A novel LC-MS approach for the detection of metabolites in DMPK studies.

Background: The profiling and quantification of drug metabolites in discovery and development bioanalysis studies is playing an increasingly important role in early candidate selection. Using a conventional tandem quadrupole mass spectrometer this activity normally requires several analytical runs to acquire the necessary analytical data.

Results: In this article we present the use of a new tandem quadrupole mass spectrometer equipped with a novel collision cell design, which allows the rapid switching between multiple reaction monitoring and full-scan MS mode.

Semi-automated data processing of hydrogen exchange mass spectra using HX-Express.

A Microsoft Excel utility, HX-Express, that significantly accelerates the analysis of hydrogen exchange mass spectrometry data is described. HX-Express generates deuterium uptake and peak width plots from peaks in mass spectral data. Data analysis is intentionally semi-automated, requiring that the user find the peaks to be analyzed.

Evaluation of multidimensional (ion-exchange/reversed-phase) protein separations using linear and step gradients in the first dimension.

The performance characteristics of multidimensional liquid chromatographic protein separations were evaluated using on-line electrospray mass detection, and a novel workflow for automated LC/MS data processing. Two-dimensional ion exchange/reversed-phase LC separations of Escherichia coli cytosol were conducted using either a continuous linear or discontinuous step gradient in the first dimension. Chromatographic profiles of the top 100 most abundant components were characterized to assess overall separation reproducibility within each mode, and to characterize differences in component distribution between the two modes of operation.

Quantitative proteomic analysis by accurate mass retention time pairs.

Current methodologies for protein quantitation include 2-dimensional gel electrophoresis techniques, metabolic labeling, and stable isotope labeling methods to name only a few. The current literature illustrates both pros and cons for each of the previously mentioned methodologies. Keeping with the teachings of William of Ockham, "with all things being equal the simplest solution tends to be correct", a simple LC/MS based methodology is presented that allows relative changes in abundance of proteins in highly complex mixtures to be determined.