Ethanol vs Isopropanol for DNA precipitation - (Sep/23/2004 )

I favour EToH for an hour or 2 at -70

I favour EToH for an hour or 2 at -70

I strongly recomend using ethanol. Isopropanol precipitates more salt and ethanol precipitated more DNA.

Hi all,

Has anyone tried isolating protein using TRIzol (phenol & guanidine isothiocyanate) from Invitrogen?
I've been using TRIzol all along to isolate RNA from my samples; and it's working fine. From the product information, it states that TRIzol can also be used to recover protein.

I've followed the protocol; but was unsuccessful in extracting protein. These are some of the problems I faced:

1. After removal of the aqueous phase ( following TRIzol-chloroform addition) containing the RNA; I added 0.3ml of 100% ethanol to precipitate DNA from the organic and interphase as stated in the protocol. The sample was mixed by inversion; and stored at room temperature for 2-3min. Following, the sample was subjected to centrifugation at 2000G; 5min at 4C to pellet the DNA. But, I did not observe the supposed DNA pellet. Wondering why is this so?

2. I proceeded to precipitate protein from the supernatant above using isopropanol. Upon adding isopropanol, I observed quite a substantial amount of precipitation which I assumed it to be protein. After sedimenting and washing the protein pellet with wash solution ( 0.3M guanidine-HCl in 95% ethanol) for 3 times of 20' each, I vortexed the protein pellet in ethanol. I added 200ul 1%SDS solution to re-dissolve the protein pellet after removal of the ethanol. But, the pellet cant be dissolved. Tried incubating the protein pellet at 50C for 10min, but the pellet did not show any signs of dissolving. Why is this so?

Would appreciate any help! Thanks in advance!

Ethanol vs Isopropanol

Depends on time, but for high yields...

I use Ethanol precipitation without adding salt or glycogen, at -20°C overnight. You can get 10 times more than 1hour Room Temperature precipitation.


This would take longer but it really works when you are desperate >_<, and salt wont interfere for further cloning and so.

Hi all!
recently i have to concentrate my DNA sample and i try isopropanol precipitation. Frustration is that i so far can't concentrate my samples even dissolving the DNA is a smaller volume at the end. Sometimes the concentration is more or less the same before and after, sometimes I get lower concentration...... Very likely I loss quite a lot of DNA during precipitation, and I'd like ask if anyone can share your experience on that.
My isopropanol ppt is done in this way:
50ul sample >+0.3M NaAcetate>+ equal volume of isopropanol> -20 for 1 hour > centrifuge > wash with 70% Etoh > centrifuge > dry and re-dissolve in 20ul

I had use isopropanol and absolute ethanol and never seen a difference. The only thing is that I stored them at -20C. I use 2.5 vol of the alcohol (very cold) and 0.5 vol of NaAc, incubate at -20C O/N or if in a hurry 1h at -80C.

Hey Guys!
So I've been having a problem precipitating out linear DNA after preforming a linearization step followed by a phenol-chloroform extraction - at every other step in the protocol that I have to do a phenol-chloroform extraction I get DNA out no problem, its only after linearization that I have been having issues. I have tried using both isopropanol and ethanol to precipitate and am using NaOAc at pH 5.2 - with no luck. Has anyone had this issue before or know if I need to be doing something else to precipitate out linear DNA?! Thanks so much for your help!!!