Abstract: A branched monodispersed polyethylene glycol represented by the formula (1): wherein X1 is a functional group that forms a covalent bond upon a reaction with a functional group present in a biofunctional molecule; n is an integer of 4 to 50, which represents number of repeating units of ethylene oxide units; and L1 represents a single bond, —NH—, -L2-(CH2)m1- or -L2-(CH2)m1-L3-(CH2)m2-, L2 represents an ether bond, an amide bond, an urethane bond or a single bond, L3 represents an ether bond, an amide bond or an urethane bond, and m1 and m2 represent each independently an integer of 1 to 5.

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 heterobifunctional monodispersed polyethylene glycol represented by formula (1) which has two adjacent monodispersed polyethylene glycol side chains and does not have a chiral center in the molecular structure: wherein X1 and Y1 are each an atomic group containing a functional group capable of forming a covalent bond upon a reaction with a functional group present in a biofunctional molecule. R1 is a hydrocarbon group or the like. n is an integer of 3 to 72. A1 represents -L1-(CH2)m1— or the like, L1 and L2 represent each an ether bond or the like, and m1 and m2 each independently represent an integer of 1 to 5. B1 represents -L3-(CH2)m3— or the like, L3 and L4 represent an amide bond or the like, and m3 and m4 each independently represent an integer of 1 to 5. Also disclosed is an antibody-drug conjugate including the heterobifunctional monodispersed polyethylene glycol.

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.

Abstract: A heterobifunctional monodispersed polyethylene glycol represented by the formula (1): wherein X1 and Y1 are each an atomic group containing a functional group capable of forming a covalent bond upon a reaction with a functional group present in a biofunctional molecule, the functional group contained in the atomic group X1 and the functional group contained in the atomic group Y1 are different from each other; R1 is a hydrocarbon group having from 1 to 7 carbon atoms or a hydrogen atom; n is an integer of 3 to 72; l is an integer of 2 to 72; and A1, B1 and C1 are as defined herein.

Abstract: A branched monodispersed polyethylene glycol represented by the formula (1): wherein X1 is a functional group that forms a covalent bond upon a reaction with a functional group present in a biofunctional molecule; n is an integer of 4 to 50, which represents number of repeating units of ethylene oxide units; and L1 represents a single bond, —NH—, -L2-(CH2)m1— or -L2-(CH2)m1-L3-(CH2)2-, L2 represents an ether bond, an amide bond, an urethane bond or a single bond, L3 represents an ether bond, an amide bond or an urethane bond, and m1 and m2 represent each independently an integer of 1 to 5.

Abstract: A heterobifunctional monodispersed polyethylene glycol represented by formula (1) which has two adjacent monodispersed polyethylene glycol side chains and does not have a chiral center in the molecular structure: wherein X1 and Y1 are each an atomic group containing a functional group capable of forming a covalent bond upon a reaction with a functional group present in a biofunctional molecule. R1 is a hydrocarbon group or the like. n is an integer of 3 to 72. A1 represents -L1-(CH2)m1— or the like, L1 and L2 represent each an ether bond or the like, and m1 and m2 each independently represent an integer of 1 to 5. B1 represents -L3-(CH2)m3— or the like, L3 and L4 represent an amide bond or the like, and m3 and m4 each independently represent an integer of 1 to 5. Also disclosed is an antibody-drug conjugate including the heterobifunctional monodispersed polyethylene glycol.