Patent ID: 8242058

Claim:
A method for forming a covalent linkage between a peptide or protein and a chemical species comprising the steps of: (a) providing the peptide or protein functionalized with one or more thioester groups; (b) reacting one or more thioester groups of the peptide or protein functionalized with the one or more thioester groups with the hydrazine group of a hydrazine-functionalized chemical species of formula: H 2 N—NH—CH 2 -M-L-R, wherein R is the chemical species, to form a hydrazide and thereby form a covalent linkage between the peptide or protein and the chemical species, wherein: R is a chemical species selected from an azido, alkenyl, alkynyl, nitrile or triazole group; M is a single bond or —C(O)NR′—, where R′ is H, an alkyl, or an aryl, and L is an optional linker group which is an optionally substituted alkylene or an optionally substituted arylene linker.