Abstract: A bio-related substance bonded to a branched and degradable polyethylene glycol derivative that is degraded in the cells represented by the following formula (A): wherein each symbol is as defined in the present specification, is provided by the present invention.

Abstract: A multi-arm, degradable polyethylene glycol derivative with a high molecular weight that does not cause vacuolation of cells is provided. A degradable polyethylene glycol derivative represented by the following formula (1): wherein n1 and n2 are each independently 45-950, W1 and W2 are each independently an oligopeptide of 2-47 residues, a1 and a2 are each independently 1-8, Q is a hydrocarbon chain having 2-12 carbon atoms and optionally containing an oxygen atom and/or a nitrogen atom, X1 and X2 are each independently a functional group capable of reacting with a bio-related substance, and L1, L2, L3, L4, L5 and L6 are each independently a divalent spacer.

Abstract: A branched degradable polyethylene glycol derivative with a high molecular weight that does not cause vacuolation of cells is provided. A branched degradable polyethylene glycol derivative represented by the following formula (1), containing, in a molecule, an oligopeptide that is degraded in the cells: wherein k1 and k2 are each independently 1-12, j1 and j2 are each independently 45-950, R is a hydrogen atom, a substituted or unsubstituted alkyl group having 1-12 carbon atoms, a substituted aryl group, an aralkyl group or a heteroalkyl group, Z is an oligopeptide that is degraded by enzyme in the cells, X is a functional group capable of reacting with a bio-related substance, and L1 and L2 are each independently a single bond or a divalent spacer.

Abstract: An intracellularly degraded branched and degradable polyethylene glycol derivative represented by the following formula (1): wherein each symbol is as defined in the present specification, that is used for modifying bio-related substances is provided by the present invention.