926-79-4Relevant academic research and scientific papers
Mechanism study on the oligomerization of amino acids into peptides by phosphorus trichloride
Zhao, Wenjie,Zhao, Dongxin,Lu, Kui
scheme or table, p. 691 - 698 (2009/05/07)
As treated by phosphorus trichloride, amino acids could oligomerize into polypeptides. Based on the results obtained by 31P-NMR and ESI-MS/MS, a possible reaction mechanism was proposed. The mechanism might undergo a penta-coordinated phosphorus intermediat. The activated amino acid was a five-membered cyclic penta-coordinated phosphorus intermediate. The nucleophilic attack of the amino group from an amino acid or peptide on the carbonyl group of intermediate led to the formation of peptide and released one equivalent dichloride phosphoric acid. The repetition of the reaction sequence generated a series of oligopeptides. Copyright Taylor & Francis Group, LLC.
Structure and dynamics of the homologous series of alanine peptides: A joint molecular dynamics/NMR study
Graf, Juergen,Nguyen, Phuong H.,Stock, Gerhard,Schwalbe, Harald
, p. 1179 - 1189 (2008/04/18)
The φ,ψ backbone angle distribution of small homopolymeric model peptides is investigated by a joint molecular dynamics (MD) simulation and heteronuclear NMR study. Combining the accuracy of the measured scalar coupling constants and the atomistic detail of the all-atom MD simulations with explicit solvent, the thermal populations of the peptide conformational states are determined with an uncertainty of R helical conformations. No significant change in the distribution of conformers is observed with increasing chain length (Ala3 to Ala7). Trivaline samples all three major conformations significantly. Tryglycine samples the four corner regions of the Ramachandran space and exists in a slow conformational equilibrium between the cis and trans conformation of peptide bonds. The backbone angle distribution was also studied for the segment Ala3 surrounded by either three or eight amino acids on both N- and C-termini from a sequence derived from the protein hen egg white lysozyme. While the conformational distribution of the central three alanine residues in the 9mer is similar to that for the small peptides Ala3-Ala7, major differences are found for the 19mer, which significantly (30-40%) samples αR helical stuctures.
Rates of reduction of N-chlorinated peptides by sulfite: Relevance to incomplete dechlorination of wastewaters
Jensen, James S.,Helz, George R.
, p. 516 - 522 (2007/10/03)
Biologically induced fragmentation of proteins during wastewater treatment produces peptides, which form long-lasting organic chloramines when the water is disinfected with Cl2. To protect aquatic wildlife from residual chlorine, including chloramines, wastewaters are often treated with sulfur dioxide or sulfite salts. This strategy incompletely eliminates residual chlorine species. Here we report that dechlorination rate constants of N- chloropeptides are 1-2 orders of magnitude smaller than those for NH2Cl and some aliphatic organic chloramines. Slow rates explain the prevalence of N- chloropeptides in dechlorinated wastewaters after faster reacting chlorine species have been eliminated. Dechlorination is subject to general acid catalysis. For N-chlorinated leucylalanine, the rate law above pH 6 in phosphate buffer at 25 °C and / ? 0.1 M is as follows: rate = (9.92 ± 0.41 x 103[H2PO4-] + 5.70 ± 0.52 x 108[H3O+] + 5.3 ± 0.2)[SO32-][Cl- Leu-Ala] (concentrations in M, time in s). Rate constants for other peptides appear to be of similar magnitude; variations in the acid-catalyzed terms among different hydrophobic peptides correlate with solvation energies of side chains. The kinetic data suggest that reducing N-chloropeptides in wastewaters by 75% or more will require reaction times generally >0.5 h at environmentally acceptable S(IV) doses and pH values. Biologically induced fragmentation of proteins during wastewater treatment produces peptides, which form long-lasting organic chloramines when the water is disinfected with Cl2. To protect aquatic wildlife from residual chlorine, including chloramines, wastewaters are often treated with sulfur dioxide or sulfite salts. This strategy incompletely eliminates residual chlorine species. Here we report that dechlorination rate constants of N-chloropeptides are 1-2 orders of magnitude smaller than those for NH2Cl and some aliphatic organic chloramines. Slow rates explain the prevalence of N-chloropeptides in dechlorinated wastewaters after faster reacting chlorine species have been eliminated. Dechlorination is subject to general acid catalysis. For N-chlorinated leucylalanine, the rate law above pH 6 in phosphate buffer at 25 °C and I≈0.1 M is as follows: rate = (9.92±0.41×103[H2 PO4- ]+5.70±0.52×108[ H3O+]+5.3±0.2) [SO32-][Cl-Leu-Ala] (concentrations in M, time in s). Rate constants for other peptides appear to be of similar magnitude; variations in the acid-catalyzed terms among different hydrophobic peptides correlate with solvation energies of side chains. The kinetic data suggest that reducing N-chloropeptides in wastewaters by 75% or more will require reaction times generally >0.5 h at environmentally acceptable SIV doses and pH values.
