The different outcomes of short and long PEG chains appear to indicate different configuration models. It is most likely that the long PEG adopts a "shroud" model where the contact of PEG chains with certain protein residues can disrupt H-bond rearrangements around the protein. Hence, the reorientation of water molecules necessary for H-bond exchange may be restricted by the PEG chain. This disruption can prolong C=O-water H-bond lifetimes, potentially causing slower H-bond reorganization around the protein.