Miniature β-Hairpin Mimetic by Intramolecular Hydrogen Bond and C-H···π Interactions

Design of a Novel Peptide with Esterolytic Activity toward PET by Mimicking the Catalytic Motif of Serine Hydrolases

Serine hydrolases have become increasingly important for recycling PET plastics. However, their properties are inherently constrained by their 3D structure, which in turn limits the conditions for their application. Considering peptides as catalysts for industrial depolymerization processes can help us to escape some of these limitations. In this article, a 25 amino acid thermostable peptide, HSH-25, was designed to depolymerize PET. The peptide incorporates a His-Ser-His motif, inspired by the catalytic triad found in the serine hydrolase family, into a β-hairpin fold. Stability of the fold was investigated by molecular dynamics simulations. Esterolytic activity of the peptide toward model substrates was detected within a pH range from pH 7 to pH 9.5. Degradation of polymeric PET substrates was confirmed by atomic force microscopy imaging on spin-coated PET thin films.

Hydrogen-bonded organic frameworks as stationary phase for open-tubular capillary electrochromatography

BACKGROUND

Capillary electrochromatography (CEC) stationary phases have always been the focus of attention. The selection of excellent stationary phases are the key to realize separate of different compounds. Hydrogen-bonded organic frameworks (HOFs) are porous materials connected by hydrogen bonds between molecules, which have the advantages of renewable, high specific surface area and mild synthesis conditions. At present, HOFs are used in gas adsorption and storage, catalysis and drug delivery. Because of its unique advantages, HOFs have a bright future as CEC stationary phases.

RESULTS

Using melamine (MA) and 1,3,6,8-tetra (4-carboxylphenyl)pyrene (H4TBAPy) as reaction monomers, a HOFs named MA/PFC-1 was synthesized by solvent evaporation at room temperature. The inner wall of the capillary column was coated with MA/PFC-1 by chemical bonding. Sulfonamides were used as the target analytes. The effects of pH, phosphate buffer solution concentration, organic additive content and applied voltage on sulfonamides separation were investigated. The MA/PFC-1-coated capillary column had good resolution (>1.5) and reproducibility. The intra-day, inter-day, column-to-column, and inter-batch precision of the retention times were 0.03%-0.09%, 0.04%-0.09%, 0.03%-0.14% and 0.06%-0.09%, respectively. The intra-day, inter-day, column-to-column, and inter-batch precision of the peak areas were 0.11%-0.25%, 0.13%-0.20%, 0.12%-0.15% and 0.08%-0.15%, respectively. The MA/PFC-1-coated capillary column was run 150 consecutive times, and the results showed no noticeable change, which proved that this method had good stability.

SIGNIFICANCE

This work applied HOFs to CEC. The results show the that MA/PFC-1-coated capillary column has good separation performance. The MA/PFC-1-coated capillary column has been successfully applied to the determination of sulfamethoxazole in tablets, which has practical application value. To open up the application of HOFs in CEC and provide a new idea for developing new CEC stationary phases.

Melamine-participant hydrogen-bonded organic frameworks with strong hydrogen bonds and hierarchical micropores driving extraction of nitroaromatic compounds

Enrichment and detection of trace pollutants in the real matrix are essential for evaluating water quality. In this study, benefiting from the good affinities of 1,3,6,8-tetra(4-carboxylphenyl)pyrene) (H4TBAPy) with itself and melamine (MA) respectively, the composite hydrogen-bonded organic frameworks (HOFs, MA/PFC-1), PFC-1 self-assembled by 1,3,6,8-tetra(4-carboxylphenyl)pyrene), were successfully constructed by the mild strategy of solvent evaporation at room temperature. Through a series of characterizations, such as Fourier transform infrared spectra, X-ray diffraction, thermal gravimetric analyses, and N2 adsorption-desorption, etc., the MA/PFC-1 was confirmed to be a stable and excellent material. In addition, it possessed high surface area, hierarchical micropores, strong hydrogen bonds, and rich function groups containing N and O heteroatoms, since the newly introduced MA could be another hydrogen bonding motif, as well as increased the polarity of reaction solvent. These advantages make MA/PFC-1 be an ideal coating material for solid phase microextraction (SPME). Satisfactory enrichment factors for nitroaromatic compounds (NACs) were got by the MA/PFC-1 fiber under the optimized conditions obtained by the control variables (extraction time of 60 min, extraction temperature of 80 °C, desorption time of 6 min, desorption temperature of 260 °C, pH value of 7, and stirring speed of 250 rpm). MA/PFC-1 was further used to develop an analytical method for NACs based on head-space SPME coupled with gas chromatography‒mass spectrometry (GC‒MS). The developed method with low limits of detection (4.30-20.83 ng L-1) and good reproducibility (relative standard deviations <8.6%). The excellent performance allowed the successful application of the developed method in the determinations of trace NACs in real water samples with recoveries of 80.1%-119%. This study proposed a mild approach to synthesize composite HOFs via doping MA and developed an environmentally friendly method for the precise determinations of NACs in the environment.

Short Peptide-Based Smart Thixotropic Hydrogels †

Thixotropy is a fascinating feature present in many gel systems that has garnered a lot of attention in the medical field in recent decades. When shear stress is applied, the gel transforms into sol and immediately returns to its original state when resting. The thixotropic nature of the hydrogel has inspired scientists to entrap and release enzymes, therapeutics, and other substances inside the human body, where the gel acts as a drug reservoir and can sustainably release therapeutics. Furthermore, thixotropic hydrogels have been widely used in various therapeutic applications, including drug delivery, cornea regeneration and osteogenesis, to name a few. Because of their inherent biocompatibility and structural diversity, peptides are at the forefront of cutting-edge research in this context. This review will discuss the rational design and self-assembly of peptide-based thixotropic hydrogels with some representative examples, followed by their biomedical applications.