| 摘要 |
Multi-armed, monofunctional, and hydrolytically stable polymers are described having the structure wherein Z is a moiety that can be activated for attachment to biologically active molecules such as proteins and wherein P and Q represent linkage fragments that join polymer arms poly<SUB>a </SUB>and poly<SUB>b</SUB>, respectively, to central carbon atom, C, by hydrolytically stable linkages in the absence of aromatic rings in the linkage fragments. R typically is hydrogen or methyl, but can be a linkage fragment that includes another polymer arm. A specific example is an mPEG disubstituted lysine having the structure where mPEG<SUB>a </SUB>and mPEG<SUB>b </SUB>have the structure CH<SUB>3</SUB>O-(CH<SUB>2</SUB>CH<SUB>2</SUB>O)<SUB>n</SUB>CH<SUB>2</SUB>CH<SUB>2</SUB>- wherein n may be the same or different for poly<SUB>a</SUB>- and poly<SUB>b</SUB>- and can be from 1 to about 1,150 to provide molecular weights of from about 100 to 100,000.
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