"high stringency" washes -NOT?

graham at biodec.wustl.edu graham at biodec.wustl.edu
Wed May 7 12:09:50 EST 1997


As Dave Haviland kindly points out, the Bolton and Mcarthy equation
given in Sambrook (Mantiatis Manual 2nd ed.) and propagated elsewhere is
dead wrong. They give:

Tm = 81.5 - 16.6 (log[Na+]) + 0.41(G/C) -0.63(form%) -600/L

rather than the correct:

Tm = 81.5 + 16.6 (log[Na+]) + 0.41(G/C) -0.63(form%) -600/L

What is it with this equation that editors and apparently scientists
find so difficult to state correcly (absolute value assumed, %GC verses
decimal)? Is it wrong in the orginal Bolton and McCarthy paper as well?
Anyone?

Apparently, adding salt raises the Tm, therefore washing at reduced salt
ands same temperature would ideed move conditions closer to the melting
temperature of hybrids.

Carry on, :)

Jim



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