AVS 52nd International Symposium
    Biomaterial Interfaces Wednesday Sessions
       Session BI1-WeA

Paper BI1-WeA1
Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) of Short Peptides-Noble Metal Surface Interactions Analyzed by Principal Component Analysis (PCA)

Wednesday, November 2, 2005, 2:00 pm, Room 311

Session: Protein-Surface Interactions
Presenter: N. Suzuki, University of Washington
Authors: N. Suzuki, University of Washington
L.J. Gamble, University of Washington
D.G. Castner, University of Washington
M. Sarikaya, University of Washington
F.S. Ohuchi, University of Washington
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Recent progress in the adaptation of combinatorial biology selection protocols to materials science has created a new class of polypeptides with specific affinity to inorganics. Here, we have used short peptide chains whose sequence consists of MHGKTQATSGTIQS in single- and triple-repeat forms, and have assessed quantitatively their binding specificity to Au, Ag and Pd surfaces by Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS). Due to high mass resolutions, ToF-SIMS is capable of providing information about specific amino acidsâ?"surface interactions as well as their mutual interactions at the surface, but numerous mass fragments from the amino acids complete the analysis. We have therefore adopted Principal Component Analysis (PCA) to the static ToF-SIMS spectra, from which characteristic information related to binding specificity was obtained by reducing the dimension of data sets. The score plot in the PCA analysis has revealed that the effect of alkali ions from buffer solution significantly alters the fragmentation patters. Once, the grouping based on alkali ions content is carried out, the loading plot within the same group suggests that the strength of a localized amino acid sequence, MHGK, observed from the triple repeated chain differentiates the binding characteristics specific to a certain type of inorganics. In addition, the inherent binding site of this peptide toward inorganics is determined from loading plots. This technique is capable of analyzing the complex, multivariate ToF-SIMS spectra from the adsorbed polypeptide films and compared to univariate methods providing unique insight about the sample.