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Structural Origins (structural + origins)

Distribution by Scientific Domains
Chemistry75%

Selected Abstracts

ECONOMIC RESTRUCTURING AND URBAN FOOD ACCESS IN THE DOMINICAN REPUBLIC

ANNALS OF ANTHROPOLOGICAL PRACTICE, Issue 1 2009
Howard Rosing
The article describes how economic restructuring in the Dominican Republic during the 1980s and 1990s established the basis for urban food access challenges during the 2000s. Primarily based on research in Santiago, the second largest Dominican city, the article provides insights into how export-oriented development strategies, expanding trade liberalization, domestic political struggles, and patriarchal relations influenced access to food for low-income residents. During the early 2000s, many Santiago residents were engaged in an elaborate, androcentric exchange network that linked gendered income-generating strategies to credit-bearing food merchants who were, in turn, conjoined to a sequence of brokers all of whom were eventually linked to domestic and international producers by credit relations. Analysis of these findings illustrates how and why this exchange network existed, the importance of credit relations to its maintenance, and the ways in which government and U.S. food policies influenced urban provisioning patterns among the most economically and socially vulnerable population of Santiago. I argue that the rapidly changing social and spatial configurations of Latin American and Caribbean cities calls for innovative applied anthropological research into the processes that structure access to food resources by food insecure groups. By focusing on household food procurement in conjunction with exchange relations for a key staple, the article highlights practices and policies that enable and constrain food access for such groups. The article provides empirical data relevant to scholars and practitioners concerned with understanding the structural origins of the present-day food crisis in developing countries. [source]

L'arséniate Na3Fe2(AsO4)3: étude structurale de la forme basse température et simulation des propriétés de conduction des cations alcalins

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2008
Najoua Ouerfelli
The crystal structure of the low-temperature garnet-like form of trisodium diiron(III) triarsenate, Na3Fe2(AsO4)3, exhibits a three-dimensional framework with small tunnels running along the [111] direction, in which the Na+ cations are located. This study demonstrates the structural origins of the different ionic conductivities of the low- and high-temperature forms. Sodium conduction properties are simulated by means of the bond-valence-sum (BVS) model; the correlations between the low- and high-temperature crystal structures are discussed. The As, Fe and Na atoms lie on special positions (Wyckoff symbols 24d, 16a and 24c, respectively). [source]

WWWWhy does nature stutter?

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 2 2001
A survey of strands of repeated amino acids
Human stuttering is a simple example of the repetition of sounds or symbols, sometimes associated with single letters, and may be used to illustrate the amazing repetition of amino acids (symbolized by a letter, e.g. W) in proteins. A survey of available databases with highly improbable strings of single amino acids is tabulated. This paper concludes with a challenge to the crystallographic community to probe the structural origins of the structure,function relationship in this neglected area. When nature stutters, we should pay attention. [source]

Prediction of the Three-Dimensional Structure for the Rat Urotensin,II Receptor, and Comparison of the Antagonist Binding Sites and Binding Selectivity between Human and Rat Receptors from Atomistic Simulations

CHEMMEDCHEM, Issue 9 2010
Soo-Kyung Kim Dr.
Abstract Urotensin-II (U-II) has been shown to be the most potent mammalian vasoconstrictor known. Thus, a U-II antagonist might be of therapeutic value in a number of cardiovascular disorders. However, interspecies variability of several nonpeptidic ligands complicates the interpretation of in vivo studies of such antagonists in preclinical animal disease models. ACT058362 is a selective antagonist for the human U-II receptor (hUT2R) with a reported Kd value of ,4,nM in a molecular binding assay, but it is reported to bind weakly to rat UT2R (rUT2R), with a Kd value of ,1,500,nM. In contrast, the arylsulphonamide SB706375 is a selective antagonist against both hUT2R (Kd=,9,nM) and rUT2R (Kd=,21,nM). To understand the species selectivity of the UT2R, we investigated the binding site of ACT058362 and SB706375 in both hUT2R and rUT2R to explain the dramatically lower (,400-fold) affinity of ACT058362 for rUT2R and the similar affinity (,10,nM) of SB706375 for both UT2Rs. These studies used MembStruk and MSCDock to predict the UT2R structure and the binding site of ACT058362 and SB706375. Based on binding energies, we found two binding modes each with D1303.32 as the crucial anchoring point (Ballesteros,Weinstein numbering given in superscript). We predict that ACT058362 (an aryl,amine,aryl or ANA ligand) binds in the transmembrane (TM) 3456 region, while SB706375 (an aryl,aryl,amine or AAN ligand) binds in the TM 1237 region. These predicted sites explain the known differences in binding of the ANA ligand to rat and human receptors, while explaining the similar binding of the AAN compound to rat and human receptors. Moreover the predictions explain currently available structure,activity relationship (SAR) data. To further validate the predicted binding sites of these ligands in hUT2R and rUT2R, we propose several mutations that would help define the structural origins of differential responses between UT2R of different species, potentially indicating novel UT2R antagonists with cross-species high affinity. [source]