Labelling of biomolecules

A method of reversibly labeling a biomolecule, the method comprising the steps of:

• a. providing a linker molecule, the linker molecule comprising a first functional group comprising a reactive center, a second functional group comprising a reactive center, and a cleavable moiety;
• b. forming a covalent bond between the biomolecule and the reactive center of the first functional group;
• C. forming a covalent bond between a first label and the reactive center of the second functional group;
• d. cleaving the cleavable moiety of the linker molecule to remove the first label and to form a third functional group comprising a reactive center;
• and
• e. forming a covalent bond between a further molecule and the reactive center of the third functional group to reform the cleavable moiety;
• wherein the further molecule comprises a fourth functional group;
• wherein the biomolecule is a polynucleotide or a peptide;
• and
• wherein the linker molecule has the following general formula:
• wherein FG represents the second functional group which is selected from one of F, Cl, Br, I, an alkene, an alkyne, an azide, an activated ester, an activated carbonate, a carbamate, an epoxide, an isothiocyanate, and an isocyanate moiety;
• Z represents a non-reactive group selected from one of an aliphatic linkage or an aromatic linkage;
• A-B—C together represent the cleavable moiety;
• Y represents a non-reactive group of an aliphatic linkage or an aromatic linkage;
• LG represents a first functional group comprising a reactive center, wherein LG is
• i) an S-Adenosyl-L-homocysteine moiety such that the linker molecule has the following general formula:
• wherein U represents an unsaturated bond selected from one of an alkene, an alkyne, an aryl group, a carbon atom comprising a carbonyl group, a sulphur atom comprising one or two S═O bonds;
• or
• ii) a halogen,
• and
• wherein the cleavable moiety A-B—C represents one of the following moieties:
• wherein Rx represents a hydrogen atom, a deuterium atom, an aliphatic linkage, or an aromatic linkage.