Re: [ccp4bb] Malic Acid interferes heavy metal binding?
Did you grow Malic Acid crystals? I see no reason why glycerol cannot be the precipitant. I am aware that at least one protein is crystallized with ethylene glycol as the precipitant. On Wed, 9 Jan 2008, JINJIN ZHANG wrote: Dear All, I have got large and nice crystals in a condition that contains 40% glycerol, 75 mM DL-Malic Acid pH7.0, and that's it! No precipitant?! No buffer?! I'm so comfused. As far as from the product website, the Malic Acid has no buffering function. I don't know whether it's a precipitant. The protein itself was stored in a buffer contains 20mM Tris pH7.5, 150mM NaCl and 10% glycerol. I'm having difficulties in getting heavy metal bound derivatives. I was wondering whether the Malic Acid interferes heavy metal binding? Does anyone has any success with crystals grow with similar conditions? Any comment and suggestion is highly appreciated. Regards, Jinjin Zhang
[ccp4bb] Malic Acid interferes heavy metal binding?
Dear All, I have got large and nice crystals in a condition that contains 40% glycerol, 75 mM DL-Malic Acid pH7.0, and that's it! No precipitant?! No buffer?! I'm so comfused. As far as from the product website, the Malic Acid has no buffering function. I don't know whether it's a precipitant. The protein itself was stored in a buffer contains 20mM Tris pH7.5, 150mM NaCl and 10% glycerol. I'm having difficulties in getting heavy metal bound derivatives. I was wondering whether the Malic Acid interferes heavy metal binding? Does anyone has any success with crystals grow with similar conditions? Any comment and suggestion is highly appreciated. Regards, Jinjin Zhang
Re: [ccp4bb] Malic Acid interferes heavy metal binding?
Dear Jinjin: Malic acid, a diprotic acid, has a pKa of about 3.4 for the first dissociation and a second at about 5.1. So it is best as a buffer within a pH range of about 2.4 to 6.1, and it at its best around best in the range of 3.4 to 5.1. If the pH of your solution is indeed 7, then it is doing little to buffer it (but the small amount of tris might). Many diprotic and polyprotic organic acids chelate metal ions. If you could substitute a different dianionic salt in the mother liquor, like a sulphate, it might help. Bill On Wed, 9 Jan 2008 18:42:06 -0500 JINJIN ZHANG [EMAIL PROTECTED] wrote: Dear All, I have got large and nice crystals in a condition that contains 40% glycerol, 75 mM DL-Malic Acid pH7.0, and that's it! No precipitant?! No buffer?! I'm so comfused. As far as from the product website, the Malic Acid has no buffering function. I don't know whether it's a precipitant. The protein itself was stored in a buffer contains 20mM Tris pH7.5, 150mM NaCl and 10% glycerol. I'm having difficulties in getting heavy metal bound derivatives. I was wondering whether the Malic Acid interferes heavy metal binding? Does anyone has any success with crystals grow with similar conditions? Any comment and suggestion is highly appreciated. Regards, Jinjin Zhang
Re: [ccp4bb] Malic Acid interferes heavy metal binding?
Hi, Heavy atoms can be unpredictable. There are rules of thumb regarding their use but these rules are frequently bent and broken. Which heavy atom derivatives have you tried, and at what (approximately) concentrations and exposure times? Does your protein have residues that *can* react with HA compounds? What do you mean when you say 'no success' - do the crystals survive unperturbed, or do they always die? There almost always is a derivative for you out there, but sometimes you have to spend time looking. If you have tyrosine residues in relative abundance you can always try iodination (let me know if you want a good working protocol), etc. More details would let us help you better! Artem _ From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] On Behalf Of JINJIN ZHANG Sent: Wednesday, January 09, 2008 6:42 PM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] Malic Acid interferes heavy metal binding? Dear All, I have got large and nice crystals in a condition that contains 40% glycerol, 75 mM DL-Malic Acid pH7.0, and that's it! No precipitant?! No buffer?! I'm so comfused. As far as from the product website, the Malic Acid has no buffering function. I don't know whether it's a precipitant. The protein itself was stored in a buffer contains 20mM Tris pH7.5, 150mM NaCl and 10% glycerol. I'm having difficulties in getting heavy metal bound derivatives. I was wondering whether the Malic Acid interferes heavy metal binding? Does anyone has any success with crystals grow with similar conditions? Any comment and suggestion is highly appreciated. Regards, Jinjin Zhang
