Vibrational circular dichroism of polyproline

Enhanced sensitivity to conformation in various proteins. Vibrational circular dichroism results

“…This spectrum is qualitatively and quantitatively similar to the VCD measured for poly(L-lysine) (D20, pH 7.1) ; Paterlini et al, 1986), for poly(L-glutamic acid) (D20, pH 7.6-11.7) (Dukor & Keiderling, 1989), and for poly(L-tyrosine) (DMSO) . We have shown that this pattern is consistent with the VCD found for type II poly(L-proline) (Kobrinskaya et al, 1988), a left-handed (three residues per turn) helical structure sometimes called the "extended helix" (Tiffany & Krimm, 1968.…”

“…From the first report of polypeptide VCD (Singh & Keiderling, 1981), application of VCD in the conformational analysis of biopolymers has, in many aspects, paralleled early use of UV-CD in this area. VCD spectra for model (and "standard" in some sense) homopolypeptides in different conformations have been measured for various vibrational modes which are specific to the amide portion of the molecule (Keiderling, 1986) and were shown to correlate to the polypeptide secondary structure (Lai & Ñafie, 1982;Sen & Keiderling, 1984;Yasui & Keiderling, 1986a,b;Paterlini et al, 1986;Yasui et al, 1987a,b;Kobrinskaya et al, 1988).…”

Structure of Condensed Phase Peptides: Insights from Vibrational Circular Dichroism and Raman Optical Activity Techniques

“…This polypeptide has such a long persistence length that liquid crystals form in some solvents at higher concentrations resulting in very strong VCD intensities . Subsequent studies with other peptides and proteins showed that these initially observed frequency and VCD sign patterns were diagnostic of the secondary structure, even for peptides in H 2 O solution, but the amide II and III bands are broader than the amide I and provide less distinct conformational evidence. − Nafie and co-workers confirmed that α-helical amide I VCD results were consistent for several peptides and also obtained spectra of the opposite sign pattern for peptides thought to form left-handed helices. ,, These amide I patterns, whose sign patterns flip for peptides made with d -amino acids, , proved, after many studies of a variety of helical peptides and proteins, to be uniquely characteristic of the helicity. ,,− Unique deuteration effects were noted for α-helices, in which the amide I′ (N-D) VCD gained a new lower frequency negative feature resulting in both a weaker and narrower (central) positive component. ,, By contrast with ECD analyses, highly aromatic peptides were shown to give straightforwardly interpretable VCD, with no side chain interference, since the aromatic vibrations were resolved from the amide bands. ,,, The observed patterns were directly relatable to those of aliphatic side-chain peptides having the same helical secondary structure.…”

“…These give distinct VCD patterns in the amide I′ (there is no amide II), and the PLP-II negative couplet directly reflects that seen in disordered peptides like PLK or PLGA at neutral pH (see Figure ). ,,− By altering the solvent, the poly-proline conformational variation could be followed with VCD to monitor the changes in the amide I frequency, sign, and band shape in forming PLP-II from PLP-I on dissolving in water. , Binding to ligands and their consequent effects on peptide conformation can also be studied with VCD, due to resolution of different modes in the vibrational region …”

Vibrational circular dichroism of polypeptides and proteins

“…Additional structure, e.g. 310-and polyproline helices, can be distinguished when other modes are included [2]. Recently we have shown that the inherent resolution characteristics of the vibrational spectrum allow VCD to determine the secondary structure of aromatic polypeptides (e.g.…”