Jacob and CCP4bb
It's not exactly what you're looking for, but my colleague Peter Baldock wrote a program called "VD to MB" a few years ago that does part of the job. It was a program to convert vapor diffusion crystallization conditions into microbatch-under-oil conditions. I tried it back then with several published and unpublished examples where crystallization had been optimized in both vapor diffusion and microbatch. I was originally sceptical, but it seemed to work remarkably well, generally getting the numbers right to within 5 or 10%. The program uses a parameter called "1/e equilibration time for 1M salt (days)". I originally used a value of 1, but I think we changed it to 0.5 for 96-well plates. Obviously the value will depend on the geometry of the plates. Does anyone have any practical information about equilibration times? Different salts have very different effects on vapor pressure. I found a list in an old "Rubber Book" (CRC Handbook of Physics and Chemistry) part of which I have pasted below. I tried quite hard to make sense of this list - hoping that it would also shed light on the protein-precipitating effect of salts - but concluded that the numbers are pretty random apart from obvious valence effects. (Someone here may be able to explain them, though!) You can download the program from http://www.douglas.co.uk/tipsntech.htm near the middle of the page. There's also an equivalent Excel spreadsheet for playing around with. See also http://www.douglas.co.uk/convert.htm for some (very old but still valid!) examples and comments. Also bear in mind that - with many proteins - roughly half of the protein is lost on the surface of VD drops for 100 + 100 nl drops. Peter also wrote an algorithm - now in our optimization software - that calculates the pH of a solution with any number of buffers in it, where the buffers can be at different concentrations too. A sort of super Henderson-Hasselbalch. If anyone is interested I'm sure Peter could show you the maths or pass on the code (it took him about a month of lunch-breaks!) Best wishes Patrick _____________________________ Reduction of vapor pressure in mmHg due to the presence of 1M salt at 100C (at which temperature the vapor pressure of water is 760 mmHg) >From Handbook of Physics and Chemistry, 76th Ed CdSO4 8.9 ZnSO4 10.4 MnSO4 10.5 FeSO4 10.7 MgSO4 12 CdI2 14.8 CdBr2 17.8 ZnCl2 18.7 CdCl2 18.8 KNO3 21.1 NH4NO3 22 NaNO3 22.5 NH4Cl 23.7 NH4Br 23.9 NH42SO4 24 KCl 24.4 Na2SO4 25 NaCl 25.2 KI 25.3 LiCl 25.5 LiNO3 25.9 NaBr 25.9 LiBr 26.2 BaNO32 27 Li2SO4 28.1 LiI 28.6 K2CrO4 29.5 Na3PO4 30 Li2CrO4 32.6 MnCl2 34 CaNO32 34.8 CoCl2 34.8 Al2S043 36.5 BaCl2 36.7 NiCl2 37 NiNO32 37.3 BaBr2 38.8 MgCl2 39 CaCl2 39.8 MgNO32 42 MgBr2 44 CaBr2 44.2 AlCl3 61 StDev 10.7 Av 27.7 CV 0.4 -- For information and discussion about protein crystallization and automation, please join our bulletin board at http://groups-beta.google.com/group/oryx_group?hl=en patr...@douglas.co.uk Douglas Instruments Ltd. DouglasHouse, EastGarston, Hungerford, Berkshire, RG177HD, UK Directors: Peter Baldock, Patrick Shaw Stewart http://www.douglas.co.uk/ Tel: 44 (0) 148-864-9090 US toll-free 1-877-225-2034 Regd. England 2177994, VAT Reg. GB 480 7371 36 > -----Original Message----- > From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On Behalf Of > Jacob Keller > Sent: 02 February 2010 22:34 > To: CCP4BB@JISCMAIL.AC.UK > Subject: [ccp4bb] Vapor diffusion calculator > > Dear Crystallographers, > > Is anybody aware of a calculator for vapor diffusion experiments to > plot > concentrations of various solvent components as a function of time? For > a > simple example, what happens when I mix a protein solution containing > 50mM > NaCl 1:1 with a reservoir containing 50% MPD but no salt? Where is the > vapor > diffusion equilibrium, and how does the drop composition change as a > function of time? More complicated would be experiments involving > volatile > components other than water, as I think, for example, ethanol would > almost > instantly equilibrate, then the water diffusion would kick in over a > longer > time scale. Even more complicated would be pH-dependent volatilities > such as > acetate. I don't think this would be impossible to figure out, but it > would > be nice if there were a pre-existing tool/server to do such. > > Regards, > > Jacob Keller > > > ******************************************* > Jacob Pearson Keller > Northwestern University > Medical Scientist Training Program > Dallos Laboratory > F. Searle 1-240 > 2240 Campus Drive > Evanston IL 60208 > lab: 847.491.2438 > cel: 773.608.9185 > email: j-kell...@northwestern.edu > *******************************************
