title: Toward Système International d'Unité-traceable protein quantification: from amino acids to proteins.
abstract: Here we present a demonstration of the proof of principle that absolute concentration of a protein within a mixture of other proteins can be measured with SI traceability. The method used was based on tryptic digestion of a protein followed by quantification using double exact matching isotope dilution mass spectrometry (IDMS) of the peptides released. To provide full SI traceability to measurements of protein concentration we demonstrated a method of SI traceable peptide quantification in which the peptide standards used were quantified by an amino acid analysis method that incorporated double exact matching IDMS and amino acid standards of known purity. The concentration of the protein was therefore determined based upon the concentration of tryptic peptides, which in turn had been quantified based upon amino acid standards. This allowed fully SI-traceable measurements of protein concentration to be made. Important caveats in the implementation of this approach are also discussed and examples of how these can have detrimental effects on the measurements are shown.
authors.affiliation: LGC, Department of Bioorganic mass spectrometry, Queens Road, Teddington, London, TW11 0LY, UK. william.burkitt@lgc.co.uk
authors.forename: William I
authors.initials: WI
authors.lastname: Burkitt
authors.forename: Caroline
authors.initials: C
authors.lastname: Pritchard
authors.forename: Cristian
authors.initials: C
authors.lastname: Arsene
authors.forename: André
authors.initials: A
authors.lastname: Henrion
authors.forename: David
authors.initials: D
authors.lastname: Bunk
authors.forename: Gavin
authors.initials: G
authors.lastname: O'Connor
mesh_terms: D000596:Amino Acids / Q000032:analysis* / Q000737:chemistry; D002853:Chromatography, Liquid; D007394:International System of Units; D007553:Isotope Labeling / Q000379:methods; D013058:Mass Spectrometry; D011506:Proteins / Q000032:analysis* / Q000737:chemistry; D040901:Proteomics / Q000379:methods
chemical_list: D000596:Amino Acids; D011506:Proteins