how to separate the nicked from of a plasmid from the closed form?

Brian Foley brianf at
Tue Jun 7 13:04:50 EST 1994

t_rolden at wrote:
: does anyone know a method to separate the nicked circular form of a plasmid
: from the covalently closed circular form?. I have a mix which contain 50% of
: each form, when I do a CsCl gradient to isolate the closed form I always have
: contamination with the open form. does anyone konw a method to separare them,
: different from the CsCl gradient?.

	In BioTechniques Volume 13 pages 550-554 (1992), Edward Hyman 
describes a method for eliminating nicked plasmid by enzymatic digestion
with exonuclease I and exonuclease III.  
	This method results in a preparation of supercoiled plasmid with
no nicked plasmid.  If you need nicked plasmid, with no supercoiled you
will have to find another method...

: Many thanks,

: T. Roldan

*  Brian Foley               *     If we knew what we were doing   *
*  Molecular Genetics Dept.  *     it wouldn't be called research  *
*  University of Vermont     *                                     *

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