title: A comparison of methods for determining total body protein.
abstract: The aim of the study was to find the optimal method (with respect to convenience and accuracy) for determining total protein in whole-body homogenates of rats. Three different protein extraction methods and five different protein concentration methods were assessed. The results were compared against a reference value measured by complete amino acid analysis after acid hydrolysis. The data demonstrated that extraction with 5% (w/v) sodium dodecylsulfate (SDS) in 0.5 N NaOH was far superior to that with water alone or to 6 N guanidine-HCl. A comparison of the Biuret, Bradford, and bicinchoninic acid methods on the SDS-NaOH-extracted samples showed that the Biuret method was optimal, giving a value that was 90% of the reference value with a small variation (2.4% of the mean). The Kjeldahl method gave the correct protein concentration only when a nitrogen factor of 5.51 +/- 0.03 (N = 5) was applied. The results suggest that extraction with SDS-NaOH followed by the Biuret procedure is a good method for measuring protein concentrations in whole body rat homogenates.
authors.affiliation: Nutrition Research Division, Food Directorate Health Canada, Tunney's Pasture, Ottawa, Ontario.
authors.forename: S P
authors.initials: SP
authors.lastname: Brooks
authors.forename: B J
authors.initials: BJ
authors.lastname: Lampi
authors.forename: G
authors.initials: G
authors.lastname: Sarwar
authors.forename: H G
authors.initials: HG
authors.lastname: Botting
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001738:Biuret Reaction; D001824:Body Constitution; D002364:Caseins / Q000032:analysis; D002457:Cell Extracts / Q000737:chemistry; D002623:Chemistry Techniques, Analytical / Q000379:methods*; D002851:Chromatography, High Pressure Liquid; D019791:Guanidine; D006146:Guanidines; D008297:Male; D009555:Ninhydrin; D011506:Proteins / Q000032:analysis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012680:Sensitivity and Specificity; D012710:Serum Albumin, Bovine / Q000032:analysis; D012967:Sodium Dodecyl Sulfate
chemical_list: D000596:Amino Acids; D002364:Caseins; D002457:Cell Extracts; D006146:Guanidines; D011506:Proteins; D012710:Serum Albumin, Bovine; D012967:Sodium Dodecyl Sulfate; D009555:Ninhydrin; D019791:Guanidine