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RE: [ccp4bb]: Q: disulphide reduction in protein structures



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Hello,  You don't say whether the data was collected at 100 K or whether a
synchrotron source was used, but one other possibility is that your
disulfide was ionized by the X-ray exposure.  See the recent PNAS paper by
Weik et al vol97 p623-628, which points out the sensitivity of disulfides to
radiation damage, even at 100 K.  (At least when collecting on ESRF
ID14-EH4.) Cheers,  Dave Timm

-----Original Message-----
From: owner-ccp4bb@dl.ac.uk [mailto:owner-ccp4bb@dl.ac.uk]On Behalf Of
Yu Wai Chen
Sent: Thursday, February 17, 2000 5:42 AM
To: CCP4
Subject: [ccp4bb]: Q: disulphide reduction in protein structures


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Dear all,

Sorry this is not a CCP4 question.

Can buried (i.e. small or no solvent accessible surface area) disulphide
bonds be reduced to cysteines in general?  I have a structure in which 2
cysteines are in the right position to form a S-S bond but the electron
density shows otherwise.  My protein was purified in reducing
conditions.  However, from other evidences (structure homology), these
should form S-S.  Does anyone know of any published structure that can
shed light on my puzzle?  Thanks a lot.

Wai
--
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Yu Wai CHEN, Ph.D. ..................   email:ywc@mrc-lmb.cam.ac.uk
 Centre for Protein Engineering,             tel:+44-(0)1223-402148
 MRC Centre, Hills Rd, Cambridge CB2 2QH, UK fax:+44-(0)1223-402140
 WWW homepage: http://www.mrc-cpe.cam.ac.uk/~ywc