New Findings in Old Geometry: Using Triangle Centers to Create Similar or Congruent Triangles

The Euler line of a triangle passes through several important points, including three specific triangle centers: the centroid, orthocenter, and circumcenter. Each of these centers is the intersection of lines related to the triangle, mainly its medians, altitudes, and perpendicular bisectors, respectively. We present three theorems which initially share a similar construction. Each involves starting with a triangle and a point. After connecting the triangle’s vertices to that point, creating additional triangles, we establish connections to either the centroids, orthocenters, or circumcenters of the new triangles

Evidence of Rock Kangaroo Seed Dispersal via Faecal Seed Storage in a Tropical Monsoon Community

While some of the plant species of the ‘Sandstone Country’ along the escarpment of western Arnhem Land produce fleshy fruits and appear to rely on biotic methods of seed dispersal, little is known about the methods by which this is achieved – and few potential dispersers co-occur in the sandstone outcrop communities. For the present study, scat collections were made on outcrops in the northeastern area of Kakadu National Park with the hope of uncovering relationships between local frugivores and fruit-producers, and providing evidence for seasonal storage of mammal-dispersed seeds in scat prior to germination. The goals of the present project were to collect and identify sandstone community macropod scat, determine the identity of seeds present in the scat, and provide support for the role of browser/grazer macropods as effective seed dispersers via faecal seed storage in an otherwise disperser-poor local fauna. Scat containing seeds was identified as belonging to the Black Wallaroo (Macropus bernardus), a rare and locally-endemic macropod considered an intermediate browser/ grazer. These seeds were successfully germinated and the seedlings identified using molecular phylogenetic techniques as Gardenia fucata (Rubiaceae), an endemic rock-specialist species – thus establishing the first confirmation of effective seed dispersal by a ‘rock kangaroo’ in this region and the first identification of a seed disperser for this uncommon Gardenia species. The results provide support for the role of browser/grazer macropods as occasional effective seed dispersers of rock-specialist plant species in the northern monsoon tropics of Australia via faecal seed storage

Conclusions

What is the function of parent–child argumentation? This chapter intends to answer the main research question that has guided the study presented in this volume and open a discussion for future research on this topic. In the first part, the chapter provides a detailed overview of the main findings of the analysis of parent–child argumentative discussions during mealtime. The role played by parents and children in the inception and development of argumentation, and the types of conclusions of their argumentative discussions are described. Subsequently, two educational targets achieved by parents and children through their argumentative interactions are presented and critically discussed. In the last part, new open questions that should guide future investigation to expand our knowledge of the role and function of argumentation between parents and children are proposed

Role of Secondary Motifs in Fast Folding Polymers: A Dynamical Variational Principle

A fascinating and open question challenging biochemistry, physics and even geometry is the presence of highly regular motifs such as alpha-helices in the folded state of biopolymers and proteins. Stimulating explanations ranging from chemical propensity to simple geometrical reasoning have been invoked to rationalize the existence of such secondary structures. We formulate a dynamical variational principle for selection in conformation space based on the requirement that the backbone of the native state of biologically viable polymers be rapidly accessible from the denatured state. The variational principle is shown to result in the emergence of helical order in compact structures.Comment: 4 pages, RevTex, 4 eps figure

Structure and Properties of the C-terminal Domain of Insulin-like Growth Factor-binding Protein-1 Isolated from Human Amniotic Fluid

Insulin-like growth factor (IGF)-binding protein-1 (IGFBP-1) regulates the activity of the insulin-like growth factors in early pregnancy and is, thus, thought to play a key role at the fetal-maternal interface. The C-terminal domain of IGFBP-1 and three isoforms of the intact protein were isolated from human amniotic fluid, and sequencing of the four N-terminal polypeptide chains showed them to be highly pure. The addition of both intact IGFBP-1 and its C-terminal fragment to cultured fibroblasts has a similar stimulating effect on cell migration, and therefore, the domain has a biological activity on its own. The three-dimensional structure of the C-terminal domain was determined by x-ray crystallography to 1.8 Angstroms resolution. The fragment folds as a thyroglobulin type I domain and was found to bind the Fe(2+) ion in the crystals through the only histidine residue present in the polypeptide chain. Iron (II) decreases the binding of intact IGFBP-1 and the C-terminal domain to IGF-II, suggesting that the metal binding site is close to or part of the surface of interaction of the two molecules

Surface Plasmon Resonance as a Tool for Ligand Binding Investigation of Engineered GPR17 Receptor, a G Protein Coupled Receptor Involved in Myelination

The aim of this study was to investigate the potential of surface plasmon resonance (SPR) spectroscopy for the measurement of real-time ligand-binding affinities and kinetic parameters for GPR17, a G protein-coupled receptor (GPCR) of major interest in medicinal chemistry as potential target in demyelinating diseases. The receptor was directly captured, in a single-step, from solubilized membrane extracts on the sensor chip through a covalently bound anti-6x-His-antibody and retained its ligand binding activity for over 24h. Furthermore, our experimental setup made possible, after a mild regeneration step, to remove the bound receptor without damaging the antibody, and thus to reuse many times the same chip. Two engineered variants of GPR17, designed for crystallographic studies, were expressed in insect cells, extracted from crude membranes and analyzed for their binding with two high affinity ligands: the antagonist Cangrelor and the agonist Asinex 1. The calculated kinetic parameters and binding constants of ligands were in good agreement with those reported from activity assays and highlighted a possible functional role of the N-terminal residues of the receptor in ligand recognition and binding. Validation of SPR results was obtained by docking and molecular dynamics of GPR17-ligands interactions and by functional in vitro studies. The latter allowed us to confirm that Asinex 1 behaves as GPR17 receptor agonist, inhibits forskolin-stimulated adenylyl cyclase pathway and promotes oligodendrocyte precursor cell maturation and myelinating ability

High resolution structures of mutants of residues that affect access to the ligand-binding cavity of human lipocalin-type prostaglandin D Synthase

Lipocalin-type prostaglandin D synthase (L-PGDS) catalyzes the isomerisation of the 9,11-endoperoxide group of PGH2 (Prostaglandin H2) to produce PGD2 (Prostaglandin D2) with 9-hydroxy and 11-keto groups. The product of the reaction, PGD2, is the precursor of several metabolites involved in many regulatory events. L-PGDS, the first member of the important lipocalin family to be recognized as an enzyme, is also able to bind and transport small hydrophobic molecules and was formerly known as \u3b2-trace protein, the second most abundant protein in human cerebro-spinal fluid. Previous structural work on the mouse and human proteins has focused on the identification of the amino acids responsible and the proposal of a mechanism for catalysis. In this paper we present the X-ray structures of the apo and holo forms (bound to PEG) of the C65A mutant of human L-PGDS to 1.40 \uc5 resolution and of the double mutant C65A K59A to 1.60 \uc5 resolution. We have also studied the apo forms of the double mutants C65A W54F and C65A W112F and the triple mutant C65A W54F W112F. Mutation of the lysine residue does not seem to affect the binding of PEG to the ligand-binding cavity and mutation of a single or both tryptophanes appears to have the same effect on the position of these two aromatic residues at the entrance of the cavity. We have also identified a solvent molecule in an invariant position in the cavity of virtually all the molecules present in the 9 asymmetric units of the crystals that we have examined. Taken together our observations indicate that the residues we have mutated appear to indeed play a role in the entrance-exit process of the substrate and/or other ligands to the binding cavity of the lipocalin

High resolution structures of mutants of residues that affect access to the ligand-binding cavity of human lipocalin-type prostaglandin D synthase

Lipocalin-type prostaglandin D synthase (L-PGDS) catalyzes the isomerisation of the 9,11-endoperoxide group of PGH2 (Prostaglandin H2) to produce PGD2 (Prostaglandin D2) with 9-hydroxy and 11-keto groups. The product of the reaction, PGD2, is the precursor of several metabolites involved in many regulatory events. L-PGDS, the first member of the important lipocalin family to be recognized as an enzyme, is also able to bind and transport small hydrophobic molecules and was formerly known as \u3b2-trace protein, the second most abundant protein in human cerebro-spinal fluid. Previous structural work on the mouse and human proteins has focused on the identification of the amino acids responsible and the proposal of a mechanism for catalysis. In this paper we present the X-ray structures of the apo and holo forms (bound to PEG) of the C65A mutant of human L-PGDS to 1.40 \uc5 resolution and of the double mutant C65A K59A to 1.60 \uc5 resolution. We have also studied the apo forms of the double mutants C65A W54F and C65A W112F and the triple mutant C65A W54F W112F. Mutation of the lysine residue does not seem to affect the binding of PEG to the ligand-binding cavity and mutation of a single or both tryptophanes appears to have the same effect on the position of these two aromatic residues at the entrance of the cavity. We have also identified a solvent molecule in an invariant position in the cavity of virtually all the molecules present in the 9 asymmetric units of the crystals that we have examined.Taken together our observations indicate that the residues we have mutated appear to indeed play a role in the entrance-exit process of the substrate and/or other ligands to the binding cavity of the lipocalin

Sleep, napping and alertness during an overwintering mission at Belgrano II Argentine Antarctic station

During Antarctic isolation personnel are exposed to extreme photoperiods. A frequent observation is a sleep onset phase delay during winter. It is not known if, as a result, daytime sleeping in the form of naps increases. We sought to assess sleep patterns - with focus on daytime sleeping - and alertness in a Latin American crew overwintering in Argentine Antarctic station Belgrano II. Measurements were collected in 13 males during March, May, July, September and November, and included actigraphy and psychomotor vigilance tasks. Sleep duration significantly decreased during winter. A total of eight participants took at least one weekly nap across all measurement points. During winter, the nap onset was delayed, its duration increased and its efficiency improved. We observed a significant effect of seasonality in the association of evening alertness with sleep onset. Our results replicate previous findings regarding sleep during overwintering in Antarctica, adding the description of the role of napping and the report of a possible modulatory effect of seasonality in the relation between sleep and alertness. Napping should be considered as an important factor in the scheduling of activities of multicultural crews that participate in Antarctica.Fil: Folgueira, Agustín Leandro. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires". Instituto de Investigaciones Biomédicas. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas; Argentina. Ministerio de Defensa. Ejército Argentino. Hospital Militar Central Cirujano Mayor "Dr. Cosme Argerich"; ArgentinaFil: Simonelli, Guido. Walter Reed Army Institute Of Research; Estados UnidosFil: Plano, Santiago Andrés. Universidad Nacional de Quilmes; Argentina. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires". Instituto de Investigaciones Biomédicas. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas; ArgentinaFil: Tortello, Camila. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires". Instituto de Investigaciones Biomédicas. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas; Argentina. Universidad Nacional de Quilmes; ArgentinaFil: Cuiuli, Juan Manuel. No especifíca;Fil: Blanchard, Abel. No especifíca;Fil: Patagua, Alejandro. No especifíca;Fil: Brager, Allison J.. Walter Reed Army Institute of Research; Estados UnidosFil: Capaldi, Vincent F.. Walter Reed Army Institute of Research; Estados UnidosFil: Aubert, André E.. Katholikie Universiteit Leuven; BélgicaFil: Barbarito, Marta. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Golombek, Diego Andrés. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Cronobiología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Vigo, Daniel Eduardo. Katholikie Universiteit Leuven; Bélgica. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires". Instituto de Investigaciones Biomédicas. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas; Argentin