<|delta F|>/<F> *c \approx < |delta I|/ I > , with c somewhere between 2.5 and 3.
Bijvoet amplitude ratios seem always more pessimistic then they should be. The 4 to 5% <|delta F|>/<F> would translate into a 10 to 12% expected difference for individual intensities. P 2009/3/20 Bernhard Rupp <b...@ruppweb.org>: > What is not true? > > Also in your case the applet estimates an expected > 4-5% signal which is quite doable with decent data. > > BR > > -----Original Message----- > From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On Behalf Of Tommi > Kajander > Sent: Friday, March 20, 2009 3:43 PM > To: CCP4BB@JISCMAIL.AC.UK > Subject: Re: [ccp4bb] Problems with phasing a protein (1300aa) > > this cant be true, > in the idea case (not Rmerge 15%, then again one can apply a resolution > cutoff, perhaps, while this sounds like a very desperate case) the > answer must be yes. didnt do the calculation right now (but it > _should_ back this up) > we for instance have solved a structure long time ago > -- and this probably wasnt on the limit (well it was at the time but > not anymore), 365 res x 8 in AU and 80 Se. > > at least looking at the SnB success list ("very" old list ) > http://www.hwi.buffalo.edu/SnB/SnBSuccesses.htm > there are plenty of others. > > -tommi > > On Mar 20, 2009, at 10:53 PM, Bernhard Rupp wrote: > >> One can estimate this from >> >> http://www.ruppweb.org/new_comp/anomalous_scattering.htm >> >> and the answer as Jim says is no. >> >> BR >> -----Original Message----- >> From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On Behalf >> Of Jim >> Pflugrath >> Sent: Friday, March 20, 2009 1:08 PM >> To: CCP4BB@JISCMAIL.AC.UK >> Subject: Re: [ccp4bb] Problems with phasing a protein (1300aa) >> >> Well, what do you expect the anomalous signal contributed from your 45 >> seleniums in a perfect world to be when the asymmetric unit contains >> 1300 >> aa? Do you think a dataset with Rmerge of ~15% is good enough to >> detect a >> signal of even 2%? (Note: I did not do the calculation, so I just >> made up >> the number of 2%.) >> >> Jim >> >> >> On Fri, 20 Mar 2009, Kumar wrote: >> >>> Hello CCP4bb members, >>> >>> I have been trying to obtain phases for a protein which contain >>> ~1300aa. >> We >>> have obtained native data to a resolution of 3.3A (Space group I222 >>> or >>> I212121). But we are having tough time phasing it. >>> ... >> > > Tommi Kajander, Ph.D. > Structural Biology and Biophysics > Institute of Biotechnology > University of Helsinki > Viikinkaari 1 > (P.O. Box 65) > 00014 Helsinki > Finland > p. +358-9-19158903 > tommi.kajan...@helsinki.fi > -- ----------------------------------------------------------------- P.H. Zwart Beamline Scientist Berkeley Center for Structural Biology Lawrence Berkeley National Laboratories 1 Cyclotron Road, Berkeley, CA-94703, USA Cell: 510 289 9246 BCSB: http://bcsb.als.lbl.gov PHENIX: http://www.phenix-online.org CCTBX: http://cctbx.sf.net -----------------------------------------------------------------
