Interaction des Ions Métalliques avec le DNA. II. Adsorption préférentielle de l'Ion césium par les Acides nucléiques

✍ Scribed by F. Doppler-Bernardi; M. Daune

• Publisher: Wiley (John Wiley & Sons)
• Year: 1969
• Tongue: English
• Weight: 564 KB
• Volume: 7
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1969.360070505

✦ Synopsis

Interaction des Ions

Mgtalliques avec le DNA. 11. Adsorption prgfihentielle de 1'Ion c6sium par les Acides nuclgiques F. DOPPLER-BERNARD1 et M. DAUNE, Centre de Recherches sur Zes Macromoldcules, Strasbourg, France

Synopsis

Preferential adsorption of cations occurs in the solvated shell surrounding polyanions, especially polynucleotides and nucleic acids. The solvation parameter r is determined from sedimentation coefficients which are considered as picnometric determinations of the specific volume of the sample. By comparing two identical concentrations (0.1M) of monovalent salts, NaCl and CsC1, and using the model of DNA described in the preceding paper, one can relate the ratio S C . / ~N , to solvation parameters rcs and r N a . On the other hand, I' can be related to the difference of energy W , between cation and water, to be extracted from the solution and placed in the vicinity of the polyanion. One finds generally a preferential solvation of the polarizable caesium ion by means of London-van der Waals interactions with bases. With reasonable assumptions, an estimate of W can be made, and the predicted value of r can be compared to the experimental one. An average of six sites is found around each base in a single-stranded polymer, but only one in the double-stranded structure. The amount of secondary structure can thus be estimated from the simple measurement of the ratio of two sedimentation constants.