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low boiling point

M.C. Diana Sara Leal Klevezas dsleal at ACADEM01.MTY.ITESM.MX
Mon Mar 27 15:13:54 EST 1995

On 24 Mar 1995, Jim Mansfield wrote:

> In article <Pine.A32.3.91.950323150650.72973A-100000 at academ01.mty.itesm.mx> dsleal at ACADEM01.MTY.ITESM.MX ("M.C. Diana Sara Leal Klevezas") writes:
> >
> >If I'm wrong regarding the pressure building up in warm tubes, the 
> >possibilities are even more exciting, here is the idea: The water boils 
> >because the molecules get excited enough to do so. If less energy is 
> >needed to boil the water, less energy might be needed to break the 
> >hidrogen bonds between DNA strands, which means that under those 
> >circumstances, one might need lower temperatures to reach DNA melting 
> >point. If this is true, the consecuences are that your Taq will last 
> >loger!!!. 
> Thankfully, hydrogen bonding and similar prcesses are not affected by
> pressure changes of the magnitute we are discussing - otherwise life
> as we know it would not be possible in Peru at all! The reason less
> energy and, hence lower temperatures, are needed at high altitudes is
> the vapour pressure of the liquid does not need to be as high before
> it matches atmospheric pressure. As the temp. of a liquid rises, so 
> does its vapour pressure. Once it reaches atmospheric pressure, voila,
> boiling. Putting a lid on the vesselwill raise the pressure of the gas
> over the liquid, raising its boiling point.
> -Jim
> -- 
> ---------------------------------------------------------------------
> Jim Mansfield                          internet: mansfield at ibd.nrc.ca
> Institute for Biodiagnostics, NRCC     phone:    (204) 984-5191
> http://www.ibd.nrc.ca/~mansfield/      fax:      (204) 984-5472
Well, we have to keep in mind that PCR is an in vitro assay. Eventough 
cells use most of the same components we add to the tube, there are cell
mechanims (not boiling, naturally) to unwind and melt DNA strands. We 
have to also remember that organisms and their cells adapt to 
enviromental pressure changes and that live sistems regulate their own 
presure to keep the whole sistem "on wheels".
Diana Sara Leal Klevezas
Centro de Investigacion Biomedica del Noreste
Monterrey, N.L. Mexico. 

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