Thiazolidine Deprotection by 2-Aminobenzamide-Based Aldehyde Scavenger for One-Pot Multiple Peptide Ligation

Strategies for one-pot peptide ligation enable chemists to access synthetic proteins at a high yield in a short time. Herein, we report a new one-pot multi-segments ligation strategy using N-terminal thiazolidine (Thz) peptide and a formaldehyde scavenger. Among our designed 2-aminobenzamide-based aldehyde scavengers, 2-amino-5-methoxy-N’,N’-dimethylbenzohydrazide showed a good ability to capture formaldehyde from Thz at pH 4.0. This scavenger had compatibility with the conditions of native chemical ligation at pH 7.5. Using this scavenger for a model peptide ligation system, we performed one-pot four-segment ligation at a high yield without significant side reactions.

Thiazolidine Deprotection by 2-Aminobenzamide-Based Aldehyde Scavenger for One-Pot Multiple Peptide Ligation

Strategies for one-pot peptide ligation enable chemists to access synthetic proteins at a high yield in a short time. Herein, we report a new one-pot multi-segments ligation strategy using N-terminal thiazolidine (Thz) peptide and a formaldehyde scavenger. Among our designed 2-aminobenzamide-based aldehyde scavengers, 2-amino-5-methoxy-N’,N’-dimethylbenzohydrazide showed a good ability to capture formaldehyde from Thz at pH 4.0. This scavenger had compatibility with the conditions of native chemical ligation at pH 7.5. Using this scavenger for a model peptide ligation system, we performed one-pot four-segment ligation at a high yield without significant side reactions.

Radiation- and Photo-Induced Oxidation Pathways of Methionine in Model Peptide Backbone under Anoxic Conditions

Within the reactive oxygen species (ROS) generated by cellular metabolisms, hydroxyl radicals (HO•) play an important role, being the most aggressive towards biomolecules. The reactions of HO• with methionine residues (Met) in peptides and proteins have been intensively studied, but some fundamental aspects remain unsolved. In the present study we examined the biomimetic model made of Ac-Met-OMe, as the simplest model peptide backbone, and of HO• generated by ionizing radiation in aqueous solutions under anoxic conditions. We performed the identification and quantification of transient species by pulse radiolysis and of final products by LC-MS and high-resolution MS/MS after γ-radiolysis. By parallel photochemical experiments, using 3-carboxybenzophenone (CB) triplet with the model peptide, we compared the outcomes in terms of short-lived intermediates and stable product identification. The result is a detailed mechanistic scheme of Met oxidation by HO•, and by CB triplets allowed for assigning transient species to the pathways of products formation.