify the phase diagram, inducing a gel−sol–gel transition. The overall picture of the interaction diagram of the E18B10−BSA reflects the shrinkage of the suspended particles due to destabilization of micelles induced by BSA and the gelator nature of the globular protein. SAXS and rheology were used to further characterize the structure and flow behavior of the polymer−protein hybrid gels and sols.
Co-reporter:Ian W. Hamley
Macromolecules 2008 Volume 41(Issue 22) pp:8948-8950
Publication Date(Web):October 28, 2008
DOI:10.1021/ma8014917
Co-reporter:M. J. Krysmann, V. Castelletto and I. W. Hamley
Soft Matter 2007 vol. 3(Issue 11) pp:1401-1406
Publication Date(Web):17 Sep 2007
DOI:10.1039/B709889H
The self-assembly of a hydrophobically modified fragment of the amyloid β (Aβ) peptide has been studied in methanol. The peptide FFKLVFF is based on Aβ(16–20) extended at the N terminus by two phenylalanine residues. The formation of amyloid-type fibrils is confirmed by Congo Red staining, thioflavin T fluorescence and circular dichroism experiments. FTIR points to the formation of β-sheet structures in solution and in dried films and suggests that aggregation occurs at low concentration and is not strongly affected by further increase in concentration, i.e. the peptide is a strong fibril-former in methanol. UV fluorescence experiments on unstained peptide and CD point to the importance of aromatic interactions between phenylalanine groups in driving aggregation into β-sheets. The CD spectrum differs from that usually observed for β-sheet assemblies formed by larger peptides or proteins and this is discussed for solutions in methanol and also trifluoroethanol. The fibril structure is imaged by transmission electron microscopy and scanning electron microscopy on dried samples and is confirmed by small-angle X-ray scattering experiments in solution.
Co-reporter:A.A. Khaydarov, I.W. Hamley, Thomas M. Legge, Sébastien Perrier
European Polymer Journal 2007 Volume 43(Issue 3) pp:789-796
Publication Date(Web):March 2007
DOI:10.1016/j.eurpolymj.2006.10.006
Asymmetric poly(styrene-b-methyl methacrylate) (PS-b-PMMA) diblock copolymers of molecular weight Mn = 29,700 g mol−1 (MPS = 9300 g mol−1MPMMA = 20,100 g mol−1, PD = 1.15, χPS = 0.323, χPMMA = 0.677) and Mn = 63,900 g mol−1 (MPS = 50,500 g mol−1, MPMMA = 13,400 g mol−1, PD = 1.18, χPS = 0.790, χPMMA = 0.210) were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. Atomic force microscopy (AFM) was used to investigate the surface structure of thin films, prepared by spin-coating the diblock copolymers on a silicon substrate. We show that the nanostructure of the diblock copolymer depends on the molecular weight and volume fraction of the diblock copolymers. We observed a perpendicular lamellar structure for the high molar mass sample and a hexagonal-packed cylindrical patterning for the lower molar mass one. Small-angle X-ray scattering investigation of these samples without annealing did not reveal any ordered structure. Annealing of PS-b-PMMA samples at 160 °C for 24 h led to a change in surface structure.
Co-reporter:Ian W. Hamley ;Valeria Castelletto Dr.
Angewandte Chemie International Edition 2007 Volume 46(Issue 24) pp:
Publication Date(Web):22 MAY 2007
DOI:10.1002/anie.200603922
With one or two exceptions, biological materials are “soft”, meaning that they combine viscous and elastic elements. This mechanical behavior results from self-assembled supramolecular structures that are stabilized by noncovalent interactions. It is an ongoing and profound challenge to understand the self-organization of biological materials. In many cases, concepts can be imported from soft-matter physics and chemistry, which have traditionally focused on materials such as colloids, polymers, surfactants, and liquid crystals. Using these ideas, it is possible to gain a new perspective on phenomena as diverse as DNA condensation, protein and peptide fibrillization, lipid partitioning in rafts, vesicle fusion and budding, and others, as discussed in this selective review of recent highlights from the literature.
Co-reporter:Ian W. Hamley
Angewandte Chemie International Edition 2007 Volume 46(Issue 43) pp:
Publication Date(Web):12 OCT 2007
DOI:10.1002/anie.200700861
The fibrillization of peptides is relevant to many diseases based on the deposition of amyloids. The formation of fibrils is being intensively studied, especially in terms of nanotechnology applications, where fibrillar peptide hydrogels are used for cell scaffolds, as supports for functional and responsive biomaterials, biosensors, and nanowires. This Review is concerned with fundamental aspects of the self-assembly of peptides into fibrils, and discusses both natural amyloid-forming peptides and synthetic materials, including peptide fragments, copolymers, and amphiphiles.
Co-reporter:Ian W. Hamley
Angewandte Chemie 2007 Volume 119(Issue 43) pp:
Publication Date(Web):12 OCT 2007
DOI:10.1002/ange.200700861
Die Bildung von Peptidfibrillen spielt eine bedeutende Rolle bei vielen Krankheiten, die durch Amyloidablagerungen verursacht werden. Intensiv erforscht wird die Bildung von Fibrillen aber auch wegen ihres großen Anwendungspotenzials in der Bionanotechnologie, wo Hydrogele aus Peptidfibrillen als Zellgerüste und als Substrate für funktionelle und responsive Biomaterialien, Biosensoren und Nanodrähte Anwendung finden können. In diesem Aufsatz werden die grundlegenden Aspekte der Selbstorganisation von Peptiden zu Fibrillen behandelt. Sowohl natürliche amyloidbildende Peptide als auch synthetische Verbindungen, z. B. Peptidfragmente, Copolymere und Amphiphile, werden diskutiert.
Co-reporter:Ian W. Hamley ;Valeria Castelletto Dr.
Angewandte Chemie 2007 Volume 119(Issue 24) pp:
Publication Date(Web):22 MAY 2007
DOI:10.1002/ange.200603922
Mit einer oder zwei Ausnahmen sind Biomaterialien “weich”, das bedeutet, sie verbinden visköse und elastische Eigenschaften. Dieses mechanische Verhalten wird durch die Bildung selbstorganisierter supramolekularer Strukturen hervorgerufen, die durch nichtkovalente Wechselwirkungen stabilisiert sind. Es ist eine grundlegende Herausforderung, die Selbstorganisation von Biomaterialien zu verstehen. In vielen Fällen können Konzepte aus der Physik und Chemie weicher Materie, die ursprünglich für Kolloide, Polymere, oberflächenaktive Substanzen, Flüssigkristalle und ähnliches entwickelt wurden, auf die Biologie übertragen werden. Mit diesem Ansatz ist es möglich, so verschiedene Phänomene wie die DNA-Kondensation, die Fibrillenbildung durch Proteine und Peptide, die Trennung von Lipiden in Schollen, die Fusion oder die Knospung von Vesikeln aus einer neuen Perspektive zu betrachten.
Co-reporter:I.W. Hamley
Progress in Polymer Science (November 2009) Volume 34(Issue 11) pp:1161-1210
Publication Date(Web):1 November 2009
DOI:10.1016/j.progpolymsci.2009.06.003
The ordering of block copolymers in thin films is reviewed, starting from the fundamental principles and extending to recent promising developments as templates for nanolithography which may find important applications in the semiconductor industry. Ordering in supported thin films of symmetric and asymmetric AB diblock and ABA triblock copolymers is discussed, along with that of more complex materials such as ABC triblocks and liquid crystalline block copolymers. Techniques to prepare thin films, and to characterise ordering within them, are summarized. Several methods to align block copolymer nanostructures, important in several applications are outlined. A number of potential applications in nanolithography, production of porous materials, templating, and patterning of organic and inorganic materials are then presented. The influence of crystallization on the morphology of a block copolymer film is briefly discussed, as are structures in grafted block copolymer films.
Co-reporter:Roanne R. Jones, Ian W. Hamley, Che J. Connon
Stem Cell Research (May 2012) Volume 8(Issue 3) pp:403-409
Publication Date(Web):1 May 2012
DOI:10.1016/j.scr.2012.01.001
Limbal epithelial stem cells play a key role in the maintenance and regulation of the corneal surface. Damage or destruction of these cells results in vascularisation and corneal opacity. Subsequent limbal stem cell transplantation requires an ex vivo expansion step and preserving cells in an undifferentiated state remains vital. In this report we seek to control the phenotype of limbal epithelial stem cells by the novel application of compressed collagen substrates. We have characterised the mechanical and surface properties of conventional collagen gels using shear rheology and scanning electron microscopy. In doing so, we provide evidence to show that compressive load can improve the stiffness of collagen substrates. In addition Western blotting and immunohistochemistry display increased cytokeratin 3 (CK3) protein expression relating to limbal epithelial cell differentiation on stiff collagen substrates. Such gels with an elastic modulus of 2900 Pa supported a significantly higher number of cells than less stiff collagen gels (3 Pa). These findings have substantial influence in the development of ocular surface constructs or experimental models particularly in the fields of stem cell research, tissue engineering and regenerative medicine.Graphical abstractDownload high-res image (442KB)Download full-size imageHighlights► Compressed collagen gels have an increased level of stiffness. ► Increased substrate stiffness influenced limbal stem cell differentiation. ► Cells differentiated, stratified and proliferated on stiff collagen substrates. ► Substrate stiffness is an important parameter in the culture of limbal stem cells.
Co-reporter:Valeria Castelletto, Ian W Hamley, Javier Perez, Ludmila Abezgauz and Dganit Danino
Chemical Communications 2010 - vol. 46(Issue 48) pp:NaN9187-9187
Publication Date(Web):2010/10/29
DOI:10.1039/C0CC03793A
The nanostructure of a peptide amphiphile in commercial use in anti-wrinkle creams is investigated. The peptide contains a matrikine, collagen-stimulating, pentapeptide sequence. Self-assembly into giant nanotapes is observed and the internal structure was found to comprise bilayers parallel to the flat tape surfaces.
Co-reporter:Emerson Rodrigo da Silva, Wendel Andrade Alves, Valeria Castelletto, Mehedi Reza, Janne Ruokolainen, Rohanah Hussain and Ian William Hamley
Chemical Communications 2015 - vol. 51(Issue 58) pp:NaN11637-11637
Publication Date(Web):2015/06/15
DOI:10.1039/C5CC03640B
The self-assembly of peptide nanotubes formed by an L-glutamic acid-based bolaamphiphile is shown to proceed via a remarkable mechanism where the peptide conformation changes from β-sheet to unordered. The kinetics of this process are elucidated via X-ray scattering and UV circular dichroism methods. The reverse transition from “unordered” to β-sheet structures is triggered by UV radiation.
Co-reporter:Charlotte J. C. Edwards-Gayle and Ian W. Hamley
Organic & Biomolecular Chemistry 2017 - vol. 15(Issue 28) pp:NaN5876-5876
Publication Date(Web):2017/06/26
DOI:10.1039/C7OB01092C
Molecular self-assembly is a multi-disciplinary field of research, with potential chemical and biological applications. One of the main driving forces of self-assembly is molecular amphiphilicity, which can drive formation of complex and stable nanostructures. Self-assembling peptide and peptide conjugates have attracted great attention due to their biocompatibility, biodegradability and biofunctionality. Understanding assembly enables the better design of peptide amphiphiles which may form useful and functional nanostructures. This review covers self-assembly of amphiphilic peptides and peptide mimetic materials, as well as their potential applications.
Co-reporter:Valeria Castelletto, David R. Nutt, Ian W. Hamley, Seyda Bucak, Çelen Cenker and Ulf Olsson
Chemical Communications 2010 - vol. 46(Issue 34) pp:NaN6272-6272
Publication Date(Web):2010/07/29
DOI:10.1039/C0CC00212G
The structure of single wall peptide nanotubes is presented for the model surfactant-like peptide A6K. Capillary flow alignment of a sample in the nematic phase at high concentration in water leads to oriented X-ray diffraction patterns. Analysis of these, accompanied by molecular dynamics simulations, suggests the favourable self-assembly of antiparallel peptide dimers into β-sheet ribbons that wrap helically to form the nanotube wall.
Co-reporter:Pasquale Palladino, Valeria Castelletto, Ashkan Dehsorkhi, Dmitry Stetsenko and Ian W. Hamley
Chemical Communications 2012 - vol. 48(Issue 78) pp:NaN9776-9776
Publication Date(Web):2012/08/13
DOI:10.1039/C2CC34665F
Here we explore the physico-chemical properties of a peptide amphiphile obtained by chemical conjugation of the collagen-stimulating peptide KTTKS with 10,12-pentacosadiynoic acid which photopolymerizes as a stable and extended polydiacetylene. We investigate the self-assembly of this new polymer and rationalize its peculiar behavior in terms of a thermal conformational transition. Surprisingly, this polymer shows a thermal transition associated with a non-cooperative increase in β-sheet content at high temperature.
Co-reporter:King Hang Aaron Lau, Valeria Castelletto, Thomas Kendall, Jan Sefcik, Ian W. Hamley, Mehedi Reza and Janne Ruokolainen
Chemical Communications 2017 - vol. 53(Issue 13) pp:NaN2181-2181
Publication Date(Web):2017/01/25
DOI:10.1039/C6CC09888F
Poly(N-substituted glycine) “peptoids” constitute a promising class of peptide-mimetic materials. We introduce the self-assembly of lipopeptoids into spherical micelles ca. 5 nm in diameter as well as larger assemblies by varying the peptoid sequence design. Our results point to design rules for the self-assembly of peptoid nanostructures, enabling the creation of stable, ultra-small peptidomimetic nanospheres.
Co-reporter:Valeria Castelletto, Ge Cheng and Ian W. Hamley
Chemical Communications 2011 - vol. 47(Issue 46) pp:NaN12472-12472
Publication Date(Web):2011/10/31
DOI:10.1039/C1CC15493A
A series of heptapeptides comprising the core sequence Aβ(16–20), KLVFF, of the amyloid β peptide coupled with paired N-terminal γ-amino acids are investigated in terms of cytotoxicity reduction and binding to the full Aβ peptide, both pointing to inhibition of fibrillisation for selected compounds. This is related to the self-assembly capacity of the heptapeptides.
Co-reporter:Ian W. Hamley, Steven Kirkham, Ashkan Dehsorkhi, Valeria Castelletto, Mehedi Reza and Janne Ruokolainen
Chemical Communications 2014 - vol. 50(Issue 100) pp:NaN15951-15951
Publication Date(Web):2014/10/30
DOI:10.1039/C4CC07511K
The self-assembled structure of toll-like receptor agonist lipopeptides containing the CSK4 peptide sequence is examined in aqueous solution. A remarkable dependence of morphology on the number of attached hexadecyl lipid chains is demonstrated, with spherical micelle structures for mono- and di-lipidated structures observed, but flexible wormlike micelles for the homologue containing three lipid chains. The distinct modes of assembly may have an important influence on the bioactivity of this class of lipopeptide.
Co-reporter:Ian W. Hamley, Ge Cheng, Valeria Castelletto, Stephan Handschin and Raffaele Mezzenga
Chemical Communications 2012 - vol. 48(Issue 31) pp:NaN3759-3759
Publication Date(Web):2012/02/22
DOI:10.1039/C2CC17583E
Ring-closing olefin metathesis reactions are used to create intra-molecularly ring closed peptides or inter-molecularly ring-closed peptide dimers based on a designed amyloid peptide sequence. The uncrosslinked peptide self-assembles into high aspect ratio nanotubes, however ring-closing leads to the formation of fibrillar and twisted/helical ribbon structures.
Co-reporter:Ian W. Hamley, Ashkan Dehsorkhi and Valeria Castelletto
Chemical Communications 2013 - vol. 49(Issue 18) pp:NaN1852-1852
Publication Date(Web):2013/01/23
DOI:10.1039/C3CC39057H
The surfactant-like peptide (Ala)6(Arg) is found to self-assemble into 3 nm-thick sheets in aqueous solution. Scanning transmission electron microscopy measurements of mass per unit area indicate a layer structure based on antiparallel dimers. At higher concentration the sheets wrap into unprecedented ultrathin helical ribbon and nanotube architectures.
Co-reporter:Ian W. Hamley
Chemical Communications 2015 - vol. 51(Issue 41) pp:NaN8583-8583
Publication Date(Web):2015/03/18
DOI:10.1039/C5CC01535A
This Feature Article discusses several classes of lipopeptide with important biomedical applications as antimicrobial and antifungal agents, in immune therapies and in personal care applications among others. Two main classes of lipopeptide are considered: (i) bacterially-expressed lipopeptides with a cyclic peptide headgroup and (ii) linear lipopeptides (with one or more lipid chains) based on bio-derived and bio-inspired amino acid sequences with current clinical applications. The applications are briefly summarized, and the biophysical characterization of the molecules is reviewed, with a particular focus on self-assembly. For several of these types of biomolecule, the formation of micelles above a critical micelle concentration has been observed while others form bilayer structures, depending on conditions of pH and temperature. As yet, there are few studies on the possible relationship between self-assembly into structures such as micelles and bioactivity of this class of molecule although this is likely to attract further attention.
Co-reporter:V. Castelletto, R. J. Gouveia, C. J. Connon, I. W. Hamley, J. Seitsonen, J. Ruokolainen, E. Longo and G. Siligardi
Biomaterials Science (2013-Present) 2014 - vol. 2(Issue 6) pp:NaN874-874
Publication Date(Web):2014/01/29
DOI:10.1039/C4BM00001C
The self-assembly of the alanine-rich amphiphilic peptides Lys(Ala)6Lys (KA6K) and Lys(Ala)6Glu (KA6E) with homotelechelic or heterotelechelic charged termini respectively has been investigated in aqueous solution. These peptides contain hexa-alanine sequences designed to serve as substrates for the enzyme elastase. Electrostatic repulsion of the lysine termini in KA6K prevents self-assembly, whereas in contrast KA6E is observed, through electron microscopy, to form tape-like fibrils, which based on X-ray scattering contain layers of thickness equal to the molecular length. The alanine residues enable efficient packing of the side-chains in a beta-sheet structure, as revealed by circular dichroism, FTIR and X-ray diffraction experiments. In buffer, KA6E is able to form hydrogels at sufficiently high concentration. These were used as substrates for elastase, and enzyme-induced de-gelation was observed due to the disruption of the beta-sheet fibrillar network. We propose that hydrogels of the simple designed amphiphilic peptide KA6E may serve as model substrates for elastase and this could ultimately lead to applications in biomedicine and regenerative medicine.
Co-reporter:Ian William Hamley, Steven Kirkham, Radoslaw M. Kowalczyk, Valeria Castelletto, Mehedi Reza and Janne Ruokolainen
Chemical Communications 2015 - vol. 51(Issue 100) pp:NaN17683-17683
Publication Date(Web):2015/10/20
DOI:10.1039/C5CC08224B
The amphiphilic polyene amphotericin B, a powerful treatment for systemic fungal infections, is shown to exhibit a critical aggregation concentration, and to form giant helically-twisted nanostructures via self-assembly in basic aqueous solution.
Co-reporter:Ian William Hamley, Steven Kirkham, Radoslaw M. Kowalczyk, Valeria Castelletto, Mehedi Reza and Janne Ruokolainen
Chemical Communications 2016 - vol. 52(Issue 5) pp:NaN1052-1052
Publication Date(Web):2015/12/21
DOI:10.1039/C5CC90557E
Correction for ‘Self-assembly of the anti-fungal polyene amphotericin B into giant helically-twisted nanotapes’ by Ian William Hamley et al., Chem. Commun., 2015, 51, 17680–17683.
![L-Lysine,S-[2,3-bis[(1-oxohexadecyl)oxy]propyl]-N-(1-oxohexadecyl)-L-cysteinyl-L-seryl-L-lysyl-L-lysyl-L-lysyl-](http://img.cochemist.com/ccimg/112300/112208-00-1.png)
![L-Lysine,S-[2,3-bis[(1-oxohexadecyl)oxy]propyl]-N-(1-oxohexadecyl)-L-cysteinyl-L-seryl-L-lysyl-L-lysyl-L-lysyl-](http://img.cochemist.com/ccimg/112300/112208-00-1_b.png)
![2,5-OXAZOLIDINEDIONE, 4-[[4-(1,1-DIMETHYLETHOXY)PHENYL]METHYL]-, (S)-](http://img.cochemist.com/ccimg/129300/129288-34-2.png)
![2,5-OXAZOLIDINEDIONE, 4-[[4-(1,1-DIMETHYLETHOXY)PHENYL]METHYL]-, (S)-](http://img.cochemist.com/ccimg/129300/129288-34-2_b.png)
