Speaker: Dr. Al Yergey, NICHD,NIH
Topic: Protein Processor: Probabilistically Using Mass Accuracy and the MS Spectrum
Date: Monday, April 16, 2012
Time: 7:30 pm
Location: Shimadzu Scientific Instrument, Inc. Training Center 7100 Riverwood Drive, Columbia, MD 21046 (Directions)
Dinner: Please join the speaker and the co-chairs for dinner at the Ram’s Head Tavern at Savage Mill, 8600 Foundry Street, Savage, MD 20763 at 5:30 pm. Contact Shelley Jackson (Shelley.Jackson@nih.hhs.gov) to let him know you will be there for dinner.
Abstract: Current approaches to protein identification rely heavily on database matching of fragmentation spectra, while ignoring (in a scoring sense) the mass accuracy of the precursor ions. We have developed a method based originally upon MALDI TOF-TOF instrumentation that uses targeted peptide mass fingerprinting results to confirm MS/MS database search identifications. The method uses 1st-order spectral data that have heretofore been ignored by most search engines, as only a subset of the peptides found in a first order mass spectrum are usually fragmented. In this method the distribution of mass errors of peptide matches in the first order spectrum is used to develop a probability model that is independent from the MS/MS database search identifications. Peptide mass matches can come from both precursor ions that have been fragmented as well as those that are tentatively identified by accurate mass alone. This additional confirmation enables us to assign protein identifications to MS/MS based scores that are otherwise considered to be only of moderate quality.