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:[email protected]] On Behalf Of Tommi Kajander Sent: Friday, March 20, 2009 3:43 PM To: [email protected] 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:[email protected]] On Behalf > Of Jim > Pflugrath > Sent: Friday, March 20, 2009 1:08 PM > To: [email protected] > 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 [email protected]
