Demethylative Alkylation of Methionine Residue by Employing the Sulfonium as the Key Intermediate

Copper(I)-nitrene platform for chemoproteomic profiling of methionine

Methionine plays a critical role in various biological and cell regulatory processes, making its chemoproteomic profiling indispensable for exploring its functions and potential in protein therapeutics. Building on the principle of rapid oxidation of methionine, we report Copper(I)-Nitrene Platform for robust, and selective labeling of methionine to generate stable sulfonyl sulfimide conjugates under physiological conditions. We demonstrate the versatility of this platform to label methionine in bioactive peptides, intact proteins (6.5-79.5 kDa), and proteins in complex cell lysate mixtures with varying payloads. We discover ligandable proteins and sites harboring hyperreactive methionine within the human proteome. Furthermore, this has been utilized to profile oxidation-sensitive methionine residues, which might increase our understanding of the protective role of methionine in diseases associated with elevated levels of reactive oxygen species. The Copper(I)-Nitrene Platform allows labeling methionine residues in live cancer cells, observing minimal cytotoxic effects and achieving dose-dependent labeling. Confocal imaging further reveals the spatial distribution of modified proteins within the cell membrane, cytoplasm, and nucleus, underscoring the platform's potential in profiling the cellular interactome.

Methods for extraction, isolation and sequencing of cyclotides and others cyclic peptides with anti-helminthic activities: An overview

The mortality rate caused by parasitic worms on their hosts is of great concern and studies have been carried out to find molecules to reduce the prevalence, host-parasite interaction, and resistance of parasites to treatments. Existing drugs on the market are very often toxic and have many side effects, hence the need to find new, more active molecules. It has been demonstrated in several works that medicinal plants constitute a wide range of new molecules that can solve this problem. Several works have already been able to demonstrate that cyclic peptides of plant origin have shown good activity in the fight against different types of helminths. Therefore, this review aims to provide a general overview of the methods and techniques of extraction, isolation, activities and mechanisms of action of cyclotides and other cyclic peptides for application in the treatment of helminthic infections.

Spontaneous, co-translational peptide macrocyclization using p-cyanoacetylene-phenylalanine

Peptide macrocycles (PMCs) are increasingly popular for the development of inhibitors of protein-protein interactions (PPIs). Large libraries of PMCs are accessible using display technologies like mRNA display and phage display. These technologies require macrocyclization chemistries to be compatible with biological milieu, severely limiting the types of technologies available for cyclization. Here, we introduce the novel non-canonical amino acid (ncAA) p-cyanoacetylene-L-Phe (pCAF), which facilitates spontaneous, co-translational cyclization through Michael addition with cysteine under physiological conditions. This new, robust chemistry creates stable macrocycles of a wide variety of ring sizes including bicyclic structures.

On-Resin Synthesis of Linear Aryl Thioether Containing Peptides and in-Solution Cyclization via Cysteine SNAr Reaction

Cyclic peptides represent one of the most promising therapeutic agents in drug discovery due to their good affinity and selectivity. Herein, an on-resin synthesis of aryl thioether containing peptides and a concise cyclization strategy via chemoselective cysteine SNAr reaction was developed. The arylation group could be incorporated into a series of amino acids and used for standard SPPS and peptides cyclization. Constructed cyclic peptides showed increased cellular uptakes compared to their linear peptides.