*** For details on how to be removed from this list visit the *** *** CCP4 home page http://www.ccp4.ac.uk ***
I222 and P2(1)2(1)2 are closely related. Change one of the crystallographic two-folds into a non-crystallographic two-fold and Bob's your uncle. Demetallized Concanavalin A crystallizes in P2(1)2(1)2. Add cations to the crystals and they'll change into the same form (I222) that you get by crystallizing the metallo-protein directly. See Becker et al. (1975) JBC 250:1513 and Reeke et al. (1978) PNAS 75:2286. Joe Becker Merck Research Labs -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Zorg Blue Sent: Wednesday, November 08, 2006 2:58 AM To: [email protected] Subject: [ccp4bb]: Pseudosymmetry and free R sets *** For details on how to be removed from this list visit the *** *** CCP4 home page http://www.ccp4.ac.uk *** Hello, We have solved the structure of a protein that crystallised in space group I222 with 1 molecule per asymmetric unit. After refining the structure to 3.5 A, we obtained a different crystal form that diffracts to higher resolution; in this case, the space group appears to be P21212, with the same unit cell as the first type of crystals and 2 molecules per asymmetric unit. The packing between the two molecules in the P21212 asymmetric unit is identical to that of symmetry-related molecules in the I222 crystals, suggesting that the space group of crystal form 1 could also be P21212, with non-crystallographic symmetry giving rise to strong pseudo-I222 symmetry at low resolution. Since we have already refined our model against the low resolution data processed in I222, what would be the best way to define a new free R set in order to continue refinement against the higher resolution P21212 data? If our interpretation is correct, I would think that using a completely new set would introduce some bias; on the other hand, is there any way to somehow take into account the pseudo-symmetry we observe? Thank you for any advice, Zorg _________________________________________________________________ Stay in touch with old friends and meet new ones with Windows Live Spaces http://clk.atdmt.com/MSN/go/msnnkwsp0070000001msn/direct/01/?href=http:/ /spaces.live.com/spacesapi.aspx?wx_action=create&wx_url=/friends.aspx&mk t=en-us ------------------------------------------------------------------------------ Notice: This e-mail message, together with any attachments, contains information of Merck & Co., Inc. (One Merck Drive, Whitehouse Station, New Jersey, USA 08889), and/or its affiliates (which may be known outside the United States as Merck Frosst, Merck Sharp & Dohme or MSD and in Japan, as Banyu - direct contact information for affiliates is available at http://www.merck.com/contact/contacts.html) that may be confidential, proprietary copyrighted and/or legally privileged. It is intended solely for the use of the individual or entity named on this message. If you are not the intended recipient, and have received this message in error, please notify us immediately by reply e-mail and then delete it from your system. ------------------------------------------------------------------------------
