Accession Number : ADA187143

Title :   Properties of DNA in the Far Infrared.

Descriptive Note : Annual rept. Jul 86-Jul 87,

Corporate Author : ARIZONA STATE UNIV TEMPE DEPT OF PHYSICS

Personal Author(s) : Lindsay, S M

PDF Url : ADA187143

Report Date : 12 Oct 1987

Pagination or Media Count : 10

Abstract : We have carried out transmission measurements as a function of power for DNA films irradiated near the absorption maximum at 43/cm using the Santa Barbara Free Electron Laser. Initial results show no non-linear effects, such as bleaching, up to power densities of a few kW/sq cm. An experiment to search for unstacking of DNA bases when the molecule is exposed to intense radiation near the 'melting mode' frequency (approx. 80/cm) is nearing completion: exposure to available FEL power does not cause significant heating of the solution. Phonon damping mechanisms are being investigated in the range 0.1 to 200/cm by both Raman and Brillioun spectroscopy measurements made as a function of temperature and mode frequency. Coupling the relaxational motion of the hydration shell appears to be the main damping mechanism. At low (GHz.) frequencies, Debye-like reorientation of the bound water dominates the loss process, while at much higher frequencies, the hydrogen-bond breaking relaxations may contribute.

Descriptors :   *DEOXYRIBONUCLEIC ACIDS, *FAR INFRARED RADIATION, *RADIATION EFFECTS, DAMPING, DENSITY, EXPOSURE(GENERAL), FILMS, FREQUENCY, HEATING, HYDRATION, INTENSITY, LOSSES, MEASUREMENT, MELTING, NONLINEAR SYSTEMS, PHONONS, POWER, RADIATION, RELAXATION, SOLUTIONS(GENERAL), SPECTROSCOPY, TRANSMITTANCE, WATER, OPTICAL PROPERTIES, MOLECULAR STRUCTURE, RADIATION ABSORPTION, FREE ELECTRON LASERS

Subject Categories : Biochemistry
      Genetic Engineering and Molecular Biology
      Radiobiology

Distribution Statement : APPROVED FOR PUBLIC RELEASE