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Amide Nitrogen (amide + nitrogen)
Selected AbstractsNitrogen-to-Protein Conversion Factors for Some Cereal Products in JapanJOURNAL OF FOOD SCIENCE, Issue 3 2008S. Fujihara ABSTRACT:, To evaluate a practical method of determining more accurately conversion factors for calculating the protein contents of foods from the total nitrogen content, 19 cereal products found in Japan were analyzed for total nitrogen, amino acid nitrogen, and amide nitrogen, and then the nitrogen-to-protein conversion factors were calculated. The average conversion factors were 5.75 for rice, 5.81 for wheat, and 5.95 for others. These values, corresponding to the proportion of the amino acid residue to amino acid nitrogen recovered from 20 amino acids, were lower than the currently applied factors to these foods, except for wheat flour and amaranth. The use of this factor for estimating the protein content results in a considerable difference from the estimate based on amino acid residue concentrations, due to the wide variations in amino acid composition and to the presence of a significant level of nonprotein nitrogen. The distribution of the protein nitrogen recovered from the amino acids to total nitrogen averaged 93%. Adjusted conversion factors corresponding to the proportion of the amino acid residue to total nitrogen averaged 5.26 for rice, 5.47 for wheat, and 5.54 for other cereal products. Protein contents estimated using these factors are in good agreement with the contents defined as amino acid residues. [source] A variety of poly(m -benzamide)s with low polydispersities from inductive effect-assisted chain-growth polycondensationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2006Tomoyuki Ohishi Abstract Chain-growth polycondensation of 3-(alkylamino)benzoic acid alkyl esters 1 was investigated for obtaining poly(m -benzamide)s with defined molecular weights and low polydispersities. Polymerization conditions were first studied to find that ethyl 3-(octylamino)benzoate (1b) polymerized in a chain polymerization manner in the presence of lithium 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS) as a base and phenyl 4-methylbenzoate (2b) as an initiator in THF at 0 °C. The molecular weight of the polymer was controlled by the feed ratio of monomer to initiator. The polymerization of 1c,i with a variety of N -alkyl groups was then carried out under the established conditions to yield well-defined poly(m -benzamide)s, which showed higher solubility than those of the corresponding poly(p -benzamide)s. Furthermore, the 4-octyloxybenzyl group on the amide nitrogen in poly1i was removed by treatment with trifluoroacetic acid (TFA) to give N -unsubstituted poly(m -benzamide) (poly1j) with a low polydispersity, which is soluble in DMAc and DMSO, contrary to the para-substituted counterpart. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4990,5003, 2006 [source] Puckering transitions of pseudoproline residuesBIOPOLYMERS, Issue 6 2009Young Kee Kang Abstract The puckering transitions of pesudoprolines such as oxazolidine and thiazolidine residues (Oxa and Thz dipeptides) with trans and cis prolyl peptide bonds were explored by optimizations along the endocyclic torsion angle ,1 using quantum-chemical methods in the gas phase and in water. The overall shapes of the potential energy surfaces for Oxa and Thz dipeptides in the gas phase and in water are similar to those for the Pro dipeptide, although there are some differences in relative stabilities of local minima and in barriers to puckering transition. On the whole, the barriers to puckering transition for Oxa and Thz dipeptides are computed to be 0.8,3.2 kcal/mol at the B3LYP/6-311++G(d,p) level in the gas phase and in water, which are lower by 0.5,1.9 kcal/mol than those for the Pro dipeptide. The n , ,* interactions for the delocalization of the lone pair of the prolyl amide nitrogen into the antibonding orbitals that are anti to the lone pair appear to play a role in stabilizing the nonplanar puckered transition states over the corresponding planar structures. The calculated barriers indicate that the down-to-up puckering transition can proceed in the orders Pro < Oxa < Thz in the gas phase and Pro , Oxa < Thz in water. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 444,455, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] The structure and dynamics in solution of Cu(I) pseudoazurin from Paracoccus pantotrophusPROTEIN SCIENCE, Issue 5 2000Gary S. Thompson Abstract The solution structure and backbone dynamics of Cu(I) pseudoazurin, a 123 amino acid electron transfer protein from Paracoccus pantotrophus, have been determined using NMR methods. The structure was calculated to high precision, with a backbone RMS deviation for secondary structure elements of 0.35 ± 0.06 A, using 1,498 distance and 55 torsion angle constraints. The protein has a double-wound Greek-key fold with two ,-helices toward its C-terminus, similar to that of its oxidized counterpart determined by X-ray crystallography. Comparison of the Cu(I) solution structure with the X-ray structure of the Cu(II) protein shows only small differences in the positions of some of the secondary structure elements. Order parameters S2, measured for amide nitrogens, indicate that the backbone of the protein is rigid on the picosecond to nanosecond timescale. [source] | ||||||||||