Arabidopsis thaliana J-class heat shock proteins: cellular stress sensors

Plants are sessile organisms that have evolved a variety of mechanisms to maintain their cellular homeostasis under stressful environmental conditions. Survival of plants under abiotic stress conditions requires specialized group of heat shock protein machinery, belonging to Hsp70:J-protein family. These heat shock proteins are most ubiquitous types of chaperone machineries involved in diverse cellular processes including protein folding, translocation across cell membranes, and protein degradation. They play a crucial role in maintaining the protein homeostasis by reestablishing functional native conformations under environmental stress conditions, thus providing protection to the cell. J-proteins are co-chaperones of Hsp70 machine, which play a critical role by stimulating Hsp70s ATPase activity, thereby stabilizing its interaction with client proteins. Using genome-wide analysis of Arabidopsis thaliana, here we have outlined identification and systematic classification of J-protein co-chaperones which are key regulators of Hsp70s function. In comparison with Saccharomyces cerevisiae model system, a comprehensive domain structural organization, cellular localization, and functional diversity of A. thaliana J-proteins have also been summarized. Electronic supplementary material The online version of this article (doi:10.1007/s10142-009-0132-0) contains supplementary material, which is available to authorized users.

On-board correction of systematic error of Earth sensors

Infrared Earth sensors are used in spacecraft for attitude sensing. Their accuracy is limited by systematic and random errors. Dominant sources of systematic errors are analyzed for a typical scanning infrared Earth sensor used in a remote-sensing satellite in a 900-km sun-synchronous orbit. The errors considered arise from 1) seasonable variation of infrared radiation, 2) oblate shape of the Earth, 3) ambient temperature of sensors, 4) changes in spin/scan period, and 5) misalignment of the axis of the sensors. Simple relations are derived using least-squares curve fitting for onboard correction of these errors. With these, it is possible to improve the accuracy of attitude determination by eight fold and achieve performance comparable to ground-based post-facto attitude computation.

Some recent developments in solid state galvanic sensors

A critical revi<:w of the possibilities of measuring the ~artlal pressure of sulfur using solid state galvanic cells )'n;;cd on AgI, C" , B-alumina, CaO-Zr02' Na2S04-I and doped ;:":;, ,,,Ilil "Iltl ,,11: auxiliary "jectrodes are presentlOu. SOIll..., df tllc!iL' sYHtcmH h,}vu inherent limltntlol1$ when <:xl'o" ...d to environments contilining both oxygen and sulfur. Electrode polarization due to electronic conduction in the solid electrolyte is a significant factor limiting the ;lC'e,"'acy of isotlwrm:l1 cell",. The electrochemical flux of{lit' !'\)ndlwl Ill}: Ion LhnHO',h tht' ('!('ctrojyt(~ C:Ul },(,! llIinlnliz(,{j pfUjJL!f cell. dL:~) i.t',11. Noni!:iot.herm~ll cells \.Jlth temperaLure compensated reference electrodes have a number of advantages over thC'ir isothermal counterparts.

Mixed ionic and electronic conduction in zirconia and its applications in metallurgy

Mixed ionic and electronic conduction in Zr02-based solid electrolytes was studied.The effect of impurities and second-phase particles on the mixed conduction parameter, P,, was measured for different types of ZrOZ electrolytes. The performance of solid-state sensors incorporating ZrOZ electrolytes is sometimes limited by electronic conduction in ZrOZ, especially at temperatures >I800 K. Methods for eliminating or minimizing errors in measured emf due to electronically driven transport of oxygen anions are discussed. Examples include probes for monitoring oxygen content in liquid steel as well as the newly developed sulfur sensor based on a ZrOz(Ca0) + CaS electrolyte. The use of mixed conducting ZrOZ as a semipermeable membrane or chemically selective sieve for oxygen at high temperatures is discussed. Oxygen transport from liquid iron to CO + C& gas mixtures through a ZrOZ membrane driven by a chemical potential gradient, in the absence of electrical leads or imposed potentials, was experimentally observed.

Evaluation of airline exercises prescribed to avoid deep vein thrombosis using fiber Bragg grating sensors

Various leg exercises have been recommended to prevent deep vein thrombosis (DVT), a condition where a blood clot forms in the deep veins, especially during long-haul flights. Accessing the benefit of each of these exercises in avoiding the DVT, which can be fatal, is important in the context of suggesting the correct and the most beneficial exercises. Present work aims at demonstrating the fiber Bragg grating (FBG)-based sensing methodology for measuring surface strains generated on the skin of the calf muscle to evaluate the suggested airline exercises to avoid DVT. As the dataset in the experiment involves multiple subjects performing these exercises, an inertial measurement unit has been used to validate the repetitiveness of each of the exercises. The surface strain on the calf muscle obtained using the FBG sensor, which is a measure of the calf muscle deformation, has been compared against the variation of blood velocity in the femoral vein of the thigh measured using a commercial electronic-phased array color Doppler ultrasound system. Apart from analyzing the effectiveness of suggested exercises, a new exercise which is more effective in terms of strain generated to avoid DVT is proposed and evaluated. (C) 2013 Society of Photo-Optical Instrumentation Engineers (SPIE)

Dual Binding Site Assisted Chromogenic and Fluorogenic Recognition and Discrimination of Fluoride and Cyanide by a Peripherally Borylated Metalloporphyrin: Overcoming Anion Interference in Organoboron Based Sensors

Peripherally triarylborane decorated porphyrin (2) and its Zn(II) complex (3) have been synthesized. Compound 3 contains of two different Lewis acidic binding sites (Zn(II) and boron center). Unlike all previously known triarylborane based sensors, the optical responses of 3 toward fluoride and cyanide are distinctively different, thus enabling the discrimination of these two interfering anions. Metalloporphyrin 3 shows a multiple channel fluorogenic response toward fluoride and cyanide and also a selective visual colorimetric response toward cyanide. By comparison with model systems and from detailed photophysical studies on 2 and 3, we conclude that the preferential binding of fluoride occurs at the peripheral borane moieties resulting in the cessation of the EET (electronic energy transfer) process from borane to porphyrin core and with negligible negetive cooperative effects. On the other hand, cyanide binding occurs at the Zn(II) core leading to drastic changes in its absorption behavior which can be followed by the naked eye. Such changes are not observed when the boryl substituent is absent (e.g., Zn-TPP and TPP). Compounds 2 and 3 were also found to be capable of extracting fluoride from aqueous medium.

Semiconductor-like Sensitivity in Metallic Ultrathin Gold Nanowire-Based Sensors

Due to the ease of modification of electronic structure upon analyte adsorption, semiconductors have been the preferred materials as chemical sensors. At reduced dimension, however, the sensitivity of semiconductor-based sensors deteriorates significantly due to passivation, and often by increased band gap caused by quantum confinement. Using first-principles density functional theory combined with Boltzmann transport calculations, we demonstrate semiconductor-like sensitivity toward chemical species in ultrathin gold nanowires (AuNWs). The sensing mechanism is governed by the modification of the electronic structure of the AuNW as well as scattering of the charge carriers by analyte adsorption. Most importantly, the sensitivity exhibits a linear relationship with the electron affinities of the respective analytes. Based on this relationship, we propose an empirical parameter, which can predict an analyte-specific sensitivity of a AuNW, rendering them as effective sensors for a wide range of chemical an alytes.

Non-enzymatic electronic detection of glucose using aminophenylboronic acid functionalized reduced graphene oxide

We report the non-enzymatic electronic detection of glucose using field effect transistor (FET) devices made of aminophenylboronic acid (APBA) functionalized reduced graphene oxide (RGO). Detection of glucose molecules was carried out over a wide dynamic range of concentration varying from 100 pM to 100 mM with a detection limit of similar to 2 nM using both covalently and non-covalently functionalized APBA-RGO complex. The normalized change in electrical conductance data shows that the FET devices made of non-covalently functionalized APBA-RGO complex (nc-APBA-RGO) exhibited a linear response to glucose aqueous solution of concentrations varying from 1 nM to 10 mM and showed 4 times enhanced sensitivity over the devices made of covalently functionalized APBA-RGO complex (c-APBA-RGO). Specificity of APBA-RGO complex to glucose is confirmed from the observation of negligible change in electrical conductance after exposure to 0.1 mM of lactose and other interfering factors. (C) 2015 Elsevier B.V. All rights reserved.

Simultaneous tunability of the electronic and phononic gaps in SnS2 under normal compressive strain

Controlled variation of the electronic properties of. two-dimensional (2D) materials by applying strain has emerged as a promising way to design materials for customized applications. Using density functional theory (DFT) calculations, we show that while the electronic structure and indirect band gap of SnS2 do not change significantly with the number of layers, they can be reversibly tuned by applying biaxial tensile (BT), biaxial compressive (BC), and normal compressive (NC) strains. Mono to multilayered SnS2 exhibit a reversible semiconductor to metal (S-M) transition with applied strain. For bilayer (2L) SnS2, the S-Mtransition occurs at the strain values of 17%,-26%, and -24% under BT, BC, and NC strains, respectively. Due to weaker interlayer coupling, the critical strain value required to achieve the S-Mtransition in SnS2 under NC strain is much higher than for MoS2. From a stability viewpoint, SnS2 becomes unstable at very low strain values on applying BC (-6.5%) and BT strains (4.9%), while it is stable even up to the transition point (-24%) in the case of NC strain. In addition to the reversible tuning of the electronic properties of SnS2, we also show tunability in the phononic band gap of SnS2, which increases with applied NC strain. This gap increases three times faster than for MoS2. This simultaneous tunability of SnS2 at the electronic and phononic levels with strain, makes it a potential candidate in field effect transistors (FETs) and sensors as well as frequency filter applications.

Properties of the correlated electronic states of pyrene and hydrogenated pyrene

Approximate calculations are reported on pyrene within the PPP model Hamiltonian using a novel restricted CI scheme which employs both molecular orbital and valence bond techniques. Also reported are detailed full CI results of the PPP model on 2,7-dihydropyrene obtained using the valence bond method. Spectral studies, charge and spin density calculations in ground and excited states, and ring current calculations in the ground state of the molecules are presented. In pyrene, the calculated excitation energies are in good agreement with experiment. The closed structure pi-conjugated molecule pyrene appears to show smaller distortions from the ground state geometry compared with the open structure pi-conjugated molecule 2,7-dihydropyrene. The ground state equilibrium structure of 2,7-dihydropyrene can be viewed as two hexatriene molecules connected by a vinyl crosslink, as is evident from bond order and ring current calculations. This is consistent with the only Kekule resonant structure possible for this molecule.

Electronic Control of Facial Selection in Additions to Sterically Unbiased Ketones and Olefins

By definition, the two faces of a pi bond are equivalent.1 However, they are rendered nonequivalent in most molecules because of the absence of a plane of symmetry encompassing the double bond and the adjacent substituents. As a result, additions to trigonal centers from the two faces need not be equally facile. Exploiting this stereodifferentiation in a controlled manner represents one of the core problems in organic synthesis. Evidently, the factors which determine such diastereoselection need to be delineated in as much detail as possible.

Electronic Properties of the Vortex State in Cuprate Superconductors

The superconducting state of the cuprates in the presence of a magnetic field has been investigated very actively in the past few years through measurements of electrical and thermal transport, ac conductivity, specific heat, and other quantities. The observed behavior is not well understood; it probes the nature of quasiparticies, vortices, and their interactions in a superconductor with nodes in the pair amplitude. We summarize here experimental results and our attempts to understand the phenomena.

Electronic Structure of Vacancy Ordered Spinels, $GaMo_{4}S_{8}$ and $GaV_{4}S_{8}$, from ab Initio Calculations

We report ab initio calculations for the band dispersions and total as well as partial densities of states for vacancy ordered, clustered spinels, GaMo4S8 and GaV4S8. Results are presented for the high temperature cubic phase for both compounds. Additionally, we discuss results of similar calculations for GaMo4S8 in an idealized cubic structure, as well as the nonmagnetic and the ferromagnetic states of the low temperature rhombohedral structure. Comparison of these results allows us to discuss the unusual aspects of the electronic structure of this interesting class of compounds, and provide estimates of the crystal-field and exchange splitting strengths.

Evolution of electronic structure with dimensionality in divalent nickelates

We investigate the evolution of electronic structure with dimensionality (d) of Ni-O-Ni connectivity in divalent nickelates, NiO (3-d), La2NiO4, Pr2NiO4 (2-d), Y2BaNiO5 (1-d) and Lu2BaNi5 (0-d), by analyzing the valence band and the Ni 2p core-level photoemission spectra in conjunction with detailed many-body calculations including full multiplet interactions. Experimental results exhibit a reduction in the intensity of correlation-induced satellite features with decreasing dimensionality. The calculations based on the cluster model, but evaluating both Ni 3d and O 2p related photoemission processes on the same footing, provide a consistent description of both valence-band and core-level spectra in terms of various interaction strengths. While the correlation-induced satellite features in NiO is dominated by poorly screened d(8) states as described in the existing literature, we find that the satellite features in the nickelates with lower dimensional Ni-O-Ni connectivity are in fact dominated by the over-screened d(10)L(2) states. It is found that the changing electronic structure with the dimensionality is primarily driven by two factors: (i) a suppression of the nonlocal contribution to screening; and (ii) a systematic decrease of the charge-transfer energy Delta driven by changes in the Madelung potential. [S0163-1829(99)09619-8].