Abstract: Disclosed is a tag for purification of peptides. The tag structure facilitates the easy cleavage of a bond formed between the tag molecule and a peptide to which it is bound under conditions which minimize, indeed preferably prevent, damage to the peptide. The tag molecules of the invention may be used to separate and/or purify a peptide from a mixture of peptides and/or other components.

Abstract: A method of ligating two or more molecules, for example, peptides to peptides or peptides to labels is provided. The method may comprise the steps: a) providing a first oligopeptide having a reactive moiety, which is a hydrazine moiety, a hydrazide moiety or an amino-óxy moiety b) providing a second oligopeptide having an activated ester moiety, c)allowing the reactive moiety of the first oligopeptide to react with the activated ester moiety of the second oligopeptide to form an oligopeptide product, in which the first and second oligopeptides are linked via a linking moiety having Formula I, II or III. The second oligopeptide may preferably be generated by thiol reagent induced cleavage of an intein fusion protein. The invention further provides labelling and ligation methods in which protein hydrazides are ligated by reaction of the hydrazide moiety with an aldehyde functionality or a ketone functionality.

Abstract: A method for synthesizing a given peptide or its derivative which contains a proline residue or a proline derivative, at proximity to, or at, the C-terminal end of said peptide is provided. The method comprises a) synthesizing on a first resin a C-terminal portion of said peptide, or its derivative, comprising at least three successive amino acid residues or their derivatives, by successive coupling of selected amino acids, small peptides or their derivatives; b) cleaving the C-terminal portion from said first resin; c) reattaching said C-terminal portion to a second resin which is generally suitable for the synthesis of peptides but is unsuitable for the formation of peptides having a proline residue positioned at the C-terminal end of said peptide; and d) coupling selected amino acids, small peptides or derivatives to the C-terminal portion.