Re: [ccp4bb] Could someone can help me to explain why EDTA-2Na can formate salt crystals
What other cations are present? Any divalent cations like Mg++ or Ca++? The Ksp of magnesium phosphate is about 10^-24, so even if you have a very small amount present, say as a contaminant with citrate or EDTA, it will crystallize. On Feb 21, 2011, at 1:22 PM, Yibin Lin wrote: Dear all, I got a lot of salt crystals in reservior solution (well solution), which contains 0.1 M phosphate/citrate ph 4.2, PEG200 47%, EDTA-2Na 0-22mM. Reservior solution appears crystals from 12mM EDTA. Could someone help me to explain why? Thank you very much! Yibin William G. Scott Contact info: http://chemistry.ucsc.edu/~wgscott/
Re: [ccp4bb] Could someone can help me to explain why EDTA-2Na can formate salt crystals
No, there are not any other cations, so I feel very strange. Everything brought from sigma. On Tue, Feb 22, 2011 at 8:58 PM, William Scott wgsc...@ucsc.edu wrote: What other cations are present? Any divalent cations like Mg++ or Ca++? The Ksp of magnesium phosphate is about 10^-24, so even if you have a very small amount present, say as a contaminant with citrate or EDTA, it will crystallize. On Feb 21, 2011, at 1:22 PM, Yibin Lin wrote: Dear all, I got a lot of salt crystals in reservior solution (well solution), which contains 0.1 M phosphate/citrate ph 4.2, PEG200 47%, EDTA-2Na 0-22mM. Reservior solution appears crystals from 12mM EDTA. Could someone help me to explain why? Thank you very much! Yibin William G. Scott Contact info: http://chemistry.ucsc.edu/~wgscott/
Re: [ccp4bb] Could someone can help me to explain why EDTA-2Na can formate salt crystals
No, there are not any other cations, so I feel very strange. Everything brought from sigma. Nothing's strange. EDTA is very poorly soluble at pH 4.2 and would become even less soluble in the presence of 47% PEG. So it crystallizes. Dima On Tue, Feb 22, 2011 at 8:58 PM, William Scott mailto:wgsc...@ucsc.eduwgsc...@ucsc.edu wrote: What other cations are present? Any divalent cations like Mg++ or Ca++? The Ksp of magnesium phosphate is about 10^-24, so even if you have a very small amount present, say as a contaminant with citrate or EDTA, it will crystallize. On Feb 21, 2011, at 1:22 PM, Yibin Lin wrote: Dear all, I got a lot of salt crystals in reservior solution (well solution), which contains 0.1 M phosphate/citrate ph 4.2, PEG200 47%, EDTA-2Na 0-22mM. Reservior solution appears crystals from 12mM EDTA. Could someone help me to explain why? Thank you very much! Yibin William G. Scott Contact info: http://chemistry.ucsc.edu/~wgscott/http://chemistry.ucsc.edu/~wgscott/
Re: [ccp4bb] Could someone can help me to explain why EDTA-2Na can formate salt crystals
Your 0.1 M Phosphate/citrate can form crystal at high PEG. Deqian From: CCP4 bulletin board [CCP4BB@JISCMAIL.AC.UK] On Behalf Of Yibin Lin [yyb...@gmail.com] Sent: Tuesday, February 22, 2011 2:24 PM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Could someone can help me to explain why EDTA-2Na can formate salt crystals No, there are not any other cations, so I feel very strange. Everything brought from sigma. On Tue, Feb 22, 2011 at 8:58 PM, William Scott wgsc...@ucsc.edumailto:wgsc...@ucsc.edu wrote: What other cations are present? Any divalent cations like Mg++ or Ca++? The Ksp of magnesium phosphate is about 10^-24, so even if you have a very small amount present, say as a contaminant with citrate or EDTA, it will crystallize. On Feb 21, 2011, at 1:22 PM, Yibin Lin wrote: Dear all, I got a lot of salt crystals in reservior solution (well solution), which contains 0.1 M phosphate/citrate ph 4.2, PEG200 47%, EDTA-2Na 0-22mM. Reservior solution appears crystals from 12mM EDTA. Could someone help me to explain why? Thank you very much! Yibin William G. Scott Contact info: http://chemistry.ucsc.edu/~wgscott/
[ccp4bb] Could someone can help me to explain why EDTA-2Na can formate salt crystals
Dear all, I got a lot of salt crystals in reservior solution (well solution), which contains 0.1 M phosphate/citrate ph 4.2, PEG200 47%, EDTA-2Na 0-22mM. Reservior solution appears crystals from 12mM EDTA. Could someone help me to explain why? Thank you very much! Yibin
Re: [ccp4bb] Could someone can help me to explain why EDTA-2Na can formate salt crystals
The pH is too low and the EDTA is insoluble. You need to be above pH ~8.0. Your best bet is to try another chelator. James On Feb 21, 2011, at 2:22 PM, Yibin Lin wrote: Dear all, I got a lot of salt crystals in reservior solution (well solution), which contains 0.1 M phosphate/citrate ph 4.2, PEG200 47%, EDTA-2Na 0-22mM. Reservior solution appears crystals from 12mM EDTA. Could someone help me to explain why? Thank you very much! Yibin
