| Abstract: | The cross-sectional radius of gyration of the deoxyribonucleoprotein (DNP) threads was measured by small-angle X-ray scattering in a wide range of ionic strengths (from 0.0005 to 2 M NaCl). For DNP in a solution of low ionic strength, this value is 30 Å. The increase of ionic strength results in partial deproteinization of DNP, while the cross-sectional radius of gyration varies from 25 Å for DNP in 0.7 M NaCl to 10 Å for DNP in 2 M NaCl. It is suggested that gradual deproteinization by the increase of NaCl concentration causes conformational changes, which are associated with the alteration of the DNP superstructure. The data are interpreted on the basis of the superhelical model of DNA packing in DNP; however, the coexistence of superhelical and unfolded regions in the DNP structure is also a possibility. |
