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Shiao Y. Wang sywang at whale.st.usm.edu
Fri Jul 22 13:49:01 EST 1994

Jory Weintraub (jpweintr at gibbs.oit.unc.edu) wrote:

: I am currently using diphenylamine reagent in a protocol to quantitate 
: DNA.  If you have used or are using diphenylamine for similar purposes, 
: please post your protocol. 

Reagent A = 1.5 g diphenylamine in 100 ml glacial acetic acid and 1.5 ml
sulfuric acid. 
Reagent B = 16 mg acetaldehyde/ml water.
Reagent C = 5 ul Reagent B per ml Reagent A; mixed just prior to use.
Reagent C + DNA = blue color. Use spectrophotometer and standard curve to
quantitate. See Can. J. Fish. Aquatic Sci. 50:996-1001 (1993) for details
on treatment of biological material.

The assay does not give a linear response above 1 to 1.5 OD in my hands. I've
always been curious as to why. It's as if the assay runs out of "something"
above a certain DNA concentration. Does anyone know if diphenylamine or
acetaldehyde degrades easily?

Shiao Wang
University of Southern Mississippi

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