期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1982
卷号：79
期号：11
页码：3518-3522
DOI：10.1073/pnas.79.11.3518
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：We have used triplet anisotropy decay techniques to measure the internal flexibility and overall rotational motion of DNA, covering a time range from 15 ns to 200 mus. Nearly monodisperse DNA fragments 65--600 base pairs long were studied by using the intercalating dye methylene blue as a triplet probe. We found that the slow end-over-end tumbling of short DNA fragments (less than or equal to 165 base pairs) is as predicted for a rigid rod. As expected, a longer DNA fragment (600 base pairs) experiences slow segmental motion of its helix axis. We found that, at the earliest times, anisotropy decays more rapidly than expected for a rigid rod, suggesting that, when bound, methylene blue monitors fast internal motion of the helix. Since the rod-like end-over-end tumbling of short fragments rules out fast bending motions, we conclude that the fast components of DNA anisotropy decay are due to twisting motion of the helix, occurring with a time constant near 50 ns.
