| abstract |
Active esters of PEG acids and related polymers are provided that have a single propionic or butanoic acid moiety and no other ester linkages. These polymer acids have a half life in water of from about 10 to 25 minutes. For example, alpha-methoxy, omega-propionic acid succinimidyl ester of PEG ("methoxy-PEG-SPA") has a nearly ideal reactivity with amino groups on proteins and other biologically active substances. The half life of methoxy-PEG-SPA is about 16.5 minutes in water. The invention also provides conjugates with proteins, enzymes, polypeptides, drugs, dyes, nucleosides, oligonucleotides, lipids, phospholipids, liposomes, and surfaces of solid materials that are compatible with living organisms, tissue, or fluid. |