It is possible that the cysteine residue in question got oxidized - the likely products are sulfinic acid SO2H or sulfonic acid SO3H. Since the two molecules in the asymmetric unit are in different environments one could be more prone to the oxidation than the other. Alternatively reaction with some other component of the buffers. Hope this helps. Bob Robert Stroud str...@msg.ucsf.edu
> On Aug 10, 2022, at 7:59 AM, Thomas, Leonard M. <lmtho...@ou.edu> wrote: > > This Message Is From an External Sender > This message came from outside your organization. > Hello All, > > I have run into something odd. In working on a structure for one of the > groups I work with regularly, on one of the cystine residues I have a very > large positive density peak at the sulfur position. The B value is > approximately 4 times the other values in the residue and on other cystine > residues. The overall structure has 2 molecules in the asymmetric unit and > the corresponding cystine on the other monomer is behaving as I would > expect. There are no disulfides in the structure. > > The data were collected on 9-2 at SSRL and all three of the data sets we > collected show the same thing, all data go to about 2.2 angstroms. We are > trying to determine the ligand binding in the molecule but this cystine is > not involved in ligand binding. In house and other synchrotron data from > previous protein preps and data collection runs of the same molecule grown in > very similar condition and crystallized in the same space group have the > residue behaving normally. > > I am open to any ideas as to what may be going on as I am rather puzzled by > this. > > Thanks for any input, > Len Thomas > > Leonard Thomas, Ph.D. > Biomolecular Structure Core, Director > Oklahoma COBRE in Structural Biology > Price Family Foundation Institute of Structural Biology > University of Oklahoma > Department of Chemistry and Biochemistry > 101 Stephenson Parkway > Norman, OK 73019-5251 > Office: (405)325-1126 > lmtho...@ou.edu <mailto:lmtho...@ou.edu> > http://www.ou.edu/structuralbiology/cobre-core-facilities/mcl > <https://urldefense.com/v3/__http://www.ou.edu/structuralbiology/cobre-core-facilities/mcl__;!!LQC6Cpwp!vztqH52xLKt23C_nQThPcg7zc4C3gXpcMs_ExWY04zFVr6qQ3vva961Rtx-wPItxBGTVlZx0EY0i1d51lwU$> > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 > <https://urldefense.com/v3/__https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1__;!!LQC6Cpwp!vztqH52xLKt23C_nQThPcg7zc4C3gXpcMs_ExWY04zFVr6qQ3vva961Rtx-wPItxBGTVlZx0EY0icx4QUeE$> ######################################################################## 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/
