Mysterious plasmid preps

Ole Skovgaard olesk at RUC.DK
Fri May 5 02:13:56 EST 1995

In article <3ob2l3$4eg at> rocket1 at (Richard Near) writes:

>We find very high OD260 readings indicating a yield of 5 or more
>mg (a ridiculous yield for 100ml bugs).  The Ratio 260/280 is 
>usually >2.  On a gel we get DNA, but consistant with much less

>Question: why the excessive OD reading in terms of yield?  I should
>also say that the final DNA pellet often seems fairly large (this 
>technique used to work).  ANY suggestions????   

>rocket1 at

My guess is that it is still (partly degraded) RNA indicating that RNase has 
not completet ists work. Fits with OD ratios.
Compare a recent prep with an old prep on a short run agarose gel. Takes U 
about 15 minutes!


****   Ole Skovgaard                  ****
****   Dept. Life. Sc. & Chemistry    ****
****   Roskilde University, DK        ****

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