Conformational changes of protein adsorbed on tailored flat substrates with different chemistries.

Changes in the bioactivity of a protein after being adsorbed on a material surface may result from conformational changes of the protein. Unfortunately, however, direct evidence of such conformational changes of proteins adsorbed on a flat material surface is sparse so far. This is because probing the conformation of an adsorbed protein on material surfaces, especially flat ones, remains a challenge due to considerable experimental difficulties. In this study, the surface-enhanced Raman scattering (SERS) technique is used to characterize the conformational changes of a protein (lysozyme) adsorbed on tailored flat gold substrates with different chemistries. Two such substrates are formed by self-assembly of octadecanethiol and thiolated PEG on gold chips (Au-C18 and Au-PEG). Preliminary results reveal that, compared to the hydrophobic Au-C18 surface, the hydrophilic Au-PEG surface has much smaller effect on the conformation of lysozyme in aqueous solution, which thereby keeps its high bioactivity. The conformational changes of lysozyme adsorbed on material surfaces with different chemistries are well correlated with changes in its bioactivity.