Maleimide PEG

4arm PEG, -((CH23NHCO(CH2)2-MAL)4, Mw 10,000
4arm PEG, -((CH23NHCO(CH2)2-MAL)4, Mw 20,000
4arm PEG, -((CH23NHCO(CH2)2-MAL)4, Mw 40,000