Combining high-throughput MALDI-TOF mass spectrometry and isoelectric focusing gel electrophoresis for virtual 2D gel-based proteomics.

The virtual two-dimensional gel electrophoresis/mass spectrometry (virtual 2D gel/MS) technology combines the premier, high-resolution capabilities of 2D gel electrophoresis with the sensitivity and high mass accuracy of mass spectrometry (MS). Intact proteins separated by isoelectric focusing (IEF) gel electrophoresis are imaged from immobilized pH gradient (IPG) polyacrylamide gels (the first dimension of classic 2D-PAGE) by matrix-assisted laser desorption/ionization (MALDI) MS. Obtaining accurate intact masses from sub-picomole-level proteins embedded in 2D-PAGE gels or in IPG strips is desirable to elucidate how the protein of one spot identified as protein 'A' on a 2D gel differs from the protein of another spot identified as the same protein, whenever tryptic peptide maps fail to resolve the issue.

High-throughput middle-down analysis using an orbitrap.

This report demonstrates the application of a capillary LC-LTQ-orbitrap system to provide automated middle-down analysis of proteolytic peptides in the mass range 3000 to 10,000 Da. The novel workflow combines an underutilized method in the orbitrap-high resolution, mass-accurate product ion measurements-with software tailored to search such data (ProSightPC 2.0) and an Asp-selective chemical cleavage approach that generates peptides across an extended mass range.