Difficult to be sure from a single angle pic but I would suggest Cys oxidation.
There is an important 20 years old paper (see below) on Cys oxidation in a tyrosine phosphatase (like yours) Best Roberti] Nature * <https://pubmed.ncbi.nlm.nih.gov/?term=%22Nature%22%5Bjour%5D&sort=date&sort_order=desc> * <https://www.ncbi.nlm.nih.gov/nlmcatalog?term=%22Nature%22%5BTitle+Abbreviation%5D> * <https://pubmed.ncbi.nlm.nih.gov/12802339/#> . 2003 Jun 12;423(6941):773-7. doi: 10.1038/nature01681. Oxidation state of the active-site cysteine in protein tyrosine phosphatase 1B Rob L M van Montfort<https://pubmed.ncbi.nlm.nih.gov/?term=van+Montfort+RL&cauthor_id=12802339> 1<https://pubmed.ncbi.nlm.nih.gov/12802339/#full-view-affiliation-1>, Miles Congreve<https://pubmed.ncbi.nlm.nih.gov/?term=Congreve+M&cauthor_id=12802339>, Dominic Tisi<https://pubmed.ncbi.nlm.nih.gov/?term=Tisi+D&cauthor_id=12802339>, Robin Carr<https://pubmed.ncbi.nlm.nih.gov/?term=Carr+R&cauthor_id=12802339>, Harren Jhoti<https://pubmed.ncbi.nlm.nih.gov/?term=Jhoti+H&cauthor_id=12802339> Roberto A Steiner www.steinerlab.org<http://www.steinerlab.org/> https://twitter.com/steiner_lab roberto.stei...@kcl.ac.uk<mailto:roberto.stei...@kcl.ac.uk> Randall Centre for Cell and Molecular Biophysics Faculty of Life Sciences and Medicine King's College London Room 3.10A New Hunt's House, Guy's Campus SE1 1UL, London, UK Phone 0044 20 78488216 Fax 0044 20 78486435 roberto.stei...@unipd.it<mailto:roberto.stei...@unipd.it> Dipartimento di Scienze Biomediche Università degli Studi di Padova Viale G. Colombo 3 35131 Padova, Italia Telefono 0039 049 8276409 Responses to emails are not expected outside of your normal working hours. On 18 Dec 2023, at 18:03, Liliana Margent <lmarg...@gradcenter.cuny.edu<mailto:lmarg...@gradcenter.cuny.edu>> wrote: You don't often get email from lmarg...@gradcenter.cuny.edu<mailto:lmarg...@gradcenter.cuny.edu>. Learn why this is important<https://aka.ms/LearnAboutSenderIdentification> Hi there, We’ve been having an issue in trying to clear regions of Fo-Fc density from a few cysteines during the refinement process. We were wondering if anyone had seen something similar so they could offer some insight on the likely chemistry at hand, and a potential refinement solution. Attached are two images of the observed extra density at two cysteines, 505 and 518. We have modeled acetylated cysteine, s-hydroxycysteine, and s-mercaptocysteine but it does not solve the density. The protein in question is a Protein Tyrosine Phosphatase known as STEP (PTPN5), with data collected to a resolution of 1.79 Å. The crystals were grown in bis-tris pH 6.65, 200mM Li2SO4, ~30% PEG3350. Of note, prior to data collection the crystal was conserved at room temp for long time where it dried, and was subsequently rehydrated with mother liquor. Thank you so much. ________________________________ To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 <Screenshot 2023-12-16 at 3.36.01 PM.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/
