scholarly journals A large family of anti‐activators accompanying XylS/AraC family regulatory proteins

2016 ◽  
Vol 101 (2) ◽  
pp. 314-332 ◽  
Author(s):  
Araceli E. Santiago ◽  
Michael B. Yan ◽  
Minh Tran ◽  
Nathan Wright ◽  
Deborah H. Luzader ◽  
...  
Author(s):  
P.R. Smith ◽  
W.E. Fowler ◽  
U. Aebi

An understanding of the specific interactions of actin with regulatory proteins has been limited by the lack of information about the structure of the actin filament. Molecular actin has been studied in actin-DNase I complexes by single crystal X-ray analysis, to a resolution of about 0.6nm, and in the electron microscope where two dimensional actin sheets have been reconstructed to a maximum resolution of 1.5nm. While these studies have shown something of the structure of individual actin molecules, essential information about the orientation of actin in the filament is still unavailable.The work of Egelman & DeRosier has, however, suggested a method which could be used to provide an initial quantitative estimate of the orientation of actin within the filament. This method involves the quantitative comparison of computed diffraction data from single actin filaments with diffraction data derived from synthetic filaments constructed using the molecular model of actin as a building block. Their preliminary work was conducted using a model consisting of two juxtaposed spheres of equal size.


Author(s):  
Maryvonne Hervieu

Four years after the discovery of superconductivity at high temperature in the Ba-La-Cu-O system, more than thirty new compounds have been synthesized, which can be classified in six series of copper oxides: La2CuO4 - type oxides, bismuth cuprates, YBa2Cu3O7 family, thallium cuprates, lead cuprates and Nd2CuO4 - type oxides. Despite their quite different specific natures, close relationships allow their structures to be simply described through a single mechanism. The fifth first families can indeed be described as intergrowths of multiple oxygen deficient perovskite slabs with multiple rock salt-type slabs, according to the representation [ACuO3-x]m [AO]n.The n and m values are integer in the parent structures, n varying from 0 to 3 and m from 1 to 4; every member of this large family can thus be symbolized by [m,n]. The oxygen deficient character of the perovskite slabs involves the existence or the co-existence of several types of copper environment: octahedral, pyramidal and square planar.Both mechanisms, oxygen deficiency and intergrowth, are well known to give rise easily to nonstoichiometry phenomena. Numerous and various phenomena have actually been characterized in these cuprates, strongly depending on the thermal history of the samples.


2019 ◽  
Author(s):  
Collen Lauriane Le ◽  
Sara Barraud ◽  
Odou Marie Francoise ◽  
Marta Spodenkiewicz ◽  
Antoine Braconnier ◽  
...  
Keyword(s):  

2018 ◽  
Vol 15 (1) ◽  
pp. 16-29
Author(s):  
Stella Babalola ◽  
Joshua O. Akinyemi ◽  
Clifford O. Odimegwu

Abstract Nigeria has one of the highest fertility rates in Africa. Data from 2013 Demographic and Health Surveys indicate a virtual stagnation of fertility rate since 2003. Low contraceptive use and pronatalist attitudes are among the factors contributing to the high fertility rate in Nigeria. In this manuscript, we pooled data from three most recent waves of Demographic and Health Surveys to examine trends in demand for children over time and identify the factors associated with change in demand for children. The data show that demand for children has declined since 2003 although not monotonically so. Variables that were positively associated with increased likelihood of desiring no additional children were residence in the South-West (as opposed to residence in the North-Central), exposure to family planning (FP) messages on the mass media, number of children ever born, educational level, and urban residence. In contrast, uncertainty about fertility desire was more widespread in 2008 compared to 2013 although less widespread in 2003 than in 2013. The likelihood of being undecided about fertility desire was positively associated with discrepancies in family size desires between husband and wife, parity and Islamic religious affiliation. Programs should aim to increase access to effective contraceptive methods and promote demand for contraceptives as a way of fostering a sustainable reduction in demand for children. Furthermore, strategies that address uncertainty by fostering women’s understanding of the social and health implications of large family sizes are relevant.


2019 ◽  
Author(s):  
Torben Sick ◽  
Niklas Keller ◽  
Nicolai Bach ◽  
Andreas Koszalkowski ◽  
Julian Rotter ◽  
...  

Covalent organic frameworks (COFs), consisting of covalently connected organic building units, combine attractive features such as crystallinity, open porosity and widely tunable physical properties. For optoelectronic applications, the incorporation of heteroatoms into a 2D COF has the potential to yield desired photophysical properties such as lower band gaps, but can also cause lateral offsets of adjacent layers. Here, we introduce dibenzo[g,p]chrysene (DBC) as a novel building block for the synthesis of highly crystalline and porous 2D dual-pore COFs showing interesting properties for optoelectronic applications. The newly synthesized terephthalaldehyde (TA), biphenyl (Biph), and thienothiophene (TT) DBC-COFs combine conjugation in the a,b-plane with a tight packing of adjacent layers guided through the molecular DBC node serving a specific docking site for successive layers. The resulting DBC-COFs exhibit a hexagonal dual-pore kagome geometry, which is comparable to COFs containing another molecular docking site, namely 4,4′,4″,4‴-(ethylene-1,1,2,2-tetrayl)-tetraaniline (ETTA). In this context, the respective interlayer distances decrease from about 4.60 Å in ETTA-COFs to about 3.6 Å in DBC-COFs, leading to well-defined hexagonally faceted single crystals sized about 50-100 nm. The TT DBC-COFs feature broad light absorption covering large parts of the visible spectrum, while Biph DBC-COF shows extraordinary excited state lifetimes exceeding 10 ns. In combination with the large number of recently developed linear conjugated building blocks, the new DBC tetra-connected node is expected to enable the synthesis of a large family of strongly p-stacked, highly ordered 2D COFs with promising optoelectronic properties.


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