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Oh bug**r, now I have to write something! Basically, for vibration there are two factors, frequency and magnitude. Any high magnitude vibration is bad, i.e. the sudden short duration, hopefully low frequency one when you drop your tray :) For the same magnitude, low frequencies (a few Hz) are worse than higher frequencies (mains frequency). High frequencies are quickly damped in a liquid environment. Measuring vibrations is fairly easy, translating that measurement into something useful is not. In the case James mentioned, we were looking at the reduced acceleration environment. Certain crystallization processes lasted over a longer time period than on the ground - in this case the presence of a halo of depleted solution around the crystal caused by the diffusion limited transport of the protein to the crystal face. Every time an astronaut exercised, this halo broke down and a growth spurt occurred (except for one astronaut who didn't exercise very hard at all, however he/she shall remain nameless). On the ground, this depletion zone is only there for a short period of time if at all. Transport and therefore growth is dominated by convection - the density differences cause flow of sample across the growing crystal face. Any effect from vibration at high frequency in a liquid medium would only be meaningful if the magnitude of that vibration was large. Diffusion processes and surface tension effects in the drop and Brownian motion and surface dynamics on the crystal face probably dominate the crystallization process at the macromolecule scale. Although I don't think vibration will be too big of an issue unless the magnitude is large I personally like small bench top Peltier controlled forced air incubators. I can rule vibration out as a variable. Vibration isolation may make a difference with large magnitude vibrations, however vibration reduction would be cheaper. The best thing to do is try a simple experiment with a few of your favorite proteins. Set up a tray in one of the rooms if a colleague has one available and duplicate trays in other incubators set at the same temperature. If there is any big difference you have your answer (assuming it is not light, temperature control or a million other differences). Frequently I have often found that nice physical explanations in crystal growth are often poor approximations and later prove to be incorrect - a little shaking might be good after all. Perhaps that is why there are so many crystallography groups in California :) Not that much use but I hope at least interesting. I'd love to hear if anyone had a nice study on this. Cheers, Eddie Edward Snell Ph.D. Assistant Prof. Department of Structural Biology, SUNY Buffalo, Hauptman-Woodward Medical Research Institute 700 Ellicott Street, Buffalo, NY 14203-1102 Phone: (716) 898 8631 Fax: (716) 898 8660 Email: [EMAIL PROTECTED] Telepathy: 42.2 GHz Heisenberg was probably here! -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of James Holton Sent: Wednesday, August 02, 2006 4:45 PM To: [EMAIL PROTECTED] Cc: [email protected] Subject: Re: [ccp4bb]: Influence of vibrations on crystallisation experiments *** For details on how to be removed from this list visit the *** *** CCP4 home page http://www.ccp4.ac.uk *** The most carefully monitored connection between crystal growth and vibration I am aware of was made by Eddie Snell's group with their experiments on the Space Shuttle: http://scripts.iucr.org/cgi-bin/paper?gr0718 E. H. Snell, T. J. Boggon, J. R. Helliwell, M. E. Moskowitz and A. Nadarajah, /Acta Cryst./ (1997). D*53*, 747-755 They saw a very clear conneciton between vibrations and crystal growth rates and indeed crystal quality. Things like "astronaut exercising" coincided with increased crystal growth rate a short time later. So, it would appear that even in the most controlled environments vibration control can be a challenge, but at least on the Shuttle, where everything gets logged, you can (could) look for relationships. Hope this is useful. -James Holton MAD Scientist [EMAIL PROTECTED] wrote: > Dear crystallographers, > > > While this is not a directly CCP4-related project, no crystal (or bad > quality ones) means not much use of CCP4 ... hence the following > inquiry. I am involved in the design of a new crystallisation lab with > temperature-controlled rooms, which we have found to be typically > quite prone to internal vibrations. A little vibration is probably not > an issue in most of the cases, but how to define what is acceptable > and what is not? > > Most of the time people define good crystallisation environment as > vibration-free, but I suspect that 0 vibration is not a value that can > be typically achieved in labs (can it be achieved at all?), and while > there are means of measuring vibration levels, I could not find any > numeric references... > > ...which leads me a long list of naive questions: > - does anyone have performed any vibration level measurement in their > labs and defined a threshold for acceptable conditions? > > - are scientists performing their crystallisation experiments in > temperature-controlled rooms satisfied with the vibration levels? > > - do some of you recommend some devices/brands to reduce vibrations > applied to the crystallisation trays? (I heard about vibration-free > shelves or insulation pads, is this any good?) > > - any advice about how to handle vibration issues welcome! > > Thank you very much to all of you in advance, > > > Ingrid Mechin >
