Characterization of metabolites of a NK1 receptor antagonist, CJ-11,972, in human liver microsomes and recombinant human CYP isoforms by liquid chromatography/tandem mass spectrometry

Identifying and overcoming bioanalytical challenges associated with chlorine-containing dehydrogenation metabolites

Liquid chromatography coupled to tandem mass spectrometry (LC/MS/MS) is a widely utilized analytical tool for quantifying small molecules in complex biological matrices. In certain situations the mass-selection capabilities of the tandem mass spectrometer may be insufficient to discriminate between the analyte of interest and its metabolites, particularly those metabolites that are isobaric with the analyte. One scenario by which isobaric interference may occur is the metabolism of a chlorine- or bromine-containing small molecule to a metabolite with the concomitant loss of 2 Da. This report describes the detection and characterization of two distinct dehydrogenation [M-2] metabolites during LC/MS/MS quantification of a chlorinated small molecule in rat plasma samples derived from a toxicokinetic study. The potential isotope-related impact of these metabolites on quantification of the parent compound was assessed. Several alternate precursor ion and product ion combinations were evaluated and shown to minimize the quantitative impact of the interfering metabolites without having to rely on their stringent chromatographic resolution from the parent compound. These results indicate that when quantifying chlorine- or bromine-containing small molecules from in vivo samples or in vitro metabolic incubations: (1) efforts to detect potential dehydrogenation metabolites should be undertaken and (2) if such metabolites are detected, the judicious choice of alternate multiple-reaction monitoring (MRM) transitions can limit their impact on quantification of the parent molecule without the need for robust chromatographic resolution.

Mass spectrometry in systems biology: an overview

As an emerging field, systems biology is currently the talk of the town, which challenges our philosophy in comprehending biology. Instead of the reduction approach advocated in molecular biology, systems biology aims at systems-level understanding of correlations among molecular components. Such comprehensive investigation requires massive information from the "omics" cascade demanding high-throughput screening techniques. Being one of the most versatile analytical methods, mass spectrometry has already been playing a significant role at this early stage of systems biology. In this review, we documented the advances in modern mass spectrometry technologies as well as nascent inventions. Recent applications of mass spectrometry-based techniques and methodologies in genomics, proteomics, transcriptomics and metabolomics will be further elaborated individually. Undoubtedly, more applications of mass spectrometry in systems biology can be expected in the near future.