EXAFS studies of the calcium salts of natural DNA and PolydA:PolydT

• Published in: Journal of inorganic biochemistry Vol. 29; no. 4; pp. 249 - 257
• Main Authors: Skuratovskii, I.Ya, Hasnain, S.S., Alexeev, D.G., Diakun, G.P., Volkova, L.I.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.04.1987; Elsevier Science
• Subjects: Animals; Biological and medical sciences; Calcium; Chickens; DNA - blood; Erythrocytes - analysis; Fourier Analysis; Fundamental and applied biological sciences. Psychology; Interactions. Associations; Intermolecular phenomena; Molecular biophysics; Nucleic Acid Conformation; Poly dA-dT; Polydeoxyribonucleotides; Spectrum Analysis; X-Rays; Molecular association; Calcium Ions; Polydeoxyribonucleotide
• ISSN: 0162-0134; 1873-3344
• DOI: 10.1016/0162-0134(87)80032-6

Preliminary EXAFS experiments were carried out on film of the Ca salts of the synthetic polynucleotide polydA:polydT at 95%, 81%, and 76% relative humidity (r.h.) and for the Ca salt of chicken erythrocyte DNA at 81% r.h. (approximately 43% GC pairs). Detailed analysis of EXAFS data shows that the Ca 2+ ion is in fairly close proximity (within 4 Å) to a number of phosphorous atoms. This is in contradiction with the recently proposed model, which assumes a close coordination between the cations and the purine and pyrimidine bases deep inside the polynucleotide molecule, so that the distance to the nearest phosphorous atoms must not be less than 5 Å. Instead, the EXAFS results suggest that the Ca 2+ ions are, for the most part, located at the periphery of individual polydA:polydT (or DNA) molecules, possibly serving as intermolecular links.