Interaction Between PEG and Conjugated Insulin: a Molecular Dynamics Simulation and Experimental Observation

An all-atom level molecular dynamics simulation using an annealing procedure was proposed and applied to examine the interaction between PEG and conjugated protein, an established method with proven effectiveness in protein stabilization. For the present study, insulin was used as the model protein, PEG with different chain lengths and topological structures were applied for the protein PEGylation. It was shown that an entangled structure including PEG and insulin can be formed. The driving force of this complex was proven to be hydrophobic interaction between PEG and the conjugated insulin, at the same time, a large number of hydrogen bonds was detected between PEG and surrounding water. An increased molecular size and decreased solvent accessible surface area of protein are observed, verifying the prolonged circulation time in vivo and the improved resistance against proteolysis and immunogenic side effects of protein-PEG conjugate. The enhanced stability of protein-PEG conjugate is also validated at accelerated denaturation environment in silico. Moreover, we also dictated there will be an optimum length for conjugated PEG, and then the protecting mechanism of linear, branch, and brush PEG was elucidated. The simulation results were validated by bioconjugation experiments between PEG and insulin. The method above provided a molecular insight into the conformation transformation of PEG-protein conjugates at all-atom level and offered an enabling tool for the molecular design of PEGylated protein pharmaceuticals.