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

1976 ◽  
Vol 54 (1) ◽  
pp. 70-76 ◽  
Author(s):  
Claudio Toniolo ◽  
Gian Maria Bonora
Keyword(s):  
Circular Dichroism ◽  
Solvent Polarity ◽  
Guanidinium Chloride ◽  
Negative Band ◽  
Circular Dichroic Spectrum ◽  
Internal Peptide ◽  
Circular Dichroïsm ◽  
Sulfur Containing ◽  
Circular Dichroic ◽  
Molar Ellipticity

The contribution to the circular dichroism of L-Ala-L-Ala, L-Nva-L-Nva, L-Val-L-Val, L-Leu-L-Leu, L-Ile-L-Ile, L-Cys(Me)-L-Cys(Me), L-Met-L-Met, and L-Phe-L-Phe internal peptide chromophores in 1,1,1,3,3,3-hexafluoropropan-2-ol were calculated 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 sulfur-containing peptides, each of the L-configuration, show a negative band at 2l5–230 nm accompanied by a more intense negative band near 200 nm. A structured weak 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 spectrum of L-Phe-L-Phe internal peptide chromophore. The effect of solvent polarity is discussed in the case of L-Val-L-Val and L-Ala-L-Ala internal peptide chromophores.Among the protected homo-trimers and tetramers only those of L-alanine are soluble in aqueous 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.

scholarly journals The nature of the circular-dichoric spectra of complexes between ribonuclease A and nucleotides

1977 ◽  
Vol 167 (3) ◽  
pp. 749-757 ◽  
Author(s):  
S M Dudkin ◽  
L V Karabashyan ◽  
M Y Karpeisky ◽  
S N Mikhailov ◽  
N S Padyukova ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Ribonuclease A ◽  
Circular Dichroic Spectrum ◽  
Nucleotide Conformation ◽  
Anti Conformation ◽  
Two Factors ◽  
Wavelength Absorption ◽  
Comparison Of The Results ◽  
Circular Dichroïsm ◽  
Circular Dichroic

The circular-dichroism and proton-magnetic-resonance spectra of complexes of ribonuclease A with dihydrouridine 3′-phosphate, 2′- and 3′-CMP, arabinosyl-3′-CMP, 1-(2-hydroxyethyl)cytosine 2′-phosphate and 1-(3-hydroxypropyl)cytosine 3′-phosphate were studied. Comparison of the results shows that non-additivity of the circular-dichroic spectrum of an enzyme-nucleotide complex may be due to: (a), alteration of the circular dichroic spectrum of the nucleotide under the influence of the asymmetric protein matrix (induced dichroism), and (b) a change in the nucleotide conformation. The contribution of each of the two factors was estimated to calculate the circular-dichoroic spectra of 2′-CMP and 3′-CMP in complex with ribonuclease A. 3′-CMP in this complex was characterized by negative circular dichroism in the long-wavelength absorption band of the nucleotide, whereas 2′-CMP was characterized by positive circular dichroism. Since both nucleotides in the complex are known to be in an anti conformation, it follows that even small changes in the conformation considerably modify the circular-dichroic spectrum of the nucleotide in complex with the enzyme.

Organic photodiodes from homochiral l-proline derived squaraine compounds with strong circular dichroism

2017 ◽  
Vol 19 (10) ◽  
pp. 6996-7008 ◽  
Author(s):  
Matthias Schulz ◽  
Majvor Mack ◽  
Oliver Kolloge ◽  
Arne Lützen ◽  
Manuela Schiek
Keyword(s):  
Circular Dichroism ◽  
Polarized Light ◽  
Active Layers ◽  
Circular Dichroïsm ◽  
Circular Dichroic ◽  
Circular Polarized Light

We demonstrate the feasibility of inserting highly circular dichroic active layers into an organic photodiode as a potential detector for circular polarized light.

scholarly journals Optical properties and denaturation by guanidinium chloride and urea of the adenosine triphosphatase of Micrococcus lysodeikticus. A comparison of four molecular forms of the enzyme

1977 ◽  
Vol 161 (2) ◽  
pp. 321-331 ◽  
Author(s):  
M Nieto ◽  
J A Ayala
Keyword(s):  
Circular Dichroism ◽  
Adenosine Triphosphatase ◽  
Quaternary Structure ◽  
Molecular Form ◽  
Polyacrylamide Gel Electrophoresis ◽  
Protein A ◽  
Molecular Forms ◽  
Guanidinium Chloride ◽  
Micrococcus Lysodeikticus ◽  
Circular Dichroïsm

1. The fluorescence and circular dichroism of four homogeneous preparations of ATPase (adenosine triphosphatase) from Micrococcus lysodeikticus differing in molecular structure and enzymic properties were examined at pH 7.5 and 25 degrees. Emission was maximum at 325 and 335 nm and the relative intensities at these wavelengths may be used to characterize the different ATPase preparations. The circular-dichroism spectra exhibited negative extrema at 208 and 220 nm, and the relative value of the molar ellipticity at these wavelengths was also different for each molecular form of the enzyme. 2. The four preparations undergo two consecutive major unfolding transitions in guanidinium chloride (midpoints at 0.94 and 1.5 M denaturant), with concomitant destruction of the quaternary structure of the protein. A comparatively minor alteration in the ATPase structure also occurred in 0.05-0.2M-guanidine and led to complete inactivation of the enzyme. The inactivation and the first unfolding transition were reversible by dilution of the denaturant; the transition with midpoint at 1.5M-guanidine was irreversible. 3. Similar results were obtained in urea, except that the successive transitions had midpoints at concentrations of denaturant of 0.4, 2.0 and 4.5M. Low concentrations of urea caused a noticeable activation of the enzyme activity and alterations of the electrophoretic mobility of the ATPase. 4. A model is proposed in which one of the major subunits, alpha, is first dissociated and unfolded reversibly by the denaturants, followed by the irreversible unfolding and dissociation of the other major subunit, beta, from subunit delta and/or the components of relative mobility 1.0 in dodecyl sulphate/polyacrylamide-gel electrophoresis (rho).

scholarly journals Thermal denaturation of Micrococcus lysodeikticus adenosine triphosphatase. Influence of temperature on the circular dichroism, fluroescence and enzymic activity of the protein

1978 ◽  
Vol 169 (2) ◽  
pp. 371-380 ◽  
Author(s):  
J A Ayala ◽  
M Nieto
Keyword(s):  
Circular Dichroism ◽  
Adenosine Triphosphatase ◽  
Thermal Denaturation ◽  
Enzymic Activity ◽  
Intrinsic Fluorescence ◽  
Guanidinium Chloride ◽  
Subunit Dissociation ◽  
Micrococcus Lysodeikticus ◽  
Maximum Stability ◽  
Circular Dichroïsm

The soluble ATPase (adenosine triphosphatase) from Micrococcus lysodeikticus underwent a major unfolding transition when solutions of the enzyme at pH 7.5 were heated. The midpoint occurred at 46 degrees C when monitored by changes in enzymic activity and intrinsic fluorescence, and at 49 degrees C when monitored by circular dichroism. The products of thermal denaturation retained much secondary structure, and no evidence of subunit dissociation was detected after cooling at 20 degrees C. The thermal transition was irreversible, and thiol groups were not involved in the irreversibility. The presence of ATP, adenylyl imidodiphosphate, CaCl2 or higher concentrations of ATPase conferred stability against thermal denaturation, but did not prevent the irreversibility one denaturation had taken place. In the presence of guanidinium chloride, thermal denaturation occurred at lower temperatures. The midpoints of the transition were 45 degrees C in 0.25 M-, 38 degrees C in 0.5 M-and 30 degrees C in 0.75 M-denaturant. In the highest concentration of guanidinium chloride a similar unfolding transition induced by cooling was observed. Its midpoint was 9 degrees C, and the temperature of maximum stability of the protein was 20 degrees C. The discontinuities occurring the the Arrhenius plots of the activity of this enzyme had no counterpart in variations in the far-u.v. circular dichroism or intrinsic fluorescence of the protein at the same temperature.

scholarly journals Fluorescence and circular-dichroism studies on the Streptomyces R61 dd-carboxypeptidase–transpeptidase. Penicillin binding by the enzyme

1973 ◽  
Vol 135 (3) ◽  
pp. 493-505 ◽  
Author(s):  
Manuel Nieto ◽  
Harold R. Perkins ◽  
Jean-Marie Frère ◽  
Jean-Marie Ghuysen
Keyword(s):  
Circular Dichroism ◽  
Thermal Denaturation ◽  
Penicillin G ◽  
Affinity Binding ◽  
Guanidinium Chloride ◽  
Positive Maximum ◽  
Peptide Substrates ◽  
High Affinity ◽  
Circular Dichroïsm ◽  
New Hypothesis

The circular dichroism of the dd-carboxypeptidase–transpeptidase from Streptomyces R61 shows in the near u.v. a set of weak extrema at 289nm (positive) and at 282, 275 and 268nm (all negative). In the far u.v. it shows negative extrema at 217–218 and 208nm, crossover at 202nm and a positive maximum at about 194nm. The u.v. absorption of the enzyme shows it to contain tyrosine and tryptophan in approx. 3.4:1 ratio. The enzyme is fluorescent with a maximum emission at 318–320nm. The near-u.v. circular dichroism of the protein is extensively affected by binding of penicillin G, but the far u.v. is unaffected. Binding of the antibiotic also causes quenching of the fluorescence of the enzyme. The latter effect has been used to study the binding of penicillin G to the enzyme and the influence exerted upon it by salts, denaturants and peptide substrates and inhibitors. High-affinity binding of penicillin appears to be comparatively slow and reversible, and can occur under conditions in which the protein is enzymically inactive. The thermal denaturation of the enzyme in guanidinium chloride at pH7 is affected by binding of the antibiotic. The presence of even large concentrations of β-mercaptoethanol neither impaired the activity of the enzyme nor prevented its inhibition by penicillin G or cephalosporin C. A new hypothesis for the molecular mechanism of the interaction of the enzyme with penicillin is proposed.

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