Helical Arrangement (helical + arrangement)

Distribution by Scientific Domains
Distribution within Chemistry


Selected Abstracts


The Three-Dimensional Arrangement of the Myocytes Aggregated Together Within the Mammalian Ventricular Myocardium

THE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 1 2009
Morten Smerup
A 3-D helical arrangement of aggregates of myocytes in a pig's heart revealed by diffusion tensor MRI. See Smerup et al., on page 1, of this issue. [source]


Hydrogen bonding and ,,, interactions in 1-benzofuran-2,3-dicarboxylic acid and its 1:1 cocrystals with pyridine, phenazine and 1,4-phenylenediamine

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2009
Hatem M. Titi
The structure of 1-benzofuran-2,3-dicarboxylic acid (BFDC), C10H6O5, (I), exhibits an intramolecular hydrogen bond between one ,COOH group and the other, while the second carboxyl function is involved in intermolecular hydrogen bonding to neighbouring species. The latter results in the formation of flat one-dimensional hydrogen-bonded chains in the crystal structure, which are ,,, stacked along the normal to the plane of the molecular framework, forming a layered structure. 1:1 Cocrystallization of BFDC with pyridine, phenazine and 1,4-phenylenediamine is associated with H-atom transfer from BFDC to the base and charge-assisted hydrogen bonding between the BFDC, monoanion and the corresponding ammonium species, while preserving, in all cases, the intramolecular hydrogen bond between the carboxyl and carboxylate functions. The pyridinium 2-carboxylato-1-benzofuran-3-carboxylic acid, C5H6N+ĚC10H5O5,, (II), and phenazinium 3-carboxylato-1-benzofuran-2-carboxylic acid, C12H9N2+ĚC10H5O5,, (III), adducts form discrete hydrogen-bonded ion-pair entities. In the corresponding crystal structures, the two components are arranged in either segregated or mixed ,,, stacks, respectively. On the other hand, the structure of 4-aminoanilinium 2-carboxylato-1-benzofuran-3-carboxylic acid, C6H9N2+ĚC10H5O5,, (IV), exhibits an intermolecular hydrogen-bonding network with three-dimensional connectivity. Moreover, this fourth structure exhibits induction of supramolecular chirality by the extended hydrogen bonding, leading to a helical arrangement of the interacting moieties around 21 screw axes. The significance of this study is that it presents the first crystallographic characterization of pure BFDC, and manifestation of its cocrystallization with a variety of weakly basic amine molecules. It confirms the tendency of BFDC to preserve its intramolecular hydrogen bond and to prefer a monoanionic form in supramolecular association with other components. The aromaticity of the flat benzofuran residue plays an important role in directing either homo- or heteromolecular ,,, stacking in the first three structures, while the occurrence of a chiral architecture directed by multiple hydrogen bonding is the dominant feature in the fourth. [source]


Crystallization and preliminary X-ray analysis of Leishmania major glyoxalase I

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 8 2005
Antonio Ariza
Glyoxalase I (GLO1) is a putative drug target for trypanosomatids, which are pathogenic protozoa that include the causative agents of leishmaniasis. Significant sequence and functional differences between Leishmania major and human GLO1 suggest that it may make a suitable template for rational inhibitor design. L. major GLO1 was crystallized in two forms: the first is extremely disordered and does not diffract, while the second, an orthorhombic form, produces diffraction to 2.0,┼. Molecular-replacement calculations indicate that there are three GLO1 dimers in the asymmetric unit, which take up a helical arrangement with their molecular dyads arranged approximately perpendicular to the c axis. Further analysis of these data are under way. [source]


Two Zosterophyll Plants from the Lower Devonian (Lochkovian) Xitun Formation of Northeastern Yunnan, China

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2009
Jinzhuang XUE
Abstract: Two zosterophyll plants are described from the Lower Devonian (Lochkovian) Xitun Formation of Qujing, Yunnan, China. Xitunia spinitheca gen. et sp. nov. has stalked sporangia laterally attached on the axis in a helical arrangement. Sporangia are dorsoventrally flattened and composed of two unequal valves; the adaxial valve is round in face view, while the abaxial valve is larger than the former, triangular or wedge-shaped, and radially bears long spiny appendages along the distal margin. Xitunia shows new variation of sporangial morphology within the zosterophylls. Zosterophyllum minorstachyum sp. nov. has K-shaped branchings at the basal parts and small-sized terminal spikes, which consist of round to elliptical sporangia arranged helically. This paper provides new data on the diversity of plant types during Lochkovian when rare vascular plants were reported. As for various species of Zosterophyllum in South China, their apparent evolutionary trend of features from the Late Silurian to Early Devonian (Emsian) is discussed. [source]


Construction of a Novel Topological Frustrated System: A Frustrated Metal Cluster in a Helical Space

CHEMISTRY - A EUROPEAN JOURNAL, Issue 36 2010
Ryuta Ishikawa
Abstract A novel topologically frustrated pentanuclear cluster helicate [{CuII(,-L)3}2CuII3(,3 -OH)]3+ (L,=3,5-bis(2-pyridyl)pyrazolate) has been synthesized and characterized. This cluster has a helical arrangement of ligands around the central metal core. Dzyaloshinsky,Moriya interactions are essential components to observe a gradual magnetization and forbidden transitions of high-field/multi-frequency (HF/MF)-ESR. The origin of the magnetic anisotropy of this compound is influenced by its helical spin structure, and consequently, the Cu5 -cluster helicate introduces a unique magnetic anisotropy. This observation is a direct evidence of the topological part of the new spin phase in a magnetic system. [source]


Preparation of C3 -Symmetric Homochiral syn -Trisnorbornabenzenes through Regioselective Cyclotrimerization of Enantiopure Iodonorbornenes

CHEMISTRY - AN ASIAN JOURNAL, Issue 8 2009
Masud Reza
Abstract C3 -symmetric homochiral (,)- syn -trisoxonorbornabenzene 1 possessing a rigid cup-shaped structure was synthesized through a novel regioselective cyclotrimerization of enantiopure iodonorbornenes catalyzed by palladium nanoclusters. The yield of the cyclotrimerization was dependent on the stability of the palladium clusters, which was ascertained from the appearance and TEM images of the reaction mixtures. The efficient preparation of (,)- syn - 1 was established in short steps, including the newly developed cyclotrimerization reaction. The thus-prepared homochiral (,)- syn - 1 can serve as a key intermediate for the synthesis of C3 -symmetric homochiral cup-shaped molecules with a helical arrangement of substituents. Introduction of several types of substituents was well demonstrated through palladium-catalyzed coupling reactions with the corresponding phosphate and triflate of (,)- syn - 1. [source]