Suppressing catalyst poisoning in the carbodiimide-fueled reaction cycle

In biology, cells regulate the function of molecules using catalytic reaction cycles that convert reagents with high chemical potential (fuel) to waste molecules. Inspired by biology, synthetic analogs of such chemical reaction cycles have been devised, and a widely used catalytic reaction cycle uses carboxylates as catalysts to accelerate the hydration of carbodiimides. The cycle is versatile and easy to use, so it is widely applied to regulate motors, pumps, self-assembly, and phase separation. However, the cycle suffers from side reactions, especially the formation of N-acylurea. In catalytic reaction cycles, side reactions are disastrous as they decrease the fuel's efficiency and, more importantly, destroy the molecular machinery or assembling molecules. Therefore, this work tested how to suppress N-acylurea by screening precursor concentration, its structure, carbodiimide structure, additives, temperature, and pH. It turned out that the combination of low temperature, low pH, and 10% pyridine as a fraction of the fuel could significantly suppress the N-acylurea side product and keep the reaction cycle highly effective to regulate successful assembly. We anticipate that our work will provide guidelines for using carbodiimide-fueled reaction cycles to regulate molecular function and how to choose optimal conditions.

Chitosan-Based Hydrogel in the Management of Dermal Infections: A Review

The main objective of this review is to provide a comprehensive overview of the current evidence regarding the use of chitosan-based hydrogels to manage skin infections. Chitosan, a naturally occurring polysaccharide derived from chitin, possesses inherent antimicrobial properties, making it a promising candidate for treating various dermal infections. This review follows a systematic approach to analyze relevant studies that have investigated the effectiveness of chitosan-based hydrogels in the context of dermal infections. By examining the available evidence, this review aims to evaluate these hydrogels' overall efficacy, safety, and potential applications for managing dermal infections. This review's primary focus is to gather and analyze data from different recent studies about chitosan-based hydrogels combating dermal infections; this includes assessing their ability to inhibit the growth of microorganisms and reduce infection-related symptoms. Furthermore, this review also considers the safety profile of chitosan-based hydrogels, examining any potential adverse effects associated with their use. This evaluation is crucial to ensure that these hydrogels can be safely utilized in the management of dermal infections without causing harm to patients. The review aims to provide healthcare professionals and researchers with a comprehensive understanding of the current evidence regarding the use of chitosan-based hydrogels for dermal infection management. The findings from this review can contribute to informed decision-making and the development of potential treatment strategies in this field.

Impact of aromatic residues on the intrinsic disorder and transitional behaviour of model IDPs

Understanding the interplay between order and disorder in intrinsically disorder proteins (IDPs), and its impact on the properties and features of materials manufactured from them, is a major challenge in the design of protein-based synthetic polymers intended for advanced functions. In this paper an elastin-like diblock co-recombinamer amphiphile (Phe-ELR) based on a hydrophobic block containing five phenylalanine (Phe) residues proximal to the carboxyl function of a glutamic acid (Glu) residue upon folding, and with Glu as the guest residue in the hydrophilic part, was engineered and its assembly behaviour compared with another amphiphilic ELR used as control. Phe-ELR was tailored in order to clarify the impact of the presence of aromatic residues in the amino acid sequence, which even in early studies by Urry's group already demonstrated a certain out-of-trend behaviour compared with other apolar amino acids, especially non-aromatic ones, on ELR behaviour. The combination of several experimental techniques indicates strong molecular interactions associated with the Phe residue, thus resulting in limited reversible character of the temperature-induced transitions during sequential thermal cycles, a lower than expected transition enthalpy, and clear differences in its supramolecular assembly with respect to the control ELR. A distinctive pre-aggregated state for the Phe-ELR under any condition of pH and temperature is found. Eventually, this state gives rise to Phe-core micelles or a solid jelly-like material, depending on the concentration, pH and presence of salts. In conclusion, it appears that the presence of aromatic residues and their ability to promote strong inter- and intramolecular interactions at any temperature and pH causes a complete modification of the order-disorder interplay present in other, non-aromatic ELRs. These molecular events have a profound impact on the physical properties of the resulting polymer when compared with other ELRs. This work helps to shed light on the limits that govern intrinsic disorder in ELRs beyond its inverse temperature transition.

Carbodiimide-fueled catalytic reaction cycles to regulate supramolecular processes

Using molecular self-assembly, supramolecular chemists can create Gigadalton-structures with angstrom precision held together by non-covalent interactions. However, despite relying on the same molecular toolbox for self-assembly, these synthetic structures lack the complexity and sophistication of biological assemblies. Those assemblies are non-equilibrium structures that rely on the constant consumption of energy transduced from the hydrolysis of chemical fuels like ATP and GTP, which endows them with dynamic properties, e.g., temporal and spatial control and self-healing ability. Thus, to synthesize life-like materials, we have to find a reaction cycle that converts chemical energy to regulate self-assembly. We and others recently found that this can be done by a reaction cycle that hydrates carbodiimides. This feature article aims to provide an overview of how the energy transduced from carbodiimide hydration can alter the function of molecules and regulate molecular assemblies. The goal is to offer the reader design considerations for carbodiimide-driven reaction cycles to create a desired morphology or function of the assembly and ultimately to push chemically fueled self-assembly further towards the bottom-up synthesis of life.

Modulating defibrillation by tryptophan-mediated photo cleavage of disulfide bonds

Dibenzyloxycarbonyl-l-cystine forms amyloid-like fibers and a hydrogel; however, on UV irradiation, Trp-mediated disulfide bond cleavage occurs, leading to defibrillation and a gel to sol transition.