There is also one case of a protein structure that I am aware of, where a
similar problem has been tackled (the phenomenon is also known as
one-dimensional disorder, according to A.J.C. Wilson - yes, the one how
invented the plot).
Check: Trame, CB & mcKay, DB (2001). Acta Cryst. D57, 1079-1090.
Boaz
----- Original Message -----
From: "George M. Sheldrick" <[EMAIL PROTECTED]>
Date: Monday, August 27, 2007 18:49
Subject: Re: [ccp4bb] Strange diffraction images
To: [email protected]
> Some small molecule crystallographers have specialized in
> solving and
> refining structures that, exactly as you describe it, consist of
> two (or
> more) interpenetrating, non-commensurable lattices. The usual
> approach is
> to decribe the crystal in up to six dimensional space. The
> programs SAINT
> and EVALCCD are able to integrate such diffraction patterns and
> SADABS is able to scale them. However the case in point is
> probably
> commensurate.
>
> George
>
> Prof. George M. Sheldrick FRS
> Dept. Structural Chemistry,
> University of Goettingen,
> Tammannstr. 4,
> D37077 Goettingen, Germany
> Tel. +49-551-39-3021 or -3068
> Fax. +49-551-39-2582
>
>
> On Mon, 27 Aug 2007, Jacob Keller wrote:
>
> > What a beautiful and interesting diffraction pattern!
> >
> > To me, it seems that there is a blurred set of spots with
> different cell dimensions, although
> > nearly the same, underlying the ordered diffraction pattern. A
> possible interpretation occurred to
> > me, that the ordered part of the crystal is supported by a
> less-ordered lattice of slightly
> > different dimensions, which, because the crystal is a like a
> layer-cake of 2-d crystals, need not
> > be commensurable in the short range with the ordered lattice.
> The nicely-ordered "cake" part of the
> > crystal you solved, but the "frosting" between is of a
> different, less ordered nature, giving rise
> > to the diffuse pattern which has slightly different lattice
> spacing. I would have to see more
> > images to know whether this apparent lattice-spacing
> phenomenon is consistent, but it at least
> > seems that way to me from the images you put on the web. I
> would shudder to think of indexing it,
> > however.
> >
> > All the best,
> >
> > Jacob Keller
> >
> > ps I wonder whether a crystal was ever solved which had two
> interpenetrating, non-commensurable
> > lattices in it. That would be pretty fantastic.
>
>
> Jacob,
>
> Some small molecule crystallographers have specialized in
> solving and
> refining structures that, exactly as you describe it, consist of two
> interpenetrating, non-commensurate lattices. The usual approach is
> to index the diffraction pattern in multiple dimensional space
> ('superspace'). The programs SAINT and EVALCCD are able to
> integrate
> diffraction patterns in up to six dimensions, SADABS is able to
> scale
> them and the refinement is almost always performed with
> Petricek's
> program JANA2000:
>
> http://www-xray.fzu.cz/jana/Jana2000/jana.html
>
> However the case in point is probably commensurate.
>
> George
>
> Prof. George M. Sheldrick FRS
> Dept. Structural Chemistry,
> University of Goettingen,
> Tammannstr. 4,
> D37077 Goettingen, Germany
> Tel. +49-551-39-3021 or -3068
> Fax. +49-551-39-2582
>
Boaz Shaanan, Ph.D.
Dept. of Life Sciences
Ben-Gurion University of the Negev
Beer-Sheva 84105
Israel
Phone: 972-8-647-2220 ; Fax: 646-1710
Skype: boaz.shaanan‎
