Microbes influence many aspects of human life from the environment to health, yet evaluating their biological pro-esses at the chemical level can be problematic. Mass spectrometry imaging (MSI) enables direct evaluation of microbial chem-ical processes at the atomic to molecular levels without destruction of valuable two-dimensional information. MSI is a label-free method that allows multiplex spatiotemporal visualization of atomic- or molecular-level information of microbial and microbe-related samples. As a result, microbial MSI has become an important field for both mass spectrometrists and microbiologists. In this review, basic techniques for microbial MSI, such as ionization methods and analyzers, are explored. In addition, we discuss practical applications of microbial MSI and various data-processing techniques.
Histidine phosphorylation (pHis) is increasingly recognized as an important post translational modification (PTM) in regulating cellular functions in eukaryotes. In order to clarify the role of pHis in mammalian cell signaling system, a global phos-phorylation study was performed in human prostate cancer cells, PC-3M, using a TiO 2 affinity chromatography. A total number of 307 pHis sites were identified on the 268 proteins among total identified 9,924 phosphorylation sites on 3,316 proteins. In addition, 22 pHis proteins were classified in enzyme category. This report provides the first database for the study of pHis in prostate cancer cells.
Mertansine, a thiol-containing maytansinoid, is a tubulin inhibitor used as the cytotoxic component of antibody-drug conjugates for the treatment of cancer. Liquid chromatography-tandem mass spectrometry was described for the determination of mertansine in rat plasma. 50-µL rat plasma sample was pretreated with 25 µL of 20 mM tris-(2-carboxyethyl)-phosphine, a reducing reagent, and further vortex-mixing with 50 µL of 50 mM N-ethylmaleimide for 3 min resulted in the alkylation of thiol group in mertansine. Alkylation reaction was stopped by addition of 100 µL of sildenafil in acetonitrile (200 ng/mL), and following centrifugation, aliquot of the supernatant was analyzed by the selected reaction monitoring mode. The standard curve was linear over the range of 1–1000 ng/mL in rat plasma with the lower limit of quantification level at 1 ng/mL. The intra- and inter-day accuracies and coefficient variations for mertansine at four quality control concentrations were 96.7–113.1% and 2.6–15.0%, respectively. Using this method, the pharmacokinetics of mertansine were evaluated after intravenous administration of mertansine at doses of 0.2, 0.5, and 1 mg/kg to female Sprague Dawley rats.