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Conformational Behaviour (conformational + behaviour)

Distribution by Scientific Domains

Chemistry	83%

Selected Abstracts

Solvent-Dependent Conformational Behaviour of Model Tetrapeptides Containing a Bicyclic Proline Mimetic

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 22 2004
Andrea Trabocchi
Abstract Two model tetrapeptides containing bicyclic analogues of either D - or L -proline were synthesised and their conformational properties were studied by NMR in different solvent systems and by molecular modelling techniques. Compound 1, with the bicyclic D -proline mimetic in the i+1 position, generated a unique trans isomer, and the peptide showed a well organised structure, in accordance with the tendency of D -proline to act as a good turn inducer with respect to its enantiomer. Peptide 2 displayed structures equilibrating from type I,II to type VI ,-turns, thus confirming the hypothesised relationship between the chirality of BGS/Bgs and proline enantiomers on nucleating compact turns. Moreover, such behaviour suggested a tool for peptidomimetic design of reverse turn peptides containing BGS/Bgs bicyclic proline mimetics, as the choice of chirality might influence the generation either of compact ,- and ,-turns or of flexible equilibrating reverse turn structures. The effect of solvent on conformational behaviour was also studied. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Conformational Behaviour of Comb-Like Poly(4-vinylpyridinium) Salts and their Complexes with Surfactants in Solution and on a Flat Surface

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 2 2007
Marat O. Gallyamov
Abstract We synthesised P4VP bromides with octyl and dodecyl pendant groups; the bromide anions in these polymer salts were further substituted with dodecylsulfate or bis(2-ethylhexylsuccinate) anions. Direct SFM visualisation of the original P4VP chains, of the macromolecular salts and of their complexes, showed that the attachment of the pendant groups and especially the complexation with the surfactants promotes stretching of the macromolecules while adsorbing on mica substrate. On the other hand, viscosimetry showed that in solution (chloroform) the comb-like chains and their complexes with dodecylsulfate had more compact conformations than those of the original P4VP. The scaling exponents describing the correlation between the contour length and the end-to-end distance of the adsorbed macromolecules were found to be ca. 3/4, which is indicative of 2D self-avoiding walk statistics. [source]

Solvent-Dependent Conformational Behaviour of Model Tetrapeptides Containing a Bicyclic Proline Mimetic

Raman spectra of putrescine, spermidine and spermine polyamines and their N -deuterated and N -ionized derivatives

JOURNAL OF RAMAN SPECTROSCOPY, Issue 5 2003
A. M. Amorim da Costa
Abstract The experimental and calculated Raman spectra of the N -hydrogenated and N -deuterated biogenic polyamines putrescine, spermidine and spermine and of their N -hydrogenated and N -deuterated hydrochloride salts in the 2000,3400 cm,1 spectral region (at distinct temperatures) are reported and analysed. A complete assignment of the N,H, C,H and N,D stretching modes is carried out, in the light of both steric and hydrogen-bonding interactions on the conformational behaviour of these systems. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Amino-substituted O6 -benzyl-5-nitrosopyrimidines: interplay of molecular, molecular-electronic and supramolecular structures

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2002
Antonio Quesada
The structures of eight 2,4,6-trisubstituted-5-nitrosopyrimidines (one of which crystallizes in two polymorphs) have been determined, including seven O6 -benzyl derivatives which are potential, or proven, in vitro inhibitors of the human DNA-repair protein O6 -alkylguanine-DNA-transferase. In the derivatives having an amino substituent at the 4-position, an intramolecular N,H,O hydrogen bond with the nitroso O as an acceptor leads to an overall molecular shape similar to that of substituted purines. There is a marked propensity for these nitroso compounds to crystallize with Z, = 2. The structure of an analogue with no nitroso group is also reported for comparative purposes. Compounds containing the N -alkyl substituents ,NHCH2COOEt, ,NHCH2CH2COOEt and ,NHCH(CH2Ph)COOEt, derived from amino acid esters, exhibit a rich variety of conformational behaviour, and in all of the nitroso compounds the bond lengths provide strong evidence for a highly polarized electronic structure. Associated with this polarization is extensive charge-assisted hydrogen bonding between the molecules, leading to supramolecular aggregation in the form of finite (zero-dimensional) aggregates, chains, molecular ladders, sheets and frameworks. [source]

Dithioether ligands containing a 2,6-disubstituted pyridine linker with two thioether-heterocycle arms

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2010
Archimede Rotondo
The structure of 2,6-bis(2-pyridyltsulfanylmethyl)pyridine (pytmp), (I), C17H15N3S2, presents a twisted conformation, with the three planar moieties almost perpendicular to each other. The structures of two related derivatives, namely 2,6-bis(6-methyl-2-pyridylsulfanylmethyl)pyridine (mpytmp), (II), C19H19N3S2, and 2,6-bis(4-methyl-2-pyrimidylsulfanylmethyl)pyridine (mprtmp) n- pentane hemisolvate, (III), C17H17N5S2·0.5C5H12, present extended planar fragments with just one quasi-perpendicular arylsulfanylmethyl side arm, such that the molecules are folded in an L-shaped conformation. All three conformations appear different from those adopted by similar compounds, demonstrating the great flexibility of such species, although such differences in conformational behaviour might drive specific coordination modes. [source]