A bifunctional vinyl-sulfonium tethered peptide induced by thio-Michael-type addition reaction

Facile preparation of sulfonium peptide and protein probes for selective crosslinking of methyllysine readers

Sulfonium is an electrophilic and biocompatible group that is widely applied in synthetic chemistry on small molecules. However, there have been few developments of peptide or protein-based sulfonium tools. We recently reported sulfonium-mediated tryptophan crosslinking and developed NleS+me2 (norleucine-dimethylsulfonium) peptides as dimethyllysine mimics that crosslink site-specific methyllysine readers. Therefore, sulfonium probes show great potential for investigating methyllysine readers and other aromatic cage-containing proteins. However, the current synthesis is not very efficient and is limited to peptide probes that, in many cases, cannot mimic protein-protein interactions. In addition to peptidyl conjugates that are valuable for reader identification, there are unavoidable methyl conjugates as side products. As a result, a robust method to prepare peptide and protein sulfonium tools with great crosslinking reactivity and selectivity is highly desirable. Here, we report a cysteine alkylation method to introduce site-specific sulfonium at protein level with excellent yield. In addition to dimethylsulfonium, we also developed cyclic sulfonium warheads that enhanced peptidyl conjugate selectivity. The method thus made it possible to prepare nucleosome probes in which LEDGF and NSD2, as H3K36 methylation readers were readily crosslinked. We thus believe this method will accelerate the development of sulfonium peptide and protein tool sets for broad applications in chemical biology studies.

The expanding repertoire of covalent warheads for drug discovery

The reactive functionalities of drugs that engage in covalent interactions with the enzyme/receptor residue in either a reversible or an irreversible manner are called 'warheads'. Covalent warheads that were previously neglected because of safety concerns have recently gained center stage as a result of their various advantages over noncovalent drugs, including increased selectivity, increased residence time, and higher potency. With the approval of several covalent inhibitors over the past decade, research in this area has accelerated. Various strategies are being continuously developed to tune the characteristics of warheads to improve their potency and mitigate toxicity. Here, we review research progress in warhead discovery over the past 5 years to provide valuable insights for future drug discovery.

Polylactic-co-glycolic acid-based nanoparticles modified with peptides and other linkers cross the blood-brain barrier for targeted drug delivery

Because of the blood-brain barrier, only a limited fraction of drugs can penetrate the brain. As a result, there is a need to take larger doses of the drug, which may result in numerous undesirable side effects. Over the past few decades, a plethora of research has been conducted to address this issue. In recent years, the field of nanomedicine research has reported promising findings. Currently, numerous types of polylactic-co-glycolic acid-based drug-delivery systems are being studied, and great progress has been made in the modification of their surfaces with a variety of ligands. In this review, the authors highlight the preparation of polylactic-co-glycolic acid-based nanoparticles and single- and dual-targeted peptide modifications for site-specific drug delivery into the brain.