Re: [ccp4bb]: substrate soaking into crystals

["Demetres D. Leonidas" <ddl@eie.gr>]

***  For details on how to be removed from this list visit the  ***
***          CCP4 home page http://www.ccp4.ac.uk         ***

Dear Manoj,

In some cases it helps if you substitute ammonium sulphate with sodium
potassium tartrate. Tartrate is much bigger than sulphate and usually
does not bind at the active site. I am not sure about the concentration
but I usually try the same concentration as the ammonium sulphate first.
However, KNa Tartrate and PEGs do not mix well and the salt precipitates
in high concentrations (e.g. greater that 1.0 M KNaTartrate and 30 %
PEG4000). In your case since you only use 0.2 M NH4(SO4)2 there should
not be any problem. Have a look at
 Leonidas et al (2001). J. Biol. Chem. 276, 15009-15017.

best of luck


Demetres

--
Demetres D. Leonidas, Ph.D.
National Hellenic Research Foundation
Institute of Biological Research & Biotechnology
48, Vassileos Constantinou Avenue
Athens 116 35, Greece
==================================================
Tel. +30-2107273763
Fax. +30-2107273758
E-mail: ddl@eie.gr
URL: http://athena.eie.gr/~demetres
==================================================