title: Whole-rat protein content estimation: applicability of the N x 6.25 factor.
abstract: The amino acid composition of the protein from three strains of rat (Wistar, Zucker lean and Zucker obese), subjected to reference and high-fat diets has been used to determine the mean empirical formula, molecular weight and N content of whole-rat protein. The combined whole protein of the rat was uniform for the six experimental groups, containing an estimate of 17.3% N and a mean aminoacyl residue molecular weight of 103.7. This suggests that the appropriate protein factor for the calculation of rat protein from its N content should be 5.77 instead of the classical 6.25. In addition, an estimate of the size of the non-protein N mass in the whole rat gave a figure in the range of 5.5% of all N. The combination of the two calculations gives a protein factor of 5.5 for the conversion of total N into rat protein.
authors.affiliation: Servei de Radioisòtops, Facultat de Biologia, Universitat de Barcelona, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Rafecas
authors.forename: M
authors.initials: M
authors.lastname: Esteve
authors.forename: J A
authors.initials: JA
authors.lastname: Fernández-López
authors.forename: X
authors.initials: X
authors.lastname: Remesar
authors.forename: M
authors.initials: M
authors.lastname: Alemany
mesh_terms: D000596:Amino Acids / Q000032:analysis*; D000818:Animals; D004032:Diet; D005260:Female; D009584:Nitrogen / Q000032:analysis*; D009765:Obesity / Q000378:metabolism; D011506:Proteins / Q000737:chemistry*; D051381:Rats; D017208:Rats, Wistar; D011924:Rats, Zucker
chemical_list: D000596:Amino Acids; D011506:Proteins; D009584:Nitrogen