Re: [ccp4bb] Vapor diffusion calculator

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CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

Previous message:
Subject: Re: unknown density
From: Vellieux Frederic Frederic {- dot -} Vellieux {- at -} IBS {- dot -} FR
Date: 2010-02-03

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Subject: Re: unknown density
From: "David J {- dot -} Schuller" djs63 {- at -} CORNELL {- dot -} EDU
Date: 2010-02-03

Subject: Re: Vapor diffusion calculator
From: Jacob Keller j-keller2 {- at -} MD {- dot -} NORTHWESTERN {- dot -} EDU
Date: 2010-02-03

Thanks very much for the reference; I have always wondered about precisely
this relationship (how much salt = how much PEG). Interestingly, the authors
note that down to PEG 1500, the MW of the PEG does not change the
corresponding salt values very much. I wonder whether anybody did this for
MPD, which would definitely be more tricky as it is volatile. Probably for
more volatile alcohols, one would simply assume the alcohol diffusion is
very fast relative to water, so could be ignored. In the short term
(minutes?), the drop would get bigger owing to influx of alcohol, but in the
longer term would equilibrate to the salt concentration of the well.

Jacob

*******************************************
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-keller2@northwestern.edu
*******************************************

----- Original Message -----
From: "Imre Toeroe"
To:
Sent: Wednesday, February 03, 2010 4:25 AM
Subject: Re: [ccp4bb] Vapor diffusion calculator

Hi,

this might be relevant here:

http://scripts.iucr.org/cgi-bin/paper?S0907444995000436

Imre

Clemens Grimm wrote:
> regardless of what such a (kinetic) calculator will calculate at the end -
> we will have to feed it with data of the type "vapour pressure vs.
> concentration and temperature" of substance X. Even without a whole
> simulation tool for the kinetics of a vapour diffusion experiment this
> will already enable us to tell what the equilibrium state/endpoint of the
> experiment will be.
> As the substances we are interested in are typically stuff like PEGs and
> at very high concentration (non-ideal behaviour!), we will need
> experimental data. For some salts there are tables. But for PEGs etc. this
> has to be generated. I feel that only having this kind of data at hand
> would already be tremendously useful!
>
> Clemens
>
>
> Zitat von Jacob Keller :
>
> 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-keller2@northwestern.edu
> *******************************************
>
>
> --------------------------------------------------
> Dr. Clemens Grimm
> Institut für Biochemie
> Biozentrum der Universität Würzburg
> Am Hubland
> D-97074 Würzburg
> Germany
> e-mail: Clemens.Grimm@biozentrum.uni-wuerzburg.de
> phone : +49 0931 888 84031
> -------------------------------------------------

CCP4bb navigation

CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

Previous message:
Subject: Re: unknown density
From: Vellieux Frederic Frederic {- dot -} Vellieux {- at -} IBS {- dot -} FR
Date: 2010-02-03

Next message:
Subject: Re: unknown density
From: "David J {- dot -} Schuller" djs63 {- at -} CORNELL {- dot -} EDU
Date: 2010-02-03