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MICROWAVE RESONANCES IN DNA
Citation:
Lindsay, S. MICROWAVE RESONANCES IN DNA. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/1-90/007 (NTIS PB90261520), 1990.
Description:
This report describes spectroscopic studies of DNA which were undertaken to better understand a physical basis for microwave absorption by this molecule. hree types of studies are described. ) The low frequency scattered light spectrum of DNA was studied by two methods. irst, Raman scattering of the vibrational modes of DNA films has studied down to about 4 wavenumbers (cm-1) using a high contrast grating monochrometer. he lowest lying vibrational mode was found at frequencies between 12 and 30 cm-1, depending upon the specific counter-ion, water content and crystal structure. econd, a tandem interferometer was used to study the spectrum from about 0.1 to 10 cm-1 (3 to 300 GHz). tudies of Li-DNA films and solutions of the plasmid pUC8 found no evidence of GHz resonances in the scattered light spectrum or in the Brillouin linewidths. ) The coupling of GHz acoustic modes to the hydration shell of DNA was studied via a coupled mode analysis of Brillouin spectra. he primary hydration shell relaxes at about 40 ps at room temperature and might permit resonances at frequencies between 20 and 200 GHz. owever, none were observed. ) Attempts to repeat experiments that appeared to show a resonance mode near 0.6 GHz were not successful. eature is seen in the spectrum of hydrated DNA near this frequency, but it may be due to overdamped torsional fluctuations of the bases making up the DNA.
