Relaxation of a single DNA molecule observed by optical microscopy

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Science  06 May 1994:
Vol. 264, Issue 5160, pp. 822-826
DOI: 10.1126/science.8171336


Single molecules of DNA, visualized in video fluorescence microscopy, were stretched to full extension in a flow, and their relaxation was measured when the flow stopped. The molecules, attached by one end to a 1-micrometer bead, were manipulated in an aqueous solution with optical tweezers. Inverse Laplace transformations of the relaxation data yielded spectra of decaying exponentials with distinct peaks, and the longest time component (tau) increased with length (L) as tau approximately L 1.68 +/- 0.10. A rescaling analysis showed that most of the relaxation curves had a universal shape and their characteristic times (lambda t) increased as lambda t approximately L 1.65 +/- 0.13. These results are in qualitative agreement with the theoretical prediction of dynamical scaling.