Poly(acrylic acid)-block-poly(l-valine):  Evaluation of β-Sheet Formation and Its Stability Using Circular Dichroism Technique

2007 ◽  
Vol 8 (9) ◽  
pp. 2801-2808 ◽  
Author(s):  
A. Sinaga ◽  
T. A. Hatton ◽  
K. C. Tam
Keyword(s):  
Circular Dichroism ◽  
Acrylic Acid ◽  
Circular Dichroïsm ◽  
Β Sheet ◽  
Poly Acrylic Acid

Preparation of Polypeptide-Dye Multilayers by an Electrostatic Assembly Process

1994 ◽  
Vol 351 ◽  
Author(s):  
Thomas M. Cooper ◽  
L. Campbell Angela ◽  
Carol Noffsinger ◽  
Janelle Gunther-Greer ◽  
Robert L. Crane ◽  
...  
Keyword(s):  
Thin Films ◽  
Circular Dichroism ◽  
Glutamic Acid ◽  
Congo Red ◽  
Copper Phthalocyanine ◽  
Electrostatic Assembly ◽  
Amino Silane ◽  
Spectrum Characteristic ◽  
Circular Dichroïsm ◽  
Β Sheet

ABSTRACTTo develop novel optical thin films, we have prepared self-assembled polypeptide films by an electrostatic process. The films were placed on a glass slide previously silanized by an amino silane and given a positive charge by immersion in aqueous acid. Subsequent immersion of the slide in aqueous anionic solutions of either poly(L-glutamic acid), congo red, copper phthalocyanine tetrasulfonic acid or p-nitroaniline-modified poly(L-glutamic acid) resulted in deposition of the anions on the surface. Following anionic immersion, the slides were dipped into a cationic poly(L-lysine) solution. Alternate dipping into anionic and cationic solutions yielded multilayers. The thin films were characterized by optical absorption and circular dichroism. The optical density increased with dipping cycles. Circular dichroism measurements of the thin films showed induced dichroism of the congo red and phthalocyanine-containing films, suggesting formation of a locally ordered dye-polypeptide complex. Solution circular dichroism measurements of the polypeptides indicated a coil conformation, while poly(Lglutamic acid)/poly(L-lysine) complexes showed circular dichroism spectrum characteristic of a β-sheet.

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.

Nature of ligand affinity and dimerization of corticotrophin-releasing factor-binding protein may be detected by circular dichroism

1996 ◽  
Vol 16 (1) ◽  
pp. 39-44 ◽  
Author(s):  
P J Lowry ◽  
S C Koerber ◽  
R J Woods ◽  
S Baigent ◽  
S Sutton ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Binding Protein ◽  
Difference Spectra ◽  
Ligand Affinity ◽  
Corticotrophin Releasing Factor ◽  
Negative Change ◽  
Α Helix ◽  
Natural Peptides ◽  
Circular Dichroïsm ◽  
Β Sheet

ABSTRACT As the association of corticotrophin-releasing factor (CRF) with its binding protein (BP) to form a dimer complex (CRF2/BP2) appears to be dependent on the nature of the ligand we have compared the circular dichroism difference spectra after association of the BP with ovine (o) CRF, human (h) CRF and the α-helical CRF(9–41) antagonist. All three ligands caused a negative change in molar ellipticity above 210 nm, with oCRF having the least and hCRF the greatest effect. Below 210 nm there was a marked divergence of difference spectra, with the reaction with the natural peptides, hCRF and oCRF, resulting in a positive change in ellipticity, whilst that with the antagonist produced a negative change. In view of the BP spectrum indicating predominantly β-sheet and the peptides showing mainly α-helix these results were interpreted as the changes above 210 nm being due to dimerization and below 210 nm to a change in the conformation of ligand on binding. The opposite change in α-helicity of the antagonist observed on binding compared with the two natural CRF peptides could have fundamental pharmacological implications.

Alpha and beta conformations of water soluble sequential iso polypeptides

1988 ◽  
Vol 53 (11) ◽  
pp. 2825-2832 ◽  
Author(s):  
Bernard Barbier ◽  
Margarita Perello ◽  
André Brack
Keyword(s):  
Circular Dichroism ◽  
Water Soluble ◽  
Helical Conformation ◽  
Molecular Weights ◽  
Helix Formation ◽  
Α Helix ◽  
Circular Dichroïsm ◽  
Β Sheet ◽  
Protected Peptides

Alternating poly(Leu-Lys) and its isopolypeptide poly(Leu-Lys-Lys-Leu) were synthesized via polycondensation of p-nitrophenyl esters of the corresponding protected peptides. Addition of one equivalent of 1-hydroxybenzotriazole and varying amounts of a tertiary base allowed to control the molecular weights of the samples. The conformation of the water soluble polypeptides was investigated by circular dichroism. Poly(Leu-Lys) adopts a β-sheet conformation in the presence of salt while poly(Leu-Lys-Lys-Leu) adopts an α-helical conformation. For polypeptides based on a 1 : 1 composition of hydrophobic (A) and hydrophilic (B) residues, the shortest repeat for the formation of a β-sheet is -AB- whereas -AABB- represents the shortest repeat for an α-helix formation.

Study of the Effect of Electric Field on Superoxide Dismutase Activity by Spectroscopy

2011 ◽  
Vol 236-238 ◽  
pp. 2445-2448 ◽  
Author(s):  
Qiang Xu ◽  
Miao Wang ◽  
Zhi Huai Yang
Keyword(s):  
Circular Dichroism ◽  
Electric Field ◽  
Biological Effect ◽  
Random Coil ◽  
Sod Activity ◽  
Electric Treatment ◽  
Helix Structure ◽  
Α Helix ◽  
Circular Dichroïsm ◽  
Β Sheet

After the SOD was treated with different strength of electric field, the interactional mechanism of electric field on SOD activity was studied by circular dichroism. The activity of SOD was enhanced under the treatment by different strength of electric field. Circular dichroism spectra showed that the secondary structure of SOD was greatly changed by electric field, as β-sheet and β-turn contents decreased, while α-helix and random coil contents increased. It was considered that the increase of the α-helix structure near the active center would lead to the inactivation of SOD. The result of this study has important meaning to explain the biological effect of electric treatment seeds.

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