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Peptide bond formation via dehydration reaction. When two amino acids form a dipeptide through a peptide bond, [1] it is a type of condensation reaction. [2] In this kind of condensation, two amino acids approach each other, with the non-side chain (C1) carboxylic acid moiety of one coming near the non-side chain (N2) amino moiety of the other.
In organic chemistry, a thiol (/ ˈ θ aɪ ɒ l /; [1] from Ancient Greek θεῖον (theion) 'sulfur' [2]), or thiol derivative, is any organosulfur compound of the form R−SH, where R represents an alkyl or other organic substituent. The −SH functional group itself is referred to as either a thiol group or a sulfhydryl group, or a ...
The carbonyl center in thioesters is more reactive toward amine than oxygen nucleophiles, giving amides: Thioesters are components of the native chemical ligation method for peptide synthesis. This reaction is exploited in native chemical ligation, a protocol for peptide synthesis. [8] In a related reaction, thioesters can be converted into ...
In organic chemistry, peptide synthesis is the production of peptides, compounds where multiple amino acids are linked via amide bonds, also known as peptide bonds. Peptides are chemically synthesized by the condensation reaction of the carboxyl group of one amino acid to the amino group of another.
However, additional molecular interactions may render the amide form less stable; the amino group is expelled instead, resulting in an ester (Ser/Thr) or thioester (Cys) bond in place of the peptide bond. This chemical reaction is called an N-O acyl shift. The ester/thioester bond can be resolved in several ways:
The conjugate base of thioacetic acid, thioacetate, is a reagent used for installing thiol groups via the displacement of alkyl halides by a two-step process. The halide is displaced to give a thioester intermediate, which is then hydrolyzed: R−X + CH 3 COS − → R−SC(O)CH 3 + X −
[4] [5] The amide group is called a peptide bond when it is part of the main chain of a protein, and an isopeptide bond when it occurs in a side chain, as in asparagine and glutamine. It can be viewed as a derivative of a carboxylic acid ( R−C(=O)−OH ) with the hydroxyl group ( −OH ) replaced by an amine group ( −NR′R″ ); or ...
In native chemical ligation, the ionized thiol group of an N-terminal cysteine residue of an unprotected peptide attacks the C-terminal thioester of a second unprotected peptide, in an aqueous buffer at pH 7.0 and room temperature. This transthioesterification step is reversible in the presence of an aryl thiol catalyst, rendering the reaction ...