MONOCHROMATIC ULTRAVIOLET ACTION SPECTRA AND QUANTUM YIELDS FOR INACTIVATION OF T1 AND T2 ESCHERICHIA COLI BACTERIOPHAGES

Much of the interest in the biological effects of ultraviolet radiation arises from the fact that different wavelengths are absorbed selectively by different chemical groups. The possibility exists, therefore, of gaining some clues as to the cellular constituents that absorb the ultraviolet radiation leading to a particular effect by comparing the efficiency of different wavelengths in producing the effect-the action spectrum-with the absorption spectra of different cellular constituents. Thus, on the basis of the relative bactericidal efficiency and absorption of different regions of the ultraviolet spectrum, Henri as early as 1914 was led to the hypothesis that the seat of the bactericidal effect was in the proteins of the nucleus. The further possibility of inducing heritable modifications by sublethal exposures to ultraviolet radiation was evident to her and was realized, apparently, in experiments with Bacillus anthracis designed expressly to test this hypothesis. Gates (1928) was the first to publish a biological action spectrum determined by the more refined technique of employing monochromatic beams of ultraviolet light. His results on the relative bactericidal effectiveness of different wavelengths focused attention on the nucleic acids. Since that time, the action spectrum technique has been applied to a number of the biological effects of ultraviolet radiation. Giese (1945), Loofbourow (1948), and Blum (1950) reviewed the different types of action spectra observed. Action spectra for the inactivation of bacteriophages have been published by a number of authors (Gates, 1934; Fluke and Pollard, 1949; Franklin et al., 1953). In general, a maximum of efficiency at about 2600 A is observed, suggest-