Chromatography Forum

hello,
i know protiens can stay in acetonitrile for very long without causing any damage to their structure. but how long can proteins stay in acetone or even methanol?

Actually, adding acetonitrile to a protein solution is a very good way to denature ("cook") a protein!

hello,
i mean proteins in gel slices can stay in acetonitrile without harm, to which these proteins are extracted from gel slices in preparation for mass spectrometry. sorry if i wasn't being clear.

What is a gel slice?
Of the solvents you mentioned acetonitrile is the best for precipitating proteins as far as I can tell (to use different words than Tom, but saying the same thing: It should normally be strongest in changing structure).

Ok.

How about in acetone? What does this do to proteins?

One can presume that in the best case it will change about all but the primary structure, in the worst case it might react with an amine rest, as an example, thus changing even the primary structure.
But then there are proteins which can literally be cooked without changing their function. (If you are ever in Glenwood Springs, CO, look at the algae in the boiling hot spring next to the pool).

mean proteins in gel slices can stay in acetonitrile without harm, to which these proteins are extracted from gel slices in preparation for mass spectrometry.

You are right in that the proteins are preserved for analysis by mass spec.

What Tom is referring to is that precipitation by organic solvents usually causes proteins to be denatured. Heat can do the same thing. The protein still has the same amino acid sequence but the shape changes, so the protein will no longer function as an enzyme.

acetone and methanol will also precipitate your protein.

you can resuspend protein precipitated with acetone and it will, in most cases, be intact (not denatured).

you may also be able to renature proteins precipitated by methanol, but i haven't tried.

Ok.

How about in acetone? What does this do to proteins?

Back in the dim distant past, addition of acetone (at -20C) was a standard method of deproteinating plasma samples for bioanalytical extraction work.

acetone and methanol will also precipitate your protein.

you can resuspend protein precipitated with acetone and it will, in most cases, be intact (not denatured).

you may also be able to renature proteins precipitated by methanol, but i haven't tried.

hi~ do you have any paper that supports this? I'm doing some research on membrane fouling, but cant seem to find any info regarding this

acetone and methanol will also precipitate your protein.

you can resuspend protein precipitated with acetone and it will, in most cases, be intact (not denatured).

you may also be able to renature proteins precipitated by methanol, but i haven't tried.

hi~ do you have any paper that supports this? I'm doing some research on membrane fouling, but cant seem to find any info regarding this

acetone has been known to precipitate (and, indeed, crystallize) proteins since at least 1926 when sumner reported the crystallization of urease from jack bean meal (Sumner, J. B., J. Biol. Chem, 69: 435 (1926)). sumner also found that he could crystallize urease from alcohol (Sumner, J. B., et al., J. Biol. Chem., 125: 37 (1938)).

i used acetone to fractionate a protein mixture with varying concentration of acetone (similar to the use of ammonium sulfate) and have used alcohols to remove proteins from solutions and bodily fluids (not too often).