WAVELENGTH DEPENDENCE FOR THE INACTIVATION OF ATP IN THE VACUUM-ULTRAVIOLET REGION ABOVE 140 nm

Radiation effects were investigated on the activity and the structure of adenosine triphosphate in the wavelength range from 140 nm to 260 nm, using monochromatized synchrotron radiation from the INS-SOR storage ring. The sample was irradiated as a thin film in vacuum. The activity of adenosine triphosphate decreased sharply below 180 nm as judged by the luminescence in the luciferin-luciferase assay. From the exponential decay of function, the cross-section for inactivation was calculated to be of the order of 10^-21 m²/photon in the range from 140 to 170 nm. No decrease was detected at wavelengths of 190 nm and above. The calculated quantum yield increased as the wavelength became shorter and reached to 0.20 at 150 nm. The release of adenine at 160 nm-irradiation was detected by thin layer chromatography; no adenosine diphosphate or adenosine monophosphate occurred. Only a trace of adenine was found after 190 nm-irradiation. These results indicate that the broad absorption peak for higher excitations attributable to the base moiety around 190 nm does not cause both structural and functional changes, while the absorption by the sugar-phosphate group produces the rupture of N -glycosidic bond, and probably leads to the loss of function.