Abstract: Disclosed is an evaluation peptide for evaluating the efficiency of a pretreatment in the quantification of a protein using a mass spectrometer, having high reliability and high general versatility. Also disclosed is an artificial standard protein comprising the evaluation peptide. Further disclosed is a method for quantifying a protein utilizing the artificial standard protein. Specifically disclosed is a method for selecting a peptide which consists of an amino acid sequence not agreeing with that in a naturally occurring protein and a variant thereof and capable of being detected by mass spectrometry and which has an amino acid that can be recognized by a protein-digesting enzyme, and using the peptide as an evaluation peptide for use in the quantification of a protein by a mass spectrometer.

Abstract: Disclosed is an evaluation peptide for evaluating the efficiency of a pretreatment in the quantification of a protein using a mass spectrometer, having high reliability and high general versatility. Also disclosed is an artificial standard protein comprising the evaluation peptide. Further disclosed is a method for quantifying a protein utilizing the artificial standard protein. Specifically disclosed is a method for selecting a peptide which consists of an amino acid sequence not agreeing with that in a naturally occurring protein and a variant thereof and capable of being detected by mass spectrometry and which has an amino acid that can be recognized by a protein-digesting enzyme, and using the peptide as an evaluation peptide for use in the quantification of a protein by a mass spectrometer.

Abstract: There are provided a peptide consisting of an amino acid sequence for simultaneously quantifying absolute amounts of metabolizing enzyme proteins in a biological sample at high sensitivity and a method for using the same. A peptide which can be detected at high sensitivity with a mass spectrometer that enables highly sensitive simultaneous quantification of metabolizing enzymes, intracellular proteins, is selected, and the amino acid sequence thereof is identified. Using a stable-isotope-labeled peptide having the same amino acid sequence as the amino acid sequence of this peptide to be quantified, a mass spectrometry by LC-MS/MS is performed at predetermined concentration levels of the stable-isotope-labeled peptide to create a calibration curve.

Abstract: A method is provided for quantifying a plasma membrane protein present by using a stable-isotope labeled peptide as a probe by mass spectrometry in a simple, quick and accurate manner. A plasma membrane protein is fragmented to prepare an oligopeptide fragment, identified by LC/MS/MS. A subject peptide for quantification is selected if the peptide is obtained by fragmenting with a protease, the peptide is specific to a target molecule, and if the peptide has a high total score value based on selective criteria for hydrophobic amino acids content, sequence conditions, number of amino acid residues, specific amino acid sequence conditions, etc. According to these criteria, a subject peptide fragment that can be ionized by ESI method is selected. By using the subject peptide for and a stable-isotope labeled peptide, the plasma membrane protein is quantified accurately by mass spectrometry.

Abstract: The present invention is to provide a method for quantifying a plasma membrane protein present in a cell membrane, by using a stable-isotope labeled peptide as a probe by mass spectrometry, in a simple, quickly and accurate manner. A plasma membrane protein is fragmented to prepare an oligopeptide fragment, identified by LC-MSMS, and by setting as essential criteria that the peptide is obtained by fragmentizing with a protease, and the peptide is specific to a target molecule, selective criteria with score are set for hydrophobic amino acids content, sequence conditions, number of amino acid residues, specific amino acid sequence conditions, etc. According to criterion for selecting a subject peptide for quantification for selecting preferentially a peptide with high score, a peptide fragment that can be ionized by ESI method is selected, and by using the subject peptide for quantification and a stable-isotope labeled peptide, the plasma membrane protein is quantified accurately by mass spectrometry.