I have soaked my crystals in sodium dithionite a reducing agent. I have not done mass spec but sequence is confirmed
On Tue, Jul 9, 2019 at 9:26 PM Bonsor, Daniel <[email protected]> wrote: > Have you mass-speced the protein before crystallization to make sure it > wasn’t derivatized during expression and/or purification, or compared the > mass spec of the crystals verses purified protein? Any fancy reagents or > other reductants used during purification? > > What about S-Acetyl-cysteine (3-letter code: SCY). > > > > Best, > > > > Dan > > > > Daniel A Bonsor PhD. > > Sundberg Lab > > Institute of Human Virology > > University of Maryland, Baltimore > > 725 W Lombard Street N370 > > Baltimore > > Maryland > > MD 21201 > > Tel: (410) 706-7457 > > > > > > *From:* CCP4 bulletin board [mailto:[email protected]] *On Behalf Of > *Lumbini > Yadav > *Sent:* Tuesday, July 09, 2019 5:22 AM > *To:* [email protected] > *Subject:* [ccp4bb] Fo-Fc density close to cysteine residue > > > > Dear all, > > > > We have found a huge Fo-Fc density close to cysteine residue (see attached > image) in the structure with resolution of 1.2A. In the crystallization > condition, we have PEG 3350, Potassium phosphate monobasic, glycerol and > protein was in Tris and NaCl. Before freezing the crystals were soaked in > mother liquor containing sodium dithionite. > > > > I have tried different modified cysteine (CSX, CSO, OCS, CME, CSS, SNC, CSD, > CXM, SCH, CSU) from the library and also SO3, SO2 and peroxide. But in > all the screenings we do see some part of Fo-Fc density unaddressed at 3 > sigma. > > > > Does anyone have an idea about what this density could be? Covalent > modification? > > > > Thanks. > > > > > > Kind regards, > > Lumbini > > > ------------------------------ > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1 > ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1
