Inhibition Of Exchange Research Articles

A novel ZnO-TiO2-Bi2WO6/Carboxymethyl chitosan composite with high antimicrobial activity and visible-light catalytic degradation of ethylene towards banana preservation in hot and humid environments

In order to solve the problem of significantly shortened storage time of bananas in hot and humid environment (e.g., 30 °C and 90 % relative humidity), this paper reports the preparation of ZnO-TiO2-Bi2WO6 (ZTB) ternary heterojunction antimicrobial photocatalysts composite carboxymethyl chitosan film (ZTB/CMCS). ZTB were prepared by hydrothermal method and composited with CMCS by surface deposition method to construct ZTB/CMCS edible nano-preservation film. It is noteworthy that the ZTB/CMCS composite film exhibited excellent antibacterial efficiency (>99.99 %) against E. coli and S. aureus suspensions (106 CFU/mL) after 24 h of incubation at 37 °C. Time-resolved photoluminescence (TRPL) spectroscopy showed that the incorporation of Zinc oxide nanoparticles (ZnO NPs) into the ZTB structure led to a decrease in fluorescence lifetime. Moreover, the interfacial interaction between ZnO and TiO2/Bi2WO6 inhibited the recombination of photogenerated electron-hole pairs, promoting carrier separation and improving photocatalytic activity. The combination of high antibacterial activity, photocatalytic degradation of ethylene and inhibition of gas exchange provided multiple protections for fruit preservation. Therefore, this work provides a novel, effective and safe method for prolonging the preservation of bananas in hot and humid environments.

Antiarrhythmic Effect of SGLT-2 Inhibitors in high-degree AV Block Caused by Heart Failure: A Case Report

Highlights: 1. The antiarrhythmic effect of SGLT-2 inhibitors, particularly empagliflozin, is a very interesting topic to discuss further. 2. In patients with high degree AV block due to HF in rural areas, the use of SGLT-2 inhibitors is quite rare in Indonesia. - Background: According to WHO's Top 10 Global Health Threats, non-communicable diseases such as heart failure contribute to more than 70% of all deaths worldwide. Several studies have shown that SGLT-2 inhibitors can considerably reduce HF. As research progresses, SGLT-2 inhibitors may lessen the risk of arrhythmias in HF patients. Case Summary: A 57-year-old female with uncontrolled hypertension came to the ED after collapsing at home. The vital signs and physical examination are normal. The preliminary ECG showed a high degree AV Block with multiple multifocal PVC. Early laboratory revealed mild hypokalemia. The patient experienced a seizure the next day, and an ECG showed total AV block with a non-sustained VT episode with PVC R on T. Following critical cardiac care and stabilization, the patient underwent echocardiography, which showed mild MR and AR with a reduced ejection fraction (47.7%). Once the patient's condition has stabilized, the patient is given 1x10mg Empagliflozin PO. Discussion: SGLT-2 inhibitors are beneficial in the treatment of heart failure and arrhythmia. SGLT-2 inhibitors have antiarrhythmic effects through a variety of pathways, such as lowering preload and afterload, inhibition of sodium-hydrogen exchange in myocardial cells, and suppression of the sympathetic nervous system.

Supramolecular self-assembly of robust, ultra-stable, and high-temperature-resistant viscoelastic worm-like micelles

HypothesisWorm-like micelles are susceptible to heating owing to the fast dynamic exchange of molecules between micelles. Inhibition of such exchange could afford robust worm-like micelles, which is expected to largely improve rheology properties at high temperatures. ExperimentsA cationic surfactant docosyl(trimethyl)azanium chloride (DCTAC) and a strongly hydrophobic organic counterion 3-hydroxy naphthalene-2-carboxylate (SHNC) were used for the worm-like micelles fabrication. The microstructure was characterized using cryogenic transmission electron microscopy and small-angle neutron scattering, and the interactions between DCTAC and SHNC were characterized using nuclear magnetic resonance spectroscopy. Rheometer was employed to measure the rheological properties of the solution. FindingsSHNC/DCTAC at the molar ration of 1:2 forms ultra-stable worm-like micelles, whose viscosity remain stable at temperature up to 130 °C. SHNC is found to strongly adsorbs on DCTAC micelle with the orientation on the surface of micelle, keeping the naphthalene backbone entire penetration into the palisade layer while both carboxylic and hydroxyl groups protrude out of the micelle. With temperature increasing, this adsorption further strengthens, resulting in the growth contour length and accompanying the enhancement of rheological properties. One SHNC molecule and two DCTAC molecules are speculated to form a stable complex via multiple interactions including hydrophobic, cationic-π, and π-π interactions, which decreases the dynamic exchange of them between micelles. These findings are helpful to understand surfactant aggregates stability and assist the development of novel stable supramolecular nanostructures. Additionally, the excellent thermal stability of this worm-like micellar fluid makes it a potential high-temperature resistant clean fracturing fluid for deep oil reservoirs.

Mining Leachates Effect on the Hydraulic Performance of Geosynthetic Clay Liners under Different Temperatures

Geosynthetic clay liners (GCLs) are often used as anti-seepage systems in landfills and at the bottom of tailing ponds. The anti-seepage performance of GCL will change under different temperatures. In this study, bentonite was mixed with test solutions at different temperatures to measure the basic performance indexes of bentonite components and analyze the permeability. The composition and micro-structure of bentonite at different temperatures were analyzed by X-ray diffraction, X-ray fluorescence spectrum, and SEM, and the change rule of permeability property with the mine leachates at different temperatures was understood by combining the macro-measured parameters with the microscopic analysis results. The research results indicate that the fluid loss of two bentonites increased with the increasing temperature due to the inhibition of ion exchange between bentonite and mixture by the increased temperature. The swelling index of the bentonite increased at high temperatures. The micro-structure analysis showed the increase of the pore size attributed to high temperature, and the uneven distribution of the pore size resulted in the increase of the intrinsic permeability. The study would provide the reference for the application of GCL in mining.

Transient On- and Off-Pathway Protein Folding Intermediate States Characterized with NMR Relaxation Dispersion.

The earliest events in the folding of a protein are in general poorly understood. We used NMR R2 relaxation dispersion experiments to study transient local collapse events in the unfolded-state (U) conformational ensemble of apomyoglobin (apoMb). Local residual secondary structure (seen in regions corresponding to the A, D, E, and H helices of the folded protein) is largely unchanged over the pH range of 2.3-2.75, yet a significant pH-dependent increase in the conformational exchange contribution to the R2 relaxation rate (Rex) indicates that transient intramolecular contacts occur on a microsecond to millisecond time scale at pH 2.75. A comparison of 15N and 13CO relaxation dispersion data at pH 2.75 for residues in the A, B, G, and H regions, which participate in the earliest folding intermediates, indicates that chain collapse and secondary structure formation are rapid and concomitant. Increasingly stabilizing conditions (lower temperature, higher pH) result in the observation of a relaxation dispersion in the C, CD, and E regions of the protein, which are known to fold at later stages. Mutation of Trp14 in the A-helix region to Ala eliminates conformational exchange throughout the protein, and the mutation of hydrophobic residues in other regions results in the selective inhibition of conformational exchange in the B, G, or H regions. The R2 dispersion data for WT apoMb at pH 2.75 and 10 °C are best fit to a four-state model ABGH ⇆ AGH ⇆ U ⇆ ABCD that includes on-pathway (AGH and ABGH) and off-pathway (ABCD) transiently folded states, both of which are required to explain the behavior of the mutant proteins. The off-pathway intermediate is destabilized at higher temperatures. Our analysis provides insights into the earliest stages of apoMb folding where the collapsing polypeptide chain samples both productive and nonproductive states with stabilized secondary structure.

PH-Dependent Regulation of Electron Flow in Photosystem II by a Histidine Residue at the Stromal Surface

In photosystem II (PSII), the secondary plastoquinone electron acceptor QB functions as a substrate that converts into plastoquinol upon its double reduction by electrons abstracted from water. It has been suggested that a histidine residue, D1-H252, which is located at the stromal surface near QB, is involved in the pH-dependent regulation of electron flow and proton transfer to QB. However, definitive evidence for the involvement of D1-H252 in the QB reactions has not been obtained yet. Here, we studied the roles of D1-H252 in PSII using a cyanobacterial mutant, in which D1-H252 was replaced with Ala. Delayed luminescence (DL) measurement upon a single flash showed a faster QB- decay at higher pH in the thylakoids from the wild-type strain due to the downshift of the redox potential of QB [Em(QB-/QB)]. This pH dependence of the QB- decay was lost in the D1-H252A mutant. The experimental Em(QB-/QB) changes were well reproduced by the density functional theory calculations for models with different protonation states of D1-H252 and with Ala replaced for H252. It was further shown that the period-four oscillation of the DL intensity by successive flashes was significantly diminished in the D1-H252A mutant, suggesting the inhibition of plastoquinone exchange at the QB pocket in this mutant. It is thus concluded that D1-H252 is a key amino acid residue that regulates electron flow in PSII by sensing pH in the stroma and stabilizes the QB binding site to facilitate the quinone exchange reaction.

ARAF protein kinase activates RAS by antagonizing its binding to RASGAP NF1

RAF protein kinases are effectors of the GTP-bound form of small guanosine triphosphatase RAS and function by phosphorylating MEK. We showed here that the expression of ARAF activated RAS in a kinase-independent manner. Binding of ARAF to RAS displaced the GTPase-activating protein NF1 and antagonized NF1-mediated inhibition of RAS. This reduced ERK-dependent inhibition of RAS and increased RAS-GTP. By this mechanism, ARAF regulated the duration and consequences of RTK-induced RAS activation and supported the RAS output of RTK-dependent tumor cells. In human lung cancers with EGFR mutation, amplification of ARAF was associated with acquired resistance to EGFR inhibitors, which was overcome by combining EGFR inhibitors with an inhibitor of the protein tyrosine phosphatase SHP2 to enhance inhibition of nucleotide exchange and RAS activation.

Еndothelial dysfunction in patients with chronic obstructive pulmonary disease: feasibility of non-medicamental treatment (literature review and personal experience)

The aim of the work was to study the feasibility of the use of non-medicamental factors for the correction of endothelial dysfunction in patients with chronic obstructive pulmonary disease. Results. Chronic obstructive pulmonary disease (COPD) is considered as a systemic disease, one of the pathogenetic components of which is endothelial dysfunction (ED), which contributes to the development of comorbid cardiovascular pathology. At the same time, the basic treatment of patients with COPD includes drugs that may adversely influence it, and some medicines for the cardiac pathology treatment can increase the bronchial obstruction. Therefore, a question of non-medicamental methods of ED correction is actual, especially beyond the acute period of the disease. Methods of hardware physiotherapy, including ozone therapy, singlet oxygen therapy and its combination with magnetic therapy, low-intensity laser radiation, ultrasound therapy, a combination of laser therapy with balneotherapy, are widely employed. These methods have antioxidant, bronchodilating and anti-inflammatory effects, promote improvement of hemodynamics, as well as rheological properties of blood and microcirculation. Interval hypoxic therapy is also used, because in response to the hypoxic stimulation, the mechanisms of the respiratory system regulation, gas exchange and blood circulation are activated. It is also promising to use haloaerosoltherapy (HAT), which due to the increase of bronchs drainage function and sanitizing effect leads to the inhibition of local inflammation, improves ventilation and gas exchange, and reduces the intensity of oxidative stress, which promotes decrease of systemic inflammation and ED, associated with it. Particularly, this effect is manifested by lowering of edothelin-1 level and the expression of adhesion molecules by lymphocytes (CD54+). Conclusions. The analysis shows that the inclusion of methods with non-medicamental influence on the endothelium can significantly increase the effectiveness of complex treatment of patients with COPD, without increasing the medicinal load on the organism, which helps to avoid undesirable side effects. The use of HAT in the rehabilitation treatment of COPD patients contributes not only to decreasing the activity of local and systemic inflammatory processes, but also is accompanied by a certain correction of ED. However, specific recommendations for the use of certain non-medicamental effects in the complex rehabilitation treatment of patients with COPD, taking into account the presence of ED, have not been developed.

Pharmacological inhibition of sodium-calcium exchange activates NADPH oxidase and induces infection-independent NETotic cell death

In addition to its function of innate immunity against invading pathogens, neutrophil extracellular traps (NETs) promote thrombosis, autoimmune disease, and cancer metastasis; therefore, unnecessary exposure to the triggers of infection-independent NET generation should be avoided. We herein show that inhibition of forward-mode Na+/Ca2+ exchange by amiloride analogs, 5-(N-ethyl-N-isopropyl)amiloride (EIPA) and 5-(N-Methyl-N-isobutyl)amiloride (MIA), triggers NETotic cell death independently of infectious stimuli. Isolated human neutrophils treated with EIPA and MIA undergo NETotic cell death by an increase of intracellular Ca2+ following activation of NADPH oxidase and the resultant upregulation of intracellular ROS. EIPA- and MIA-mediated intracellular Ca2+ increase is attributed to the competitive binding of EIPA and MIA against Na+ to Na+/Ca2+ exchanger 1 (NCX1). These results demonstrate a new mechanism of infection-independent NET generation and implicate NCX1 as a physiologic regulator of intracellular calcium balance and NETotic cell death.

Gas exchange, growth, and production of mini-watermelon under saline water irrigation and phosphate fertilization

In the semi-arid region of Northeastern Brazil, due to the occurrence of excess salts, both in the water and soil, plants are constantly exposed to various conditions of abiotic stress. Thus, it is extremely important to identify methods capable of minimizing the effects of salt stress on plants as a way to ensure the expansion of irrigated areas. In this context, the objective of this study was to evaluate the gas exchange, growth, and production of mini-watermelon irrigated with saline waters and fertilized with phosphorus. The experiment was conducted in pots under greenhouse conditions in Pombal, PB, Brazil, using a randomized block design in a 5 x 4 factorial scheme, corresponding to five levels of electrical conductivity of irrigation water—ECw (0.3, 1.3, 2.3, 3.3, and 4.3 dS m-1), four phosphorus doses— PD (60, 80, 100, and 120% of the recommendation), and with three replicates. Watermelon plants cv. Sugar Baby were sensitive to water salinity greater than 0.3 dS m-1, with more pronounced inhibition of gas exchange, growth, and production. Reduction in the CO2 assimilation rate of watermelon plants cv. Sugar Baby was associated with factors of stomatal and non-stomatal origin. Phosphorous doses corresponding to 73 and 88% of the recommended values promoted an increase in the intercellular CO2 concentration and stem diameter of mini-watermelon plants. P2O5 doses ranging from 60 to 120% of the recommendation did not mitigate the effects of salt stress on the cultivation of watermelon cv. Sugar Baby.

Integrating Catalytic Processes and Modern Electrolyte Concepts into Electrosynthesis.

Electrosynthesis is frequently presented as an intrinsically sustainable, safe and efficient method. While this is indeed often the case, this assessment cannot be easily generalized, as a number of challenges need to be addressed on the way to more efficient and truly sustainable processes. These challenges comprise the necessity for employing large amounts of supporting electrolyte additives along with the concomitant separation and waste issues. A further problem is the kinetic inhibition of the heterogeneous electron exchange, which in many instances leads to a decreased selectivity and an increased energy consumption ( 'overpotential' ). Another challenge is the apparent restriction of electrosynthesis to redox reactions, which seems to exclude important redox-neutral processes such as rearrangements, cycloadditions and substitutions from the scope of applications. Herein, catalytic approaches and electrolyte concepts are presented, which can help to overcome the abovementioned issues. For illustration of the principles, examples from our recent research activities are used.

Photo-Control of RAS Nucleotide Exchange Reaction using Peptide Inhibitor Modified with Spiropyran Derivative

Ras is a kind of GTPase protein, and it regulates cellular signal transduction. For example, some information such as cell growth and cell differentiation from in vitro to in vivo of downstream by cycling between GTP active form and GDP inactive form. GDP-GTP exchange of Ras is induced by binding of GEF(Guanine Exchange Factor) to Ras. Recently some kinds of peptide which bind to GEF binding region or allosteric binding region. Then, they cause inhibition of nucleotide exchange, were reported. It is known that mutated Ras (G12D etc.) continues transducing permanently, so it is the factor of making cancer cells. Then, it is called cancer gene. From this, the study that develops molecule target medicine only abnormality protein is recognized and controlled is attempted so as not to affect normal cells. Photochromic molecule, spiropyran isomerize between ring-closed spiro (SP) and ring-opened merocyanine(MC) forms photo-reversibly upon visible and ultraviolet lights. It is known that MC form of spiropyran has a polarity, so it exhibits electric interaction each other at peptide. Therefore, peptide also change the secondary structure between alpha-helix and random coil. In this study, we designed and synthesized peptide inhibitor of Ras based on interface structure between Ras and GEF. The synthesized petide RRFCGIYCTNACKTCEGNRR composed of four cysteine residues. These cysteine residues were modified with SP-maleimide(SP-MA) stoichiometrically. The secondary structural change of the SOS mimic peptide induce by photo-isomerization of SP-MA were examined by CD spectrum. The photo-control of nucleotide exchange of Ras using the peptide inhibitor was examined. We also synthesized several peptide inhibitors which have different number of cysteine residues and examined the inhibitory effect of the peptides.

Photo-Control of RAS GDP-GTP Exchange using the SOSαH Mimicking Peptides Modified with Spiropyran Derivative

Ras is a kind of GTPase protein, and it regulates cellular signal transduction. For example, some information such as cell growth and cell differentiation from in vitro to in vivo of downstream by cycling between GTP active form and GDP inactive form. GDP-GTP exchange of Ras is induced by binding of GEF(Guanine Exchange Factor) to Ras. Recently some kinds of peptide which interfere binding of GEF resulting in inhibition of GDP-GTP exchange, were reported. Synthetic peptide mimicking αH helix of SOS inhibited the Ras GDP-GTP exchange in the presence of SOS (Son Of Sevenless). Photochromic molecule, spiropyran isomerize between ring-closed spiro (SP) and ring-opened merocyanine (MC) forms photo-reversibly upon visible and ultraviolet lights. It is known that the zwitterion of MC forms exhibit dimerization. Previously, it has been demonstrated that the peptides modified with spiropyran derivatives change their secondary structure accompanied by formation of spiropyran dimerization photoreversibly. In this study, we designed and synthesized the peptides which have two cysteines and analogous to the SOS αH-helix. The two cysteine residues of the peptides were modified with SP-maleimide(SP-MA) stoichiometrically. The spiropyran incorporated into the peptide exhibited SP-MC isomerization upon visible light and ultraviolet light irradiations. The secondary structural change of the SOS mimic peptide induce by photo-isomerization of SP-MA were examined. Furthermore, photoreversible inhibition of Ras GDP-GTP exchange in the presence of SOS with the photochromic peptide was analyzed using fluorescent GDP analogues.

Interactive effects of biostimulants and water stress on potted Pinot noir grapevines

Seaweeds extracts (SWE) are innovative and non-polluting tools that have become popular as biostimulants. Their effects on Pinot noir water potential, gas exchanges and fruit quality under drought stress and full irrigation were evaluated during the 2017 growing season. Differential irrigations were applied and Pinot Noir grapevines have been sprayed two times at label doses (3 g/L) during the vegetative growth, with the Ascophyllum nodosum exract, starting from veraison. During the season, measurements of single leaf gas exchange and stem water potential were made; moreover parameters of technological maturity (°Brix, acidity, pH) and phenological one were analyzed. The inhibition of gas exchange and increase of stomatal limitation induced by drought stress were not reduced by SWE where A.nodosum had positive effects on midday stem water potential. Under full irrigation SWE increased leaf gas exchange. No particular effect was observed on the technological parameters after the treatment. The application of the seaweed extract improved polyphenols accumulation in stressed theses, increasing wine grapes quality. A.nodosum can be useful to reduce negative effects of abiotic stress such lack of water and to improve polyphenols content in grapes, especially in genotypes with a limited phenolic profile like Pinot Noir variety.

Potential mechanisms underlying the cardiovascular benefits of sodium glucose cotransporter 2 inhibitors: a systematic review of data from preclinical studies.

There is growing evidence from Phase III randomized clinical trials of the cardiovascular benefits of sodium glucose cotransporter 2 (SGLT2) inhibitors in patients with diabetes mellitus. It is hypothesized that these benefits are mediated by mechanisms other than glucose control. To address this, we performed a systematic review of data from preclinical studies examining the direct cardioprotective effects of SGLT2 inhibitors. Medline, EMBASE, CINAHL, and International Pharmaceutical Abstracts databases were searched for preclinical studies that examined the potential cardioprotective effects of SGLT2 inhibitors. Submission documents to the US Food and Drug Administration, European Medicines Agency, and Japanese Pharmaceutical and Medical Devices Agency for the registration of SGLT2 inhibitors were also reviewed. A total of 36 reports were included in the final analysis. The potential direct cardiovascular benefits of SGLT2 inhibitors include: augmentation of signal transducer and activator of transcription 3; inhibition of sodium hydrogen exchange; reduction of atherosclerosis; modulation of natriuretic peptides; vasodilation; modulation of sympathetic tone; and reduction of inflammation, oxidative stress, endoplasmic reticulum stress, and cardiac glucose uptake via down-regulation of SGLT1 expression. There are a number of mechanisms by which SGLT2 inhibitors may exert cardiovascular benefits beyond glycaemic control.

Microbial fuel cells coupling with the three-dimensional electro-Fenton technique enhances the degradation of methyl orange in the wastewater.

The emission of the source effluent of azo dyes has resulted in a serial of environmental problems including of the direct damage of the natural esthetics, the inhibition of the oxygen exchange, the shortage of the photosynthesis, and the reduction of the aquatic flora and fauna. A bioelectrochemical platform (3D-EF-MFCs) combining two-chamber microbial fuel cells and three dimensional electro-Fenton technique were delicately designed and assembled to explore the decolorization, bio-genericity performance of the methyl orange, and the possible biotic-abiotic degradation mechanisms. The 3D-EF-MFCs processes showed higher decolorization efficiencies, COD removals, and better bioelectricity performance than the pure electro-Fenton-microbial fuel cell (EF-MFC) systems. The two-chamber experiments filling with the granular activated carbons were better than the single-chamber packing system on the whole. The moderate increase of Fe2+ ions dosing in the cathode chamber accelerated the formation of •OH, which further enhanced the degradation of the methyl orange (MO). The cathode-decolorization and COD removals were decreased with the increase of MO concentration. However, the degradation performance of MO was indirectly improved in the anode compartment at the same conditions. The bed electrodes played a mediator role in the anode and cathode chambers, certainly elevated the voltage output and the power density, and lowered the internal impedance of EF-MFC process.

Glutathione-Responsive Selenosulfide Prodrugs as a Platform Strategy for Potent and Selective Mechanism-Based Inhibition of Protein Tyrosine Phosphatases.

Dysregulation of protein tyrosine phosphorylation has been implicated in a number of human diseases, including cancer, diabetes, and neurodegenerative diseases. As a result of their essential role in regulating protein tyrosine phosphorylation levels, protein tyrosine phosphatases (PTPs) have emerged as important yet challenging therapeutic targets. Here we report on the development and application of a glutathione-responsive motif to facilitate the efficient intracellular delivery of a novel class of selenosulfide phosphatase inhibitors for the selective active site directed inhibition of the targeted PTP by selenosulfide exchange with the active site cysteine. The strategy leverages the large difference in extracellular and intracellular glutathione levels to deliver selenosulfide phosphatase inhibitors to cells. As an initial exploration of the prodrug platform and the corresponding selenosulfide covalent inhibitor class, potent and selective inhibitors were developed for two therapeutically relevant PTP targets: the Mycobacterium tuberculosis virulence factor mPTPA and the CNS-specific tyrosine phosphatase, striatal-enriched protein tyrosine phosphatase (STEP). The lead selenosulfide inhibitors enable potent and selective inhibition of their respective targets over a panel of human PTPs and a representative cysteine protease. Kinetic parameters of the inhibitors were characterized, including reversibility of inhibition and rapid rate of GSH exchange at intracellular GSH concentrations. Additionally, active site covalent inhibitor-labeling with an mPTPA inhibitor was rigorously confirmed by mass spectrometry, and cellular activity was demonstrated with a STEP prodrug inhibitor in cortical neurons.

Nucleotide Dependence of Subunit Rearrangements in Short-Form Rubisco Activase from Spinach

Higher-plant Rubisco activase (Rca) plays a critical role in regulating the activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). In vitro, Rca is known to undergo dynamic assembly-disassembly processes, with several oligomer stoichiometries coexisting over a broad concentration range. Although the hexamer appears to be the active form, changes in quaternary structure could play a role in Rubisco regulation. Therefore, fluorescent labels were attached to the C-termini of spinach β-Rca, and the rate of subunit mixing was monitored by measuring energy transfer as a function of nucleotide and divalent cation. Only dimeric units appeared to exchange. Poorly hydrolyzable substrate analogues provided locked complexes with high thermal stabilities (apparent Tm = 60 °C) and an estimated t1/2 of at least 7 h, whereas ATP-Mg provided tight assemblies with t1/2 values of 30-40 min and ADP-Mg loose assemblies with t1/2 values of <15 min. Accumulation of ADP to 20% of the total level of adenine nucleotide substantially accelerated equilibration. An initial lag period was observed with ATP·Mg, indicating inhibition of subunit exchange at low ADP concentrations. The ADP Ki value was estimated to exceed the Km for ATP (0.772 ± 96 mM), suggesting that the equilibration rate is a function of the relative contributions of high- and low-affinity states. C-Terminal cross-linking generated covalent dimers, required the N-terminal extension to the AAA+ domain, and provided evidence of different classes of sites. We propose that oligomer reorganization may be stalled during periods of high Rubisco reactivation activity, whereas changes in quaternary structure are stimulated by the accumulation of ADP at low light levels.

Effects of Sodium-Glucose Cotransporter 2 Inhibitors for the Treatment of Patients With Heart Failure

ImportanceOnly 1 class of glucose-lowering agents—sodium-glucose cotransporter 2 (SGLT2) inhibitors—has been reported to decrease the risk of cardiovascular events primarily by reducing the risk of the development or progression of heart failure. In a landmark trial called Empagliflozin, Cardiovascular Outcomes, and Mortality in Type 2 Diabetes [EMPA-REG Outcomes], long-term treatment with empagliflozin prevented fatal and nonfatal heart failure events but did not reduce the risk of myocardial infarction or stroke in diabetic patients.ObservationsThe beneficial effect of SGLT2 inhibitors on heart failure cannot be explained by their actions on glycemic control or as osmotic diuretics. Instead, in the kidneys, SGLT2 functionally interacts with the sodium-hydrogen exchanger, which is responsible for the majority of sodium tubular reuptake following filtration. The activity of sodium-hydrogen exchanger is markedly increased in patients with heart failure and may be responsible for both resistance to diuretics and to endogenous natriuretic peptides. In addition, in the heart, empagliflozin appears to inhibit sodium-hydrogen exchange, which may in turn lead to a reduction in cardiac injury, hypertrophy, fibrosis, remodeling, and systolic dysfunction. Furthermore, the major pathophysiological derangements of heart failure and a preserved ejection fraction may be mitigated by the actions of SGLT2 inhibitors to reduce blood pressure, body weight, and fluid retention as well as to improve renal function. The benefits of spironolactone in patients with heart failure with either a reduced or a preserved ejection fraction may also be attributable to the actions of the drug to inhibit the sodium-hydrogen exchange mechanism.Conclusions and RelevanceThe benefits of SGLT2 inhibitors in heart failure may be mediated by the inhibition of sodium-hydrogen exchange rather than the effect on glucose reabsorption. This hypothesis has important implications for the design and analysis of large-scale outcomes trials involving diabetic or nondiabetic patients with chronic heart failure.

Structural and functional characterization of a DARPin which inhibits Ras nucleotide exchange

Ras mutations are the oncogenic drivers of many human cancers and yet there are still no approved Ras-targeted cancer therapies. Inhibition of Ras nucleotide exchange is a promising new approach but better understanding of this mechanism of action is needed. Here we describe an antibody mimetic, DARPin K27, which inhibits nucleotide exchange of Ras. K27 binds preferentially to the inactive Ras GDP form with a Kd of 4 nM and structural studies support its selectivity for inactive Ras. Intracellular expression of K27 significantly reduces the amount of active Ras, inhibits downstream signalling, in particular the levels of phosphorylated ERK, and slows the growth in soft agar of HCT116 cells. K27 is a potent, non-covalent inhibitor of nucleotide exchange, showing consistent effects across different isoforms of Ras, including wild-type and oncogenic mutant forms.