Circular Dichroism of Nitrate Esters: A Planar Symmetry Rule for the Nitrato Chromophore

1972 ◽  
Vol 50 (11) ◽  
pp. 1719-1728 ◽  
Author(s):  
R. E. Barton ◽  
L. D. Hayward
Keyword(s):  
Circular Dichroism ◽  
Carbon Atom ◽  
Point Group ◽  
Symmetry Plane ◽  
Solvent Polarity ◽  
Molecular Geometry ◽  
Absorption Bands ◽  
Nitrate Esters ◽  
Planar Symmetry ◽  
Circular Dichroïsm

Conformational analysis of nitrate esters based on X-ray and spectroscopic data showed the nitrato group to be coplanar with the α carbon atom and, in the preferred rotamer, the nitro moiety to be antiperiplanar to the β carbon atom. Three optically active absorption bands not apparent in the isotropic electronic spectra were resolved in the circular dichroism spectra. Band I (270 nm) reflected nitrato group libration changing sign and magnitude with changes in temperature and solvent polarity. Differences in rotatory strength of band III (210 nm) for cis- and trans-dinitrates indicated transition moment coupling. A planar symmetry rule for chromophores in the Cs point group correlated the molecular geometry and sign of band II for 42 nitrate esters: when the lowest-energy rotamer of the nitrate ester is viewed down the O—C bond with the nitro group uppermost rotatory contributions to band II (230 nm) are positive for perturbing atoms to the right and negative for those to the left of the nitrato symmetry plane.

Circular Dichroism and Ultraviolet Absorbance of Calf Thymus DNA in Presence of CH3HgOH

1979 ◽  
Vol 34 (3-4) ◽  
pp. 259-265 ◽  
Author(s):  
Michael S. Clegg ◽  
Dieter W. Gruenwedel
Keyword(s):  
Circular Dichroism ◽  
Absorption Band ◽  
Calf Thymus Dna ◽  
Absorbance Spectrum ◽  
Absorption Bands ◽  
Long Wavelength ◽  
Ultraviolet Absorbance ◽  
Rotational Strength ◽  
Calf Thymus ◽  
Circular Dichroïsm

Abstract The changes that one observes upon the addition of CH3HgOH in the circular dichroism spec­trum and ultraviolet absorbance spectrum of native calf thymus DNA, dissolved in buffered (pH 6.8) solutions of Na2SO4 at pNa 2.0, 1.5, 1.0, and 0.0, respectively (pNa = - log [Na+]), are shown to be due to denaturation brought about by the organomercurial interacting with the base moieties of the polymer. The changes are characterized by an extensive shift of both spectra to longer wavelengths, by a decrease of the rotational strength of the long-wavelength positive dichroic absorption band, and by an increase in the UV absorbance at λmax . Both the hyperchromicity Hλ of calf thymus DNA and the normalized decrease of the rotational strength of its long-wavelength positive dichromic band, Ω , display cooperativity when plotted against the methylmercury concentration pM (pM = - log [CH3HgOH]added) at a given salt strength. Rotational strength data, evaluated by integration of the area under the positive and negative dichroic absorption bands, have been tabulated for selected values of pNa and pM. They are compared with data available from the literature. In absence of CH3HgOH, and with varying salt strength, native calf thymus DNA exhibits alterations in the long-wavelength positive dichroic absorption band that are interpreted as representing B → C transitions in agreement with currently held views regarding their origin. Similar salt-induced alterations have been noted in the case of denatured DNA; their meaning in terms of DNA geometry remains unclear at this point in time.

scholarly journals Detection by low-temperature magnetic circular-dichroism spectroscopy of optical absorption bands due to molybdenum (V) in the form of xanthine oxidase giving the Desulpho Inhibited e.p.r. signal

1986 ◽  
Vol 233 (1) ◽  
pp. 107-110 ◽  
Author(s):  
J Peterson ◽  
C Godfrey ◽  
A J Thomson ◽  
G N George ◽  
R C Bray
Keyword(s):  
Circular Dichroism ◽  
Low Temperature ◽  
Xanthine Oxidase ◽  
Absorption Spectra ◽  
Magnetic Circular Dichroism ◽  
Electronic Absorption Spectra ◽  
Visible Region ◽  
Absorption Bands ◽  
Magnetic Circular Dichroism Spectroscopy ◽  
Circular Dichroïsm

The magnetic circular-dichroism (m.c.d.) spectra in the temperature range 1.5-100 K and the electronic absorption spectra at 4.2 and 295 K were measured for a number of desulpho xanthine oxidase derivatives. There were no significant differences between the absorption spectra that could be attributed to molybdenum. However, the visible-region m.c.d. spectrum of the ethanediol-treated metalloprotein (which gives rise to the Desulpho Inhibited e.p.r. signal) contained features assignable to Mo(V) absorption bands. This is the first report of the detection of optical bands of Mo(V) in an enzyme in the presence of other chromophoric centres.

Magnetic circular dichroism in the A, B and C absorption bands of KBr: In+

1976 ◽  
Vol 42 (3) ◽  
pp. 530-532 ◽  
Author(s):  
P.W.M. Jacobs ◽  
M.J. Stillman ◽  
K. Oyama Gannon ◽  
D.J. Simkin
Keyword(s):  
Circular Dichroism ◽  
Magnetic Circular Dichroism ◽  
Absorption Bands ◽  
Circular Dichroïsm

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.

Solvation dependence observed in the electronic dissymmetry factor spectra: how much information are we missing by analyzing the circular dichroism spectra alone?

2016 ◽  
Vol 18 (20) ◽  
pp. 13912-13917 ◽  
Author(s):  
Cody L. Covington ◽  
Prasad L. Polavarapu
Keyword(s):  
Circular Dichroism ◽  
Absorption Spectra ◽  
Solvent Polarity ◽  
Circular Dichroism Spectra ◽  
Electronic Circular Dichroism ◽  
Circular Dichroïsm

The electronic dissymmetry factor (EDF) spectra reveal that for [1,1′-binaphthalene]-2,2′-diol the experimental EDF spectra show solvent polarity dependent effects that are not apparent in the electronic circular dichroism or absorption spectra.

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