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Trapping of megabase-sized DNA molecules during agarose gel electrophoresis
- Source :
- Proceedings of the National Academy of Sciences of the United States. Jan 19, 1999, Vol. 96 Issue 2, p453, 6 p.
- Publication Year :
- 1999
-
Abstract
- Megabase DNA molecules become trapped in agarose gels during electrophoresis if the electric field exceeds a few volts per cm. Fluorescence microscopy reveals that these molecules invariably arrest in U-shaped conformations. The field-vs.-size dependence for trapping indicates that a critical molecular tension is required for trapping. The size of unligated [Lambda]-ladders, sheared during gel electrophoresis at a given field, coincides with the size of molecules trapped at that field, suggesting that both processes occur through nick melting near the vertex of the U-shape. Consistently, molecules nicked by exposure to UV radiation trap more readily than unexposed ones. The critical trapping tension at the vertex is estimated to be 15 pN, a force sufficient to melt nicks bent around gel fibers, and, according to our model, trap a molecule. Strategies to reduce molecular tension and avoid trapping are discussed.
Details
- ISSN :
- 00278424
- Volume :
- 96
- Issue :
- 2
- Database :
- Gale General OneFile
- Journal :
- Proceedings of the National Academy of Sciences of the United States
- Publication Type :
- Academic Journal
- Accession number :
- edsgcl.54119737