Once upon a time I worked in a group that was interested in developing crystallization in microfluidics. This was before the time that Fluidigm existed and we had not heard of crystallization with the aid of microfluidics at the time. We had good reason to try to make a system that was as small and light as possible - it had something to do with the cost of shipping proteins and precipitants - less was better. And we also wanted all protein drops to be fully enclosed, out of safety considerations.
Like Tassos, we were very worried what would happen if you scaled back drops along the lines of this discussion - several uL downto tens of nanoliters. If the stochastic process had a major influence over this process, we thought that we would never get any crystals. So we set up side-by-side experiments at larger volumes and smaller volumes - basically scanning several orders of magnitude - expecting a decrease of the number of crystals when volumes decrease. To our great surprise the outcome was that smaller volumes almost always gave MORE (I almost want to say 'dramatically more') crystals, more nucleation, and indeed in various cases the crystals grew much faster also. Indeed, it was trivial to observe that the surface-to-volume ratio was the primary driver for the nucleation process. We had control over geometry to some extent and were able to observe surfaces while crystals grow. The crystals would most commonly nucleate on a surface. So although there probably is something to stochastic aspects, it is clear that other aspects can be more important and "overrule" the stochastic considerations. The somewhat unpleasant consquence is of course that results acquired in very small volumes (with larger surface-to-volume ratio) cannot necessarily be repeated in larger volumes (smaller surface-to-volume ratio). This is not a flame, even if heat might be a good thing on a night with temperatures predicted far below 0F. ?:-) Mark -----Original Message----- From: Anastassis Perrakis <[EMAIL PROTECTED]> To: CCP4BB@JISCMAIL.AC.UK Sent: Wed, 16 Jan 2008 6:17 am Subject: Re: [ccp4bb] crystallisation robot > Oryxnano 50+50 nL? >? > Demetres? >? ? Which, indirectly, brings up an interesting (but not relevant to the Oryx) question.? ? Nucleation is a process that does have a stochastic aspect.? ? Thus, one could argue that compromising to 200-300 nl might be better than either extremes of 50nl (too small volume and less chance for nucleation) or 1000 nl (too much sample).? ? any comments ? (let the flames begin).? ? A.? ? PS1? another interesting issue that has has been hardly touched in these emails is the real sample loss: left in wells and not easy to recover, lost because of contamination with system liquid, etc ...? ? PS2? I see lots of people with new robots. please do have a look at the www.BIOXHIT.org page and if you have a few minutes to assemble a table we will be happy to add your specs to our pages. it can be a nice resource and it has already enough things and already one response to my last email ;-) To make life easier to potential contributors we can provide an Excel sheet to fill up with your specs - just ask.? ? On Jan 16, 2008, at 12:46, Demetres D. Leonidas wrote:? ? >? > David Briggs wrote:? >> I'll defend the honour of the phoenix... (again)? >>? >> Bernhard Rupp 100+100 nl? >> Dave Briggs (and all users at Univ of Manchester, UK) 100+100nl? >> Others..? >>? >> Only time we have ANY problems is when the nano dispensing tip >> gets >> clogged. Often a good wash whilst still on the machine will >> clear the >> blockage.? >>? >> Dave? >>? >>? >>? >>? >> -->> ============================? >> David C. Briggs PhD? >> Father & Crystallographer? >> http://www.dbriggs.talktalk.net <http://www.dbriggs.talktalk.net>? >> AIM ID: dbassophile? >> ============================? >? > --> Demetres D. Leonidas, Ph.D.? > Structural Biology & Chemistry Group? > Institute of Organic and Pharmaceutical Chemistry? > The National Hellenic Research Foundation? > 48, Vassileos Constantinou Avenue? > Athens 116 35, Greece? > ==================================================? > Tel. +30 210 7273841 (office)? > +30 210 7273895 (lab) Fax. +30 210 7273831? > E-mail: [EMAIL PROTECTED] > URL: http://athena.eie.gr? > ==================================================? ________________________________________________________________________ More new features than ever. Check out the new AIM(R) Mail ! - http://webmail.aim.com
