THE DEPENDENCE OF PNEUMOCOCCAL TRANSFORMATION ON THE MOLECULAR WEIGHT OF DEOXYRIBOSE NUCLEIC ACID

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Abstract
Exposure of solutions of transforming factor to 9-kilocycle sound waves causes scissions of the molecules with a concomitant fall in transforming activity. The addition of S-(2-aminoethyl)isothiuronium bromide hydrogen bromide during sonic treatment eliminates inactivation of transforming factor by secondary effects. By plotting the logarithm of the relative transforming activity of the sonic fragments versus the reciprocal molecular weight and analyzing the curves by the conventional target theory, the critical molecular weight for streptomycin, erythromycin, and micrococcin was found to be 1 million. This value may reflect either the minimum size required for effective attachment to a bacterial site or the minimum size required for genetic incorporation, or a combination of both.