Aquaporin Gating: A New Twist to Unravel Permeation through Water Channels

Aquaporins (AQPs) are small transmembrane tetrameric proteins that facilitate water, solute and gas exchange. Their presence has been extensively reported in the biological membranes of almost all living organisms. Although their discovery is much more recent than ion transport systems, different biophysical approaches have contributed to confirm that permeation through each monomer is consistent with closed and open states, introducing the term gating mechanism into the field. The study of AQPs in their native membrane or overexpressed in heterologous systems have experimentally demonstrated that water membrane permeability can be reversibly modified in response to specific modulators. For some regulation mechanisms, such as pH changes, evidence for gating is also supported by high-resolution structures of the water channel in different configurations as well as molecular dynamics simulation. Both experimental and simulation approaches sustain that the rearrangement of conserved residues contributes to occlude the cavity of the channel restricting water permeation. Interestingly, specific charged and conserved residues are present in the environment of the pore and, thus, the tetrameric structure can be subjected to alter the positions of these charges to sustain gating. Thus, is it possible to explore whether the displacement of these charges (gating current) leads to conformational changes? To our knowledge, this question has not yet been addressed at all. In this review, we intend to analyze the suitability of this proposal for the first time.     

Extracting Stray Magnetic Fields from Thin Ferromagnetic Layers in Hybrid Superconducting/Ferromagnetic Heterostructures

Journal of Superconductivity and Novel Magnetism - Hybrid Nb(20)/Cu(5)/Py(2), Nb(20)/Cu(5)/Co(40) and Nb(20)/Cu(d $$_{Cu}$$ )/Py(2)/Cu(5)/Co(40) heterostructures (values in nanometers and d...     

An overview of biorefinery-derived platform chemicals from a cellulose and hemicellulose biorefinery

Until recently, most of energy and industrially produced chemicals were derived from fossil fuel-based resources. This along with the continued depletion of finite fossil resources and their attributed adverse environmental impacts, alternatively sourced and more sustainable resources are being pursued as feedstock replacements. Thus, biomass has been identified as an alternate renewable and more sustainable resource as a means to reduce this sector’s dependence on fossil fuel-based resources and to alleviate their environmental impacts. As such, lignocellulosic biomass has been further identified and demonstrated as an abundant renewable resource for the production of biofuels, platform chemicals, and their respective value-added products. This review article provides an overview of the techniques developed for the valorization of biomass in the production of platform chemicals within a biorefinery and the status for commercialization.     

Predicting Emissions from the Chemical and Energy Industries: Progress in Applying Modeling Approaches

Theoretical Foundations of Chemical Engineering - A review of international experience in the development and implementation of emissions monitoring systems based on mathematical models at...     

Technological properties of chickpea (Cicer arietinum): Production of snacks and health benefits related to type-2 diabetes

Chickpea (Cicer arietinum) is one of the most consumed pulses worldwide (over 2.3 million tons enter the world market annually). Some chickpea components have shown, in preclinical and clinical studies, several health benefits, including antioxidant capacity, and antifungal, antibacterial, analgesic, anticancer, antiinflammatory, and hypocholesterolemic properties, as well as angiotensin I-converting enzyme inhibition. In the United States, chickpea is consumed mostly in the form of hummus. However, the development of new products with value-added bioactivity is creating new opportunities for research and food applications. Information about bioactive compounds and functional properties of chickpea ingredients in the development of new products is needed. The objective of this review was to summarize available scientific information, from the last 15 years, on chickpea production, consumption trends, applications in the food industry in the elaboration of plant-based snacks, and on its bioactive compounds related to type 2 diabetes (T2D). Areas of opportunity for future research and new applications of specific bioactive compounds as novel food ingredients are highlighted. Research is key to overcome the main processing obstacles and sensory challenges for the application of chickpea as ingredient in snack preparations. The use of chickpea bioactive compounds as ingredient in food products is also a promising area for accessibility of their health benefits, such as the management of T2D.     

Sensitivity considerations in the control of generalized plants

A comparison sensitivity matrix is derived for a generalized plant for which the controlled and measured variables are not necessarily the same. The sensitivity of the control signal to plant and controller parameter variations is characterized. It is shown that sensitivity reduction is possible only when the controlled and measured variables are appropriately related. A relationship between comparison sensitivity and exogenous signal attenuation is shown     

Outgoing longwave flux estimation: improvement of angular modelling using spectral information

A radiance-to-flux conversion is needed to estimate radiative fluxes at the top of the atmosphere from directional measurements made by broadband (BB) radiometers on satellites. Such a conversion is known to be one of the major sources of error in the resulting instantaneous shortwave and longwave fluxes. This paper analyzes the possibility to improve the radiance-to-flux conversion for the longwave radiation when spectral information about the radiation is available through a set of narrow-band (NB) measurements. The study is based on a database of spectral radiance fields at the top of the atmosphere built using radiative transfer computation. The analysis of this database shows that there exists a certain degree of correlation between the angular and the spectral behaviors of the radiation field. According to the type and the accuracy of the spectral information, this correlation allows a 25-55% reduction of the error introduced by the radiance-to-flux conversion with respect to a simple model that uses only broadband information. The method discussed in this paper might be used when broadband radiometer and spectral imager data are available together like the combination of Geostationary Earth Radiation Budget (GERB) and Spinning Enhanced Visible and Infrared Radiometer Imager (SEVIRI) or the combination of CERES and MODIS.     

The S5-S6 linker of repeat I is a critical determinant of L-type Ca2+ channel conductance

The alpha1-subunits of the skeletal and cardiac L-type calcium channels (L-channels) contain nearly identical pore regions (P-regions) in each of the four internal homology repeats. In spite of this high conservation of the P-regions, native skeletal L-channels exhibit a unitary conductance that is only about half that of native cardiac L-channels. To identify structural determinants of this difference in L-channel conductance, we have characterized unitary activity in cell-attached patches of dysgenic myotubes expressing skeletal, cardiac, and chimeric L-channel alpha1-subunits. Our results demonstrate that the S5-S6 linker of repeat I (IS5-IS6 linker) is a critical determinant of the difference in skeletal and cardiac unitary conductance. The unitary conductances attributable to the wild-type skeletal (CAC6; approximately 14 pS) and cardiac (CARD1; approximately 25 pS) alpha1-subunits expressed in dysgenic myotubes are identical to those observed in native tissues. Chimeric alpha1-subunits containing skeletal sequence for the first internal repeat and all of the putative intracellular loops (SkC15), the IS5-IS6 linker and the intracellular loops (SkC51), or only the IS5-IS6 linker (SkC49) each exhibit a low, skeletal-like unitary conductance (< or = 17 pS). Constructs in which the IS5-IS6 linker is of cardiac origin (CARD1 and CSk9) display cardiac-like conductance (approximately 25 pS). Unitary conductance and the rate of channel activation are apparently independent processes, since both SkC51 and SkC49 exhibit low, skeletal-like conductance and rapid, cardiac-like rates of ensemble activation. These results demonstrate that the IS5-IS6 linker strongly influences the single channel conductance of L-channels in a manner that is independent from the rate of channel activation.