AVS 53rd International Symposium
    Applied Surface Science Thursday Sessions
       Session AS-ThP

Paper AS-ThP1
TOF-SIMS Analysis of pH Dependent Structure of Protein-A Immobilized on ITO Coated Substrate

Thursday, November 16, 2006, 5:30 pm, Room 3rd Floor Lobby

Session: Aspects of Applied Surface Science Poster Session
Presenter: M. Kudo, Seikei University, Japan
Authors: N. Kato, Seikei University, Japan
M. Higuchi, Seikei University, Japan
S. Aoyagi, Shimane University, Japan
M. Kudo, Seikei University, Japan
Correspondent: Click to Email
It is known that the environmental conditions, such as pH and temperature, control the reactivity of the protein immobilized on the biosensor surface. For example, at pH < 3.0, protein-A which is used as antigen for immunosensor can not bind to immunoglobulin-G (IgG). In contrast, for pH = 7.0, protein-A can bind to IgG. To explain this difference on reactivity, it is important to examine the structural change of protein-A caused by varying pH condition. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is one of the most useful techniques for the investigation of biomaterial surfaces because of its ability to provide detailed molecular information on material surfaces. However the TOF-SIMS spectra of protein samples are very complex with multiple fragments resulting from each of the 20 amino acids. It was shown that information theory can select the appropriate peaks of secondary ions characterizing samples out of numerous candidate peaks in the TOF-SIMS spectra with the calculation of mutual information.@footnote 1@ In this study, the structural change of protein-A caused by varying pH condition was analyzed by TOF-SIMS with the information theory and principal component analysis (PCA). PCA of the TOF-SIMS spectra from protein-A immobilized on ITO coated glass showed explicit distinction between the chemical structures at pH=7.4 and pH=3.0. The calculation of mutual information for TOF-SIMS spectral data at the two pH conditions provided specific peaks related to protein-A at each pH condition. From comparison between the variation of the specific peaks at each pH condition and the amino acid sequences of Protein-A, the structural change of protein-A caused by varying the pH condition will be discussed. @FootnoteText@ @footnote 1@S. Aoyagi, M. Hayama, U. Hasegawa, K. Sakai, M. Tozu, T. Hoshi, M. Kudo, J. Surf. Sci. Nanotech. 1, 67 (2003).