Hill Plots Research Articles

Why do aging households in agriculture prefer land abandonment to transfer? Evidence from hill plots in Sichuan, China

AbstractIncreased aging of the agricultural population may lead to a reconfiguration of land elements, but existing studies have not analyzed this on a plot level. China's vast hilly and mountainous regions will have a more serious impact on agricultural aging, but this context has still not received enough attention. Based on primary data from 2602 plots and 1080 farm households in the hilly areas of Sichuan, using human capital theory and instrumental variables approach, it is found that aging in agriculture will promote the abandonment of plots in the hilly areas, especially those that are remote, small in size and poor condition. Aging in agriculture will inhibit the out‐migration of plots in the hilly areas, and aging increases the abandonment of plots. In addition, this paper finds that the imperfect development of the land transfer market in hilly areas and the strong farmers' land endowment effect are the main reasons limiting land transfer. However, the inhibitory effect of the endowment effect diminishes with age. This study helps to rationally view the value of abandoned land and provides a new research perspective for parcel redistribution.

Comparison of clot waveform analysis with or without adjustment between prothrombin time and activated partial thromboplastin time assays to assess in vitro effects of direct oral anticoagulants

BackgroundClot waveform analysis (CWA) reportedly enhances the interpretation of clotting time measurement. This study aimed to compare CWA between prothrombin time (PT) and activated partial thromboplastin time (APTT) assays for better understanding how to apply CWA for assessing effects of direct oral anticoagulants (DOACs). MethodsSamples were prepared by spiking plasma with rivaroxaban, apixaban, edoxaban, or dabigatran. To compensate the influence of fibrinogen, CWA parameters were adjusted by unifying maximum changes in transmittance in clotting reaction curves detected by the optical system. ResultsNon-adjusted PT-CWA parameters unexpectedly rose at low drug concentrations but declined at high drug concentrations while adjusted PT-CWA parameters exhibited dose-dependent decrease. Both non-adjusted and adjusted APTT-CWA parameters showed dose-dependent decrease. Adjusted CWA parameters were applicable to Hill plot analysis. All DOACs exhibited Hill coefficients indicating positively cooperative effects regarding most adjusted PT-CWA parameters. Regarding adjusted APTT-CWA parameters, rivaroxaban, apixaban, and edoxaban exhibited Hill coefficients indicating no or negatively cooperative effects. The observed differences between PT-CWA and APTT-CWA suggested the implication of thrombin positive feedback in DOAC effects. ConclusionThe results revealed distinct features of DOAC effects in extrinsic and intrinsic pathways. To ascertain the clinical implication, further studies using clinical samples are needed.

Experimentally validated modeling of dynamic drug-hERG channel interactions reproducing the binding mechanisms and its importance in action potential duration.

Background and ObjectiveAssessment of drug cardiotoxicity is critical in the development of new compounds and modeling of drug-binding dynamics to hERG can improve early cardiotoxicity assessment. We previously developed a methodology to generate Markovian models reproducing preferential state-dependent binding properties, trapping dynamics and the onset of IKr block using simple voltage clamp protocols. Here, we test this methodology with real IKr blockers and investigate the impact of drug dynamics on action potential prolongation. MethodsExperiments were performed on HEK cells stably transfected with hERG and using the Nanion SyncroPatch 384i. Three protocols, P-80, P0 and P 40, were applied to obtain the experimental data from the drugs and the Markovian models were generated using our pipeline. The corresponding static models were also generated and a modified version of the O´Hara-Rudy action potential model was used to simulate the action potential duration. ResultsThe experimental Hill plots and the onset of IKr block of ten compounds were obtained using our voltage clamp protocols and the models generated successfully mimicked these experimental data, unlike the CiPA dynamic models. Marked differences in APD prolongation were observed when drug effects were simulated using the dynamic models and the static models. ConclusionsThese new dynamic models of ten well-known IKr blockers constitute a validation of our methodology to model dynamic drug–hERG channel interactions and highlight the importance of state-dependent binding, trapping dynamics and the time-course of IKr block to assess drug effects even at the steady-state.

Distinguishing the transitions of fluorescence spectra of tryptophan-134 and 213 in BSA induced by bindings of UV filters, oxybenzone-3, and avobenzone

Abstract Oxybenzone-3 (OBZ) and avobenzone (ABZ), commercially available ultraviolet-light filters for sunscreens, are known to induce photosensitizing allergy as an adverse effect, similar to an analgesic ketoprofen (KTP) due to their benzophenone moiety. The present study focused on OBZ and ABZ's protein binding compared to the related analgesics, KTP, diclofenac (DCF), and ibuprofen (IBP). The bovine serum albumin (BSA) was used as a protein model, measuring the fluorescent spectral peak shifts (i) and Stern–Volmer analysis (i) of its intrinsic tryptophans. Moreover, their adsorption types (iii) were verified using the singular value decomposition (SVD) computation of fluorescence spectra. For (i), (ii), and (iii), KTP and DCF caused a no-shift peak, an ordinary dynamic quenching, and a simple Langmuir adsorption. We found OBZ exhibiting (i) red-shift and (ii) including static quenching, ABZ suggesting (i) blue-shift and (iii) binding to multiple bind sites, and IBP indicating (i) blue-shift and (iii) multivalent bindings. Integrating the results, it can be understood that OBZ interacts with subdomain IA (around W134) in BSA, while ABZ interacts with subdomain IIA (around W213) in BSA. Moreover, IBP is bound to BSA with a cooperative effect, certified by Hill's plot. OBZ and ABZ had their individual binding sites on a protein, suggesting the exchange between OBZ and ABZ might reduce their own adverse effect. The present study verified the effectiveness of the SVD computation in distinguishing the details of the adsorption manner of ligands around the intrinsic fluorescent probes.

Mechanistic studies on substrate inhibition and substrate activation of ribonuclease A: experimental and in silico investigation

Ribonuclease A (RNase A) is an endonuclease that plays a significant role in antimicrobial activity by the cleavage and hydrolysis of ssRNA. In this study, the interactions between RNase A and cCMP have been investigated, through molecular docking and a 200 ns molecular dynamics simulation. The enzyme kinetic properties were analyzed using saturation curve, Eadie-Hofstee, and Hill plots. The docking results indicate that the cCMP-RNase A complexes are stabilized through hydrophobic interaction, hydrogen bonding, and π-π stacking interaction. The most binding site is observed in the catalytic cleft, especially at residue His12 and His119. Enzyme-ligand docking study indicates that cCMP binds to residues located in the internal cavity of the catalytic site and shows three phases of binding modes. The analysis of MD simulations shows that RMSD, Rg, and RMSF reach equilibrium. The ΔGbinding of the cCMP-RNase A was negative (-619.673 kJ/mol), The comparison between the results pre and post MD simulation showed that ΔGbinding after MD simulation causes to more stable the structure than before simulation. Experimental methods such as saturation, Eadie-Hofstee, and Hill plots confirm theoretical data and show three phases of binding modes as well. Two significant events are demonstrated in the interaction between RNase A and cCMP: substrate activation and substrate inhibition are observed in concentrations below and above 0.8 mM, respectively, for cCMP. Choosing the appropriate concentration of cCMP is very important in investigation of ribonuclease A’s catalytic behavour, especially for exploration of the effects of some drugs on biological behaviours related to ribonuclease A. Communicated by Ramaswamy H. Sarma

Flexible extreme value inference

We introduce flexible small sample modeling for extremes by introducing the new numerical characteristics of heavy tail. We illustrate in this article advantages of such flexibility. In this article, we show that we can obtain asymptotic normality of generalized Hill estimators by application of Karamata’s representation for regularly varying tails. Second order regularity conditions however better relates to Edgeworth types of normal approximations albeit requiring larger data samples. Finally both expansions are prone for bootstrap and other subsampling techniques. All existing results indicate that proper representation of tail behavior play a special and somewhat intriguing role in that context. The application of this new methodology is simple and flexible, handsome for real data sets. Alternative and powerful versions of the Hill plot are also introduced and illustrated on real data of snow extremes from Slovakia. We also demonstrate the importance of box-plot based techniques for small samples.

"Canopy fingerprints" for characterizing three-dimensional point cloud data of soybean canopies.

Advances in imaging hardware allow high throughput capture of the detailed three-dimensional (3D) structure of plant canopies. The point cloud data is typically post-processed to extract coarse-scale geometric features (like volume, surface area, height, etc.) for downstream analysis. We extend feature extraction from 3D point cloud data to various additional features, which we denote as 'canopy fingerprints'. This is motivated by the successful application of the fingerprint concept for molecular fingerprints in chemistry applications and acoustic fingerprints in sound engineering applications. We developed an end-to-end pipeline to generate canopy fingerprints of a three-dimensional point cloud of soybean [Glycine max (L.) Merr.] canopies grown in hill plots captured by a terrestrial laser scanner (TLS). The pipeline includes noise removal, registration, and plot extraction, followed by the canopy fingerprint generation. The canopy fingerprints are generated by splitting the data into multiple sub-canopy scale components and extracting sub-canopy scale geometric features. The generated canopy fingerprints are interpretable and can assist in identifying patterns in a database of canopies, querying similar canopies, or identifying canopies with a certain shape. The framework can be extended to other modalities (for instance, hyperspectral point clouds) and tuned to find the most informative fingerprint representation for downstream tasks. These canopy fingerprints can aid in the utilization of canopy traits at previously unutilized scales, and therefore have applications in plant breeding and resilient crop production.

First Report of Bacterial Leaf Streak of Barley (Hordeum vulgare) Caused by Xanthomonas translucens pv. translucens in British Columbia, Canada.

Bacterial leaf streak (BLS) of barley is caused by the Gram-negative bacterial pathogen Xanthomonas translucens (Sapkota et al. 2020). In 2021, we observed multiple hill plots with BLS symptomatic plants in a barley stripe rust nursery in Vancouver, BC, Canada. We collected 29 leaf samples showing typical BLS symptoms (e.g. necrotic lesions; Fig. S1) and stored at 4 oC until bacterial isolation. Samples were surface-sterilized in 10% NaOCl for 20 sec and rinsed twice. About 1 cm2 of leaf tissue containing BLS characteristic lesions was macerated in 200 μL sterile H2O on a petri dish, incubated for 15 min, and 10 μl of the homogenates was streaked onto Wilbrink's - Boric Acid - Cephalexin (WBC) agar medium. Plates were incubated at 28-30 oC for 48 hrs. Four single colonies were obtained: BC10-1-2a (USask BC10-2a), BC10-1-2b (USask BC10-2b), UBC026 and UBC028. Colonies were grown in WBC broth and gDNA was extracted using E.Z.N.A. Bacterial DNA Kit (Omega Bio-Tek) or DNeasy Plant Pro Kit® (Qiagen) following manufacturer protocols. Genus-level identification was achieved using 16S rRNA sequencing with 27F/1492R primers (Lane 1991) of UBC026 (1,399 bp; NCBI # OP327375) and UBC028 (1,415 bp; NCBI #OP327376). Complete 16S rRNA sequences (1,533bp) of BC10-2a and BC10-2b (1,533 bp) were extracted from the draft whole-genome sequences (WGS) generated in this study. The 16S rRNA sequence homology values of 99.0-100% were recorded between the 4 strains. BLAST analyses of the 16S rRNA sequences to GenBank entries exhibited 99.5-100% similarity values (100% coverage) with the pathotype strains of Xtt DSM 18974T (LT604072) and X. translucens pv. undulosa (Xtu) CFBP 2055 (CP074361). Whole genomes of BC10-2a (JANUQY01) and BC10-2b (JANUQZ01) were sequenced (150-bp; reads 33.1 million; mean coverage 2125x) using NovaSeq Illumina, assembled (Unicycler v0.4.8; Wick et al. 2017) and analyzed to identify the strains to the species-level (Tambong et al. 2021). WGS of strains USask BC10-2a and USask BC10-2b exhibited genome-based DNA-DNA hybridization (dDDH; Meier-Kolthoff et al. 2013) and BLAST-based average nucleotide identity (ANIb; Richter et al. 2015) of 100%. The two strains also showed dDDH and ANIb of 90.4% (species-leel cut-off of 70%) and 98.780% and 98.80% (cut-off of 96%), respectively, with Xtt DSM 18974T (LT604072). In contrast, the WGS of BC10-2a and BC10-2b exhibited only 78.2% dDDH homology values with Xtu CFBP 2055T, suggesting that the strains are genetically more similar to Xtt. The assignment of these strains to Xtt is corroborated by phylogenomic analysis (Fig. S2; Meier-Kolthoff and Göker 2019) that showed the two strains clustering together (100% bootstrap) with the type strain DSM 18974T. These data suggest that these strains are taxonomically members of Xtt. Identification was also confirmed to the genus-level by LAMP assay using published X. translucens primers (Langlois et al. 2017). Pathovar-level identification was confirmed using a cbsA and S8.pep multiplex PCR diagnostic assay (Roman-Reyna et al. 2022). Koch's postulates were verified by greenhouse inoculation via leaf infiltration of UBC026 and UBC028 on 21-day old barley plants (line HB522) using an inoculum of 108 CFU ml-1 followed by re-isolation of the bacteria on WBC. The inoculated plants showed typical BLS symptoms similar to those observed in the field (Fig. S1). Water-inoculated plants had no symptoms. To our knowledge, this is the first published report of BLS of barley in British Columbia.

Phytate-Induced Dose-Response Auto-Activation of Enzyme in Commercial Recombinant Phytase From Escherichia coli.

Microbial phytase is one of the most widely used enzymes in food industries like cattle, poultry, and aquaculture food. Therefore, understanding the kinetic properties of the enzyme is very important to evaluate and predict its behavior in the digestive system of livestock. Working on phytase is one of the most challenging experiments because of some problems, including free inorganic phosphate (FIP) impurity in phytate (substrate) and interference reaction of the reagent with both phosphates (product and phytate impurity). In the present study, FIP impurity of phytate was removed, and then it was shown that the substrate (phytate) has a dual role in enzyme kinetics: substrate and activator. phytate impurity was decreased by two-step recrystallization prior to the enzyme assay. The impurity removal was estimated by the ISO30024:2009 method and confirmed by Fourier-transform infrared (FTIR) spectroscopy. The kinetic behavior of phytase activity was evaluated using the purified phytate as substrate by non-Michaelis-Menten analysis, including Eadie-Hofstee, Clearance, and Hill plots. The possibility of an allosteric site on phytase was assessed by molecular docking. The results showed a 97.2% decrease in FIP due to recrystallization. The phytase saturation curve had a sigmoidal appearance, and Lineweaver-Burk plot with a negative y-intercept indicated the positive homotropic effect of the substrate on the enzyme activity. A right-side concavity of Eadie-Hofstee plot confirmed it. Hill coefficient was calculated to be 2.26. Molecular docking also showed that Escherichia coli phytase molecule has another binding site for phytate very close to the active site, called "allosteric site". The observations strongly propose the existence of an intrinsic molecular mechanism in Escherichia coli phytase molecules to be promoted for more activity by its substrate, phytate (positive homotropic allosteric effect). In silico analysis showed that phytate binding to the allosteric site caused new substrate-mediated inter-domain interactions, which seems to lead to a more active conformation of phytase. Our results provide a strong basis for animal feed development strategies, especially in the case of poultry food and supplements, regarding a short food passage time in their gastrointestinal tract and variable concentration of phytate along with it. Additionally, the results strengthen our understanding of phytase auto-activation as well as allosteric regulation of monomeric proteins in general.

Statistical Analysis of APXS‐Derived Chemistry of the Clay‐Bearing Glen Torridon Region and Mount Sharp Group, Gale Crater, Mars

AbstractThe Glen Torridon stratigraphic sequence marks the transition from the low energy lacustrine‐dominated Murray formation (Mf) (Jura member: Jm) to the more diverse Carolyn Shoemaker formation (CSf) (Knockfarril Hill member: Knockfarril Hill; Glasgow member: Glasgow). This transition defines a change in depositional setting. Alpha Particle X‐ray Spectrometer (APXS) results and statistical analysis reveal that the bulk primary geochemistry of Mf targets are broadly in family with CSf targets, but with subtle compositional and diagenetic trends with increasing elevation. APXS results reveal significant compositional differences between Jura_GT and the stratigraphically equivalent Jura on Vera Rubin ridge (Jura_VRR). The data define two geochemical facies (high‐K or high‐Mg), with a strong bimodal grain distribution in Jura_GT and Knockfarril Hill. The contact between Knockfarril Hill and Glasgow is marked by abrupt sedimentological changes but a similar composition for both. Away from the contact, the Knockfarril Hill and Glasgow plot discretely, suggesting a zone of common alteration at the transition and/or a gradual transition in provenance with increasing elevation in the Glasgow member. APXS results point to a complex history of diagenesis within Glen Torridon, with increasing diagenesis close to the Basal Siccar Point unconformity on the Greenheugh pediment, and with proximity to the beginning of the clay sulfate transition. Elemental mobility is evident in localized enrichments or depletions in Ca, S, Mn, P, Zn, Ni. The highly altered Hutton interval, in contact with the unconformity on Tower butte, is also identified on Western Butte, indicating that the “interval” was once laterally extensive.

Pharmacokinetic and pharmacodynamic assessment of histamine H3 receptor occupancy by enerisant: a human PET study with a novel H3 binding ligand, [11C]TASP457.

Histamine H3 receptor antagonists and inverse agonists have been extensively developed to treat sleep-wake, neurocognitive, and allied disorders. However, potential adverse effects, including insomnia, hampered the clinical use of these drugs, possibly due to their persistent interaction with the target molecules. The purpose of the present study was to estimate the pharmacokinetics and pharmacodynamics of enerisant, a novel antagonist and inverse agonist for histamine H3 receptors. To measure the histamine H3 receptor occupancy by enerisant, positron emission tomography studies using [11C]TASP457, a specific radioligand for histamine H3 receptors, were performed in 12 healthy men at baseline and at 2h after oral administration of enerisant hydrochloride. For three of these subjects, two additional scans were performed at 6 and 26h after the administration. Relationships between the receptor occupancy by enerisant and its dose and plasma concentrations were then analyzed. Administration of enerisant hydrochloride decreased the radioligand binding in a dose-dependent manner. The estimated receptor occupancy values at 2h varied as a function of its dose or plasma concentration. The time course of the occupancy showed persistently high levels (> 85%) in the two subjects with higher doses (25 and 12.5mg). The occupancy was also initially high at 2h and 6h with the lower dose of 5mg, but it decreased to 69.7% at 26h. The target engagement of enerisant was demonstrated in the brains of living human subjects. The occupancy of histamine H3 receptors by enerisant at 2h can be predicted by applying the plasma concentration of enerisant to Hill's plot. The preliminary time-course investigation showed persistently high brain occupancy with high doses of enerisant despite the decreasing plasma concentration of the drug. Five milligrams or less dose would be appropriate for the treatment for narcolepsy with initially high occupancy allowing for effective treatment of narcolepsy, and then the occupancy level would be expected to decrease to a level to avoid this drug's unwanted side effect of insomnia at night, although further research is warranted to confirm the statement since the expected decrease is based on the finding in one subject. This study was retrospectively registered with ClinicalTrials.gov (NCT04631276) on November 17, 2020.

Fusarium head blight detection from spectral measurements in a field phenotyping setting — A pre-registered study

Spectroscopic methods can contribute to addressing the field phenotyping bottleneck problem in crop breeding programs. In disease resistance phenotyping, spectral signatures can be analysed to derive infection severity scores and to screen breeding lines. Hyperspectra of winter wheat spikes were acquired in a Fusarium head blight phenotyping trial at the milk- and wax-ripening phenological phases. Disease severity ratings were simultaneously performed by an expert on a 9-point visual scale. Ordinal support vector machine models were then trained to assign hill plots to the individual severity levels. The predictive models' performance was evaluated for data collection timing, spectral pre-processing and permitted rating-error tolerance. The models trained to spectra acquired at the milk-ripening phase were sufficiently accurate to reliably distinguish between low, medium and high symptom severity; with accuracy approaching 100% for two-point error tolerance. However, deterioration in prediction quality was noted for the wax-ripening campaign, presumably due to spike-drying. After aggregation of the spectra using the median function no gain could be associated with further pre-processing. Modest performance improvements obtained with two schemes do not justify the additional data acquisition costs involved, but standard normal variate could be advantageous for some scenarios with mean-aggregated spectra. In addition to phenotyping, the results are discussed in relation to large-scale farming applications. Elevated infection risk detection prior to anthesis is recommended for fungicide treatment, considering the pathogen biology. The study is accompanied by a publicly-available dataset and the computational scripts employed to obtain the results.

1,3-Alternate Calix[4]arene Functionalized With Pyrazole and Triazole Ligands as a Highly Selective Fluorescent Sensor for Hg2+ and Ag+ Ions.

We report here the synthesis of a 1,3-alternate calix[4]arene 8, with bis-pyrazolylmethylpyrenes on the one end and bis-triazolylmethylphenyls on the other end, as a homoditropic fluorescent sensor for both Hg2+ and Ag+ ions. Calix[4]arene 3, with lower-rim bis-pyrazolylmethylpyrenes in cone conformation, was also synthesized as a control compound. UV-Vis and fluorescence spectra were used for metal ions screening, and we found that both ligands 8 and 3 showed strong excimer emission of pyrenes when they are as a free ligand in CHCl3/MeOH (v/v, 3:1) solution; however, they both showed a high selectivity toward Hg2+ and Ag+ ions with strong fluorescence quenching and yet with different binding ratios. The fluorescence of ligand 8 was strongly quenched by Hg2+ but was only partially quenched by Ag+ ions; however, the fluorescence of ligand 3 was strongly quenched by Hg2+, Ag+, and Cu2+ ions. Job plot experiments showed that ligand 8 formed a 1:2 complex with both Hg2+ and Ag+ ions; ligand 3 formed a 1:1 complex with Hg2+, but it formed a 2:3 complex with Ag+. The binding constant of ligand 3 with Hg2+ and Ag+ ions was determined by the Benesi-Hildebrand plot of UV-vis titration experiments to be 2.99 × 103 and 3.83 × 103 M−1, respectively, while the association constant of ligand 8 with Hg2+ and Ag+ was determined by Hill plot to be 1.46 × 1012 and 9.24 × 1011 M−2, respectively. Ligand 8 forms a strong complex with either two Hg2+ or two Ag+ ions using both the upper and lower rims of the 1,3-alternate calix[4]arene as the binding pockets; hence, it represents one of the highly selective fluorescent sensors for the homoditropic sensing of Hg2+ and Ag+ ions.

Dipodal Molecular Device as Fluorescent Sensor for Na(I) Detection

A novel dipodal fluorescent sensor, N1,N3-bis(2-(2,3,4-trihydroxybenzylidene)amino)ethylmalo namide (MEP), suitable for the practical measurement of sodium concentration has been successfully developed and characterized by several spectroscopic techniques. The design of the dipodal scaffold includes a central unit, spacer, and fluorophore moiety as structural key features. The fluorescence sensor MEP adopts a photoinduced electron transfer mechanism and shows excellent selectivity for Na(I) among other biologically and environmentally important metal ions, viz., Na(I), K(I), Al(III), Cr(III), Fe(III), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) in DMSO by demonstrating a remarkable enhancement in the fluorescence intensity from 345.5 to 705.5 a.u. at λmax = 532.9 nm. The 1:2 binding stoichiometry between the ligand and Na(I) ion was confirmed by Stern–Volmer and Hill plots. The association constant determined for the ligand with the sodium metal ion is found to be very high, 7.7 × 106 M–2, which may be attributed to the trapping of sodium ions into the pseudo cavities of the ligand created by interaction of the ligand and sodium ions. The studies explore potential applications of the ligand for Na(I) ions detection in environmental and industrial applications.

Cooperativity, absolute interaction, and algebraic optimization

We consider a measure of cooperativity based on the minimal interaction required to generate an observed titration behavior. We describe the corresponding algebraic optimization problem and show how it can be solved using the nonlinear algebra tool SCIP. Moreover, we compute the minimal interactions and minimal molecules for several binding polynomials that describe the oxygen binding of various hemoglobins under different conditions. We compare their minimal interaction with the maximal slope of the Hill plot, and discuss similarities and discrepancies with a view towards the shapes of the binding curves.

Threshold selection and trimming in extremes

We consider removing lower order statistics from the classical Hill estimator in extreme value statistics, and compensating for it by rescaling the remaining terms. Trajectories of these trimmed statistics as a function of the extent of trimming turn out to be quite flat near the optimal threshold value. For the regularly varying case, the classical threshold selection problem in tail estimation is then revisited, both visually via trimmed Hill plots and, for the Hall class, also mathematically via minimizing the expected empirical variance. This leads to a simple threshold selection procedure for the classical Hill estimator which circumvents the estimation of some of the tail characteristics, a problem which is usually the bottleneck in threshold selection. As a by-product, we derive an alternative estimator of the tail index, which assigns more weight to large observations, and works particularly well for relatively lighter tails. A simple ratio statistic routine is suggested to evaluate the goodness of the implied selection of the threshold. We illustrate the favourable performance and the potential of the proposed method with simulation studies and real insurance data.

Photophysical Studies of a Catechol Based Polyfunctional Dipodal Chelator: Application for Optical Probe for Selective Detection of Fe(III).

A novel catechol based dipodal fluorescent chelator N,N'-bis[3-[(E)-(2,3-dihydroxyphenyl)methyleneamino]propyl]propanediamide(MPC), has been developed and its photophysical behaviour was studied by experimental (UV-VIS and fluorescence) and DFT method. The design of the molecule has been inspired from the naturally occurring siderophore enterobactin, a catechol based chelator with amide linkage, that shows an excellent binding efficiency towards Fe(III). The dipodal molecule (MPC) presented here, carries two catechol pendant binding moieties linked to the malonate central unit through propylene spacers by amide linkage. MPC showed good selectivity for Fe(III) at 10-4M concentration in aqueous medium amongst the biologically and environmentally important metal ions chosen viz., Na(I), K(I), Al(III), Cr(III), Fe(III), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II), by demonstrating a remarkable quenching in the fluorescent emission from 262a.u. to 55a.u. at λmax = 477nm. Also, the pre-organized assembled ligand favored an efficient Fe (III) encapsulation through coordination by imine nitrogen and catecholate oxygen donors. High formation constant (log β = 31.3) for 1:1 metal-ligand complex evaluated by both potentiometric and spectrophotometric methods, established the strong binding efficiency of the ligand for Fe(III) metal ion. The binding stoichiometry in the complex was also confirmed from Stern -Volmer and Hill Plot analysis. Further investigation on the emission behavior of MPC in a completely DMSO system explored its suitability for extensive applications in the areas such as, metallurgy, material science, iron contamination remedial in the materials etc.. DFT studies suggest that the ligand displays a U-shaped geometry with a parallel π-stacking and the hydrogen bond between two arms. The experimental infrared, electronic, fluorescence, 1H nmr, 13C nmr spectra were correlated with the theoretical results. The nature of electronic transitions were identified from the TDDFT calculation. The ligand forms a hexa-coordinated complex with six Fe-O bonds extending an orthorhombic geometry due distortion from a regular octahedron.

Distinct features of bivalent direct thrombin inhibitors, hirudin and bivalirudin, revealed by clot waveform analysis and enzyme kinetics in coagulation assays

AimsBivalent direct thrombin inhibitors (DTIs), hirudin and bivalirudin, bind to the active site and exosite 1 of thrombin irreversibly and reversibly, respectively. The present study aims to assess in vitro...

Linkage analysis reveals allosteric coupling in Kir2.1 channels.

Potassium-selective inward rectifier (Kir) channels are a class of membrane proteins necessary for maintaining stable resting membrane potentials, controlling excitability, and shaping the final repolarization of action potentials in excitable cells. In addition to the strong inward rectification of the ionic current caused by intracellular blockers, Kir2.1 channels possess "weak" inward rectification observed in inside-out patches after prolonged washout of intracellular blockers. The mechanisms underlying strong inward rectification have been attributed to voltage-dependent block by intracellular Mg2+ and polyamines; however, the mechanism responsible for weak rectification remains elusive. Hypotheses include weak voltage-dependent block and intrinsic voltage-dependent gating. Here, we performed a conductance Hill analysis of currents recorded with a double-ramp protocol to evaluate different mechanisms proposed for weak inward rectification of Kir2.1 channels. Linkage analysis in the form of a Hill plot revealed that the ramp currents could be best explained by allosteric coupling between a mildly voltage-dependent pore gate (gating charge ∼0.18 eo) and a voltage sensor (gating charge ∼1.7 eo). The proposed voltage sensor stabilized the closing of the pore gate (coupling factor ∼31). We anticipate that the use of linkage analysis will broaden understanding of functional coupling in ion channels and proteins in general.

Exploiting intra-cultivar variation to select forBarley yellow dwarf virus-PAV(BYDV-PAV) resistance in barley

Selection within elite barley cultivars is assumed to be ineffective due to the belief that inbred cultivars are highly homogeneous. The objective of the present work was to evaluate a selection procedure (Honeycomb design) applied within five barley cultivars (Manel, Rihane, Kounouz, Lemsi, and Imen) and two Tunisian landraces (Ardhaoui and Djebali) under ultra-low plant density (1.2 plants m−2) towards selecting high-performance lines with resistance to Barley yellow dwarf virus-PAV (BYDV-PAV). Lines selected through this process were further field-evaluated in hill plots under artificial BYDV-PAV inoculation and uninoculated control conditions during the 2016–2017 cropping season. Artificial inoculation in the field caused a severe reduction in agronomic performance traits, with yield loss reaching around 60%. However, two lines (IH16-H1 and IH4-L0) originating from cultivar Imen were significantly superior over the mother variety in the control field, showing at the same time minimum yield loss after BYDV-PAV inoculation not exceeding 10%, similar to the resistant check. Genotyping of the lines for the Ryd2 and Ryd3 resistance genes and assessment of visual symptoms in the field associated with reduction in yield revealed an additive effect of the genes conferring resistance to BYDV-PAV. However, there were lines with genotypic patterns that did not match the patterns of the source material, providing insights for exploitable intra-cultivar diversity within the barley cultivars and landraces assessed.