When adding a linker to the N-terminal amino acid, the linker is preferably a N-PG-amido-PEGX-acid where PG is a protecting group such as the Fmoc group, the BOC group, the CBZ group or any other group amenable to peptide synthesis and X is 2, 4, 6, 8, 12, 24 or any other discrete PEG which may be available.