DNA intercalators tilt, wobble, and twirl: elucidating DNA overstretching (Conference Presentation)

Adam S. Backer; Andreas S. Biebricher; Graeme A. King; Iddo Heller; Gijs J. L. Wuite; Erwin J. G. Peterman

doi:10.1117/12.2507066

4 March 2019 DNA intercalators tilt, wobble, and twirl: elucidating DNA overstretching (Conference Presentation)

Adam S. Backer, Andreas S. Biebricher, Graeme A. King, Iddo Heller, Gijs J. L. Wuite, Erwin J. G. Peterman

Proceedings Volume 10884, Single Molecule Spectroscopy and Superresolution Imaging XII; 1088408 (2019) https://doi.org/10.1117/12.2507066
Event: SPIE BiOS, 2019, San Francisco, California, United States

Abstract

DNA phase transitions drive life processes and are key to the development of DNA-based biotechnologies. Accordingly, quantifying the physical properties of DNA is an essential endeavor. However, the narrow width (2 nm) of the DNA molecule prohibits direct visualization of its structural dynamics using optical microscopy. To address this challenge, we employ concurrent polarization imaging and DNA manipulation to probe the orientations and rotational dynamics of DNA-intercalated dyes—small fluorescent molecules that bind between adjacent DNA base pairs. The method uses optical tweezers to precisely extend, align and (re)orient a single DNA molecule within the image plane of a fluorescence microscope. Our data shows that at extensions beyond the so-called “overstretching transition” intercalators adopt a dramatically tilted orientation relative to the DNA-axis (approx. 54 degrees), distinct from the perpendicular orientation (approx. 90 degrees) normally observed at lower extensions. Strikingly, by imaging single intercalated dye molecules with polarized illumination, we also demonstrate that intercalators rapidly rotate (i. e. “twirl”) about the DNA-axis, revealing underlying Brownian twisting dynamics of the DNA substrate. Taken together, these results shed new insight on S-DNA: a DNA phase that forms under tension that, at present, is not well understood.

Conference Presentation

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Adam S. Backer, Andreas S. Biebricher, Graeme A. King, Iddo Heller, Gijs J. L. Wuite, and Erwin J. G. Peterman "DNA intercalators tilt, wobble, and twirl: elucidating DNA overstretching (Conference Presentation)", Proc. SPIE 10884, Single Molecule Spectroscopy and Superresolution Imaging XII, 1088408 (4 March 2019); https://doi.org/10.1117/12.2507066

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KEYWORDS

Molecules

Biotechnology

Luminescence

Microscopes

Optical microscopy

Optical tweezers

Polarization

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