Abstract: The monofunctional branched poly(ethylene glycol) (PEG) has a general formula shown in formula (1), and the bio-related substance modified by the monofunctional branched PEG has a general formula shown in formula (2), wherein X1 and X2 are each independently a hydrocarbon group having 1 to 20 carbon atoms, n1 and n2 are each independently an integer selected from 1 to 1000, n3 is an integer selected from 11 to 1000, L1, L2 are each independently a linking group, p is 0 or 1, q is 0 or 1, R1 is a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, D is a bio-related substance, Z is a linking group, and Z can react with the bio-related substance to form a residue group L3. The PEG-modified bio-related substance maintains good biological activity, and has better solubility and a longer half-life in vivo.

Abstract: The monofunctional branched poly(ethylene glycol) (PEG) has a general formula shown in formula (1), and the bio-related substance modified by the monofunctional branched PEG has a general fomula shown in formula (2), wherein X1 and X2 are each independently a hydrocarbon group having 1 to 20 carbon atoms, n1 and n2 are each independently an integer selected from 1 to 1000, n3 is an integer selected from 11 to 1000, L1, L2 are each independently a linking group, p is 0 or 1, q is 0 or 1, R1 is a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, D is a bio-related substance, Z is a linking group, and Z can react with the bio-related substance to form a residue group L3. The PEG-modified bio-related substance maintains good biological activity, and has better solubility and a longer half-life in vivo.