Solvent effect on the conformational behaviour of amino acid and oligopeptide derivatives

Adaptive Aggregation of Peptide Model Systems

“…The NH stretching band of Ac-Ala-OMe has been observed before in CH 2 Cl 2 , with a solvent red shift of 26 cm –1 for the C 5 conformation, similar to that observed for Ac-Gly-OEt. Solvent effects of this size mask the glycine/alanine substitution shift on the NH stretching wavenumber, which amounts to −5 cm –1 on the basis of the jet spectra and may be attributed to an inductive effect of the C α methyl group, possibly combined with distortion of the intramolecular C 5 contact due to the backbone departure from planarity.…”

Improvement of Light Switching Contrast of Liquid Crystalline Composite Gel by Adding Polar Organic Solvent

“…In the case of the (Cy(11) 2 /5CB/DMSO ¼ 0.5/97.5/2.0 mol%) composite, although the morphology of the fibrils was basically similar to that of the fibrils of the (Cy(11) 2 /5CB ¼ 0.5/99.5 mol%) composite, the width of fibrils was larger and there were more open spaces among them. It has been reported that a solvent has a strong effect on the aggregation structure, such as molecular packing or a higher-order structure, through intermolecular hydrogen bonding of the amide bond because the hydrogen bonding of the amide bond is sensitive to characteristics of the solvent, such as polarity, being the donor or acceptor for hydrogen bonding, and the dielectric constant [21,22]. In our system, the addition of DMSO had an influence on the fibrous aggregation structure of the Cy(11) 2 which selfassembles via intermolecular hydrogen bonding.…”

Quantitative characterisation of the hydrogen bonding behaviour on the acceptor functions in oligopeptide derivatives with a fluorinated alcohol

“…Previous investigations on the solvent effect on the conformational behaviour of oligopeptides have shown that, due to the ability of HFiP to act as a strong proton donor, while exhibiting almost no proton acceptor properties, the conformational behaviour of the peptide function in an HFiP solution differs significantly from that in solution in water or methylene chloride. 14 Hence, the first step of our investigation will be focused on the influence of HFiP on the conformational equilibrium of the peptide molecules dissolved in apolar solvents. As a consequence of the proton attack on the carbonyl functions the nearest environment in the peptide backbone will be changed and consequently result in a shift of the 1 H NMR signals of the NH and C α H next to the acceptor function.…”

“…However, as the amide I band profiles indicate, the population of the stable conformers is different in the two solvents due to the properties of the solvents. 14 In this paper we will show how the equilibrium constants for the 1 : 1 complexation of the selective acceptor functions in oligopeptide and amino acid derivatives with alcohol can be calculated. In order to locate the potential acceptor functions for an alcohol attack we started with a qualitative study using 1 H NMR and IR titration.…”