RESULTS OF IRRADIATING SACCHAROMYCES WITH MONOCHROMATIC ULTRA-VIOLET LIGHT

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Abstract
II. Tests of the survival of yeast cells of 15 day and 24 hr. cultures indicate that the older resting cells are more resistant to ultra-violet irradiation effects than cells undergoing rapid cell division. The effects of temp. changes within the range of normal growth are small (temp. coeff. 1.10). Possible inhibitory effects due to the action of u.-v. radiation on the malt agar medium and to toxic substances diffused from cells killed by irradiation were not found. Within the range used (variation of the intensity up to 30%), the rate of absorption of quanta by the cell does not produce any marked change in the lethal effects observed.[long dash]III. The u.-v. absorption curve of Saccharomyces cerevisiae is approximated by plotting the incident energies required to cause "death" of 50% of the cells against the wave-length. The curve is essentially similar to absorption curves of certain enzymes and nucleoprotein derivatives. The suggestion is made that the effects of u.-v. irradiation may result from the absorption of energy by these nucleoproteins.

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