Enhancing the thermal stability of proteins is an important task for protein engineering. There are several ways to increase the thermal stability of proteins in biology, such as greater hydrophobic interactions, increased helical content, decreased occurrence of thermolabile residues, or stable hydrogen bonds. Here, we describe a well-defined polymer based on β-helical polyisocyanotripeptides (TriPIC) that uses biological approaches, including hydrogen bonding and hydrophobic interactions for its exceptional thermal stability in aqueous solutions. The multiple hydrogen bonding arrays along the polymer backbone shield the hydrophobic core from water. Variable temperature CD and FTIR studies indicate that, on heating, a better packed polymer conformation further stiffens the backbone. Driven by hydrophobic interactions, TriPIC solutions give fully reversible hydrogels that can withstand high temperatures (80 °C) for extended times. Cryo-scanning electron microscopy (cryo-SEM), small-angle X-ray scattering (SAXS), and thorough rheological analysis show that the hydrogel has a bundled architecture, which gives rise to strain stiffening effects on deformation of the gel, analogous to many biological hydrogels.

A conjugated polymer centered on fluorene and 2,1,3-benzothia-diazole (PFBT) is prepared for sensing CO2 in situ with high sensitivity and low background. Upon introducing CO2, the weaker electrostatic repulsion and stronger hydrophobic interactions between neighboring PFBT molecules enhance the interchain contacts compared to that without CO2, leading to the energy transfer from fluorene to 2,1,3-benzothia-diazole sites and the emission color shift from blue to green, which is sensitive to sensing CO2 in atmospheric air with a content of ∼400 ppm. Importantly, PFBT is employed to monitor photosynthesis and respiration upon cycling day and night in situ.Keywords: CO2; conjugated polymers; energy transfer; in situ detection; photosynthesis;

Hybrid nanocomposites consisting of uniform Fe3O4 nanoparticles and boron nitride (BN) nanospheres were synthesized via an ethanol-thermal reaction method. The spherical BN nanoparticles (BNNSs) with average diameter 150 nm have been uniformly coated with dense ultra-small Fe3O4 nanoparticles (with average diameter of 10 nm), forming novel Fe3O4@BNNS nanocomposites. Magnetic measurement by using vibrating sample magnetometer (VSM) indicates that the Fe3O4 coating is superparamagnetic, and the nanocomposites can be physically manipulated at a low magnetic field. Preliminary biocompatibility study has also been performed to evaluate the toxicity of the nanocomposites. The nanocomposites show cytocompatibility at low concentration and have little effect on cell viability of MCF-7, MCF-10 and Hela cell lines. The Fe3O4@BNNS nanocomposites may find a wide range of potential applications including water treatment, catalysts, carriers for boron neutron capture therapy and magnetic-targeted drug delivery.

Detection of carbon dioxide (CO2) is of fundamental importance in diverse applications ranging from environmental analysis to agricultural production. In this work, a hybrid probe based on guanidinium-pendent oligofluorene (G-OF) and water-soluble conjugated polythiophene (PTP) has been developed for the turn on detection of CO2 with low background signal, taking advantage of the efficient fluorescence quenching of the tight aggregate of G-OF/PTP. In the presence of CO2, the electrostatic repulsion between G-OF and PTP can be effectively enhanced through protonation of the side chains, leading to the disaggregation and thus the “turn-on” fluorescence. The strategy allows for the light-up visible detection of CO2 with high sensitivity. Importantly, this system is capable of sensitively monitoring the concentration changes of CO2 in the process of the photosynthesis, which represents a concept to monitor the photosynthesis based on water-soluble conjugated polymers.

The cationic conjugated poly[3-(3′-N,N,N-triethylamino-1′-propyloxy)-4-methyl-2,5-thiophene hydrochloride] (PMNT) has been developed for high-throughput screening of photodynamic antimicrobial chemotherapy photosensitizers (PSs). The bacterial number can be detected quantitatively by PMNT via various fluorescence quenching efficiencies. The photosensitized inactivation of bacteria is not efficient with ineffective PSs, and thus the bacteria grow exponentially and can be coated tightly by PMNT through electrostatic and hydrophobic interactions, resulting in aggregates and fluorescence quenching of PMNT, whereas, conversely, effective PSs lead to original and strong fluorescence of PMNT. This new platform of high-throughput screening is promising for discovering new PSs.Keywords: biosensor; conjugated polymers; fluorescence; high-throughput screening; photosensitizer;

In recent years, supramolecular organization of thiophene derivatives, oligo- and polythiophene, have been developed with various designs to achieve complex functions. Here, we describe the synthesis and characterization of a conjugated polymer with thymidine side chain bases and polythiophene backbones (PTT) instead of phosphate bonds in DNA, and the PTT exhibits exceptional fluorescence quenching efficiency upon binding of Cu2+ ions in aqueous medium, which is suggested to be electron transfer from the π* orbit at the excited state of PTT to the 3d orbit of Cu2+ ions and subsequent Cu2+-mediated interpolymer π-stacking aggregation. Furthermore, Cu2+ ions can be selectively and easily monitored by the fluorescence quenching of PTT, which can be used for detection of Cu2+ ions with good selectivity and high sensitivity in aqueous medium. Both experimental and theoretical methods have been devoted to demonstrate the strong affinity and steric interaction of PTT toward Cu2+. These findings will illustrate new directions for the design of nucleobase-functionalized materials with transition metals responsive activity.Keywords: conjugated polythiophene; Cu2+; fluorescence quenching; sensor; thymidine;

A new strategy has been designed for visualized detection of the conformation changes of calmodulin bound to target peptide (CaM-M13) based on the conformation sensitive property of a water-soluble conjugated polythiophene derivative (PMNT) and the electrostatic interactions of PMNT/CaM-M13. Interestingly, the direct visualized PMNT color changes under UV irradiation and the turbidity changes of samples in aqueous medium can be applied to detect the conformation changes as well as the controllable assembly of PMNT/CaM-M13 with Ca2+ in aqueous medium. Because of the specific binding of Ca2+, the assembly of PMNT/CaM-M13 can be applied to sense calcium as well.Keywords: assembly; calcium; CaM-M13; conformation changes; conjugated polythiophene