Re: [ccp4bb] zinc with HEPES

[Boaz Shaanan]

Could it be that the pH is too high? Zn is amphoteric and you might be seeing a precipitate of Zn(OH)2. Boaz   Boaz Shaanan, Ph.D.                                         Dept. of Life Sciences                                      Ben-Gurion University of the Negev                          Beer-Sheva 84105                                            Israel                                                                                                                  E-mail: bshaa...@bgu.ac.il Phone: 972-8-647-2220  Skype: boaz.shaanan                  Fax:   972-8-647-2992 or 972-8-646-1710                          From: CCP4 bulletin board [CCP4BB@JISCMAIL.AC.UK] on behalf of Rajesh Kumar [ccp4...@hotmail.com] Sent: Friday, May 11, 2012 7:26 PM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] zinc with HEPES Dear All, This question sounds simple but I dont know the answer. I was preparing a 24 well crystal screen. When I try to use 10 mM  ZnSO4 with HEPES (pH 7.6) buffer it precipitates. I tried both ZnCl2 and Zn acetate the effect is same.   I dont know why this Zn in not compatible with HEPES. Could you please tell me why is this? I appreciate your help. Thanks Rajesh