Dominique MARIE marie at sb-roscoff.fr
Mon Nov 25 09:45:25 EST 1996

	Tanks for the responses about DNase treatment, especially for Martin and 
Temi. More informations are necessary for a good understanding of my 
difficulties. I work with picophytoplankton, and I would like to measure the 
RNA content of prochlorophytes. This organism have a small size ranging from 
0.4 to 0.6 microns and can be distinghuised from heterotrophic bacteria on 
the base of his chlorophyll content. The use of detergents will cause 
damages resulting in the loss of the chlorophyll emission and these 
prochlorophytes will become undistinghuisable from the bacteriplankton.
	The samples are fixed with aldehydes in order to keep the pigment contents 
into the cells. Samples are collected during oceanographic cruises, and the 
concentrations of picoplanktonic cells are to low and cells are to fragile 
to applied physical treatments such as centrifugation, filtrations, that 
induce artifacts. How can fixatives interfere with DNase digestion ? 
	I already have tested the effect of componds including EDTA without 
success. I have not tested the effect of DNase on fresh samples because in 
my point of view, it's a to large molecule that do not penetrate the membranes.

Have a nice day.


e-mail: marie at sb-roscoff.fr

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