Rayleigh scattering of Mössbauer radiation in hydrated oriented DNA fibers

Abstract

SYNOPSISThe Rayleigh scattering of Mossbauer radiation has been measured on oriented hydrated fibres of A-NaDNA. The elastic and inelastic scattering intensities have been determined at different temperatures from 275 to 310 K in the Q range 0.7-3.3 k'. The elastic intensity has a main maximum at Q = 1.92 k' due to an ordered structure of water along the DNA double helices. From the temperature dependence of the elastic intensity under the water peak maximum, the mean square displacement of water oxygens in the direction parallel to the DNA axis has been deduced. It varies from 0.110 A' at 275 K up to 0.345 A' at 310 K. The thermal diffuse scattering intensity is also peaked at the same Q value of the elastic intensity, indicating the presence of coherent vibrational excitations propagating along the ordered water filaments.

Evidence for a new transition in polyribonucleotides from raman optical activity

“…30 Another interesting result comes from Rayleigh scattering of Mössbauer radiation in fibres of A-NaDNA used to probe ordered water structure along the DNA double helices which revealed that, in the temperature range 2-37°C, which is similar to the range for the ROA studies reported here, there is a rapid increase in the mean square atomic displacements of the water oxygen atoms in the direction parallel to the double helices. 31 Recently, there have been reports of transitions between conformational substates in a DNA oligonucleotide 32,33 and in single molecules of phenylalanine specific transfer RNA 34 detected from measurements of fluorescence lifetimes of attached dye molecules. In fact, the existence of conformational substates was already implied in earlier work on hydrogen-deuterium exchange in doublehelical RNA and DNA molecules because it was recognized that the exchange occurred within a distinct state generated by base-pair opening: 35,36 the open segments were modelled as mobile defects, associated with solitons, which can slide along the double helix with very small enthalpy change.…”

Mössbauer acquisition system for Rayleigh scattering experiments

“…This allows the experimental separation of the elastic and inelastic components of the radiation scattered on materials which do not contain Mössbauer isotopes. [2][3][4][5][6][7][8][9] It is obvious that in ordinary x-ray diffraction measurements, using an x-ray tube source, this separation is not possible. In particular, the RSMR makes possible the high precision determination of the mean square atomic displacement ͗u 2 ͘.…”

A PC-based set-up for Rayleigh scattering of Mössbauer radiation

“…The recoilless emission and absorption of low-energy gamma rays, combined with the high selectivity of the nuclear resonance absorption phenomenon, permits an energy resolution of a few 10 −8 eV. A scattering technique based on the Mössbauer effect has already been applied to solid state investigations [1][2][3][4][5][6][7][8][9][10][11]. However, experiments on Rayleigh scattering of Mossbauer radiation are difficult, essentially due to low brilliance of Mossbauer sources and practical arrangements for these kinds of measurements have not been described in detail in the literature.…”