Comments on: The Phase Diagram in Protein Crystallization http://www.P212121.com/2009/11/15/the-phase-diagram-in-protein-crystallization/ Protein Crystallography there is an Easier Way Mon, 06 Sep 2010 23:18:47 -0400 http://wordpress.org/?v=2.8.5 hourly 1 By: BR http://www.P212121.com/2009/11/15/the-phase-diagram-in-protein-crystallization/comment-page-1/#comment-1287 BR Mon, 16 Nov 2009 06:52:27 +0000 http://www.P212121.com/?p=7079#comment-1287 Most of these diagrams are drawn incorrectly. Think about where the solubility line originates from - can the graph as drawn be parallel to an axis in principle? In practice, examine the solubility functions for salts and PEGS. There is also no difference thermodynamically between the metastable and 'labile' zone - everything between the solubility line and the spinodal decomposition line is metastable and supersaturated. 'Labile' means something different in thermodynamics than in colloquial terms. The correct description of this part of the metastable region is one of spontaneous homogeneous nucleation. Consult the schematic G/x diagrams that illustrate how the solubility line, metastable region, and instability line are derived. BR Most of these diagrams are drawn incorrectly. Think about where the solubility line originates from – can the graph as drawn be parallel to an axis in principle? In practice, examine the solubility functions for salts and PEGS. There is also no difference thermodynamically between the metastable and ‘labile’ zone – everything between the solubility line and the spinodal decomposition line is metastable and supersaturated. ‘Labile’ means something different in thermodynamics than in colloquial terms. The correct description of this part of the metastable region is one of spontaneous homogeneous nucleation. Consult the schematic G/x diagrams that illustrate how the solubility line, metastable region, and instability line are derived.

BR

]]> By: Sean http://www.P212121.com/2009/11/15/the-phase-diagram-in-protein-crystallization/comment-page-1/#comment-1286 Sean Mon, 16 Nov 2009 04:54:54 +0000 http://www.P212121.com/?p=7079#comment-1286 I agree the situation is quite complicated and this post does not cover all the details. As I am sure you already know this type of phase diagram has been used quite often such as in this paper on <a href="http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6WN5-4D4JRY7-3-11&_cdi=6953&_user=7778205&_orig=search&_coverDate=11%2F30%2F2004&_sk=999659996&view=c&wchp=dGLbVlb-zSkzk&md5=59c2b5a5b3aba5ffe3867c697236e591&ie=/sdarticle.pdf" rel="nofollow">Protein crystallization & phase diagrams</a>, a <a href="http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6VS6-4DB5RWS-2-7&_cdi=6254&_user=7778205&_orig=search&_coverDate=10%2F01%2F2004&_sk=999859994&view=c&wchp=dGLbVlW-zSkWb&md5=e07d0c6ef25db6c0ac224557738d4a83&ie=/sdarticle.pdf" rel="nofollow">paper</a> by Chayen, an <a href="http://www.mitegen.com/products/jen_screens/Background_Information.pdf" rel="nofollow">explanation</a> by Jena Bioscience or <a href="http://www-structmed.cimr.cam.ac.uk/Course/Crystals/Theory/dialysis.jpg" rel="nofollow">this figure</a> from Cambridge. I do not know of any incorrect statements in this post, but will gladly update it if they are specifically brought to my attention. Thanks for sharing the link on the physical chemistry of protein crystallization. Unfortunately, I do not have a copy of your book to consult. I agree the situation is quite complicated and this post does not cover all the details.
As I am sure you already know this type of phase diagram has been used quite often such as in this paper on Protein crystallization & phase diagrams, a paper by Chayen, an explanation by Jena Bioscience or this figure from Cambridge.

I do not know of any incorrect statements in this post, but will gladly update it if they are specifically brought to my attention. Thanks for sharing the link on the physical chemistry of protein crystallization. Unfortunately, I do not have a copy of your book to consult.

]]> By: BR http://www.P212121.com/2009/11/15/the-phase-diagram-in-protein-crystallization/comment-page-1/#comment-1285 BR Mon, 16 Nov 2009 04:13:39 +0000 http://www.P212121.com/?p=7079#comment-1285 Hi All - the situation is not quite as described here, and actually more complicated. I suggest to consult Chapter 3 in my book and to revise this posting accordingly. The difference between thermodynamic phase diagrams and the tentative (to conjectural) kinetic information pasted into the 'crystallization diagrams' is explained there. For those who are curious, the underlying thermodynamic theory is on http://www.ruppweb.org/Xray/tutorial/PC_of_crystallization.htm Best, BR Hi All -

the situation is not quite as described here, and actually more complicated. I suggest to consult Chapter 3 in my book and to revise this posting accordingly. The difference between thermodynamic phase diagrams and the tentative (to conjectural) kinetic information pasted into the ‘crystallization diagrams’ is explained there. For those who are curious, the underlying thermodynamic theory is on http://www.ruppweb.org/Xray/tutorial/PC_of_crystallization.htm

Best, BR

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