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Point 3: Use the saxs model for preliminary phasing of your HA derivative Jürgen ...................... Jürgen Bosch Johns Hopkins Bloomberg School of Public Health Department of Biochemistry & Molecular Biology Johns Hopkins Malaria Research Institute 615 North Wolfe Street, W8708 Baltimore, MD 21205 Phone: +1-410-614-4742 Lab: +1-410-614-4894 Fax: +1-410-955-3655 http://web.mac.com/bosch_lab/ On Mar 12, 2012, at 16:30, "Anastassis Perrakis" <[log in to unmask]> wrote: > Hi David - > > I think you have four hurdles to overcome: > > 1. How good is a SAXS envelope > 2. How will you place it in the right place > 3. How will you extend from ~15-20 A to around 4 A > 4. How will you extend from 4 A to beyond > > Steps 2 and 4 might be the easiest - albeit far from trivial. > Point 1 can be argued... > > However, I have not seen anyone cracking 3 in a convincing manner... > (in the absence of serious NCS) > > I hope the next emails prove me wrong though! > > A. > > On 12 Mar 2012, at 21:10, David Briggs wrote: > >> Hi CCP4bb, >> >> I would like to ask about "envelope phasing" - specifically with SAXS data. >> >> There are papers (1) and tutorials (2) describing how this might be >> done, but I have also found comments on the ccp4bb, such as this one >> (http://www.proteincrystallography.org/ccp4bb/message11690.html) which >> are somewhat less optimistic. >> >> I get the impression from my reading around that SAXS envelope phasing >> is somewhat difficult to do unless you have some NCS you can use to >> help the phase extension process. Does anybody have any >> opinions/evidence/examples/anecdotes/tips about how SAXS envelope >> phasing can be done successfully? >> >> Cheers, >> >> Dave >> >> (1) - eg - http://scripts.iucr.org/cgi-bin/paper?dz5081 >> (2) - eg - http://www.phaser.cimr.cam.ac.uk/index.php/Using_Electron_Density_as_a_Model >> >> ============================ >> David C. Briggs PhD >> Father, Structural Biologist and Sceptic >> ============================ >> University of Manchester E-mail: >> [log in to unmask] >> ============================ >> Webs : http://flavors.me/xtaldave >> Twitter: @xtaldave >> Skype: DocDCB >> ============================