Instead of calculating the drop composition, there is a simple device, refractometer, which you can use to measure the actual composition of the drop (based on the refraction indices of the components). Some of us even used it in the old days. It's possible that with nano-size drops some tricks will have to be applied though.
Boaz
----- Original Message -----
From: Jacob Keller <
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Date: Wednesday, February 3, 2010 0:34
Subject: [ccp4bb] Vapor diffusion calculator
To:
[log in to unmask]> 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:
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>