I believe Wayne Hendrickson's lab has had such a case with a 10-fold
symmetric mollusc hemocyanin crystal. This must have been in the early
90's and to my knowlwedge they were never able to solve the structure
even though it diffracted beyond 2 Anstrom.
I'm not sure if this work has been published but you can check the paper
describing a single domain of this protein complex or contact one of its
authors.
Bart
J Mol Biol. 1998 May 15;278(4):855-70.
Crystal structure of a functional unit from Octopus hemocyanin.
Cuff ME, Miller KI, van Holde KE, Hendrickson WA.
Jacob Keller wrote:
I am still eagerly awaiting a biomacromolecular quasicrystal with a five-fold symmetric diffraction
pattern. It seems that this is entirely possible, if one gets roughly Penrose-tile shaped oligomers
somehow. But wow, how would you solve that thing? I guess one would have to modify software from
the small molecule or matsci folks.
Jacob
==============Original message text===============
On Mon, 27 Aug 2007 11:19:15 am CDT "George M. Sheldrick" wrote:
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
===========End of original message text===========
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Jacob Keller
Northwestern University
6541 N. Francisco #3
Chicago IL 60645
(847)467-4049
[EMAIL PROTECTED]
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