Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 108, Issue 39, Pages 16153-16158Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1105547108
Keywords
DNA conformation; electrophoresis; polymer physics; knots; microfluidic
Categories
Funding
- Singapore-MIT Alliance for Research and Technology (SMART)
- National Science Foundation (NSF) [CBET-0852235]
- Directorate For Engineering
- Div Of Chem, Bioeng, Env, & Transp Sys [0852235] Funding Source: National Science Foundation
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We experimentally study the effects of a uniform electric field on the conformation of single DNA molecules. We demonstrate that a moderate electric field (similar to 200 V/cm) strongly compresses isolated DNA polymer coils into isotropic globules. Insight into the nature of these compressed states is gained by following the expansion of the molecules back to equilibrium after halting the electric field. We observe two distinct types of expansion modes: a continuous molecular expansion analogous to a compressed spring expanding, and a much slower expansion characterized by two long-lived metastable states. Fluorescence microscopy and stretching experiments reveal that the metastable states are the result of intramolecular self-entanglements induced by the electric field. These results have broad importance in DNA separations and single molecule genomics, polymer rheology, and DNA-based nanofabrication.
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