Hi,

I was doing experiment of extracting out plasmid DNA from E.Coli. I'm wondering why do we need to centrifuge the bacteria pallet at 4 degree celcius initially and at room temperature at near end of the experiment.

 

My deduction is that at 4 degree celcius, all the enzymes present will stop its activity. This cool temperature will also prevent overheating of rotor.

 

Can someone clarify this for me? Is there another conditions that tell us what temperature we should use for centrifugation?

 

Thanks in advance for anyone who replies this message.

4C lowers the solubility of DNA allowing it percipitated and pellet better.

When you spin it a second time in 70% EtOH at room temperature you do so that salt contamination that has previously percipitated will redisolve. As the DNA has already pelleted you do not have to worry about it not doing so at room temerature.