Analysis of the ethidium bromide bound to DNA by photoacoustic and FTIR spectroscopy

Under physiological conditions B-form DNA is an exceedingly stable structure. However, experimental evidences obtained through nuclear magnetic resonance and fluorescence anisotropy suggest that the structure of the double helix fluctuates substantially. We describe photoacoustic phase modulation frequency measurements of ethidium bromide (Eb) with calf thymus, DNA. As in fluorescence phase modulation measurements, we used an intercalating dye as a probe; however, we monitored the triplet excited state lifetime at different ionic strengths. The triplet lifetime of Eb varied from about 0.30 ms, with no DNA present, to 20 ms, (at a DNA:Eb molar ratio of 5). With salt titration, this value falls, to about 2.0 ms. This result suggests, a strong coupling between the phenantridinium ring of the ethidium and the base pairs because of the stacking movement of the DNA molecule under salt effect. This, effect may be understood considering DNA as a polyelectrolyte. The counterions, in the solution shield the phosphate groups, reducing the electrostatic repulsion force between them, hence compacting the DNA molecule. The results from Fourier transform infrared demonstrated two important bands: 3187 cm(-1) corresponding to the symmetric stretching of the NH group of the bases, and 1225 cm(-1) corresponding to the asymmetric stretching of phosphate groups shifted toward higher wavenumbers, suggesting a proximity between the intercalant and base pairs and a modification of the DNA backbone state, both induced by salt accretion.

SOME CONSEQUENCES OF A SYMMETRY IN STRONG DISTRIBUTIONS

Some polynomials and interpolatory quadrature rules associated with strong Stieltjes distributions are considered, especially when the distributions satisfy a Certain symmetric property. (C) 1995 Academic Press, Inc.

Electronic and structural properties of the (001) SrZrO3 surface

The structural and electronic properties of SrZrO3 selected surfaces were investigated by means of density functional theory applied to periodic calculations at B3LYP level. The relaxation effects for two symmetric and asymmetric terminations are analyzed. The electronic and energy band properties are discussed on the basis of band structure as well density of states. There is a more significant rumpling in the SrO as compared to the ZrO2 terminated surfaces. The calculated indirect gap is 4.856, 4.562, 4.637 eV for bulk, ZrO2 and asymmetric terminations, respectively. The gap becomes direct; 4.536 eV; for SrO termination. The contour in the (110) diagonal plane indicates a partial covalent character between Zr and 0 atoms for the SrO terminated surface. (c) 2007 Elsevier B.V. All rights reserved.

Fluctuations of doublet splittings using the annular billiard

We study the statistical distribution of quantum energy splittings due to a dynamical tunneling. The system. The annular billiard, has whispering quasimodes due to a discrete symmetry that exists even when chaos is present in the underlying classical dynamics. Symmetric and antisymmetric combinations of these quasimodes correspond to quantum doublet states whose degeneracies decrease as the circles become more eccentric. We construct numerical ensembles composed of splittings for two distinct regimes, one which we call semiclassical for high quantum numbers and high energies where the whispering regions are connected by chaos, and other which we call quantal for low quantum numbers, low energies, and near integrable where dynamical tunneling is not a dominant mechanism. In both cases we observe a variation on the fluctuation amplitudes, but their mean behaviors follow the formula of Leyvraz and Ullmo [J. Phys. A 29, 2529 (1996)]. A description of a three-level collision involving a doublet and a singlet is also provided through a numerical example.

Effect of Different Solvent Ratios (Water/Ethylene Glycol) on the Growth Process of CaMoO4 Crystals and Their Optical Properties

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Damage Characterization Using Guided-Wave Linear Arrays and Image Compounding Techniques

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Robust Bayesian analysis of heavy-tailed stochastic volatility models using scale mixtures of normal distributions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Dinuclear Azide-Bridged Copper(II) Complex as Building Block for the Assembly of a 2D-Supramolecular Array

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)