Writhing number of supercoiled DNA from its scanning force microscopy imaging
作者:
G. Zuccheri,
G. A. Ranieri,
C. Nigro,
B. Samorì,
期刊:
Journal of Vacuum Science&Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena
(AIP Available online 1995)
卷期:
Volume 13,
issue 1
页码: 158-160
ISSN:1071-1023
年代: 1995
DOI:10.1116/1.587974
出版商: American Vacuum Society
关键词: DNA;MOLECULAR STRUCTURE;MICROSCOPY;CALCULATION METHODS;INTEGRALS;CONFIGURATION
数据来源: AIP
摘要:
Scanning force microscopy can routinely image supercoiled DNA molecules under liquids or in air and the complete three‐dimensional path of the chain can be identified. This makes it possible to evaluate the writhing number (Wr) of the coiled curve described by the chain axis in the imaged conformation of the molecule.Wris a much better descriptor of supercoiling than the linking deficit (ΔLk) which has been commonly used so far.Wrof the DNA axis curve can be roughly estimated by the signed‐intersection approach or calculated as the Gauss integral of the curve itself. We applied both methods to a model closed simple curve and to coiled DNA molecules exhibiting one or two turns of the chain about their superhelical axis.
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