I don't think that individual atoms can be RESOLVED at 2A resolution. Even if we forget that hydrogen is also an atom, it is still true that peaks in electron density corresponding to, say, covalently bonded atoms are not separated. If atomic positions at 2A would be over-determined, we won't need geometry restraints. Atomic resolution begins somewhere around 1.2A (not surprisingly since this is about the length of covalent bond). I think there is some confusion regarding the term "atomic resolution" because at some point in the past it signified the ability to refine atomic positions (vs just threading CA backbone through tubes of density). But then I am not old enough to pretend to be an expert on this.
Cheers, Ed. On Thu, 2008-05-15 at 12:11 -0400, [EMAIL PROTECTED] wrote: > On 14 May, Mark Del Campo wrote: > > At what refinement resolution or resolution ranges would you call a > > structure "high resolution" vs. > > "low resolution"? I realize that this may boil down to semantics (e.g. > > some may classify structures as > > "medium resolution"), but I wanted to get an opinion from the pros. > > A sensible definition of high resolution would be that resolution at > which the structure is computationally over-determined, which is about > 2 angstroms or better for a complete data set. This would also be a > sensible definition for what is called atomic resolution, because the > atoms are resolved as spheres or better, so that the position is > over-determined. > > Regards, > -- Edwin Pozharski, PhD, Assistant Professor University of Maryland, Baltimore ---------------------------------------------- When the Way is forgotten duty and justice appear; Then knowledge and wisdom are born along with hypocrisy. When harmonious relationships dissolve then respect and devotion arise; When a nation falls to chaos then loyalty and patriotism are born. ------------------------------ / Lao Tse /
