Patent ID: 7851565

Claim:
A water-soluble polymeric reagent of the structure: POLY-[Y—S—W] x wherein: POLY is a water soluble polymer; Y has the formula —(CR 1 R 2 )n-, where n is 3 to 8, and each of R 1 and R 2 is independently selected from hydrogen, lower alkyl, lower alkenyl, and a non-interfering substituent, where two groups R 1 and R 2 on different carbon atoms may be linked to form a cycloalkyl or aryl group; S is a sulfur atom attached to an sp 3 hybridized carbon of Y; S—W is a thiol, protected thiol, or thiol-reactive thiol derivative; x=1-25; and if POLY is a linear polyethylene glycol, x=1, and Y is a linear alkyl chain then POLY has a molecular weight of at least 500, wherein when S—W is the disulfide linkage ortho-pyridyl disulfide and POLY is a linear polyethylene glycol, at least one R 1 on a carbon adjacent to said disulfide linkage is lower alkyl.