Database of proteinogenic amino acid reference spectra for Bismuth-cluster ToF-SIMS. II. Positive polarity

The number of time-of-flight secondary ion mass spectrometry studies on biological tissues and cells strongly increased since the development of primary ion sources that allow not only elemental but also molecular analysis. Still, substantial fragmentation during ionic bombardment results in a large amount of peaks, rendering data analysis complex. Complete and trustable sets of reference spectra for the main biological building blocks such as proteins, sugars, and lipids are required. Here, the authors provide a database of reference spectra for the 21 proteinogenic amino acids + glycine for bismuth instruments. Paper 1 of this two-part article series contains the negative polarity spectra and Paper II the positive polarity spectra. These reference spectra were obtained with the primary ion Bi3+, and spectra for the primary ions Bi1+ and Bi3++ are contained in the supplementary material as ASCII files.