Photochemical activation of polyethylene glycol and its application in PEGylation of protein

A simple and rapid procedure is developed for activation of polyethylene glycol (PEG) for making PEG-protein conjugate. PEG was activated in a photochemical reaction of PEG and a photolinker, 1-fluoro-2-nitro-4-azidobenzene. The activated PEG efficiently conjugated with glucose oxidase (GOD) in 60 min at 37 °C without any additional reagent. PEGylated GOD was found to have enhanced thermal and storage stability. After 15 min of thermal injury at 70 °C it retained more than 50% of activity while the native enzyme was completely deactivated. At ambient temperature PEGylated enzyme was found to retain about 80% of initial activity even after a month and PEG conjugation was also found to stabilize the enzyme against change in pH of reaction medium. It is anticipated that the method would be useful for PEGylation of biomolecules including proteins and nucleic acids to improve their properties as drugs and also enhance the solubility in organic solvents.