AVS 49th International Symposium
    Biomaterials Monday Sessions
       Session BI+VT-MoA

Paper BI+VT-MoA9
Time-of-Flight Secondary Ion Mass Spectrometry Analysis of Conformational Changes in Adsorbed Protein Films

Monday, November 4, 2002, 4:40 pm, Room C-201

Session: Protein Surface Interactions
Presenter: N. Xia, University of Washington
Authors: N. Xia, University of Washington
C.J. May, Yale University
S.L. McArthur, University of Washington
D.G. Castner, University of Washington
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Characterizing the identity, composition, conformation, and orientation of adsorbed proteins is essential for the development of biocompatible devices. Static time-of-flight secondary mass spectrometry (ToF-SIMS) is a powerful surface analytical technique for analyzing adsorbed protein films. However, the ToF-SIMS experiment is done under vacuum, and drying adsorbed proteins for analysis can denature or change their conformation. In this study, trehalose coating was used to inhibit these conformational changes from occurring during sample preparation for ToF-SIMS analysis. Surface plasmon resonance (SPR) analysis showed that air-dried films of trehalose-stabilized antibodies retained a significant proportion of their hydrated antigen binding activity. In contrast, air-drying without trehalose protection resulted in the adsorbed protein films losing most of their antigen binding activity. Structural differences between trehalose-stabilized and unstabilized protein films were then analyzed with static ToF-SIMS. By application of principle component analysis (PCA) to the ToF-SIMS spectra, the biological activity difference observed in SPR was correlated to changes in protein conformation. Trehalose-protected proteins retained a greater degree of their original conformation than the unprotected proteins. This suggests that static ToF-SIMS has the capability to distinguish conformational differences in adsorbed protein films. Moreover, trehalose protection can be used for static ToF-SIMS analysis of adsorbed protein films to obtain structural information that is more relevant to the structure of the proteins in aqueous conditions.