Branched discrete PEG constructs

A single molecule construct that modulates the in vivo pharmacokinetics of a biologically active molecule and has a polydispersity index of 1 represented by:

• where,
• (a) A is a biologically active group or a chemically reactive or reactable moiety;
• (b) the wavy line, , is a linear discrete polyethylene glycol chain containing between about 4 and 48 discrete ethylene oxide residues optionally substituted with N, S, Si, Se, P, aryl groups, or alkyl groups;
• and having chemically reactive or reactable end groups that are independently reactable;
• and optionally having branching side chains which can contain diagnostic or therapeutic groups and being cleavable;
• (c) BC is a branching core containing a carbon core with 3 or 4 reactable sites, one of said carbon reactable sites being unique, for attachment of and the other 2 or 3 carbon reactable sites being independently reactive or reactable moieties, for attachment of respectively;
• and
• (d)
• are part of
• where the solid lines, are discrete polyethylene glycol containing chains that have between about 8 and 72 ethylene oxide residues and have a terminal moiety, wherein the terminal moiety is a methyl group, a methoxy group, or a charged group wherein each charged group independently is an amine group, a carboxylate group, a phosphate group, a sulfonate group, or a zwitterionic group.