Spec vs Flourimeter for [DNA] ?

Leonard N. Bloksberg bloksber at pilot.msu.edu
Tue Nov 30 11:02:00 EST 1993

Question about the Hoefer TK100 DNA flourimeter.
I have 3 samples of plasmid DNA, all are subclones of the same clone in 
pBlueScriptKS- or empty vector, all double CsCl banded, look great on gels,
etc.  When I measure my DNA concentration on an LKB Biochrom Ultrospec II
spectrophotometer as A260, I get 1 set of readings and when I measure on the 
Hoefer TK100 DNA flourimeter I get another.  The 260/280 ratios are all 1.80.  
The spec give a very consistent reading of 3x the flourimeter reading.  Which 
do I believe and why?  Can anyone offer some insight or warnings?  The 
exact concentration is important to me for titrating DNA binding proteins.  
Thanks in advance.  I will post a summary of important points if warrented.
	Leonard N. Bloksberg
	Bloksber at pilot.msu.edu
	Dept. of Crop and Soil Science
	Michigan State University

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