Good morning! Max asked about histidine rings and Stephano said:
I also had asked a similar question some time ago, and Bruce said that it should be easy to build such restraints using his programs.
Perhaps I should clarify. I used the word "easy" in the sense that physicists often use that word -- that is, I see it as a solvable math problem. That doesn't mean that I know the solution off the top of my head, just that it is no harder than solving a geometry problem. Shelly mentioned a bit of code she has written for rotating a phosphate group. I haven't seen this code, but I would guess that it is the sort of "easy" solution I was refering to. The central point here is that Ifeffit (and by extension, Artemis) allows you to write such things as the distance between atoms in the form of an almost arbitrary algebraic expression. Given that handling a rigid group like a histidine ring is no more than a geometry problem and given that geometry problems are solved by algebra, Ifeffit (and by extension, Artemis) are completely up to this task. For the sake of complete disclosure, I should say that I have never, not even once in my career, measured or analyzed data on a sample containing a histidine ring. That should provide the complete context for my assertion that the problem is "easy". ;-) HTH, B -- Bruce Ravel ----------------------------------- ravel@phys.washington.edu Code 6134, Building 3, Room 405 Naval Research Laboratory phone: (1) 202 767 2268 Washington DC 20375, USA fax: (1) 202 767 4642 NRL Synchrotron Radiation Consortium (NRL-SRC) Beamlines X11a, X11b, X23b National Synchrotron Light Source Brookhaven National Laboratory, Upton, NY 11973 My homepage: http://feff.phys.washington.edu/~ravel EXAFS software: http://feff.phys.washington.edu/~ravel/software/exafs/