VCD studies on cyclic peptides assembled from L‐α‐amino acids and a trans‐2‐aminocyclopentane‐ or trans‐2‐aminocyclohexane carboxylic acid

Abstract

The increasing interest in peptidomimetics of biological relevance prompted us to synthesize a series of cyclic peptides comprising trans‐2‐aminocyclohexane carboxylic acid (Achc) or trans‐2‐aminocyclopentane carboxylic acid (Acpc). NMR experiments in combination with MD calculations were performed to investigate the three‐dimensional structure of the cyclic peptides. These data were compared to the conformational information obtained by electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) spectroscopy. Experimental VCD spectra were compared to theoretical VCD spectra computed quantum chemically at B3LYP/6‐31G(d) density functional theory (DFT) level. The good agreement between the structural features derived from the VCD spectra and the NMR‐based structures underlines the applicability of VCD in studying the conformation of small cyclic peptides. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.

Vibrational circular dichroism of a 2,5‐diketopiperazine (DKP) peptide: Evidence for dimer formation in cyclo LL or LD diphenylalanine in the solid state

“…VCD is indeed very sensitive to minute conformational changes, hence a very good probe of molecular conformation . It has been widely applied to peptides, as a powerful tool for determining their secondary structure, in particular in the Amide I (C = O stretch) region . β‐sheets and coils have, for example, different Amide I spectra from that of the α‐helix .…”

“…28,29 It has been widely applied to peptides, as a powerful tool for determining their secondary structure, in particular in the Amide I (C = O stretch) region. [30][31][32][33][34][35][36][37][38][39] β-sheets and coils have, for example, different Amide I spectra from that of the α-helix. 40 VCD is also very sensitive to the aggregation state and allows the characterization of various size entities ranging from dimers 41 to β-sheets or fibrils formation, 42 as well as self-assemblies in solution or in the solid state.…”

Induced Folding of Protein‐Sized Foldameric β‐Sandwich Models with Core β‐Amino Acid Residues

“…[9] Successes have also been achieved with homologated amino acids, which can be used to build short turns [10] and cyclic a/b-peptides as hairpin models. [11] Sheet-like self-organization has been observed for a/b-peptides at the air/water interface [12] and in fibrillous b-peptidicn anostructures. [13] The construction of water-soluble, sizable, and well-folded b-sheet mimetic a/b-peptides with b-amino acids in arbitrary positions, however,i sad ifficult task.…”

Structure analysis of proteins, peptides and metal complexes by vibrational circular dichroism

“…Cyclic penta-and hexapeptides comprising -homoamino acids (trans-2-aminocyclopentane or trans-2-aminocyclohexane carboxylic acid) were also studied by VCD 15 . They showed similar VCD spectra which indicates that the conformation of the trans-derivatives are determined by the steric structure of the trans-2-aminocyclopentane or trans-2-aminocyclohexane carboxylic acids.…”