Molecules: You'd better learn to live with them.
Friday's mention of chromatography got me thinking about HPLC. HPLC, or high-performance (alternately high-pressure) liquid chromatography, is a way of separating mixtures. It can be a pain to do, but there are times when absolutely nothing else will do. You can purify just about anything with it, from small molecules (drugs) to biomolecules.
The most common HPLC is "reversed phase", with a greasy solid phase and a mix of something polar and less polar (typically water and a polar organic solvent, like methanol or acetonitrile). Just the solvents work fine for a lot of small molecules - columns often come with a sample chromatograph showing that yes, in fact, the column successfully separates these five components with 65% acetonitrile, 35% water. To separate stuff that isn't very polar at all, like DNA, we need a helping hand. Enter TEAA.
TEAA is a good buffer for DNA purification because the greasy triethylammonium cations allow the DNA anion to interact with the greasy reverse phase. It's also a good HPLC buffer for a few other reasons - it's soluble in organic solvents, for one, which is critical. It's also volatile (only a bit, but enough to stink), which means that if you end up trying to concentrate your sample later by drying it down, you have a fighting chance at removing a good chunk of the buffer by putting it under vacuum. This is hardly foolproof, though, and drying down a lot of TEAA will still yield some schmutz - much less, though, than if you'd used something totally nonvolatile, like phosphate buffers.
Comments
There is also triethylammonium bicarbonate - unstoppered gallon jug, water, TEA, Dry Ice; swirl it, baby! Vacs off nice as you please. Best employed as an assignment to others.
Posted by: Uncle Al | May 2, 2007 1:37 PM