IUCr Newsletter - Volume 20, Number 4 - (Page 2)
Acta Cryst. (2012). A68, 667–674 (http://doi.org/jww)
Fifty years of aperiodic crystals
After von Laue had shown, in 1912, that crystals diffract X-rays and have
ordered arrays of atoms, it was assumed that an essential property of crystals
was their lattice periodicity. In 1982 quasicrystals were discovered showing
crystals with fivefold symmetry axes, which exclude lattice periodicity. This
was, however, not the first case of a crystal without lattice periodicity. In the
beginning of the 1960s more and more examples were found, such that in
1982 quite a number of crystallographers were aware of their existence. A
brief history of the slowly growing idea that crystals are not necessarily lattice
periodic, culminating in the discovery of quasicrystals, is given.
Patterson pattern for a Fibonacci
chain: the chain appears along a
horizontal line, the ‘physical space’.
Acta Cryst. (2012). B68, 667–676 (http://doi.org/jwx)
Solvatomorphism of 9,9’-[1,3,4-thiadiazole-2,5diylbis(2,3-thiophendiyl-4,1-phenylene)]bis[9Hcarbazole]: isostructurality, modularity and order–
B. stöGeR, P. Kautny, D. LumPi, e. ZoBetZ anD j. FRöhLich
The title compound features an unusual tendency to cocrystallize with
solvent molecules. The resulting solvates do not feature strong hydrogen
bonds, nor are the molecules arranged in framework structures. To describe
the structural diversity of six solvates of the title compound, we applied the
concept of modularity which was originally developed for inorganics and
minerals. Moreover, for one structure we used the formalism of order–disorder theory to explain the pseudo-symmetry and the twinning of the structure.
The order–disorder structure of the
MEK solvate. The largest regions
that are equivalent in all polytypes
are indicated to the right by brackets.
Acta Cryst. (2012). C68, o452–o455 (http://doi.org/jwz)
2,4-Dimethyl-1,3-thiazole-5-carboxylic acid: an X-ray structural study
at 100 K and Hirshfeld surface analysis
D.K. haZRa, m. muKheRjee, m. heLLiweLL anD a.K. muKheRjee
Single-crystal X-ray structure analysis of a new thiazolecarboxylic acid
derivative (I) determined using a high-quality data set collected at 100 K
shows an interplay of strong and weak hydrogen bonds. Three types of
eight-, ten-, and fifteen-member supramolecular synthons are edge-fused
to form a two-dimensional framework in (I). Additional reinforcement
within the framework is provided by S…S interactions. Intermolecular
contacts in (I) are predominantly of H…H, N…H, O…H and S…H
type, which can account for about 80% of the Hirshfeld surface area.
Formation of the two-dimensional framework in thiazolecarboxylic acid derivative (I).
Acta Cryst. (2012). D68, 1622–1631 (http://doi.org/jw2)
AMPLE: a cluster-and-truncate approach to solve the crystal
structures of small proteins using rapidly computed ab initio
j. BiBBy, R.m. KeeGan, o. mayans, m.D. winn anD D.j. RiGDen
Ab initio protein structure prediction, by programs such as Rosetta, can provide
starting models for solving novel structures from crystallographic data. Rather than
trying to construct the single best model, we generate ensembles which are known
to work well in molecular replacement (MR). We have demonstrated the feasibility of an approach based on identification and extraction of incomplete but locally
accurate search models from rapidly obtained Snapshots along structure solution by AMPLE. A cluster of ab initio models
ab initio predictions. 43% of a set of small is generated by structural alignment (top). Multiple truncated ensembles (e.g.
lower left) are derived from it, varying in their treatment, and trialled by MR. A
(<120 residues) proteins were successfully solved.
successful solution and rebuild are compared to the final structure lower right.
IUCr Newsletter ♦ Volume 20, Number 4 ♦ 2012
Table of Contents for the Digital Edition of IUCr Newsletter - Volume 20, Number 4
IUCr Newsletter - Volume 20, Number 4
Letter from the President
Crystallographic Meeting Reports
Index to Advertisers
Crystallographic Meetings Calendar
IUCr Newsletter - Volume 20, Number 4