The invention provides compound of the general formula:in which each X independently represents a polymer chain n represents an integer greater than 1 Q represents a linker Y represents an amide group and Z represents either —CH.(CH2L)2 or —C(CH2L)(═CH2), in which each L independently represents a leaving group. The compounds are useful reagents for the conjugation of polymers to proteins, the resulting conjugates being novel and also forming part of the invention.
