Shouldn't the ability to distinguish enantiomers also depend upon the degree of asymmetry of the particle itself? (or pseudosymmetry, I suppose)
With SAXS it should be easier to distinguish right-handed and left-handed lock washers than it is to tell a right-handed from a left-handed wall screw. On Fri, Jun 26, 2015 at 2:14 PM, Reza Khayat <rkha...@ccny.cuny.edu> wrote: > That's interesting. Enantiomer differences can be detected at worse than > 20Angstrom resolution in EM reconstructions. What do you think is the > reason for this? > > > Reza Khayat, PhD > Assistant Professor > Department of Chemistry > City College of New York > 85 Saint Nicholas Terrace, CDI 12318 > New York, NY 10031 > http://www.khayatlab.org/ > 212-650-6070 > > -----Original Message----- > From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of > Zbyszek Otwinowski > Sent: Friday, June 26, 2015 11:43 AM > To: CCP4BB@JISCMAIL.AC.UK > Subject: Re: [ccp4bb] How to fit BioSAXS shape to the Structure > > At low resolution, without interpretable anomalous signal, neither SAXS > nor molecular replacement with SAXS model, can distinguish correct from > inverted solution. So inverted model will fit crystal data equally well. > > Only phase extension to much higher resolution (e.g. 5A) can help. > > > > > > Yes, SAXS has an enantiomer problem - mirror image DAMMIN/F > > reconstructions will give the same fit to the raw scattering data, > > whereas your protein structure will only fit one hand. > > > > SUPCOMB can certainly deal with this problem, as detailed in > > http://www.embl-hamburg.de/biosaxs/manuals/supcomb.html > > > > > > > > > > [image: David Briggs on about.me] > > > > David Briggs > > about.me/david_briggs > > <http://about.me/david_briggs> > > > > On 26 June 2015 at 12:04, Reza Khayat <rkha...@ccny.cuny.edu> wrote: > > > >> Hi, > >> > >> Follow up question on SAXS. Does SAXS have an enantiomer problem > >> like electron microscopy? In other words, does the calculated model > >> possess the correct handedness or can both handedness of a model fit > >> the scattering profile just as well? > >> > >> Best wishes, > >> Reza > >> > >> Reza Khayat, PhD > >> Assistant Professor > >> City College of New York > >> 85 St. Nicholas Terrace CDI 12308 > >> New York, NY 10031 > >> (212) 650-6070 > >> www.khayatlab.org > >> > >> On Jun 26, 2015, at 6:50 AM, David Briggs <drdavidcbri...@gmail.com> > >> wrote: > >> > >> SASTBX has an online tool for achieving this: > >> http://sastbx.als.lbl.gov/cgi-bin/superpose.html > >> > >> > >> > >> [image: David Briggs on about.me] > >> > >> David Briggs > >> about.me/david_briggs > >> <http://about.me/david_briggs> > >> > >> On 26 June 2015 at 11:39, Ashok Nayak <ashokgocrac...@gmail.com> wrote: > >> > >>> Dear Weifei, > >>> > >>> It can also be done manually in Pymol by changing the mouse mode > >>> from > >>> 3 > >>> button viewing to 3 button editing and later moving the envelope > >>> onto the X-ray structure or vice-versa, however the best fit can be > >>> achieved in SUPCOMB. > >>> > >>> regards > >>> Ashok Nayak > >>> CSIR-CDRI, Lucknow > >>> India > >>> > >>> > >> > >> > > > > > Zbyszek Otwinowski > UT Southwestern Medical Center at Dallas > 5323 Harry Hines Blvd. > Dallas, TX 75390-8816 > Tel. 214-645-6385 > Fax. 214-645-6353 >
