Hogan M, Wang J, Austin R H, Monitto C L, Hershkowitz S
Proc Natl Acad Sci U S A. 1982 Jun;79(11):3518-22. doi: 10.1073/pnas.79.11.3518.
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.
我们使用三线态各向异性衰减技术来测量DNA的内部柔韧性和整体旋转运动，时间范围从15纳秒到200微秒。通过使用嵌入染料亚甲蓝作为三线态探针，研究了长度为65 - 600个碱基对的几乎单分散的DNA片段。我们发现，短DNA片段（小于或等于165个碱基对）的缓慢的端对端翻滚正如刚性棒所预测的那样。正如预期的那样，较长的DNA片段（600个碱基对）其螺旋轴会经历缓慢的片段运动。我们发现，在最早的时间，各向异性衰减比刚性棒预期的要快，这表明，结合时，亚甲蓝监测到螺旋的快速内部运动。由于短片段的棒状端对端翻滚排除了快速弯曲运动，我们得出结论，DNA各向异性衰减的快速成分是由于螺旋的扭曲运动，其时间常数接近50纳秒。
