Mysterious plasmid preps

[Ole Skovgaard]

In article <3ob2l3$4eg at news.bu.edu> rocket1 at bu.edu (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
>yield.

>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 bu.edu
>thanks

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!

yours

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