Nitrogen （N） is an essential macronutrient that affects plant growth and development. N is an important component of chlorophyll, amino acids, nucleic acids, and secondary metabolites. Nitrate is one ...of the most abundant N sources in the soil. Because nitrate and other N nutrients are often limiting, plants have developed sophisticated mechanisms to ensure adequate supply of nutrients in a variable environment. Nitrate is absorbed in the root and mobilized to other organs by nitrate transporters. Nitrate sensing activates signaling pathways that impinge upon molecular, metabolic, physiological, and developmental responses locally and at the whole plant level. With the advent of genomics technologies and genetic tools, important advances in our understanding of nitrate and other N nutrient responses have been achieved in the past decade. Furthermore, techniques that take advantage of natural polymor- phisms present in divergent individuals from a single species have been essential in uncovering new components. However, there are still gaps in our understanding of how nitrate signaling affects biolog- ical processes in plants. Moreover, we still lack an integrated view of how all the regulatory factors iden- tified interact or crosstalk to orchestrate the myriad N responses plants typically exhibit. In this review, we provide an updated overview of mechanisms by which nitrate is sensed and transported throughout the plant. We discuss signaling components and how nitrate sensing crosstalks with hormonal pathways for developmental responses locally and globally in the plant. Understanding how nitrate impacts on plant metabolism, physiology, and growth and development in plants is key to improving crops for sustainable agriculture.
The adenosine modulation system mostly operates through inhibitory A1 (A1R) and facilitatory A2A receptors (A2AR) in the brain. The activity‐dependent release of adenosine acts as a brake of ...excitatory transmission through A1R, which are enriched in glutamatergic terminals. Adenosine sharpens salience of information encoding in neuronal circuits: high‐frequency stimulation triggers ATP release in the ‘activated’ synapse, which is locally converted by ecto‐nucleotidases into adenosine to selectively activate A2AR; A2AR switch off A1R and CB1 receptors, bolster glutamate release and NMDA receptors to assist increasing synaptic plasticity in the ‘activated’ synapse; the parallel engagement of the astrocytic syncytium releases adenosine further inhibiting neighboring synapses, thus sharpening the encoded plastic change. Brain insults trigger a large outflow of adenosine and ATP, as a danger signal. A1R are a hurdle for damage initiation, but they desensitize upon prolonged activation. However, if the insult is near‐threshold and/or of short‐duration, A1R trigger preconditioning, which may limit the spread of damage. Brain insults also up‐regulate A2AR, probably to bolster adaptive changes, but this heightens brain damage since A2AR blockade affords neuroprotection in models of epilepsy, depression, Alzheimer's, or Parkinson's disease. This initially involves a control of synaptotoxicity by neuronal A2AR, whereas astrocytic and microglia A2AR might control the spread of damage. The A2AR signaling mechanisms are largely unknown since A2AR are pleiotropic, coupling to different G proteins and non‐canonical pathways to control the viability of glutamatergic synapses, neuroinflammation, mitochondria function, and cytoskeleton dynamics. Thus, simultaneously bolstering A1R preconditioning and preventing excessive A2AR function might afford maximal neuroprotection.
The main physiological role of the adenosine modulation system is to sharp the salience of information encoding through a combined action of adenosine A2A receptors (A2AR) in the synapse undergoing an alteration of synaptic efficiency with an increased inhibitory action of A1R in all surrounding synapses. Brain insults trigger an up‐regulation of A2AR in an attempt to bolster adaptive plasticity together with adenosine release and A1R desensitization; this favors synaptotocity (increased A2AR) and decreases the hurdle to undergo degeneration (decreased A1R). Maximal neuroprotection is expected to result from a combined A2AR blockade and increased A1R activation.
This article is part of a mini review series: “Synaptic Function and Dysfunction in Brain Diseases”.
The main physiological role of the adenosine modulation system is to sharp the salience of information encoding through a combined action of adenosine A2A receptors (A2AR) in the synapse undergoing an alteration of synaptic efficiency with an increased inhibitory action of A1R in all surrounding synapses. Brain insults trigger an up‐regulation of A2AR in an attempt to bolster adaptive plasticity together with adenosine release and A1R desensitization; this favors synaptotocity (increased A2AR) and decreases the hurdle to undergo degeneration (decreased A1R). Maximal neuroprotection is expected to result from a combined A2AR blockade and increased A1R activation.
This article is part of a mini review series: “Synaptic Function and Dysfunction in Brain Diseases”.
This work presents potential applications of low-cost fused deposition modeling 3D-printers to fabricate multiuse 3D-printed electrochemical cells for flow or batch measurements as well as the ...3D-printing of electrochemical sensing platforms. Electrochemical cells and sensors were printed with acrylonitrile butadiene styrene (ABS) and conductive graphene-doped polylactic acid (G-PLA) filaments, respectively. The overall printing operation time and estimated cost per cell were 6 h and $ 6.00, respectively, while the sensors were printed within minutes (16 sensor strips of 1 × 2 cm in 10 min at a cost of $ 1.00 each sensor). The cell performance is demonstrated for the amperometric detection of tert-butylhydroquinone, dipyrone, dopamine and diclofenac by flow-injection analysis (FIA) and batch-injection analysis (BIA) using different working electrodes, including the proposed 3D-printed sensor, which presented comparable electroanalytical performance with other carbon-based electrodes (LOD of 0.1 μmol L−1 for dopamine). Raman spectroscopy and scanning electron microscopy of the 3D-printed sensor indicated the presence of graphene nanoribbons within the polymeric matrix. Electrochemical impedance spectroscopy and heterogeneous electron transfer constants (k0) for the redox probe Ru(NH3)6+3 revealed that a glassy-carbon electrode presented faster electron transfer rates than the 3D-printed sensor; however, the latter presented lower LOD values for dopamine and catechol probably due to oxygenated functional groups at the G-PLA surface.
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•Low-cost fused deposition modeling (FDM) 3D-printers to produce cells and electrodes.•Multiuse cells for flow- (FIA) and batch-injection analysis (BIA) as well for batch condition.•Designs and printing conditions accessible for any FDM 3D-printers.•Graphene-doped PLA printed sensors for voltammetric and amperometric detection.•Electroanalytical performance similar to GCE modified with carbon nanomaterials.
Herein, we report a complete additively manufactured (AM) electrochemical sensing platform. In this approach, a fully AM/3D-printed electrochemical system, using a conventional low-cost 3D printer ...(fused deposition modeling) fabricating both the conductive electrodes and the nonconductive/chemically inert electrochemical cell is reported. The electrodes (working, counter, and pseudo-reference) are AM using a conductive fused-filament comprised of a mixture of carbon black nanoparticles and polylactic acid (CB/PLA). AM components partially coated with silver ink presented a similar behavior to a conventional Ag/AgCl reference electrode. The performance of the AM working electrode was evaluated after a simple and fast polishing procedure on sandpaper and electrochemical activation in a NaOH solution (0.5 mol L–1). Following the electrochemical activation step, a considerable improvement in the electrochemical behavior (current intensity and voltammetric profile) was obtained for model analytes, such as dopamine, hexaammineruthenium(III) chloride, ferricyanide/ferrocyanide, uric acid, and ascorbic acid. Excellent repeatability (RSD = 0.4%, N = 10) and limit of detection (0.1 μmol L–1) were obtained with the all complete AM electrochemical system for dopamine analysis. The electrochemical performance of the developed system (after simple electrochemical activation of the working electrode) was similar or better than those obtained using commercial glassy carbon and screen-printed carbon electrodes. The results shown here represents a significant advance in AM (3D printing) technology for analytical chemistry.
Abstract
We use ESA/Gaia astrometry together with SEGUE and LAMOST measurements of the GD-1 stellar stream to explore the improvement on the Galactic gravitational potential that these new data ...provide. Assuming a realistic universal model for the dark matter halo together with reasonable models of the baryonic components, we find that the orbital solutions for GD-1 require the circular velocity at the Solar radius to be $V_{\rm circ}({\rm R}_\odot) =244\pm 4{\rm \, km\, s^{-1}}$, and also that the density flattening of the dark halo is $q_{\rho }=0.82^{+0.25}_{-0.13}$. The corresponding Galactic mass within $20{\rm \, kpc}$ was estimated to be $M_{\rm MW}(\lt 20{\rm \, kpc})=2.5\pm 0.2 \times 10^{11} {\rm \, M_\odot }$. Moreover, Gaia’s excellent proper motions also allowed us to constrain the velocity dispersion of the GD-1 stream in the direction tangential to the line of sight to be $\lt 2.30{\rm \, km\, s^{-1}}$ (95 per cent confidence limit), confirming the extremely cold dynamical nature of this system.
► Highly rapid, selective and sensitive amperometric detection of H2O2 in milk. ► Prussian-blue modified electrode with improved stability and precision. ► Association with batch-injection analysis ...provided high analytical frequency. ► Satisfactory recovery values for milk analysis.
We report a highly rapid, precise, selective and sensitive analytical method for the determination of hydrogen peroxide in milk using a batch-injection analysis (BIA) with amperometric detection at a Prussian-blue bulk modified graphite-composite electrode. An electronic micropipette injected 100μL aliquots of 10-fold diluted samples (high and low-fat milk) directly onto the modified electrode immersed in the BIA cell. The analytical features of our proposed method includes low RSD between injections (0.76%, n=9), low detection limit (10μmolL−1), elevated analytical frequency (up to 80h−1) and satisfactory recovery values for spiked samples. A fresh and highly reproductive electrode surface can be easily obtained by simple mechanical polishing (RSD=1.6%, n=5). The storage stability of the PB-modified graphite-composite surpassed 1year keeping equivalent performance as initially presented. The association of BIA with an improved amperometric detector provides great promise for routine monitoring of hydrogen peroxide in milk and other beverages.
The mathematical representation of large data sets of electronic energies has seen substantial progress in the past 10 years. The so-called Permutationally Invariant Polynomial (PIP) representation ...is one established approach. This approach dates from 2003, when a global potential energy surface (PES) for CH5 + was reported using a basis of polynomials that are invariant with respect to the 120 permutations of the five equivalent H atoms. More recently, several approaches from “machine learning” have been applied to fit these large data sets. Gaussian Process (GP) regression is such an approach. Here, we consider the implementation of the (full) GP due to Krems and co-workers, with a modification that renders it permutationally invariant, which we denote by PIP-GP. This modification uses the approach of Guo and co-workers and later extended by Zhang and co-workers, to achieve permutational invariance for neural-network fits. The PIP, GP, and PIP-GP approaches are applied to four case studies for fitting data sets of electronic energies: H3O+, OCHCO+, and H2CO/cis-HCOH/trans-HCOH with the goal of assessing precision, accuracy in normal-mode analysis and barrier heights, and timings. We also report an application to (HCOOH)2, where the full PIP approach is possible but where the PIP-GP one is not feasible. However, by replicating data, which is feasible in this case, the GP approach is able to represent the data with precision comparable to that of the PIP approach. We examine these assessments for varying sizes of data sets in each case to determine the dependence of properties of the fits on the training data size. We conclude with some comments on the different aspects of computational effort of the PIP, GP, and PIP-GP approaches and also challenges these methods face for more “rugged” PESs, exemplified here by H2CO/cis-HCOH/trans-HCOH.
•Nitrate modulates hormonal pathways to adapt plant biology to environmental cues.•Hormones participate in local and systemic nitrogen signaling to regulate root and shoot growth.•Nitrate ...availability crosstalk with hormones to influence root system architecture.•This nitrate:hormone crosstalk also influences metabolism, uptake and stress responses.•Nitrate delays flowering time via the gibberellin signaling pathway.
Nitrate is an essential macronutrient for plants, a primary nitrogen source in natural and human-made ecosystems. Nitrate can also act as a signaling molecule that directs genome-wide gene expression changes with an impact on plant metabolism, physiology, growth and development. Nitrate and phytohormone signaling pathways crosstalk to modulate growth and developmental programs in a multifactorial manner. Nitrate-signaling controls plant growth and development using molecular mechanisms that involve phytohormone-signaling pathways. In contrast, many phytohormones modulate or impact nitrate signaling in interconnected pathways. In this review, we explore recent progress in our understanding of well-documented connections between nitrate and phytohormones such as auxin, cytokinin and abscisic acid. We also discuss recent studies connecting nitrate to other phytohormones such as ethylene, salicylic acid, gibberellins and brassinosteroids. While many molecular details remain to be elucidated, a number of core signaling components at the intersection between nitrate and the major hormonal pathways have been described. We focus on established interactions of nitrate and different hormonal pathways to bring about cellular, growth and developmental processes in Arabidopsis thaliana.
Despite an unprecedented global gain in knowledge since the emergence of SARS-CoV-2, almost all mechanistic knowledge related to the molecular and cellular details of viral replication, pathology and ...virulence has been generated using early prototypic isolates of SARS-CoV-2. Here, using atomic force microscopy and molecular dynamics, we investigated how these mutations quantitatively affected the kinetic, thermodynamic and structural properties of RBD-ACE2 complex formation. We observed for several variants of concern a significant increase in the RBD-ACE2 complex stability. While the N501Y and E484Q mutations are particularly important for the greater stability, the N501Y mutation is unlikely to significantly affect antibody neutralization. This work provides unprecedented atomistic detail on the binding of SARS-CoV-2 variants and provides insight into the impact of viral mutations on infection-induced immunity.
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