Hi Frank, I worked with protein purification buffers and crystallization buffers containing 20mM potassium cacodylate for five years or so. And yes, the only precaution I used was gloves while weighing the chemical and while making buffers etc. And not just me, but all of my former colleagues worked with cacodylate. Then, there's those nasty chemicals for heavy atom soaks like mercury and tantalum compounds that are equally hazardous. And... many other chemicals we used on a daily basis in the lab but we don't suspect as much as we should.
Nucleosome core particles stubbornly refuse to crystallize if you leave out cacodylate, not just from the crystallization buffers but also from the protein purification buffers. Yes, there are folks who accidentally left it out and never gotten crystals of nucleosomes. I don't rule out that someday someone may very well be able to substitute cacodylate for some other chemical and successfully crystallize nucleosomes. It might be hard to interpret the kind of studies you suggest and here's why, in my opinion. Even if one showed that there was no need for cacodylate for, say, a 1000 different proteins, I would definitely not exclude it from a crystallization screen for my favorite protein because we have not gotten to that point in crystallography where one can predict crystallization conditions for a new macromolecule with great accuracy. In my opinion, it's all relative. There are probably more chances of me being killed by a reckless bicyclist in Boston/Cambridge than by cacodylate. ;-) Cheerios! Raji On Fri, Nov 9, 2012 at 7:26 AM, Frank von Delft <frank.vonde...@sgc.ox.ac.uk > wrote: > Hi all - > > Anybody know > a) how hazardous is cacodylate? > b) does it really matter for crystallization screens? > > It seems by far the most hazardous component of the standard screens; > this 2011 paper seems to think so (bizarrely, I can't access it from > Oxford): > http://onlinelibrary.wiley.**com/doi/10.1111/j.1365-2818.** > 1977.tb01136.x/abstract<http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2818.1977.tb01136.x/abstract> > > and this is site says lethal dose is 0.5-5g/kg: > http://cameochemicals.noaa.**gov/chemical/4468<http://cameochemicals.noaa.gov/chemical/4468> > meaning 2ml of a 0.1M solution contains 1/10th lethal dose...? (Someone > should check my maths...) [Coarse screens come mixed 2ml per condition.] > > > Has anybody done careful experiments that showed it really mattered for a > given crystal -- or even an entire screen? > > So I'm inclined to toss it out entirely rather than make crystallization > screening a "hazardous activity". (We're being subjected to a safety > review.) > > > Thoughts welcome. > phx > -- Raji Edayathumangalam Instructor in Neurology, Harvard Medical School Research Associate, Brigham and Women's Hospital Visiting Research Scholar, Brandeis University
