Conformation studies on the sodium and cesium salts of calf thymus deoxyribonucleic acid (DNA)

✍ Scribed by Gerald Cohen; Henryk Eisenberg

• Publisher: Wiley (John Wiley & Sons)
• Year: 1966
• Tongue: English
• Weight: 611 KB
• Volume: 4
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1966.360040404

✦ Synopsis

Synopsis

$elutions of calf thymus NaRNA in 0.2M NaCl and CsDNA in 0.2M CsCl (fragmented by sonic irradiation to a molecular weighb of about 5 X 106) were examined by electron microscopy, light scattering, and viscosity measurements. Electron microscopy showed that the molecular fragments are rodlike in shape and that the distribution of their lengths is sharp (LJL,, -1.06). The weight-average number of nucleotides 2, per DNA molecule derived from light scattering was found to be in very good agreement with the value L, derived from electron microscopy. The z-average length L, derived from light scattering at 25OC. was found to be ahout 89% of the Corresponding value derived by electron microscopy. Similarly, the value of L, derived from intrinsic viscosity at 25OC. on the basis of a rodlike model was found to be about 87% of the corresponding value derived by electron microscopy. It is concluded that the molecules are slightly flexible and do not assume their full contour length in solution because of the disorienting effect of Brownian motion. The intrinsic viscosity was found to increase linearly with decreasing temperature toward a limiting value corresponding to the fully stretched length of the macromolecules at 0°K.; a reasonable value for the modulus of elasticity could be calculated. It was also found that no differences in conformation could be detected in the two systems CsDNA-0.2M CsCl and NaDNA-0.2M NaCl.