Aggregated DNA in ethanol solution

FEBS Letters

Rupprecht, Allan²  Piškur, Jure¹ 

[1] Department of Genetics, Institute of Molecular Biology, University of Copenhagen, Øster Farimagsgade 2A, DK-1353 Copenhagen K, Denmark;Division of Physical Chemistry, Arrhenius Laboratory, University of Stockholm, S-10691 Stockholm, Sweden

关键词: Nucleic acid;    Secondary structure;    Tertiary structure;    Denaturation;    Ethanol;    Aggregation;   

DOI  :  10.1016/0014-5793(95)01206-T

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

A recently developed mechanochemical method has provided a new, efficient tool for studies on the thermal stability and structure of aggregated DNA in ethanol-water solutions. At low ethanol concentrations DNA is fully soluble and is in the B form. However, with increasing ethanol concentration the melting temperature of DNA, T _m, decreases. At a critical ethanol concentration dependent on the nature and concentration of the counterion, aggregation of the DNA molecules sets in. This is reflected in a marked increase in T _m indicating that the aggregated DNA molecules are thermally more stable than the dissolved ones. However, they are still in the B form. In general, T _m of aggregated DNA also decreases with further increasing ethanol concentration and is dependent on the nature of the counterion, but T _m is not affected by the concentration of the counterion (excess salt) in the ethanol-water solution. When the ethanol concentration reaches the range of 70–80% (v/v), the B-to-A conformational transition occurs in the case of Na-, K- and CsDNA. Above this transition point the A form is more stable than the B form due to the reduced water activity and to increased interhelical interactions. At very high ethanol concentrations, above 85% and dependent on the nature of the counterion, a drastic change in the thermal behaviour is observed. Apparently such a strong interhelical interaction is induced in the aggregated DNA that the DNA is stabilized and cannot adopt a random coil state even at very high temperatures. This stability of DNA in the P form is fully reversed if the ethanol concentration is lowered and the activity of water, thereby, is restored.

【 授权许可】

Unknown