Methods for concentrating plasmid DNA - (May/09/2006 )
people have varying ideas here, but this is what I do:
1.decant ppt solution; don't stress if a little is still left but try to get most of it
2.add 70% (I don't worry so much about volume, just dump between 500ul and 1ml...make sure to use plenty, it's cheap stuff)
3. you can do a quick vortex here if the DNA is small, or 'finger-flick' the eppy a few times. it isn't necessary to resuspend the pellet, and sometimes it doesn't even dislodge, but you want to disturb it at least a little
4. spin at high (~15K rpm) 10min or so
5. pellet will be SOFT. this means decant very carefully...I frequently draw the spnt off SLOWLY with a pasteur pipet or 200ul tip...the pellet will dislodge easily. longer spins can help a bit, but also take more time and aren't really necessary, just be careful 
6. invert tube. allow to dry, resuspend.
I hope this works for you?
hi LLL1969 ! if you resuspend the DNA in 70% EtOH there is every possibility that you loose some amount of DNA. but hydrophilic contaminants entrapped in the pellet is thoroughly removed.
otherwise just flick the pellet in 70% EtOH as aimikins said and centrifuge to pellet down the DNA.
allow the pellet to dry and later resuspend in the solution desired. remember donot dry the pellet completely as this would affect its dissolution in the solvent.
Thanks... for all your advices
I join LLL1969 to thank you all. All this advice and suggestion have been really useful.
Have you never tried using a Centricon, fom MiliPore? Works great.
hi asad
could you please elaborate on this one. i regularly use centricon c-10 (now known as ym-10) for concentrating proteins. how do you adapt for dna...pcr products around 1 kbp, and vectors like puc19.
- viv
precipitate with your favorite solvent and resuspend in a smaller volume
How silly I am.
About the solvent, can it be isopropanol 100% and then Ethanol to wash the pellet?
What other solvents are interesting?
Thank you very much for your quick reply
It can be 70% ethanol to wash the pellet. ( in my lab, i use 1000 ul than centrifuge it for 2 min at 14000
as for isopropanol, only after removing the clear lysate into another micro-centrifuge tube than you add. you only wash the pellet using ethanol after removing the supernatant.
precipitate with your favorite solvent and resuspend in a smaller volume
How silly I am.
About the solvent, can it be isopropanol 100% and then Ethanol to wash the pellet?
What other solvents are interesting?
Thank you very much for your quick reply
It can be 70% ethanol to wash the pellet. ( in my lab, i use 1000 ul than centrifuge it for 2 min at 14000
as for isopropanol, only after removing the clear lysate into another micro-centrifuge tube than you add. you only wash the pellet using ethanol after removing the supernatant.
hi fred what is the recipie of the butanol???
any dilution ?? or u add some other reagents??/
