Agreed. Lots of thermal action is reflected in a high Wilson B and is consistent with a low diffraction limit: if average I keeps decreasing with resolution, it has to go below the limit of measurement at a lower resolution than a more sedate crystal, which will have a lower B and a higher diffraction limit.
A good way to get a reliable B factor for low resolution data is to analyze a "relative Wilson plot." Call your crystal of interest crystal two, and a high resolution crystal with a reliably known B factor crystal 1. Then plot the ln of the ratio of the <I>s of the two crystals vs rho. The plot will be linear and the intercept will give the scale (scale = exp (-intercept/2)) for crystal 2 relative to crystal 1 and the slope will give the difference in temperature factors (= -slope/2) between the two crystals. I learned this procedure in the 1970s from George Reeke, who encoded it in the late lamented ROCKS software suite, and I believe that he learned it from one of the wizards in the Lipscomb lab during the carboxypeptidase days. Joe Becker Merck Research Laboratories -----Original Message----- From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] On Behalf Of Eleanor Dodson Sent: Thursday, July 26, 2007 5:21 AM To: [email protected] Subject: Re: [ccp4bb] High Wilson B It is hard to get a resonable estimate of Wilson B with 4.5A to 3A data, but yes - if the crystal stops diffracting at 3A that seems reasonable to me Eleanor Michael Colaneri wrote: > Dear colleagues, > > I have a B of 75A**2 from Wilson statistics 4.7 to 3 A res, good > straight line. Has anyone seen a B so high in Wilson statistics? > > ( I understand that it is best to have higher res but I do not). > > Thanks. > > Mike Colaneri ------------------------------------------------------------------------------ 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. ------------------------------------------------------------------------------
