title: Considering the advantages and pitfalls of the use of isotopically labeled protein standards for accurate protein quantification.
abstract: To ensure comparability of results in clinical proteomics, methods for accurate and traceable quantification of proteins are required. Typically this is done for recombinant proteins using isotopically labeled peptides as internal standards (IS). However, in order to perform quantification in complex matrices such as human serum, isotopically labeled protein standards have been suggested for use as IS to account for losses in sample preparation. The isotopic diluent must be chemically and physically identical to the analyte of interest, having the same amino acid sequence, post-translational modifications, secondary and tertiary structure. It must not be assumed but rather proven that the isotopic diluent is a true mimic, and here we consider both the advantages and potential pitfalls encountered when using isotopically labeled protein IS.
authors.affiliation: LGC, Queens Road, Teddington, UK. caroline.pritchard@ lgcgroup.com
authors.forename: Caroline
authors.initials: C
authors.lastname: Pritchard
authors.forename: Milena
authors.initials: M
authors.lastname: Quaglia
authors.forename: Alison E
authors.initials: AE
authors.lastname: Ashcroft
authors.forename: Gavin
authors.initials: G
authors.lastname: O'Connor
mesh_terms: D000595:Amino Acid Sequence; D002851:Chromatography, High Pressure Liquid / Q000592:standards; D013006:Growth Hormone / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007553:Isotope Labeling; D013058:Mass Spectrometry / Q000592:standards; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D040901:Proteomics / Q000592:standards; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism / Q000592:standards; D012015:Reference Standards
chemical_list: D011506:Proteins; D011994:Recombinant Proteins; D013006:Growth Hormone