摘要：

Light scattering and low gradient viscometric studies of new sodium desoxypentose nucleate (DNA) samples from calf thymus have been carried out. These together with earlier measurements are interpreted on the basis of new values for the specific refractive index increment and the extinction coefficient. It is concluded that carefully prepared samples of DNA have a weight average molecular weight of about six million and a molecular shape resembling a stiff coil whose root-mean-square end-to-end separation is 5000 . and whose contour length is 20,000 . The following evidence corroborates these findings: (1) The molecular weight calculated fron the sedimentation constant-intrinisc viscosity formula of Mandelkern and Flory, (2) the end-to-end separation calculated from the Flory-Fox equation, (3) the agreement with the Riseman-Kirkwood relation between rotary diffusion constant and intrinsic viscosity for coils and (4) preliminary electron microscope studies by R. C. Williams. If intrinsic viscosity and rotary diffusion constants are interpreted in terms of an ellipsoid of revolution with no hydration axial ratios in the range of 400 to 500 are obtained but the literal interpretation of these values must be rejected.

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