Used for long-acting pegylation of biopharmaceuticals. Linear structure, holds same functional groups in both ends, improve the pegylation efficiency on protein drugs. Including: Mal-peg-mal -dimaleimidyl poly(ethylene glycol)] Sc-peg-sc -disuccinimidyl poly(ethylene glycol)] Ma-peg-ma -dimethacryloyl poly(ethylene glycol)] Aa-peg-aa -diacryloyl poly(ethylene glycol)] Eo-peg-eo -diglycidyl poly(ethylene glycol)] Alkyne -peg- alkyne -diallyl poly(ethylene glycol)] N3-peg-n [, -diazido poly(ethylene glycol)] Ocn-peg-nco -diisocyanato poly(ethylene glycol)] Ohc-peg-cho -diformyl poly(ethylene glycol)] Hs-peg-sh -dimercapto poly(ethylene glycol)] H2n-peg-nh2 -diamino poly(ethylene glycol)] Hooc-peg-cooh --dicarboxyl poly(ethylene glycol)] Ho-peg-oh [poly(ethylene glycol)]