by Peter Nollert
March 2, 2012 09:08
Many proteins can be crystallized with the help of the molecular crowding agent PEG (polyethylene glycol). How many proteins? The Biological Macromolecule Crystallization Database (BMCD ver. 4.03) lists that 46% of all protein crystallization crystallizations contain some sort of PEG (that's 20,179 PEG-containing conditions out of a total of 43,406 listed protein crystallizations).
This begs the question: which of the many different PEGs are most useful? - and therefore ought to be available in every protein crystallization lab? To answer this question we've put together a list with commonly used PEGs (see Fig below).
Figure: These 12 different polyethylene glycols cover ca. 88% of all PEGs induced crystallization space (as derived from the BMCD 4.03)..
In other words: if you've got stocks for all of these 12 Polyethylene Glycol solutions:
PEG 200
PEG 300
PEG 400
PEG 1000
PEG 3350
PEG 4000
PEG 6000
PEG 8000
PEG 10,000
PEG 20,000
PEG 2000 MME
PEG 5000 MME
you're covering ca. 88% of all PEG-induced protein crystallization conditions (according to the crystallization conditions from the BMCD 4.03).
The pioneers that have discovered this immensely important protein crystallization reagents class are Alex McPherson, A. Brzozowski and S. Tolly. Their publications helped lift the science of protein crystallization out of the dark ages:
McPherson A Jr (1976). Crystallization of proteins from polyethylene glycol. The Journal of biological chemistry, 251 (20), 6300-3 PMID: 977570
Brzozowski AM, & Tolley SP (1994). Poly(ethylene) glycol monomethyl ethers - an alternative to poly(ethylene) glycols in protein crystallization. Acta crystallographica. Section D, Biological crystallography, 50 (Pt 4), 466-8 PMID: 15299403
Whenever we get a crystallization hit containing PEG we're standing on the shoulders of these giants.
Cheers,
Peter