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Double-stranded DNA in methanol-ethanol-buffer solvent system.

E Kay
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Abstract

DNA in a solvent system consisting of roughly equal volumes of methanol and ethanol and 5% buffer has a conservative circular dichroism (CD) spectrum of very low intensity above 220 nm and an increase of epsilon258 comparable to that of denatured DNA (about 40%). A direct comparison of this spectrum with the CD of single-stranded DNA reveals many differences, indicating DNA in this solvent system has a conformation different from that of denatured DNA. When the alcohols are removed, the B form conformation and normal epsilon258 are restored in native DNA, while single-stranded DNA remains denatured. A double-stranded structure of DNA in the methanol-ethanol-buffer solvent system is confirmed by the neutral cesium chloride density gradient centrifugation of DNA in which one chain is labeled with [14C]thymidine and the other [3H]5-bromodeoxyuridine. The doubly labeled DNA exposed to the alcohol solvent system has a centrifugal pattern identical with that of control DNA; the two radioactivities cosediment and form a superimposing band, distinctly different from that of single-stranded DNA; 3H-labeled (thymidine) chains sediment further than 14C-labeled chains (5-bromo-deoxyuridine). Denatured DNA exhibits varying CD spectra depending on solvents. It is suggested that single-stranded DNA in different solvent systems assumes different modes of base stacking.

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AnimalsBromodeoxyuridineCattleCircular DichroismDNAEscherichia coliEthanolHot TemperatureMethanolNucleic Acid ConformationNucleic Acid DenaturationThymidineThymus GlandJournal ArticleResearch Support, U.S. Gov't, Non-P.H.S.Research Support, U.S. Gov't, P.H.S.

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E Kay. 1976-11-30. Double-stranded DNA in methanol-ethanol-buffer solvent system.. https://doi.org/10.1021/bi00669a007

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