Use of double-depleted C-13 and N-15 culture media for analysis of whole cell bacteria by MALDI time-of-flight and Fourier transform mass spectrometry

by Stump, Michael J.; Jones, Jeffrey James; Fleming, Richard C.; Lay Jr, Jackson Oliver; Wilkins, Charles L.

In the present paper, results demonstrating the significant advantages of matrix-assisted laser desorption/ ionization (MALDI) analysis of whole cell samples of bacteria grown on double isotopically-depleted (C-13 and N-15) media are presented. It is shown that several advantages accrue for MALDI with a 9.4 T Fourier transform mass spectrometer (FTMS). Of particular note, for analysis of whole cells, sample preparation is simple and chemical interference is reduced. Moreover, ion coalescence problems are minimized, and data-base identification of proteins facilitated. Furthermore, high resolution mass spectra obtained from such whole cells show significant improvement in apparent mass resolving power and mass measurement accuracy, whether time-of-flight or FTMS MALDI is used. As a consequence, it becomes possible to detect subtle details in the chemistry of the organism, such as the presence of both post-translationally modified and unmodified versions of the same proteins. This approach is also adaptable to direct assay of over-expressed proteins from Escherichia coli cultures and should facilitate studies aimed at the detection of medically important cellular biomarker proteins. (C) 2003 American Society for Mass Spectrometry.

Journal of the American Society for Mass Spectrometry
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1879-1123; 1044-0305