Methods for the formation of disulphide bonds

A method for increasing the display rates of an antibody fragment on the surface of bacteriophage particle, comprising

• (a) artificially introducing a first cysteine residue within ten amino acids of the N-terminus of a coat protein of a bacteriophage and artificially introducing a second cysteine residue within fifteen amino acids of the C-terminus of the antibody fragment,
• (b) artificially introducing lysine or arginine amino acid within five amino acids of the artificially introduced first and/or second cysteine residue of step (a),
• wherein said lysine or arginine amino acid positively affects the reactivity of at least one of said artificially introduced cysteine residues,
• (c) causing or allowing the attachment of the coat protein to the antibody fragment,
• wherein said attachment is caused by the formation of a disulphide bond between the first cysteine residue comprised in said coat protein and the second cysteine residue comprised in said antibody fragment.