Synthesis and study of the conformational stability of sequential polypeptides containing δ-benzyloxycarbonyl-L-ornithine and benzyl esters of L-aspartic and L-glutamic acids

1978 ◽  
Vol 56 (5) ◽  
pp. 622-627 ◽  
Author(s):  
Nga Ho-Duc ◽  
Hubert Daoust ◽  
Serge St-Pierre
Keyword(s):  
Circular Dichroism ◽  
Conformational Stability ◽  
Helical Conformation ◽  
Dilute Solution ◽  
Coil Transition ◽  
Solution Methods ◽  
Benzyl Esters ◽  
Circular Dichroïsm

The synthesis of the sequential polypeptides (N-δ-Z-L-Orn-γ-BzI-L-Glu)n and (N-δ-Z-L-Orn-β-BzI-L-Asp)n by solution methods is described. Both polypeptides are α helical in chloroform as shown by circular dichroism. However, the conformation in this solvent is rather fragile, since small additions of TFA to a dilute solution of the polypeptides in chloroform is sufficient to cause the helix-to-coil transition, as demonstrated by cd and nmr. It is postulated that the low stability of the helical conformation is attributed, in this case, to a cooperative collapse of the ordered conformation.

Scanning microcalorimetry and circular dichroism study of melting of the natural polypeptides in the left-handed helical conformation

1993 ◽  
Vol 12 (1) ◽  
pp. 85-91 ◽  
Author(s):  
Alexander A. Makarov ◽  
Ivan A. Adzhubei ◽  
Irina I. Protasevich ◽  
Vladimir M. Lobachov ◽  
Natalia G. Esipova
Keyword(s):  
Circular Dichroism ◽  
Helical Conformation ◽  
Left Handed ◽  
Circular Dichroïsm

Oligopeptide-porphyrin interactions studied by circular dichroism spectroscopy: the effect of metalloporphyrin axial ligands on peptide matrix conformation

2008 ◽  
Vol 12 (12) ◽  
pp. 1270-1278 ◽  
Author(s):  
Vladimír Setnička ◽  
Jan Hlaváček ◽  
Marie Urbanová
Keyword(s):  
Aqueous Solution ◽  
Circular Dichroism ◽  
Conformational Changes ◽  
Helical Conformation ◽  
Compact Structure ◽  
Axial Ligands ◽  
Metal Derivatives ◽  
Derivatives Of ◽  
Circular Dichroïsm ◽  
Β Sheet

Vibrational (VCD) and electronic circular dichroism (ECD) spectroscopies were used to investigate non-covalent interactions between the cationic tripeptide L-lysyl-L-alanyl-L-alanine (KAA) and the anionic porphyrin meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) in aqueous solution. Also studied were the interactions between KAA and the three metal derivatives of TPPS (copper(II), iron(III), and manganese(III)), each of which has a different number of axial ligands. VCD spectra in the amide I' ( C = O stretching vibration) region are extremely sensitive to peptide conformation, and, consequently, provide direct information about the conformational changes of host oligopeptide matrices caused by electrostatic interaction with guest porphyrin molecules. We found that pure KAA adopts a left-handed polyproline II (PPII) helical conformation when dissolved in aqueous solution at near-neutral pH values. When mixed with metal-free TPPS under the same conditions, VCD intensities were markedly reduced in the amide I' region and a new negative band was observed at 1634 cm−1; both findings indicating the transition of the PPII conformation into a less compact structure having similarities to β-sheet, herein termed a β-sheet-like conformation. In the case of the metal derivatives of TPPS studied, only variations in the VCD intensities in the amide I' region were observed. Compared to the results for pure KAA, the binding of Cu (II) TPPS , which has no axial ligand, resulted in the greatest decrease in amide I' VCD intensity. Nevertheless, the shape of a VCD spectrum characteristic for a PPII conformation was maintained, thereby indicating the presence of an “extended” PPII conformation in the Cu (II) TPPS -KAA complex. Conversely, Mn (III) TPPS , which has two axial ligands, did not significantly affect the PPII conformation of KAA in the Mn (III) TPPS -KAA complex. The effects of the metalation and axial ligation of TPPS on the conformation of KAA in peptide-porphyrin complexes are discussed, together with the results of our ECD study.

Circular dichroism of aqueous solutions and gels of partial benzyl esters of the polysaccharide gellan

1993 ◽  
Vol 76 (1) ◽  
pp. 95-97 ◽  
Author(s):  
Vittorio Crescenzi ◽  
Mariella Dentini ◽  
Sergio Maschio ◽  
Maurizio Segatori
Keyword(s):  
Circular Dichroism ◽  
Aqueous Solutions ◽  
Benzyl Esters ◽  
Circular Dichroïsm

Protamines. VII. Circular Dichroism Study of Salmine A I

1981 ◽  
Vol 36 (3-4) ◽  
pp. 305-309 ◽  
Author(s):  
G. M. Bonora ◽  
F. Bertanzon ◽  
V. Moretto ◽  
C. Toniolo
Keyword(s):  
Aqueous Solution ◽  
Circular Dichroism ◽  
Statistical Methods ◽  
Basic Protein ◽  
Helical Conformation ◽  
Counter Ions ◽  
Conformational Preferences ◽  
Main Components ◽  
The Right ◽  
Circular Dichroïsm

Salmine A I, one of the components of the protamine from salmon, has been purified and characterized. The conformational preferences of salmine A I have been examined as a function of pH, added salts, presence of helix-supporting solvents, and temperature, using circular dichroism. It has been found that this small basic protein adopts predominantly an unordered conformation in aqueous solution. Addition of counter-ions, in particular perchlorate, and 2-chloroethanol induces to various extents the onset of the right-handed α-helical conformation. The results are discussed in comparison with those previously reported on the three main components of clupeine, the protamine from herring, and with the published conformational predictions by various statistical methods

Circular dichroism of helical polynucleotide chains

1967 ◽  
Vol 297 (1448) ◽  
pp. 150-162 ◽  
Keyword(s):  
Circular Dichroism ◽  
Nucleic Acids ◽  
Helical Structure ◽  
Optical Rotatory Dispersion ◽  
Random Coil ◽  
Helical Conformation ◽  
Polyadenylic Acid ◽  
V Region ◽  
Circular Dichroïsm ◽  
Circular Dichroic

In contrast to relatively well developed experimental and theoretical studies on polypeptides and proteins (see Gratzer 1967 and McLachlan 1967, this volume) the investigation of optical activity of polynucleotides and nucleic acids were very restricted. The optical rotatory dispersion curves of polynucleotides examined in the visible and near u. v. fit one-term Drude equation regardless of the conformation (Fresco 1961; Levedahl & James 1957; Ts’o, Helmkamp & Sander 1962). Recent circular dichroism (c. d.) measurements of several polynucleotides and nucleic acids (figure 1) indicated clearly the presence of dichroic bands in the u. v. region of base absorption which can be related to the dissymmetrical helical conformation (Brahms 1963). The intensity of circular dichroic bands decreases strongly under the conditions in which the helical structure is unstable and goes to random coil form (Brahms 1964; Brahms & Mommaerts 1964). Thus polyadenylic acid (poly A ) is known according to X-ray data to exist at acid pH in a helical two strand and right handed conformation (Rich, Davies, Crick & Watson 1961). In acid solution the same polyadenylic acid exhibits strong circular dichroic bands which disappear at high temperature (figure 2).

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