Distinct Structural Types Research Articles

Differential Subcellular Localization of RIC-3 Isoforms and Their Role in Determining 5-HT3 Receptor Composition

RIC-3 has been identified as a chaperone molecule involved in promoting the functional expression of nicotinic acetylcholine and 5-HT(3) receptors in mammalian cells. In this study, we examined the effects of RIC-3a (isoform a) and a truncated isoform (isoform d) on RIC-3 localization, mobility, and aggregation and its effect on 5-HT3 receptor composition in mammalian cells. Human RIC-3a possesses an amino-terminal signal sequence that targets it to the endoplasmic reticulum where it is distributed within the reticular network, often forming large diffuse "slicks" and bright "halo" structures. RIC-3a is highly mobile within and between these compartments. Despite the propensity for RIC-3a to aggregate, its expression enhances the level of surface 5-HT3A (homomeric) receptors. In contrast, RIC-3a exerts an inhibitory action on the surface expression of heteromeric 5-HT3A/B receptors. RIC-3d exhibits an altered subcellular distribution, being localized to the endoplasmic reticulum, large diffuse slicks, tubulo-vesicular structures, and the Golgi. Bidirectional trafficking between the endoplasmic reticulum and Golgi suggests that RIC-3d constitutively cycles between these two compartments. In support of the large coiled-coil domain of RIC-3a being responsible for protein aggregation, RIC-3d, lacking this cytoplasmic domain, does not aggregate or induce the formation of bright aggregates. Regardless of these differences, isoform d is still capable of enhancing homomeric, and inhibiting heteromeric, 5-HT3 receptor expression. Thus, both isoforms of RIC-3 play a role in determining 5-HT3 receptor composition.

Structural systematics of 4,4′-disubstituted benzenesulfonamidobenzenes. 1. Overview and dimer-based isostructures

One hundred 4,4'-disubstituted benzenesulfonamidobenzenes, X-C(6)H(5)-SO(2)-NH-C(6)H(5)-Y, where X, Y = NO(2), CN, CF(3), I, Br, Cl, F, H, Me, OMe, have been synthesized and their crystal structures determined. The resulting set of 133 structures, which includes polymorphic forms, is used to make a comparative study of the molecular packing and the nature of the intermolecular interactions, including the formation of hydrogen-bonding motifs and the influence of the two substituents X and Y on these features. Nine distinct supramolecular connectivity motifs of hydrogen bonding are encountered. There are 74% of all the structures investigated which exhibit one of two motifs based on N-H...O=S interactions, a dimer or a chain. There are three other, infrequent motifs, also employing N-H...O=S links, which exhibit more complexity. Four different chain motifs result from either N-H...O=N, N-H...C[triple-bond]N or N-H...OMe interactions, arising from the presence of a nitro (position Y), nitrile (X or Y) or methoxy (Y) substituent. The program XPac [Gelbrich & Hursthouse (2005). CrystEngComm, 7, 324-336] was used to systematically analyse the packing relationships between crystal structures. Similar discrete (zero-dimensional) and extended (one-dimensional and two-dimensional) structure components, as well as cases of isostructurality were identified. A hierarchy for the classification of the 56 distinct structure types of this set is presented. The most common type, a series of 22 isostructures containing the simple centrosymmetric N-H...O=S-bonded dimer, is discussed in detail.

The 24-Angstrom Structure of Respiratory Syncytial Virus Nucleocapsid Protein-RNA Decameric Rings

Respiratory syncytial virus (RSV), a nonsegmented, negative-sense RNA-containing virus, is a common cause of lower respiratory tract disease. Expression of RSV nucleocapsid protein (N) in insect cells using the baculovirus expression system leads to the formation of N-RNA complexes that are morphologically indistinguishable from viral nucleocapsids. When imaged in an electron microscope, three distinct types of structures were observed: tightly wound short-pitch helices, highly extended helices, and rings. Negative stain images of N-RNA rings were used to calculate a three-dimensional reconstruction at 24 A resolution, revealing features similar to those observed in nucleocapsids from other viruses of the order Mononegavirales. The reconstructed N-RNA rings comprise 10 N monomers and have an external radius of 83 A and an internal radius of 40 A. Comparison of this structure with crystallographic data from rabies virus and vesicular stomatitis virus N-RNA rings reveals striking morphological similarities.

Synthesis, structure and spectroscopic characterization of Ni(II), Co(II), Cu(II) and Zn(II) complexes with saccharinate and pyrazole

Four mononuclear mixed-ligand complexes of Co(II), Ni(II), Cu(II) and Zn(II), with saccharin (sac) and pyrazole (Hpz) were synthesized and characterized on the basis of elemental analysis, FT-IR spectroscopy, magnetic susceptibility, thermal analysis data and X-ray diffraction. The [Co(sac) 2(Hpz) 2(H 2O) 2] ( 1) and [Ni(sac) 2(Hpz) 2(H 2O) 2] ( 2) had similar molecular structures but distinct monoclinic crystal structure types (space group P2 1/ n for 1 and P2 1/ c for 2); the members of each pair of ligands were mutually trans. The saccharinate ligands were N-coordinated. The copper complex showed the same coordination environment as the Co and Ni complexes but crystallizes in the triclinic space group P 1 ¯ and presented pseudo-Jahn–Teller distortion along the O(w)–Cu–O(w) bonds. The [Zn(sac) 2(pz) 2] complex was tetrahedrally coordinated and crystallized in the monoclinic space group C2/ c. Thermal decomposition of the complexes in a nitrogen atmosphere resulted in removal of the water molecules and pyrazole ligands at relatively low temperature and formation of stable metal saccharinates as intermediates, which also decomposed at higher temperatures, about 300 °C.

Metal Ions May Suppress or Enhance Cellular Differentiation in Candida albicans and Candida tropicalis Biofilms

Candida albicans and Candida tropicalis are polymorphic fungi that develop antimicrobial-resistant biofilm communities that are characterized by multiple cell morphotypes. This study investigated cell type interconversion and drug and metal resistance as well as community organization in biofilms of these microorganisms that were exposed to metal ions. To study this, Candida biofilms were grown either in microtiter plates containing gradient arrays of metal ions or in the Calgary Biofilm Device for high-throughput susceptibility testing. Biofilm formation and antifungal resistance were evaluated by viable cell counts, tetrazolium salt reduction, light microscopy, and confocal laser scanning microscopy in conjunction with three-dimensional visualization. We discovered that subinhibitory concentrations of certain metal ions (CrO(4)(2-), Co(2+), Cu(2+), Ag(+), Zn(2+), Cd(2+), Hg(2+), Pb(2+), AsO(2)(-), and SeO(3)(2-)) caused changes in biofilm structure by blocking or eliciting the transition between yeast and hyphal cell types. Four distinct biofilm community structure types were discerned from these data, which were designated "domed," "layer cake," "flat," and "mycelial." This study suggests that Candida biofilm populations may respond to metal ions to form cell-cell and solid-surface-attached assemblages with distinct patterns of cellular differentiation.

Carbohydrate analysis and serological classification of typical and atypical isolates of Aeromonas salmonicida: A rationale for the lipopolysaccharide-based classification of A. salmonicida

The cell envelope of Aeromonas salmonicida contains a lipopolysaccharide (LPS) essential for the physical integrity and functioning of bacterial cell membrane. Using a recently developed in-source fragmentation technique, we screened 39 typical and atypical isolates of A. salmonicida and established their O-chain polysaccharide structure by capillary electrophoresis–mass spectrometry (CE–MS), compositional and linkage analyses and comparison to the previously determined O-chain polysaccharide structure of A. salmonicida strain A449. These studies have demonstrated that A. salmonicida isolates fall into three distinct structural types, types A–C, based on chemical structures of their respective O-chain polysaccharide components. Subsequent immunoblotting and serological studies with salmon polyclonal antisera produced to formalin-fixed cells of A. salmonicida strains A449, N4705 and 33659 representing three structural types A–C revealed that variations in the O-chain polysaccharide structure have led to significant serological differences between strains belonging to type A and non-type A, where non-type A species include chemically separated structural types B and C. Due to the presence of common antigenic determinants shared by their respective O-chain polysaccharide components, serological cross-reactions were observed between A. salmonicida strains belonging to structural types B and C. These findings suggest the possibility of developing LPS-based classification system of A. salmonicida sub-species consisting of two serologically distinct types, type A and non-type A.

Diversity of crystal structure with different lanthanide ions involving in situ oxidation–hydrolysis reaction

A series of lanthanide and lanthanide-transition metal compounds with isonicotinic acid (Hina) and oxalate ligands have been synthesized under hydrothermal reactions. X-Ray crystal structure analyses reveal that they have a rich structural chemistry. Three distinct structure types were exhibited with decreasing lanthanide radii: [LnCu(ina)(2)(C(2)O(4))].H(2)O (Ln=La 1, Pr 2, Nd 3) for type I, [Ln(ina)(C(2)O(4))(H(2)O)(2)] (Ln=Sm 4, Eu 5, Gd 6) for type II, and [Ln(ina)(C(2)O(4))(0.5)(OH)] (Ln=Tb 7, Dy 8, Er 9) for type III. The structure of type I has a 3d-4f heterometallic structure and consists of 1D channels along the b axis, which filled with guest water molecules. They exhibit a first 3D uninodal eight-connected framework with a unique 3(6).4(18).5(3).6 topology. Type II has 2D Ln-ina-C(2)O(4) 4(4)-nets, the nitrogen donors of the ina ligand are not coordinated to any of the metal ions, inducing the lower dimensional networks. Type III consists of 2D Ln-C(2)O(4) layers pillared by ina ligands to form a pillared-layer framework. The structure evolution is due to the versatile coordination modes of ina and oxalate ligands as well as the lanthanide contraction effect. Notably, the oxalate ligand was in situ synthesized from orotic acid through an oxidation-hydrolysis reaction. The type III materials show high thermal stability; luminescence properties of Nd 3, Sm 4, Eu 5, Tb 7 are also investigated.

Small molecule inhibitors of Abeta assembly

The Aβ peptide assembles into a variety of distinct types of structures in vitro and in the brain which have different biological consequences. Differential effects of inhibitory small molecules suggest that a sequential monomer – oligomer – fibril mechanism is overly simplistic and that soluble toxic oligomers and fibrils can be formed in common or separate pathways depending on the local environment. As a result, the effects of inhibitors are often assay-dependent because multiple pathways are operating. This review discusses strategies for teasing apart the intricate protein–protein interactions that result in Aβ assembly.

On the hydrophobicity of peptides: Comparing empirical predictions of peptide log P values

Peptides are of great therapeutic potential as vaccines and drugs. Knowledge of physicochemical descriptors, including the partition coefficient logP, is useful for the development of predictive Quantitative Structure-Activity Relationships (QSARs). We have investigated the accuracy of available programs for the prediction of logP values for peptides with known experimental values obtained from the literature. Eight prediction programs were tested, of which seven programs were fragment-based methods: XLogP, LogKow, PLogP, ACDLogP, AlogP, Interactive Analysis's LogP and MlogP; and one program used a whole molecule approach: QikProp. The predictive accuracy of the programs was assessed using r(2) values, with ALogP being the most effective (r( 2) = 0.822) and MLogP the least (r(2) = 0.090). We also examined three distinct types of peptide structure: blocked, unblocked, and cyclic. For each study (all peptides, blocked, unblocked and cyclic peptides) the performance of programs rated from best to worse is as follows: all peptides - ALogP, QikProp, PLogP, XLogP, IALogP, LogKow, ACDLogP, and MlogP; blocked peptides - PLogP, XLogP, ACDLogP, IALogP, LogKow, QikProp, ALogP, and MLogP; unblocked peptides - QikProp, IALogP, ALogP, ACDLogP, MLogP, XLogP, LogKow and PLogP; cyclic peptides - LogKow, ALogP, XLogP, MLogP, QikProp, ACDLogP, IALogP. In summary, all programs gave better predictions for blocked peptides, while, in general, logP values for cyclic peptides were under-predicted and those of unblocked peptides were over-predicted.

On the structure of the aedeagus of shield bugs (Heteroptera, Pentatomidae): III. Subfamily asopinae

This communication is the third one in a series of papers treated the morphological review of the aedeagi of Pentatomidae and its possible taxonomic significance. Fully inflated internal structures of the aedeagus of 18 species of Asopinae were studied. The examination of the Asopinae confirmed the monophyly of this taxon and revealed three distinct types of the aedeagal structure within the subfamily. These types differ in the structure of the theca, median penal plates, and ventral, ventrolateral, and apical conjuctival lobes. These characters can be used in phylogenetic analysis as well as in a tribal classification of asopines.

Reduced multireference coupled cluster method with singles and doubles: Perturbative corrections for triples

The reduced multireference coupled-cluster method with singles and doubles (RMR CCSD) that employs multireference configuration interaction wave function as an external source for a small subset of approximate connected triples and quadruples, is perturbatively corrected for the remaining triples along the same lines as in the standard CCSD(T) method. The performance of the resulting RMR CCSD(T) method is tested on four molecular systems, namely, the HF and F(2) molecules, the NO radical, and the F(2) (+) cation, representing distinct types of molecular structure, using up to and including a cc-pVQZ basis set. The results are compared with those obtained with the standard CCSD(T), UCCSD(T), CCSD(2), and CR CCSD(T) methods, wherever applicable or available. An emphasis is made on the quality of the computed potentials in a broad range of internuclear separations and on the computed equilibrium spectroscopic properties, in particular, harmonic frequencies omega(e). It is shown that RMR CCSD(T) outperforms other triply corrected methods and is widely applicable.

The first manganese trialkoxysilanethiolates: Formation, properties and structure of solvent ligated complexes – [Mn{SSi(OBu t) 3} 2(MeCN)] and [Mn{SSi(OBu t) 3} 2(MeOH) 4

First manganese(II) trialkoxysilanethiolates have been prepared using tri- tert-butoxysilanethiol as the ligand source and their structure determined by X-ray diffraction. Acetonitrile or methanol used as reaction solvents was found to enter Mn coordination sphere. Obtained heteroleptic silanethiolate complexes represent two distinct structural types. Either O, S-chelation by tri- tert-butoxysilanethiolate ligand and simultaneous electronic assistance provided by acetonitrile in [Mn{SSi(OBu t ) 3} 2(MeCN)] or formation of four intramolecular, interligand O–H ⋯ O hydrogen bonds in the case of [Mn{SSi(OBu t ) 3} 2(MeOH) 4] serve to stabilize the complexes.

Independent structural and valence state transitions in the cation-ordered double perovskites Ba 2−xSr xTbIrO 6

Synchrotron X-ray and neutron powder diffraction were used to investigate the formation, structure and bonding in the double perovskite Ba 2− x Sr x TbIrO 6 solid solutions. The results showed that these oxides all exhibit ordering of the Tb and Ir cations in a double perovskite-type structure. Three distinct structural types differing in symmetry and/or valence states were formed depending on the precise Ba:Sr ratio on the perovskite A site; x ⩽ 0.3 cubic ( Fm 3 ¯ m ) with Tb 4+ and Ir 4+; 0.4 ⩽ x ⩽ 1.0 cubic ( Fm 3 ¯ m ) with Tb 3+ and Ir 5+ and x ⩾ 1.2 monoclinic ( P2 1/ n) with Tb 3+ and Ir 5+. The transitions between these appear to be first order in nature.

Multifractal structure in nonrepresentational art

Multifractal analysis techniques are applied to patterns in several abstract expressionist artworks, painted by various artists. The analysis is carried out on two distinct types of structures: the physical patterns formed by a specific color ("blobs") and patterns formed by the luminance gradient between adjacent colors ("edges"). It is found that the multifractal analysis method applied to "blobs" cannot distinguish between artists of the same movement, yielding a multifractal spectrum of dimensions between about 1.5 and 1.8. The method can distinguish between different types of images, however, as demonstrated by studying a radically different type of art. The data suggest that the "edge" method can distinguish between artists in the same movement and is proposed to represent a toy model of visual discrimination. A "fractal reconstruction" analysis technique is also applied to the images in order to determine whether or not a specific signature can be extracted which might serve as a type of fingerprint for the movement.

The silence of the ribosomal RNA genes.

Over the past decade emerging evidence has indicated that epigenetic factors control and regulate nuclear processes. The genes encoding ribosomal RNA (rRNA) represent an ideal model to study how epigenetics and chromatin can modulate gene expression. The reason for this is that in each cell, the rRNA genes exist in two distinct types of chromatin structure: an 'open' one corresponding to transcriptionally active genes and a 'closed' one representing the silent genes. Recent studies indicate that an epigenetic network mediates the transcriptional state of rDNA. Interplay of DNA methylation, histone modification and chromatin-remodeling activities establishes silencing at the rDNA locus in higher eukaryotes as well as at the underdominant genes in hybrid cells. The aim of this review is to summarize current knowledge about the active and silent states of rRNA genes and of nucleolar organizing regions and to analyze the mechanisms involved in the establishment and inheritance of rDNA silencing.

Zinc(II)-benzoato complexes immobilised in mesoporous silica host

Mesoporous silica (MS) was synthesised using amphiphilic PEO–PPO–PEO surfactant (Pluronic F127). This chemically stable matrix composed of micropores and mesopores was used as host system for two bactericidal zinc(II) complexes of distinct structure types. The composite materials were characterised by thermogravimetry (TGA), IR spectroscopy, X-ray diffraction (XRD), N 2 adsorption, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Different loadings were achieved for the respective complexes. Their values were comparable with those obtained by incorporation of ibuprofen into MCM-41. The correlation of the results of XRD, nitrogen adsorption/desorption, X-ray structural analysis of the complexes and their interactions with the silica walls is discussed in the paper. Finally, the time dependence of the release of the complexes from the mesoporous system was investigated.

Comparative Analysis of the Curnow and Malykhin–Konnov–Komarov (MKK) Circuits as Representations of Coupled-Cavity Slow-Wave Structures

Two lumped element models of coupled-cavity slow-wave structures, one due to Curnow (1965) and another due to Malykhin, Konnov, and Komarov (MKK) (2003), are compared. The basis of comparison is the level of accuracy with which the models reproduce the cold circuit phase velocity and characteristic impedance of the structures as functions of frequency, as obtained from numerical solutions of Maxwell's field equations. Two distinct types of coupled-cavity structure are analyzed using these two models. These are a C-band double staggered ladder circuit and an L-band slot coupled Hughes-type structure. We find for the C-band case, both the Curnow and MKK models give excellent representations of both the cavity and slot bands, but for the L-band case the Curnow model has no solution when an attempt is made to fit both the cavity and slot bands, while the MKK model accurately represents both bands in this case.

3D seismic expression of fluid migration and mud remobilization on the Gjallar Ridge, offshore mid‐Norway

AbstractThis paper presents a three‐dimensional (3D) seismic analysis of sediment remobilization and fluid migration in a 2000‐km2 area above the Gjallar Ridge located in the Vøring Basin, offshore Norway. Three distinct types of mounded structures have been identified as resulting from focused fluid/gas migration and associated mud remobilization and intrusion. Type A structures are gently mounded, and we infer that these structures formed because of in situ remobilization of Middle Eocene to Lower–Middle Oligocene fine‐grained sediments in response to fluid and minor sediment injection via deep‐seated normal faults. Type B structures comprise relatively steep‐sided mounds and are restricted to the pre‐Miocene interval. They are often located above narrow zones of discontinuous low‐amplitude reflections resembling gas chimneys. Some of the Type B structures are associated with stacked amplitude anomalies and possible mud volcanoes at the base Pleistocene indicating their long‐term significance as vertical fluid conduits. Type C structures comprise discrete mound features that seem to jack up the Top Palaeocene (Top Brygge) horizon. These are similar to hydrothermal mounds found elsewhere on the Norwegian Margin and associated with igneous sill intrusion during North Atlantic breakup. This study highlights the utility of 3D seismic data for mapping of fluid and sediment mobilization through time over large basinal areas.

Optical study of the structural change in ReS2 single crystals using polarized thermoreflectance spectroscopy

In this report the optical properties of ReS2 are characterized using polarized thermoreflectance (PTR) measurements in the temperature range between 25 and 300 K. Single crystals of ReS2 were grown by chemical vapor transport method using Br2 as a transport agent. Crystal morphologies of the as-grown rhenium disulfides were shown to possess two different kinds of the structural phases after crystallization. Observing in detail on the crystallized solids, the crystal phases can be essentially divided into two distinct types of normal triclinic layer and tetragonal structure. The PTR experiments were done with optical polarizations along and perpendicular to the crystals' b-axis for both layer and tetragonal crystals. From the experimental analyses of PTR measurements the occurrence of structural change in ReS2 is mostly probable caused by the atomic bonding deformation along -axis, which is parallel to the Re4 parallelogram consisted diamond chains. Temperature dependences of the band-edge transitions for the different structural phases of ReS2 are analyzed. The parameters that describe temperature variations of the transition energies and broadening parameters for both layered and tetragonal ReS2 are evaluated and discussed.

Dépliage 3-D des anticlinaux bordant le synclinal fermé de la vallée des Ponts, Jura central, Suisse

The Ponts valley syncline is a closed basin within the Neuchâtel Jura fold and thrust belt. This syncline, apparently uplifted to an altitude of around 1000m is closed in the SW by an anticline with an oblique WNW-ESE direction. The 3-D geometry of the entire structure is examined and unfolded in detail. This syncline is filled with an unexpectedly thick series (~400m) of Tertiairy Molasse, as revealed by the CS-AMT (controlled source audio-magneto-telluric) and a reflexion seismic line. The latter also documents internal compressional structures within the well layered upper freshwater Molasse series. The 3-D configuration of the top Malm limestones has been constructed for the entire area based on new detailed geologic and structural mapping, hundreds of dip measurements, as well as geophysical data. The Malm marker bed displays three distinct types of structures: 1) Thrust faults with shallow dips, vergent to the NW and/or SE that are associated with folds interpreted as fault bend folds; 2) high angle inverse faults, mostly with a SE vergence are interpreted as inverted normal faults, inherited from a modest Oligo-Miocene extensional phase in a NW-SE direction; and 3) tear faults with a dominant N-S direction, probably inherited from an Oligocene extensional phase in association with the opening of the Rhine and Bresse grabens. Tear faults accommodate important lateral changes in fold geometry during the Late Miocene main folding-and-thrusting phase. All deformations are easily explained in an entirely thin-skinned fashion, taking place above a thick detachment horizon within Triassic evaporite series.