Ethanol precipitations: disposable 30 ml tubes?

brett brett at BORCIM.WUSTL.EDU
Sun Jan 28 14:27:48 EST 1996

>Greetings Ferocious Mages of Nucleic Acids--
>        I fear I have a contamination problem, so I would like to find a brand 
>of disposable tube which can be spun quickly.  I fear that plasmids from 
>my maxipreps of probe plasmids may get into my RNA preps.  I do all my larger 
>ethanol precipitations (> 15 mls) in a small set of 30 ml corex tubes I have. 
> I would like to use a disposable tube for these ethanol precipitations, but I 
>think that falcon blue tubes would fall to pieces at the speeds (12,000 rpm in 
>an SS-34 rotor) which I find useful for precipitating small quantities of DNA 
>(100 micrograms) out of 25 mls of solution.  Is there an appropriate tube/spin 
>system for ethanol precipitations of larger volumes using disposable tubes.
>        I don't think that washing up is a solution to the problem, because 
>currently after using the corex tubes, I rinse them with water, soak them 
>overnight with 10% (v/v) HCl to the brim, then I wash the tubes normally in 
>soapy water etc. using a reserved set (ie post acid) of bottle brushes.  
>Finally the tubes are baked at 180C for 7 hours.  
>        Many thanks,
>        Harry
>Harry.Witchel at Bristol.AC.UK

You think there is residual DNA after all that?!? I seriously doubt it is
causing you major contamination. Try to PCR something up from a water rinse, or
try to electroporate competent cells. Hard to beleive you'd find anything.
More likely plasmid floating around your lab is getting into the cleaned
tubes. Still, you could buy a second set of tubes (I know they're
expensive) for this purpose, or increase you washing conditions (chromic
acid:H2SO4). Good luck.

Brett Lindenbach
Program in Immunology                              
Washington University - St Louis                  
brett at                             

"I own my own pet virus. I get to pet and name her." - Cobain

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