This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. We are working with Marshall Bern to optimize his search algorithms. He is writing de novo software to be used on toxin and HIV samples. A paper describing this work is in press: Constrained de novo Sequencing of Peptides with Application to Conotoxins Swapnil Bhatia, Yong J. Kil, Beatrix Ueberheide, Brian Chait Lemmuel Tayo, Bingwen Lu, John R. Yates, III, Marshall Bern J. Computational Biology, In press