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Structure of isolated tyrosyl-glycyl-glycine tripeptide. A comparative conformational study with peptides containing an aromatic ring

100%

Barrera Guisasola E., Masman M., Enriz R., Rodríguez A.

Open Chemistry

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2010

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vol. 8

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issue 3

566-575

EN

The potential energy surface (PES) of tyrosyl-glycyl-glycine (YGG) tripeptide in solution was explored using EDMC (Electrostatically Driven Monte Carlo) and in the gas-phase by means of ab initio quantum chemical calculations. The theoretical computational analysis revealed that this tripeptide possesses a significant molecular flexibility. A C7 backbone conformation was the most energetically preferred for the central Gly residue, using both methodologies. Some new stable conformers that have not been previously reported were identified in the gas phase as well. This study points out the interplay of backbone and side-chain contributions in determining the relative stabilities of energy minima. In addition, the peptide backbone of YGG was compared with other small peptides containing aromatic side-chains (Phe-Gly-Gly and Trp-Gly-Gly). The comparison with experimental X-ray results was also satisfactory. [...]

2

Ab initio and infrared spectral study of 4′-substituted phenylthiolbenzoates

88%

Ivanova B., Arnaudov M.

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EN

The geometry of the 4′-cyano-(4′-CNPTB) and the 4′-methoxy-(4′-MePTB) phenylthiolbenzoates were obtained by ab initio calculations employing 6–31G basis set at Hartee-Fock level of theory. The results predict an extended form of the molecules and torsional angle between the phenyl rings at 90.85(6)0 and 90.87(3)0, respectively. On the basis of vibrational analysis the frequency assignment was carried out. The calculated frequencies were compared with the experimental IR spectral data in carbon tetrachloride, carbon disulfide solutions and in solid state.

3

Theoretical study of structure, vibrational and electronic spectra of isomers of methyl-3-methoxy-2-propenoate

88%

Virdi A., Gupta V., Sharma A.

Open Chemistry

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2004

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vol. 2

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issue 3

456-479

EN

A systematic quantum mechanical study of the possible conformations, their relative stabilities, vibrational and electronic spectra and thermodynamic parameters of methyl-3-methoxy-2-propenoate has been reported for the electronic ground (S0) and first excited (S1) states using time-dependent and time-independent Density Functional Theory (DFT) and RHF methods in extended basis sets. Detailed studies have been restricted to the E-isomer, which is found to be substantially more stable than the Z-isomer. Four possible conformers c′Cc, c′Tc, t′Cc, t′Tc, of which the first two are most stable, have been identified in the S0 and S1 states. Electronic excitation to S1 state is accompanied with a reversal in the relative stability of the c′Cc and c′Tc conformers and a substantial reduction in the rotational barrier between them, as compared with the S0 state. Optimized geometries of these conformers in the S0 and S1 states are being reported. Based on suitably scaled RHF/6-31G** and DFT/6-311G** calculations, assignments have been provided to the fundamental vibrational bands of both these conformers in terms of frequency, form and intensity of vibrations and potential energy distribution across the symmetry coordinates in the S0 state. A complete interpretation of the electronic spectra of the conformers has been provided.

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3 Open Chemistry

1 2010

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1 Arnaudov M.

1 Barrera Guisasola E.

1 Enriz R.

1 Gupta V.

1 Ivanova B.

1 Masman M.

1 Rodríguez A.

1 Sharma A.

1 Virdi A.

Structure of isolated tyrosyl-glycyl-glycine tripeptide. A comparative conformational study with peptides containing an aromatic ring

Ab initio and infrared spectral study of 4′-substituted phenylthiolbenzoates

Theoretical study of structure, vibrational and electronic spectra of isomers of methyl-3-methoxy-2-propenoate