Hi Hugh A data/parameter ratio of 0.5 does seem low even at 3.4 Ang, I would expect it closer to 1 (say 0.8 to 0.9) depending on the solvent content. Why is it low - is your completeness low? What matters from the point of view of what Rfree you should expect, all being well, is the observation/parameter ratio, i.e. counting restraints as observations. Your Rfree of 29 looks low for Rwork = 25 given that your observation/parameter ratio must be close to 1, unless of course you have increased it by adding a lot of additional restraints. Also you didn't say what are your parameters: are you refining individual B factors for example? - if so this will significantly reduce the observation/parameter ratio and is probably not advisable at 3.4 Ang.
Cheers -- Ian > -----Original Message----- > From: owner-ccp...@jiscmail.ac.uk [mailto:owner-ccp...@jiscmail.ac.uk] On > Behalf Of hugh morgan > Sent: 23 September 2009 13:48 > To: CCP4BB@JISCMAIL.AC.UK > Subject: Observation:parameter ratio > > Hi, > We are attempting to address a referees comment concerning our > data/parameter ratio for a 3.4 A structure. Although the ratio is only > 0.5, the R/Rfree is 25/29, which seems acceptable. Ideally I would like to > include a reference showing a graph or table of data:parameter vs > resolution but I have been unable to find such a paper. Please could > someone point me in the right direction. > Thanks in advance > > Hugh > > P.S. It would be nice to know if this table has been published > http://www- > structmed.cimr.cam.ac.uk/Course/Basic_refinement/Refinement.html > > or something similar to this, which includes higher resolution structures > http://dirac.cnrs-orleans.fr/plone/Members/hinsen/data-parameter-ratio-i n- > x-ray-structure-determination > > Disclaimer This communication is confidential and may contain privileged information intended solely for the named addressee(s). It may not be used or disclosed except for the purpose for which it has been sent. If you are not the intended recipient you must not review, use, disclose, copy, distribute or take any action in reliance upon it. If you have received this communication in error, please notify Astex Therapeutics Ltd by emailing i.tic...@astex-therapeutics.com and destroy all copies of the message and any attached documents. Astex Therapeutics Ltd monitors, controls and protects all its messaging traffic in compliance with its corporate email policy. The Company accepts no liability or responsibility for any onward transmission or use of emails and attachments having left the Astex Therapeutics domain. Unless expressly stated, opinions in this message are those of the individual sender and not of Astex Therapeutics Ltd. The recipient should check this email and any attachments for the presence of computer viruses. Astex Therapeutics Ltd accepts no liability for damage caused by any virus transmitted by this email. E-mail is susceptible to data corruption, interception, unauthorized amendment, and tampering, Astex Therapeutics Ltd only send and receive e-mails on the basis that the Company is not liable for any such alteration or any consequences thereof. Astex Therapeutics Ltd., Registered in England at 436 Cambridge Science Park, Cambridge CB4 0QA under number 3751674
