Ignore my post.. should be a proton on one of the oxygens in carbonate. Interesting question! ________________________________ From: CCP4 bulletin board [[email protected]] on behalf of Jordan Baumhardt [[email protected]] Sent: Thursday, November 10, 2016 2:57 PM To: [email protected] Subject: Re: [ccp4bb] Nitrate versus Carbonate
If I had to speculate, the polarity vector vs. atomic geometry would be the difference to utilize. The pKa of carbonate is around 6.3 for the first oxygen, so at physiological pH I would assume the majority of carbonate is in the deprotonated form.. Thus distributing the polarity vector between the two charged oxygens unlike nitrate. Interested to hear what others think, Jordan ________________________________ From: CCP4 bulletin board [[email protected]] on behalf of Keller, Jacob [[email protected]] Sent: Thursday, November 10, 2016 2:41 PM To: [email protected] Subject: [ccp4bb] Nitrate versus Carbonate Dear Crystallographers, I don’t think there is any feasible way crystallographically to distinguish between nitrate and carbonate or bicarbonate—correct? But that is not my main question. My main question is: given that nitrate and carbonate are both very important and also very different physiologically, and therefore they must be distinguished/recognized by cells, how is this done, since the ions are so similar in structure? Is there some aspect of these ions that differs dramatically of which I am not aware? What kind of “handles” could a protein grab onto to distinguish between nitrate and carbonate/bicarbonate? JPK ******************************************* Jacob Pearson Keller, PhD Research Scientist HHMI Janelia Research Campus / Looger lab Phone: (571)209-4000 x3159 Email: [email protected]<mailto:[email protected]> ******************************************* ________________________________ UT Southwestern Medical Center The future of medicine, today.
