title: PAS-cal: A repetitive peptide sequence calibration standard for MALDI mass spectrometry.
abstract: Mass spectrometers equipped with matrix-assisted laser desorption/ionization (MALDI-MS) require frequent multipoint calibration to obtain good mass accuracy over a wide mass range and across large numbers of samples. In this study, we introduce a new synthetic peptide mass calibration standard termed PAS-cal tailored for MALDI-MS based bottom-up proteomics. This standard consists of 30 peptides between 8 and 37 amino acids long and each constructed to contain repetitive sequences of Pro, Ala and Ser as well as one C-terminal arginine residue. MALDI spectra thus cover a mass range between 750 and 3200 m/z in MS mode and between 100 and 3200 m/z in MS/MS mode. Our results show that multipoint calibration of MS spectra using PAS-cal peptides compares well to current commercial reagents for protein identification by PMF. Calibration of tandem mass spectra from LC-MALDI experiments using the longest peptide, PAS-cal37, resulted in smaller fragment ion mass errors, more matching fragment ions and more protein and peptide identifications compared to commercial standards, making the PAS-cal standard generically useful for bottom-up proteomics.
authors.affiliation: Chair for Proteomics and Bioanalytics, Technische Universität München, Freising, Germany; Institute of Pathology, Research Unit Analytical Pathology, Helmholtz Zentrum München, Neuherberg, Germany; Munich Center for Integrated Protein Science, CIPS-M, Munich, Germany.
authors.forename: Stefan K
authors.initials: SK
authors.lastname: Maier
authors.forename: Ksenia
authors.initials: K
authors.lastname: Bashkueva
authors.forename: Christoph
authors.initials: C
authors.lastname: Rösli
authors.forename: Arne
authors.initials: A
authors.lastname: Skerra
authors.forename: Bernhard
authors.initials: B
authors.lastname: Kuster
mesh_terms: D000595:Amino Acid Sequence; D002138:Calibration; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry*; D040901:Proteomics / Q000379:methods; D020449:Repetitive Sequences, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D010455:Peptides
keywords: Calibration; LC-MALDI; MALDI-TOF-MS; PMF; Protein identification; Technology