Linear oligopeptides. XXVII. Contribution to the circular dichroism of internal peptide chromophores

Abstract

-l~cxall~1oropro~~a1~-2-ol were calci~lated by subtracting the total molar ellipticity values of N-and C-protected homo-trimers from those of the pertinent protected homo-tetramers.The circular dichroism of the internal peptide chromophore of aliphatic hydrocarbon-and s~llfur-containing peptides, each of the L-configuration, show a negative band at 21 5-230 nm accompanied by a more intense negative band near 200 nm. A structi~red wcak and negative band near 260 nm along with bands at 240 nm (negative), 222 nm (positive), and 210.5 nm (negative) of progressively increasing intensity are apparent in the circular dichroic spectrilln of L-Phe-L-Phe internal peptide chro~nophore. The elfect of solvent polarity is discilssed in thc case of L-Val-L-Val and L-Ala-L-Ala internal peptide chromophores.Among the protected ho~no-trimers and tetramers only those of L-alanine are soluble in aqileoils solution; consequently, the effect of water as a function of temperature, urea, and guanidinium chloride on the L-Ala-L-Ala internal peptide chromophore circular dichroism was established.CLAUDIO TONIOLO et GIAN MARIA BONORA. Can. J. Chem. 5'470 (1976). On a calci~le la contribution des chro~nophores peptidiques internes ail dichroismc circillaire Parmi les homo trimkres et tetramkres protCgCs seulement cells de la L-alaninc sont solubles dans des solutions aqueuses; par consCquent I'effet dc I'ea~i cn fonction de la temperature,

Circular Dichroism and Its Empirical Application to Biopolymers

“…30). A number of other workers (Lord and Cox, 1973;Mattice and Harrison, 1975;Toniolo and Bonora, 1976) have used longer oligomers to determine the CD of an average amide with an a-carbon of the alanine type. Figure 34 compares results from Toniolo and Bonora (1976).…”

From self‐assembled peptide‐ynes to peptide polyacetylenes and polydiacetylenes

“…In the CD experiments carried out in MeOH (at 1.5 mM concentration for all of the four compounds) we obtained different profiles for 1–4 . These distinct features are due to the different amino acid sequences (intrinsic chirality of each residue) and peptide lengths (formation of chiral secondary structures) characteristic of peptides 1–4 accompanied by the presence in 2–4 of the Phe benzyl chromophores, the electronic transitions of which in the far‐UV region are known to overlap those of the peptide group . In THF, however, all of the four compounds exhibited similar CD curves with an intense negative maximum at 230 nm which we attributed to a β‐sheet‐like conformation (Figure D) .…”

Enantioselective Merger of Aminocatalysis with π‐Lewis Acid Metal Catalysis: Asymmetric Preparation of Carbo‐ and Heterocycles

“…The far‐UV CD spectrum of the Ac/O t Bu‐blocked L ‐Tle homohexamer in TFE (2,2,2‐trifluoroethanol) exhibits a strong negative maximum below 200 nm accompanied by a negative shoulder near 225 nm (Figure 2). This pattern, which does not change over the temperature range from 25 to 0 °C (spectra not shown), is indicative of an unordered peptide conformation 53. Upon addition of water to the TFE solution, the CD spectrum of this highly hydrophobic peptide changes significantly, eventually (in a TFE/H 2 O 20:80 solvent mixture) assuming the shape typical of a β sheet‐like conformation (a negative maximum at 222 nm followed by a positive maximum near 207 nm) 54.…”