methods to prevent digestion by REs?

Bill Jack jack at
Tue Apr 26 08:39:18 EST 1994

In article <1994Apr26.023734.3271 at>, Rapu Lak
<rapulak at> wrote:

> In article <9404221408.AA29527 at> Basavaraju
> Shankarappa, bsh at MED.PITT.EDU writes:
> >Hi folks:
> >	We... need  a method that will prevent 
> >digestion by restriction enzyme at one site while allowing it to cut at
> >the other site.  
> >	I remember seeing an article or a note somewhere 
> >which said that it is possible to use an oligo as a band-aid on the
> sequence 
> >where you want to avoid digestions by the RE.  More like forming a triple
> >helix at the position.  Does anyone know of the full reference of this
> article

 Reference is Ferrin, L.J. and Camerini-Otero, R.D. (1991) Science
254:1494-1497. Also see Koob, M. et al. (1986) Nucleic Acids Research 20,

Which site is it? Some can be preferentially blocked by overlapping
methylation, if the appropriate methylase is available. If this plasmid
needs to be routinely cut, it may make sense in the long run to introduce a
silent mutation to destroy the second site.

Bill Jack
New England Biolabs
jack at

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