On a side note, I have created a web server that, based on your sample buffer, makes a crude attempt at prediciting conditions within a screen that may form salt crystals (though this probably should be taken with a grain of..... salt, ahem!).
http://www.pageforaday.com/xtalwizard/salt.php > Date: Thu, 14 May 2009 09:37:05 -0400 > From: ar...@xtals.org > Subject: Re: [ccp4bb] Na/K Phosphate > To: CCP4BB@JISCMAIL.AC.UK > > The reason for the odd K/Na combination is solubility - mixed phosphate is > more soluble than either of the individual ones. > > I try to avoid high phosphate conditions as the Plague. It's great for > molecular biology but horrible for crystallization because phosphate + a > variety of other ions = lovely salt crystals. It all usually ends up in > tears. > > If you absolutely must make phosphate buffers - just open up any basic > practical biochemistry book, there are standard ratios (both by weight and > by volumes of molar solutions) that produce specified pH in a wide range. > > Artem > > > Dear all, > > > > Quite a few crystallisation conditions in the screens feature > > 'sodium/potassium phosphate'. I'm curious to know why such a Na/K mix > > is there. As the pH is mostly determined by the (H2PO4)- to (HPO4)2- > > ratio, is there such a need to have both cations? If so, is the Na to > > K ratio important? > > > > On the more practical side of things, if you want to explore an > > initial hit based on sodium/potassium phosphate, how would you go > > about it - e.g. what phosphate buffers would you make and at what > > ratio would you mix them? > > > > Thanks in advance, > > Geoffrey Kong > > _________________________________________________________________ Insert movie times and more without leaving Hotmail®. http://windowslive.com/Tutorial/Hotmail/QuickAdd?ocid=TXT_TAGLM_WL_HM_Tutorial_QuickAdd1_052009
