Structure determination according to "Nature"

William Tivol tivol at
Tue Apr 16 15:57:47 EST 1996

Hakon Hope (hhope at wrote:
: In the March 7, 1996 issue of Nature (p 27) appears an 
: article that among other items contains the following 
: description of present-day methods for structure 
: determination from x-ray data:

: "Such structure determinations must still be done by a 
: trial-and-error methodology, in which diffraction spot 
: intensities are calculated for various possible atomic 
: geometries and compared with experimental intensities." 
: (This is just part of the description. The article 
: contains more, equally valuable information.)

: I may be overly sensitive, but it seems to me that both the
: journal and the authors need an explanation of how 
: crystallographers go about their business. 
: Any suggestions?

Dear Hakon,
	A letter to the editor from a long-time xtalogrfr, such as you,
might go a long way.  I suppose the quote applies, to a limited degree,
to the process of refinement, where trial structures for proteins are
constructed from aa residues and placed in physically/chemically reason-
able positions, and the residual is minimized.  They are obviously over-
looking both the phasing to get the initial density map and such proceed-
ures as energy minimization to select likely conformations.
				Bill Tivol

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