Studies on nucleic acids. VIII. Changes in the stability of DNA secondary structure by interaction with divalent metal ions
✍ Scribed by H. Venner; Ch. Zimmer
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1966
- Tongue
- English
- Weight
- 828 KB
- Volume
- 4
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
The melting temperature of a natural DNA is decreased in the presence of increasing amounts of copper ions, whereas other divalent metal ions stabilize the DNA secondary structure a t low ionic strength. At 1.28 X lO-4M, Cuz+ produces a decrease of T,,, depending on base composition. At very low Cu*+ concentrations (0.5 Cuz+/2 DNA-P) a stabrlization of the DNA conformation appears due to an interaction between Cu*+ and phosphate groups of the DNA molecule. In this case the normal trend of GC deperidence of T, exists similar to that with Na+ and Mg*+ aa counterions. If copper ions are in excw, the observed destabilization k stronger for DNAs rich in guanine plus cytosine than for those rich in adenine plus thymine. A sharp decrease of T,,, occurs between 0.5-0.8 Cu2+/2 DNA-P and 1.5 Cuz+/2 DNA-P. The breadth of the transition decreases at high Cup+ concentration with further addition of copper ions. Denaturation and renaturation experiments indicate that Cue + ions exceeding the phosphate equivalents interact with the bases and reduce the forces of the DNA helix conformation. Evidence k presented, that the destabilization effect produced by Cue+ k possibly due to an interaction with guanine sites of the DNA molecule.
* Some of these results were first discussed at the meeting of Arbeitsgemeinschaft Biochemie Jena, October 17-19, 1963, and a brief report waa presented earlier.l** Furthermore an abstract of this work waa presented at the Universities of Koln (Inst. fur Genetik), Frankfurt/Main (Inst. fur Therapeutische Biochemie), Freiburg (Biochem. Inst. der Med. Fakultat and at the Med. Fomchungsanstalt der Max-Planck-Geeellschaft, Gottingen, in September 1964. 321
* It was necessary to develop special methods for DNA isolation, since in some cases the general method of Narmurl@ led to more unsatisfactory results than given in Table I.