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Advances in time‐of‐flight secondary ion mass spectrometry analysis of protein films

This article reviews the advances made in the analysis of protein films by time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). ToF‐SIMS has been used extensively to analyze biological samples owing to its high surface sensitivity, high mass resolution, molecular specificity and imaging capabilities. The fact that its information depth for molecular fragments is typically 1–2 nm, which is smaller than the dimensions of most proteins, makes it an ideal technique for analyzing protein films. Multivariate analysis (MVA) techniques are well suited for analyzing the large, complex data sets generated from ToF‐SIMS experiments on biological samples and have become widely used for interpreting ToF‐SIMS spectra and images. In recent years, new advances in polyatomic or cluster ion sources have improved spectral quality, reduced sample damage and enabled depth profiling of some organic samples. Also, cationization and other matrix enhancement methods have been developed, which significantly increase the yield of molecular fragments from biological samples. This review will cover the modern ToF‐SIMS analysis methods that are currently employed to characterize protein films along with the opportunities and challenges for future advances in ToF‐SIMS analysis of these films. Copyright © 2006 John Wiley & Sons, Ltd.