Volume 10mM MS(PEG)8 0.00 0.67 1.33 2.66 5.32 5.32 2.66 1.33 0.67 0.67 Conclusion The use of MS(PEG) n series of PEGylation reagents can selectively label a protein at their free amino sites to improve solubility and bioactivity. field of biopharmaceuticals has begun to use the process of covalently bonding PEG