Shearing DNA by heat - a question

colossus... s535290 at
Wed May 21 18:07:25 EST 1997

> If you are pleased with the results of blocking membranes with denatured
> that's fine; it certainly is easier to manipulate denatured DNA and it
> will be
> more effective than undenatured DNA.  I do take exception to the claim
> that
> autoclaving can shear ds DNA; it CAN'T and in fact denatured DNA is
> quite
> resistant (relative to undenatured) to shearing, which is a mechanical
> process
> requiring physical stress; the stiffness of ds DNA is what makes it so
> prone to
> mechanical shearing. Even before DNA gets near the 121-123 C temperature
> of
> autoclaves, assuming it's dissolved in water or very low salt, it will
> be
> completely denatured and thus essentially refractory to shearing. 

true enough...for controlled shearing of DNA, nothing beats nebulization
though...not sonication, not enzymatic methods. 



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