title: QTIPS: a novel method of unsupervised determination of isotopic amino acid distribution in SILAC experiments.
abstract: Stable incorporation of labeled amino acids in cell culture is a simple approach to label proteins in vivo for mass spectrometric quantification. Full incorporation of isotopically heavy amino acids facilitates accurate quantification of proteins from different cultures, yet analysis methods for determination of incorporation are cumbersome and time-consuming. We present QTIPS, Quantification by Total Identified Peptides for SILAC, a straightforward, accurate method to determine the level of heavy amino acid incorporation throughout a population of peptides detected by mass spectrometry. Using QTIPS, we show that the incorporation of heavy amino acids in baker's yeast is unaffected by the use of prototrophic strains, indicating that auxotrophy is not a requirement for SILAC experiments in this organism. This method has general utility for multiple applications where isotopic labeling is used for quantification in mass spectrometry.
authors.affiliation: Institute for Systems Biology, Seattle, Washington 98103, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Dilworth
authors.forename: Ramsey A
authors.initials: RA
authors.lastname: Saleem
authors.forename: Richard S
authors.initials: RS
authors.lastname: Rogers
authors.forename: Hamid
authors.initials: H
authors.lastname: Mirzaei
authors.forename: John
authors.initials: J
authors.lastname: Boyle
authors.forename: John D
authors.initials: JD
authors.lastname: Aitchison
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry* / Q000378:metabolism; D007553:Isotope Labeling / Q000379:methods*; D007554:Isotopes / Q000737:chemistry*; D013058:Mass Spectrometry; D053858:Metabolic Networks and Pathways; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry*; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000378:metabolism
chemical_list: D000596:Amino Acids; D007554:Isotopes; D010446:Peptide Fragments
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