Thermodynamic and (1)H NMR Study of Proton Complex Formation of Histidine-containing Cyclodipeptides in Aqueous Solution
A thermodynamic and (1)H NMR study of proton complex formation in aqueous solution of some L-histidine-containing cyclic L-dipeptides has been carried out.The enthalpic and entropic changes associated with protonation of the cyclodipeptides, obtained by potentiometric and calorimetric measurements, together with the (1)H NMR data and NOESY experiments, enable the role played by non-covalent interactions in proton complex formation to be assessed.In addition, a comparison with c(Gly-His) permits the influence of side-chain residues on the conformation of protonated species to be observed.
Dichlorotris(dimethylamino)phosphorane as Dehydration Reagent for the Preparation of Activated (-ONp, -OPcp, -NSu)Esters of N-Protected Multifunctional Amino Acids
Dichlorotris(dimethylamino)phosphorane (5) is an excellent reagent for the preparation of the activated esters of N-protected amino acids 7-9.Besides 4-nitrophenyl-, pentachlorophenyl-, and N-hydroxysuccinimide esters of various N-protected amino acids, in the presence of HOBt benzyloxycarbonyl-threonine N-hydroxysuccinimide ester was obtained for the first time.
Appel, Rolf,Glaesel, Ursula
p. 3511 - 3516
(2007/10/02)
Specificity of -chymotrypsin. The -chymotrypsin-catalyzed hydrolysis of N-acylamino acid p-nitrophenyl esters.
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Bechet et al.
p. 2566,2567-2569
(2007/10/06)
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