title: Robust protein quantitation in chromatographic fractions using MALDI-MS of tryptic peptides.
abstract: A method is introduced to evaluate protein concentrations using the height sum of all MALDI-MS peaks that unambiguously match theoretic tryptic peptide masses of the protein sought after. The method uses native chromatographic protein fractionation prior to digestion but does not require any depletion, labeling, derivatization, or preparation of a compound similar to the analyte. All peak heights of tryptic peptides are normalized with the peak height of a unique standard peptide added to the MALDI-MS samples. The sum of normalized peak heights, S(n), or the normalized mean peak height, M(n), reflects the concentration of the respective protein. For fractions containing various proteins, S(n) and M(n) can be used to compare concentrations of a protein between different fractions. For fractions with one predominating protein, they can be used to estimate concentration ratios between fractions, or to quantify the fractional protein concentration after calibration with pure protein solutions. Initial native fractionation retains the possibility to apply all conventional analytic procedures. Moreover, it renders the method relatively robust to MS mass accuracy. The method was validated with albumin, transferrin, alpha1-antitrypsin, and immunoglobulin G within highly complex chromatographic fractions of pathological and normal sera, which contained the respective intact native protein in dominating as well as minor concentrations. The correlation found between S(n) and the protein concentration as determined with ELISA showed that the method can be applied to select markers for distinguishing between normal and pathological serum samples.
authors.affiliation: Institute of Biochemistry I, Medical Faculty, Friedrich Schiller University, D-07740 Jena, Germany.
authors.forename: Renate
authors.initials: R
authors.lastname: Bublitz
authors.forename: Stefan
authors.initials: S
authors.lastname: Kreusch
authors.forename: Günther
authors.initials: G
authors.lastname: Ditze
authors.forename: Margarete
authors.initials: M
authors.lastname: Schulze
authors.forename: Gerhard A
authors.initials: GA
authors.lastname: Cumme
authors.forename: Christine
authors.initials: C
authors.lastname: Fischer
authors.forename: Adrienne
authors.initials: A
authors.lastname: Winter
authors.forename: Horst
authors.initials: H
authors.lastname: Hoppe
authors.forename: Heidrun
authors.initials: H
authors.lastname: Rhode
mesh_terms: D001798:Blood Proteins / Q000032:analysis* / Q000737:chemistry; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D004797:Enzyme-Linked Immunosorbent Assay; D010449:Peptide Mapping; D010455:Peptides / Q000737:chemistry / Q000302:isolation & purification*; D021241:Spectrometry, Mass, Electrospray Ionization; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D014357:Trypsin / Q000378:metabolism*
chemical_list: D001798:Blood Proteins; D010455:Peptides; D014357:Trypsin