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Published February 19, 2013 | Supplemental Material + Published
Journal Article Open

Biomechanics of DNA structures visualized by 4D electron microscopy


We present a technique for in situ visualization of the biomechanics of DNA structural networks using 4D electron microscopy. Vibrational oscillations of the DNA structure are excited mechanically through a short burst of substrate vibrations triggered by a laser pulse. Subsequently, the motion is probed with electron pulses to observe the impulse response of the specimen in space and time. From the frequency and amplitude of the observed oscillations, we determine the normal modes and eigenfrequencies of the structures involved. Moreover, by selective "nano-cutting" at a given point in the network, it was possible to obtain Young's modulus, and hence the stiffness, of the DNA filament at that position. This experimental approach enables nanoscale mechanics studies of macromolecules and should find applications in other domains of biological networks such as origamis.

Additional Information

© 2013 National Academy of Sciences. Contributed by Ahmed H. Zewail, January 10, 2013 (sent for review December 3, 2012). Published online before print February 4, 2013. We thank Professors Charles M. Lieber, Chad A. Mirkin, Carlos Bustamante, and John M. Thomas for insightful remarks, as well as Dr. S. T. Park for helpful discussions. This work was supported by the National Science Foundation Grant DMR-0964886 and Air Force Office of Scientific Research Grant FA9550-11-1-0055 in the Physical Biology Center for Ultrafast Science and Technology at Caltech supported by the Gordon and Betty Moore Foundation. U.J.L. is grateful for a postdoctoral fellowship from the Swiss National Science Foundation. Author contributions: U.J.L. and A.H.Z. designed research, performed research, and wrote the paper. The authors declare no conflict of interest. This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1300630110/-/DCSupplemental.

Attached Files

Published - PNAS-2013-Lorenz-2822-7.pdf

Supplemental Material - pnas.201300630SI.pdf

Supplemental Material - sm01.mov

Supplemental Material - sm02.mov

Supplemental Material - sm03.mov


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