TOF-SIMS imaging of adsorbed proteins on topographically complex surfaces with Bi3 primary ionsReport as inadecuate

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, Volume 6, Issue 3, pp 135–141

Received: 14 April 2011Accepted: 30 June 2011


Although previous studies have demonstrated that TOF-SIMS is a powerful method for the characterization of adsorbed proteins due to its specificity and surface sensitivity, it was unclear from earlier work whether the differences between proteins observed on uniform flat surfaces were large enough to facilitate clear image contrast between similar proteins in small areas on topographically complex samples that are more typical of biological tissues. The goal of this study was to determine whether Bi3 could provide sufficiently high sensitivity to provide clear identification of the different proteins in an image. In this study, 10 μm polystyrene microspheres were adsorbed with one of three different proteins, human serum albumin HSA, bovine serum albumin BSA, and hemoglobin. Spheres coated with HSA were then mixed with spheres coated with either BSA a very similar protein or hemoglobin a dramatically different protein, and deposited on silicon substrates. Fluorescent labeling was used to verify the SIMS results. With maximum autocorrelation factors MAF processing, images showed clear contrast between both the very different proteins HSA and hemoglobin and the very similar proteins HSA and BSA. Similar results were obtained with and without the fluorescent labels. MAF images were calculated using both the full spectrum and only characteristic amino acid fragments. Although better image contrast was obtained using the full spectrum, differences between the spheres were still evident when only the amino acid fragments were included in the analysis, suggesting that we are truly observing differences between the proteins themselves. These results demonstrate that TOF-SIMS, with a Bi3 primary ion, is a powerful technique for characterizing interfacial proteins not only on large uniform surfaces, but also with high spatial resolution on the topographically complex samples typical in biological analysis.

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Author: B. J. Tyler - C. Bruening - S. Rangaranjan - H. F. Arlinghaus


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