Christopher H. Becker

Byonic is the name of a software package for peptide and protein identification by tandem mass spectrometry. This software, which has only recently become commercially available, facilitates a much wider range of search possibilities than previous search software such as SEQUEST and Mascot. Byonic allows the user to define an essentially unlimited number of variable modification types. Byonic also allows the user to set a separate limit on the number of occurrences of each modification type, so that a search may consider only one or two chance modifications such as oxidations and deamidations per peptide, yet allow three or four biological modifications such as phosphorylations, which tend to cluster together. Hence, Byonic can search for tens or even hundreds of modification types simultaneously without a prohibitively large combinatorial explosion. Byonic's Wildcard Search allows the user to search for unanticipated or even unknown modifications alongside known modifications. Finally, Byonic's Glycopeptide Search allows the user to identify glycopeptides without prior knowledge of glycan masses or glycosylation sites.

A new method is presented for quantifying proteomic and metabolomic profile data by liquid chromatography-mass spectrometry (LC-MS) with electrospray ionization. This biotechnology provides differential expression measurements and enables the discovery of biological markers (biomarkers). Work presented here uses human serum but is applicable to any fluid or tissue. The approach relies on linearity of signal versus molecular concentration and reproducibility of sample processing. There is no use of isotopic labeling or chemically similar standard materials. Linear standard curves are reported for a variety of compounds introduced into human serum. As a measure of analytical reproducibility for proteome and metabolome sampling, median coefficients of variation of 25.7 and 23.8%, respectively, were determined for approximately 3400 molecular ions (not counting their numerous isotopes) from 25 independently processed human serum samples, corresponding to a total of 85000 individual molecular ion measurements.

Matrix-assisted laser desorption time-of-flight mass spectrometry has been used to produce quasi-molecular ion signals from underivatized mixed-base single-stranded DNA oligomers ranging from 10 to 67 nucleotides in length. These results were obtained with a new matrix material, 3-hydroxypicolinic acid (3-hydroxypyridine-2-carboxylic acid) which showed significant improvement over many previously reported matrices studied in terms of mass range available, signal-to-noise ratio, and the ability to analyze mixed-base oligomers. The desorption and simultaneous ionization was by pulsed laser light at 10 to 50 mJ/cm2, studied at 266, 308, and 355 nm. Spectra taken at 266 nm provided the smallest amounts of doubly charged and dimer ions--characteristics desirable for DNA sequencing by this technology. Negative-ion spectra were uniformly superior to positive-ion spectra. This new matrix also is quite effective for molecular weight determinations of peptides and proteins in both positive- and negative-ion modes.