Concave Face Research Articles

New planktic species of Kirchneriella Schmidle (Chlorophyceae, Selenastraceae) from Brazilian freshwaters

New planktic species of Kirchneriella Schmidle (Chlorophyceae, Selenastraceae) from Brazilian freshwaters. In the samples collected from an artificial lake, located in the metropolitan region of Sao Paulo, an interesting algal population morphologically similar to Kirchneriella Schmidle was found. The crescent-shaped cells were oriented, inside the colony, with their convex faces toward the periphery of the colony resembling those of K. roselata Hindak. However, the remaining portions of the mother cell wall with more or less radial arrangement similar to the connective mucilaginous threads of the genus Selenodictyon Uherkovich & Schmidt ex Comas & Komarek were also observed. After further studies based on light microscope, the studied material proves to be morphologically distinguishable from K. roselata, although it never forms rosette-like groups, which are typical in K. roselata. The remaining parts of the mother cell wall more or less radially disposed near the cells (autospores just released from the mother cell wall) are not connective threads. Thus, a new species, K. brasiliana, is described in this paper. According to literature, the main diagnostic feature of Selenodictyon is the crescent-shaped cells attached by their concave faces to mucilaginous stalks like in Dictyosphaerium; however, remaining portions of the mother cell wall more or less radially oriented were also formed in some Kirchneriella populations. Therefore, the authors consider that such feature could be misinterpreted as connective mucilaginous threads, which raises doubts regarding the validity of Selenodictyon.

Reduced depth inversion illusions in schizophrenia are state-specific and occur for multiple object types and viewing conditions.

Schizophrenia patients are less susceptible to depth inversion illusions (DIIs) in which concave faces appear as convex, but what stimulus attributes generate this effect and how does it vary with clinical state? To address these issues, we had 30 schizophrenia patients and 25 well-matched healthy controls make convexity judgments on physically concave faces and scenes. Patients were selectively sampled from three levels of care to ensure symptom heterogeneity. Half of the concave objects were painted with realistic texture to enhance the convexity illusion; the remaining objects were painted uniform beige to reduce the illusion. Subjects viewed the objects with one eye while laterally moving in front of the stimulus (to see depth via motion parallax) or with two eyes while remaining motionless (to see depth stereoscopically). For each group, DIIs were stronger with texture than without, and weaker with stereoscopic information than without, indicating that patients responded normally to stimulus alterations. More importantly, patients experienced fewer illusions than controls irrespective of the face/scene category, texture, or viewing condition (parallax/stereo). Illusions became less frequent as patients experienced more positive symptoms and required more structured treatment. Taken together, these results indicate that people with schizophrenia experience fewer DIIs with a variety of object types and viewing conditions, perhaps because of a lessened tendency to construe any type of object as convex. Moreover, positive symptoms and the need for structured treatment are associated with more accurate 3-D perception, suggesting that DII may serve as a state marker for the illness.

The effect of punch's shape on die compaction of pharmaceutical powders

This paper investigates the compaction of pharmaceutical powders using different shapes of punches. We introduce a model of mechanical behaviour Drucker–Prager Cap (DPC), using the approach of compressible continuous media. The model parameters that are depending on the material density, were identified from experimental data and a calibration process was applied on Microcrystalline Cellulose (MCC) powder. In addition, the mathematical formulation of the boundary problem of compaction in rigid tools brings back to an optimization problem with constraint, which is solved by finite element method. The Drucker–Prager Cap model, which is implemented in Abaqus/Standard software, was employed using a user subroutine, USDFLD. Three kinds of typical pharmaceutical tablets are considered: flat-face tablet and concave face tablet with two different depths. Results of simulations of die compaction cycle as compression, decompression and ejection, reproduce the powder compaction process for the studied shaped punches. The effects of the punch's shape on the compaction process were observed on the distribution and the maximum of stress and density in the compact. Examination of the density gradient according to the shape, suggests a capping tendency, which increases with the punch depth. This study illustrates the potentiality of the FEM method, which could be used as an efficient tool to predict the density and the stress distributions into shaped compacts and to provide a diagnostic of the capping problems.

Study of Q224K, V152G double mutation in bean PGIP2, an LRR protein for plant defense—An in silico approach

Polygalacturonase inhibiting proteins (PGIPs) are leucine-rich repeat (LRR) proteins from plants that are organized into multigene families. They act as specific inhibitors against Polygalacturonases (PGs) from phytopathogens and share high sequence identity within species. We performed in silico mutation (Q224K and V152G) in PGIP2 from Phaseolus vulgaris to corresponding residues of another member, PGIP1. This mutation is known to cause 100% loss of inhibition against the PG of fungus Fusarium phyllophilum (Fp). A comparative analysis between PGIP2 and the double mutant, using 50 ns molecular dynamics simulations explored structural difference affecting PG binding properties. Simulations revealed that the mutation at 224, strains this residue which acts as a lock for the PGIP-PG complex through main chain H-bond. Changes in secondary structural elements and strain in the bend region along the convex face of the solenoidal protein affected the flexibility of the mutant protein. At the concave interacting face of the mutant, subtle changes in the sidechain behavior of the PG-binding residues occurred in a concerted manner revealing flipping of aromatic rings to be crucial to avoid steric clash with FpPG in PGIP2. Docking PGIP2 and the mutant protein individually to FpPG illustrated the inability of the latter to inhibit FpPG leaving its active site free. Our study demonstrates that the effect of mutation affects the flexibility of the protein along the convex face, while binding specificity is altered through the concave face imparting minimal change in the typical structure supported by the LRRs.

ChemInform Abstract: Forming Tertiary Organolithiums and Organocuprates from Nitrile Precursors and Their Bimolecular Reactions with Carbon Electrophiles to Form Quaternary Carbon Stereocenters.

AbstractA general procedure for the synthesis of the organo‐metal reagents and their highly diastereoselective reaction with carbon electrophiles from the sterically more hindered concave face is presented.

Identifying a Safe Zone for Midface Augmentation Using Anatomic Landmarks for the Infraorbital Foramen

Midface augmentation is commonly used to improve the appearance of concave faces and to achieve balance in the facial contour. It can also be an adjunct to orthognathic or reconstructive surgery. However, an inherent risk of midface augmentation is injury to the infraorbital nerve where it exits the infraorbital foramen (IOF). This can result in significant morbidity, including loss of sensation to the midface, nasal sidewall, upper lip, and lower eyelid. The authors identify a safe zone of dissection in the midface for subperiosteal placement of infraorbital, paranasal, malar, and submalar implants, which avoids injury to the infraorbital nerve. Given the popularity of transconjuctival and intraoral access to the midface skeleton, the authors identified relevant bony and dental landmarks from radiographic images and measured distances between the IOF and these landmarks. Forty-four computed tomography scans of adult hemifaces were used to accurately locate the IOF in relation to the anatomic landmarks. Most often, the IOF's location correlated with the second premolar on a vertical axis. The average distance between the IOF and the infraorbital rim, piriform aperture, tip of the second premolar cusps, and lateral orbital rim was approximately 8.61, 17.43, 41.81, and 25.93 mm (respectively) in men and 8.25, 15.69, 37.33, and 24.21 mm (respectively) in women. A safe zone of dissection for midface augmentation has been identified, which differs from previous findings. Awareness of this zone may help clinicians locate the IOF and avoid injury to the nerve.

New maimetshid wasps in Cretaceous amber from Myanmar (Insecta: Hymenoptera)

The extinct, exclusively Cretaceous wasp family Maimetshidae is newly recorded from Earliest Cenomanian Burmese amber. Two new genera and species are described. Burmaimetsha concava gen. et sp. nov., based on a male and a female, is most similar to Guyotemaimetsha Perrichot, Nel & Néraudeau, from Albian-Cenomanian French amber, but differs in its larger mandibles, distinctly concave face, elongate antennomeres, and forewing with cell [1Rs] smaller and fourth abscissa of Rs shorter. Maimetshasia kachinensis gen. et sp. nov., is based on a male, and is characterized by asymmetric mandibles with two and three teeth, by its forewing venation without cross-vein 2rs-m, with cell [1M] large and trapezoidal, and vein 2Rs+M very short, and by the hind wing without a free apex of Rs. The family was evidently widespread in the Cretaceous, and the new records extend the paleobiogeographical range to the South-East of Eurasia. A discussion about the possible biology of Maimetshidae is provided.

Chemically Isolating Hot Spots on Concave Nanocubes

We report a simple and general strategy for selectively exposing and functionalizing the sharp corners of concave nanocubes, which are the SERS hot spots for such structures. This strategy takes advantage of the unique shape of the concave cubes by coating the particles with silica and then etching it away to expose only the corner regions, while maintaining the silica coating in the concave faces. These corner regions can then be selectively modified for improved enhancement and signal response with SERS.

DFT and MP2 study of the interaction between corannulene and alkali cations

Corannulene is an unsaturated hydrocarbon composed of fused rings, with one central five-membered ring and five peripheral six-membered rings. Its structure can be considered as a portion of C60. Corannulene is a curved π surface, but unlike C60, it has two accessible different faces: one concave (inside) and one convex (outside). In this work, computational modeling of the binding between alkali metal cations (Li(+), Na(+), and K(+)) and corannulene has been performed at the DFT and MP2 levels. Different corannulene···M(+) complexes have been studied and the transition states interconnecting local minima were located. The alkali cations can be bound to a five or six membered ring in both faces. At the DFT level, binding to the convex face (outside) is favored relative to the concave face for the three alkali cations studied, as it was previously published. This out preference was found to decrease as cation size increases. At the MP2 level, although a similar trend is found, some different conclusions related to the in/out preference were obtained. According to our results, migration of cations can take place on the convex or on the concave face. Also, there are two ways to transform a concave complex in a convex complex: migration across the edge of corannulene and bowl-to-bowl inversion.

Sulfonate pseudohalides of boron subphthalocyanine

The crystal structures of three sulfonate pseudohalide derivatives of boron subphthalocyanine (BsubPc) are described and compared with four structures of three published sulfonate derivatives. Benzenesulfonate boron subphthalocyanine [(benzenesulfonato)(subphthalocyaninato)boron, C(30)H(17)BN(6)O(3)S, (I)] crystallizes in the space group P-1 with Z = 2. The structure contains two centrosymmetric π-stacking interactions between the concave faces of the isoindoline units in the BsubPc ligands. 3-Nitrobenzenesulfonate boron subphthalocyanine [(3-nitrobenzenesulfonato)(subphthalocyaninato)boron, C(30)H(16)BN(7)O(5)S, (II)] crystallizes in the space group P2(1)/c with Z = 4. The structure contains an intermolecular S-O···π interaction from the sulfonate group to a five-membered N-containing ring of an isoindoline unit on the concave side of a neighbouring BsubPc ligand, at a distance of 3.151 (3) Å. The crystal of methanesulfonate boron subphthalocyanine [(methanesulfonato)(subphthalocyaninato)boron, C(25)H(15)BN(6)O(3)S, (III)] was produced via sublimation and it is not a solvate, in contrast with two previously published structures of the same compound. Compound (III) crystallizes in the space group P2(1)/n with Z = 2, and its structure is similar to that of the more common compound Cl-BsubPc.

HMGB1-Facilitated p53 DNA Binding Occurs via HMG-Box/p53 Transactivation Domain Interaction, Regulated by the Acidic Tail

Facilitated binding of p53 to DNA by high mobility group B1 (HMGB1) may involve interaction between the N-terminal region of p53 and the high mobility group (HMG) boxes, as well as HMG-induced bending of the DNA. Intramolecular shielding of the boxes by the HMGB1 acidic tail results in an unstable complex with p53 until the tail is truncated to half its length, at which point the A box, proposed to be the preferred binding site for p53(1-93), is exposed, leaving the B box to bind and bend DNA. The A box interacts with residues 38-61 (TAD2) of the p53 transactivation domain. Residues 19-26 (TAD1) bind weakly, but only in the context of p53(1-93) and not as a free TAD1 peptide. We have solved the structure of the A-box/p53(1-93) complex by nuclear magnetic resonance spectroscopy. The incipient amphipathic helix in TAD2 recognizes the concave DNA-binding face of the A box and may be acting as a single-stranded DNA mimic.

Estudo morfofuncional dos rins de cães da raça Golden Retriever afetados pela distrofia muscular (GRMD)

A Distrofia Muscular de Duchenne (DMD) é uma miopatia severa de caráter recessivo ligada ao cromossomo X e o modelo animal de estudo mais relevante é o Golden Retriever Muscular Dystrophy (GRMD). Além das severas alterações que ocorrem na musculatura estriada, muitos estudos mostram que outras estruturas, inclusive viscerais, podem se mostrar alteradas nesta patologia. Desta forma, este trabalho objetivou análisar e comparar possíveis alterações estruturais e funcionais do rim em cães GRMD. Neste modelo de estudo, foi possível observar a presença das faces convexa e côncava, do hilo renal e dos pólos craniais e caudais dos rins. O órgão mostrou-se envolto por uma cápsula fibrosa. Em um corte sagital do órgão, notou-se a presença das regiões cortical e medular e da pelve renal. Na análise microscópica foi possível identificar a zona medular e cortical com suas estruturas: os corpúsculos renais formados pelo glomérulo e pela cápsula de Bowman, os túbulos contorcidos proximais e distais, os ductos coletores, vasos sanguíneos e os segmentos das Alças de Henle. As dosagens séricas de creatinina e uréia encontram-se dentro dos limites de normalidade. Desta forma, de acordo com os nossos resultados, podemos concluir que os animais afetados estudados, não apresentaram alterações estruturais ou funcionais dos rins, o que nos permitir sugerir que apesar da ingestão hídrica comprometida, a estrutura renal, mantem- se preservada nos animais GRMD.

Cover Picture: A Mechanistic Study on the Nucleation and Growth of Au on Pd Seeds with a Cubic or Octahedral Shape (ChemCatChem 10/2012)

Shape-Controlled Synthesis of Pd–Au Bimetallic Nanocrystals The cover picture shows that Pd–Au bimetallic nanocrystals with a number of different morphologies, including hybrid dimers, core–shell nanocubes with flat faces, and core–shell nanocubes with concave faces, could all be synthesized by controlling the growth mode of Au on Pd cubic seeds. In their full paper on p. 1668 ff., Younan Xia et al. investigate the seed-mediated growth of Pd–Au bimetallic nanocrystals with a variety of controlled morphologies by manipulating the reaction kinetics through a set of experimental parameters, including the concentration of reductant, the amount of precursor, the temperature, and the Pd nanocrystals employed as the seeds. The high-index facets associated with a concave surface can potentially enhance the performance of Au-based nanocatalysts in a range of industrially important reactions.

Origins of Stereoselectivities of Dihydroxylations of cis-Bicyclo[3.3.0]octenes

Stereoselectivities of the dihydroxylations of cis-bicyclo[3.3.0]octene intermediates for a projected total synthesis of chromodorolide A have been explored experimentally. The reaction occurs unexpectedly on the apparently more hindered (concave) face; this result has been explained through computational studies using B3LYP and B3LYP-D3 methods. Torsional effects are largely responsible for the stereoselectivity encountered in the chromodorolide A synthesis. Many literature examples have been reported on related cases. QM calculations show that the stereoselectivities of dihydroxylations of fused cyclopentenes are influenced by the conformational rigidity or flexibility of the substrate. Torsional, electrostatic, and steric effects can all influence stereoselectivity, and the rigidity or flexibility of conformations of reactants provides a predictive guide to stereoselectivity.

Experimental and Computational Investigation of the Mechanism of Carbon Dioxide/Cyclohexene Oxide Copolymerization Using a Dizinc Catalyst

A detailed study of the mechanism by which a dizinc catalyst copolymerizes cyclohexene oxide and carbon dioxide is presented. The catalyst, previously published by Williams et al. (Angew. Chem. Int. Ed. 2009, 48, 931), shows high activity under just 1 bar pressure of CO2. This work applies in situ attenuated total reflectance infrared spectroscopy (ATR-FTIR) to study changes to the catalyst structure on reaction with cyclohexene oxide and, subsequently, with carbon dioxide. A computational investigation, using DFT with solvation corrections, is used to calculate the relative free energies for various transition states and intermediates in the cycle for alternating copolymerization catalyzed by this dinuclear complex. Two potentially competing side reactions, sequential epoxide enchainment and sequential carbon dioxide enchainment are also investigated. The two side-reactions are shown to be thermodynamically disfavored, rationalizing the high selectivity exhibited in experimental studies using 1. Furthermore, the DFT calculations show that the rate-determining step is the nucleophilic attack of the coordinated epoxide molecule by the zinc-bound carbonate group in line with previous experimental findings (ΔΔG353 = 23.5 kcal/mol; ΔG‡353 = 25.7 kcal/mol). Both in situ spectroscopy and DFT calculations indicate that just one polymer chain is initiated per dizinc catalyst molecule. The catalyst adopts a “bowl” shape conformation, whereby the acetate group coordinated on the concave face is a spectator ligand while that coordinated on the convex face is the initiating group. The spectator carboxylate group plays an important role in the catalytic cycle, counter-balancing chain growth on the opposite face. The DFT was used to predict the activities of two new catalysts, good agreement between experimental turn-over-numbers and DFT predictions were observed.

Structural Basis for Membrane Binding Specificity of the Bin/Amphiphysin/Rvs (BAR) Domain of Arfaptin-2 Determined by Arl1 GTPase

Membrane-sculpting BAR (Bin/Amphiphysin/Rvs) domains form a crescent-shaped homodimer that can sense and induce membrane curvature through its positively charged concave face. We have recently shown that Arfaptin-2, which was originally identified as a binding partner for the Arf and Rac1 GTPases, binds to Arl1 through its BAR domain and is recruited onto Golgi membranes. There, Arfaptin-2 induces membrane tubules. Here, we report the crystal structure of the Arfaptin-2 BAR homodimer in complex with two Arl1 molecules bound symmetrically to each side, leaving the concave face open for membrane association. The overall structure of the Arl1·Arfaptin-2 BAR complex closely resembles that of the PX-BAR domain of sorting nexin 9, suggesting similar mechanisms underlying BAR domain targeting to specific organellar membranes. The Arl1·Arfaptin-2 BAR structure suggests that one of the two Arl1 molecules competes with Rac1, which binds to the concave face of the Arfaptin-2 BAR homodimer and may hinder its membrane association.

A Mechanistic Study on the Nucleation and Growth of Au on Pd Seeds with a Cubic or Octahedral Shape

AbstractThis article reports a systematic study on the seed‐mediated growth of Pd–Au bimetallic nanocrystals with a variety of controlled morphologies. The key to the success of this synthesis is to manipulate the reaction kinetics by controlling a set of experimental parameters, which include the amount of ascorbic acid used as a reductant, the amount of HAuCl4 as a precursor to elemental Au, the reaction temperature, and the type of seeds employed. Starting from Pd nanocubes of 18 nm in edge length, Pd–Au bimetallic nanocrystals with a number of morphologies, which includes hybrid dimers, core–shell nanocubes with flat faces, and core–shell nanocubes with concave faces could all be obtained by simply speeding up the reduction of HAuCl4. The same synthesis and control could also be extended to seeds based on Pd octahedrons. For the first time, it was possible to generate Pd@Au core–shell nanocubes and octahedrons with concave faces. The Pd@Au core–shell nanocubes with concave faces exhibited enhanced activity in catalyzing the oxidization of ascorbic acid relative to their counterparts with flat faces or the cubic Pd seeds.

Crystal structure of JlpA, a surface-exposed lipoprotein adhesin of Campylobacter jejuni

The Campylobacter jejuni JlpA protein is a surface-exposed lipoprotein that was discovered as an adhesin promoting interaction with host epithelium cells, an early critical step in the pathogenesis of C. jejuni disease. Increasing evidence ascertained that JlpA is antigenic, indicating a role of JlpA in immune response during the infectious process. Here, we report the crystal structure of JlpA at 2.7Å resolution, revealing a catcher's mitt shaped unclosed half β-barrel. Although the apparent architecture of JlpA is somewhat reminiscent of other bacterial lipoproteins such as LolB, the topology of JlpA is unique among the bacterial surface proteins reported to date and therefore JlpA represents a novel bacterial cell surface lipoprotein. The concave face of the structure results in an unusually large hydrophobic basin with a localized acidic pocket, suggesting a possibility that JlpA may accommodate multiple ligands. Therefore, the structure provides framework for determining the molecular function of JlpA and new strategies for the rational design of small molecule inhibitors efficiently targeting JlpA.

Different crystal forms of a rich hydrogen bond acceptor compound resulting from alternative C–H⋯O and orthogonal CO⋯CO molecular interaction patterns

The racemic compound 2,4,6,8-tetracarbomethoxybicyclo[3.3.0]octa-2,6-diene-3,7-diol 3 is known to form a solvent-free crystal structure (Polymorph I) through repetition of a centrosymmetric dimeric unit that is constructed by concave face to concave face association of two shallow dish-shaped tetraester 3 molecules. Compounds employing such awkwardly shaped repeat units are known to be prone to yielding more than one crystal form. Systematic screening has now revealed a second solvent-free crystal form (Polymorph II), and also a family of essentially isostructural lattice inclusion compounds (Inclusion form I), of 3. The X-ray crystal structures of Polymorph II, and the p-xylene and cyclohexanol compounds of the inclusion crystal form, are described. The predominant weak interactions in all three crystal forms comprise C–H⋯O and orthogonal CO⋯CO attractive forces and their different arrangements are compared and contrasted.

Cryo Electron Tomography of Herpes Simplex Virus during Axonal Transport and Secondary Envelopment in Primary Neurons

During herpes simplex virus 1 (HSV1) egress in neurons, viral particles travel from the neuronal cell body along the axon towards the synapse. Whether HSV1 particles are transported as enveloped virions as proposed by the ‘married’ model or as non-enveloped capsids suggested by the ‘separate’ model is controversial. Specific viral proteins may form a recruitment platform for microtubule motors that catalyze such transport. However, their subviral location has remained elusive. Here we established a system to analyze herpesvirus egress by cryo electron tomography. At 16 h post infection, we observed intra-axonal transport of progeny HSV1 viral particles in dissociated hippocampal neurons by live-cell fluorescence microscopy. Cryo electron tomography of frozen-hydrated neurons revealed that most egressing capsids were transported independently of the viral envelope. Unexpectedly, we found not only DNA-containing capsids (cytosolic C-capsids), but also capsids lacking DNA (cytosolic A-/B-capsids) in mid-axon regions. Subvolume averaging revealed lower amounts of tegument on cytosolic A-/B-capsids than on C-capsids. Nevertheless, all capsid types underwent active axonal transport. Therefore, even few tegument proteins on the capsid vertices seemed to suffice for transport. Secondary envelopment of capsids was observed at axon terminals. On their luminal face, the enveloping vesicles were studded with typical glycoprotein-like spikes. Furthermore, we noted an accretion of tegument density at the concave cytosolic face of the vesicle membrane in close proximity to the capsids. Three-dimensional analysis revealed that these assembly sites lacked cytoskeletal elements, but that filamentous actin surrounded them and formed an assembly compartment. Our data support the ‘separate model’ for HSV1 egress, i.e. progeny herpes viruses being transported along axons as subassemblies and not as complete virions within transport vesicles.