Dear Flavio, That does seem to me a bit of a mystery that you have there. Ie It isn’t as if you are doing back soaking ie now with a mother liquor minus a heavy atom. Hopefully others will provide insights, Best wishes, John Emeritus Professor John R Helliwell DSc
> On 22 Apr 2025, at 10:04, Flavio Di Pisa <[email protected]> wrote: > > > Dear community, > > I’ve observed differences when crystallizing the same protein using two > different setups: microbatch under (Al’s) oil and vapor diffusion sitting > drop. > > The protein crystallizes in a condition containing 50 mM cadmium as one of > the precipitating agents. In the sitting drop setup, I observe 2 well-defined > cadmium ions at the so-called mineralization site (please see PDB entry 5lg8 > and the related paper: https://www.pnas.org/doi/10.1073/pnas.1614302114), > with occupancies close to 1, as confirmed by the anomalous signal, plus other > "anomalous blob" near to this site. > > However, in the microbatch under oil setup, I never observe these cadmium > ions. Instead, I consistently detect only one cadmium ion with high > occupancy, and occasionally a second one with lower occupancy. > > In summary, crystallizing the same protein using these two setups results in > different metal-binding behavior. > > My question is: could it be that in microbatch under oil, ions might diffuse > away from the mineralization site? Could this account for the reduced number > of cadmium ions observed? Additionally, and more importantly, could the > crystallization setup influence the soaking efficiency of other metals, such > as iron (the natural substrate of this protein)? > > I’ve attached two screenshots: > > One (orange blob) represents the protein crystallized via vapor diffusion, > showing two well-defined anomalous peaks. > > The other shows the same site in a crystal grown via microbatch, where only > one anomalous signal (in white) is visible. > > I hope I’ve been clear. Thank you in advance, and I wish you all a great day! > > Best regards, > Flavio > > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 > > <Schermata del 2025-04-22 10-54-23.png> > <Schermata del 2025-04-22 10-54-51.png> ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/
