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Ab initio study of hydrogen bond complexes of ring compounds containing the H2N-C=Y moiety with water

100%

Liu T., Liu G.-D., Yu Z.-Y.

Open Chemistry

2010

vol. 8

issue 5

1117-1126

Ab initio calculations, including natural charge population and natural resonance theory analyses, have been carried out to study the two-way effects between hydrogen bonds (H-bonds) and the intramolecular resonance effect by using the H-bonded complexes of ring compounds containing the H2N-C=Y moiety (C=Y bond is contained in the six-membered or five-membered rings) with water as models. The amino groups in the four monomers of ring compounds (FAYs, Y represents the heavy atoms in the substituent groups, =CH, =N, =SiH, and =P, respectively) can all serve as H-bond donors (HD) and H-bond acceptors (HA) to form stable H-bonded complexes with water. The HD H-bond and resonance effect enhance each other (positive two-way effects) whereas the HA H-bond and resonance effect weaken each other (negative two-way effects). The resonance effect in FAY(1) (C=Y bond is contained in the six-membered rings) is weaker than that in formamide, and those in FAY(2) and FAY(3) (C=Y bonds are contained in the five-membered rings). The two-way effects between H-bond and resonance effect exist in the H-bonded complexes of ring compounds containing the H2N-C=Y moiety with water. [...]

Molecular dynamics of (Z)-1-(2-hydroxy-5-methyl-3-nitrophenyl)ethanone oxime and (E)-2-hydroxy-5-methylacetophenone thiosemicarbazone in solution studied by NMR spectroscopy

100%

Mamedov I., Eichhoff U., Maharramov A., Bayramov M., Mamedova Y.

Open Chemistry

2012

vol. 10

issue 1

241-247

The formation of hydrogen bonds and the molecular dynamics for molecules (Z)-1-(2-hydroxy-5-methyl-3-nitrophenyl)ethanone oxime and (E)-2-hydroxy-5-methylacetophenone thiosemicarbazone, (E)-4-bromoacetophenone thiosemicarbazone have been investigated in solution using NMR. The results confirm the formation of different O-H…O type intramolecular hydrogen bonds in the oxime molecule. The rotational barrier energy and energy of intramolecular hydrogen bonds have been determined.

Structural comparison of endomorphin-2 and its conformationally restricted analog

88%

Borics A., Gach K., Fichna J., Sobolewski D., Toth G., Janecka A.

Open Chemistry

2012

vol. 10

issue 1

172-179

In the present study, the effect of a conformational constraint introduced into the endomorphin-2 (Tyr-Pro-Phe-Phe-NH2, EM-2) structure was studied using computational analysis and radioligand binding assay. EM-2 was modified by connecting nitrogen atoms of both phenylalanine residues by a methylene bridge. The obtained analog did not bind to the µ- or δ-opioid receptors in the in vitro studies. The computational analysis of this analog showed twisted, type IV turns and the absence of canonical β-turns typical for the EM-2 structure, which can be explained by the lack of hydrogen bonds involving Phe4. Our results show that the introduction of chemical constraint in the EM-2 structure has a significant effect on opioid receptor affinity and in vitro bioactivity.

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3 Open Chemistry

2 2012

1 2010

1 Bayramov M.

1 Borics A.

1 Eichhoff U.

1 Fichna J.

1 Gach K.

1 Janecka A.

1 Liu G.-D.

1 Liu T.

1 Maharramov A.

1 Mamedov I.

1 Mamedova Y.

1 Sobolewski D.

1 Toth G.

1 Yu Z.-Y.

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Ab initio study of hydrogen bond complexes of ring compounds containing the H2N-C=Y moiety with water

Molecular dynamics of (Z)-1-(2-hydroxy-5-methyl-3-nitrophenyl)ethanone oxime and (E)-2-hydroxy-5-methylacetophenone thiosemicarbazone in solution studied by NMR spectroscopy

Structural comparison of endomorphin-2 and its conformationally restricted analog