Bernhard Refmac doesn't specify a target value for the chiral volume, it just specifies 'positive' or 'negative'. It presumably uses the chiral volume computed from the input co-ords as the target, so this is updated as the refinement proceeds. I guess the goal isn't to restrain the geometry to a particular value of the chiral volume, since that's already determined by the bond lengths & angles (apart from the sign ambiguity obviously), but rather just to prevent it from inverting to the other hand. Note that it doesn't have to be a chiral centre to use a chiral volume restraint, for a non-chiral centre where inversion is equivalent to rotation (if you ignore the atom labels), it can still be used to prevent inversion, since that would result in atom labels being swapped (all non-planar atom centres are chiral if you include the atom labels!).
Don't know how Shel-X handles it, I guess George will answer that. Cheers -- Ian > -----Original Message----- > From: owner-ccp...@jiscmail.ac.uk [mailto:owner-ccp...@jiscmail.ac.uk] On > Behalf Of Bernhard Rupp > Sent: 04 April 2009 05:21 > To: CCP4BB@jiscmail.ac.uk > Subject: chiral volume target value > > Dear All, > > assuming the chiral volume definition with r() a Cartesian position vector > > Vc = [r(N)-r(Ca)]*([r(C)-r(Ca)]x[r(Cb)-r(Ca)]) > > I always get about -0.65 A**3 > > Is this correct? Are there any target values? > > In a SHELX manual I read + 2.5 for the chiral volume - seems to > be different. > > (not to be confused with the pseudo-torsion target of +34 deg) > > Thx, BR > ----------------------------------------------------------------- > Bernhard Rupp > b...@ruppweb.org > http://www.ruppweb.org/ > ----------------------------------------------------------------- > The hard part about playing chicken > is to know when to flinch > ----------------------------------------------------------------- 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
