Alanine dipeptide aqueous

BM Pettitt, M Karplus. The potential of mean force surface for the alanine dipeptide in aqueous solution A theoretical approach. Chem Phys Lett 121 194-201, 1985. 

Figure 4.7 Ramachandran s map of alanine dipeptide in the gas phase and aqueous solution (see Colour Plate section). Energy contours are in kcal/mol.

As an example of the relative performance of explicit and implicit solvation models in calculations of conformational equilibria, Scarsi et al. [60] compared the calculated conformational properties obtained by the CHARMM force field of liquid 1,2-dichloroethane and of terminally blocked alanine dipeptide in aqueous solution. They employed (i) a systematic conformational search with solvation energies cal-... 

V. Renugopalakrishnan Could you comment on the conformation of L-alanine dipeptide in water What values do you observe for 0 and Have you conducted conformational studies using your method in non-aqueous solvents ... 

Levine The dipeptide conformations we have observed using the lanthanide probes in aqueous solution have all been fairly extended structures with 0, W values of —60° and +140°. We note however that in the case of L-alanyl L-alanyl L-alanine the conformation adopted approaches that of a simple helix (Figure 6). We do not find that the preferred conformation of the L-alanyl L-alanine dipeptide is either the C5 or the C form in aqueous solution. We have not investigated the peptide conformations in non-aqueous solvents using the lanthanides as n.m.r. probes but such systems are reviewed by B. C. Mayo Chem. Soc. Rev. 2 (1) p. 49 (1973). The conformations of the diastereomers of phenylalanyl alanine in chloroform confirm the stereochemistry of the 7-member H-bonded ring (Martinelli, Honiberg, and Sternson Tetrahedron 29, p. 1671, (1973)). 

Molecular-dynamics computer simulations of three different molecular conformations (a, and C ) of alanine dipeptide (225) in aqueous solution have been carried out. ... 

Fig. 8.14 Typical snapshot structure of the alanine dipeptide in aqueous solution. Two peptide C=0 groups of the alanine dipeptide are forming directly hydrogen bonds with four H2O molecules (WAT2, WAT12, WAT27, and WAT44). The local backbone conformation of the alanine dipeptide was defined by two dihedral angles, p and tf/ (Reproduced with permission from Okamoto et al. [20]. Copyright 2013 The chemical society of Japan)...

D. J. Tobias and C. L. Brooks,/. Phys. Chem., 96(9), 3864-3870 (1992). Conformational Equilibrium in the Alanine Dipeptide in the Gas Phase and Aqueous Solution A Comparison of Theoretical Results. 

JC Purdie, NL Benoiton. Piperazinedione formation from esters of dipeptides containing glycine, alanine and sarcosine the kinetics in aqueous solution. J Chem Soc Perk Trans 2, 1845, 1973. 

The Merck process group subsequently published a more detailed route amenable towards multikilogram scales (Blacklock et al., 1988). This synthesis begins with treatment of alanine with phosgene to produce A-carboxyanhydride (NCA) 16 (Scheme 10.3). Under basic aqueous conditions this anhydride is coupled with proline to produce, upon acidic work-up, the dipeptide alanyl-proline (14). Enalapril is then prepared in one synthetic step by a diastereoselective reductive amination between ethyl-2— oxo-4-phenylbutyrate (13) and 14. This reaction was the subject of extensive optimization, and it was found that the highest diastereoselectivity was obtained by hydrogenation over Raney nickel in the presence of acetic acid (25%), KF (4.0 equiv.), and 3 A molecular sieves (17 1 dr). Enalapril is then isolated in diastereomerically pure form as its maleate salt (Huffman and Reider, 1999 Huffman et al., 2000). 

As might be expected, the search for an even better artificial sweetener continues. Alitame is a dipeptide formed from aspartic acid and alanine, with an unusual amide at the carboxylate end of the alanine. It is 2000 times as sweet as sucrose— 1 pound of alitame has the sweetening power of I ton of sucrose In addition, because an amide bond is more stable than an ester bond, alitame is more stable to hydrolysis than is aspartame. Therefore, alitame keeps its sweetness in aqueous solution better than aspar-... 

We have been more concerned with the nature of the water around proteins and peptides. To this end we have investigated the structure and energetics of the solvent, both ordered and disordered around the enzyme lysozyme, in the triclinic crystal[l7d]. In addition to lysozyme, we have characterized the water structure and fluctuations in the crystal of a cyclic hexapeptide, (L-Ala-L-Pro-D-Phe)9[20]. and studied the effect of solvent on the conformation of the dipeptide of alanine[2l] and on the equilibria between extended and helical alanine polypeptides such as those discussed in the previous section[22]. The latter systems simulate aqueous solution conditions rather than crystalline environment. 

L-Carnosine (P-alanyl-L-histidine) [305-84-0] M 226.2, m 258-260 (dec), 260 (capillary tube), 262 (dec), [a] +20,5 (c 1.5, H2O), pKf 2.64, pKf 6.83, pKf 9.51. Likely impurities are histidine and P-alanine. Crystallise L-carnosine from water by adding EtOH in excess. RecrystaUise it from aqueous EtOH by slow addition of EtOH to a strong aqueous solution of the dipeptide. Its... 

Organisms do not use single amino acids as biocatalysts, but rather macromolecules comprised of them - enzymes - with nearly perfect selectivities in the functions they perform. But already the combination of just two amino acids to a dipeptide often creates a much better catalyst for the synthesis of caibohydiates under aqueous conditions (45, 46). Alanine for example catalyses the formation of erythrose with 7% ee (44) and the dipeptide L-Ala-L-Ala with 33% ee (46). How exactly peptides evolved under prebiotic conditions is another topic of debate as peptide formation from amino acids in water is thermodynamically not favored, requiring special conditions and activations (47). 

Peptide Synthesis. Reagent (1) has been used as a coupling reagent in the synthesis of benzyloxycarbonylalanylalanine (3). Initial treatment of benzyloxycarbonylalanine with (1) in acetonitrile at 45 °C for 12 h followed by reaction with an excess of an aqueous solution (pH 8-9) of alanine gave the protected dipeptide in 85% yield (eq 6). No reference to the stereochemistry of the starting materials or product was made. 

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