Sodium Phosphate Research Articles

Improving the survival under gastric conditions of a potential multistrain probiotic produced in co-culture

Process and culture medium composition in bioreactor could be optimized in order to find the best conditions that improve survival of probiotic microorganism under exposure to gastric conditions such low pH and bile salts. Therefore, this study aimed to optimize agitation, yeast extract, and di-sodium phosphate (Na2HPO4) concentration to improve the survival under gastric conditions of a multistrain consortium produced in a laboratory bioreactor. Viability, survival low pH (3.00), bile salt tolerance, and antagonistic activity against the pathogen Streptococcus agalactiae were evaluated. As the main result, a high concentration of di-sodium phosphate (2.63% w/v) increased the viability of L. lactis A12 (9.05 to 9.46 Log10 CFU/mL) and Priestia species (0.00 to 6.88 Log10 CFU/mL), survival to pH 3.00 (60 to 93%), survival of bile salts (58– 93%) antagonistic activity (8.74 to 15.56 mm), and final pH of culture medium (4.34 to 6.95). Optimal conditions that improved probiotics characteristics were 150 RPM, 0.83% w/v yeast extract, and 2.63% w/v Na2HPO4. Co-culture of L. lactis A12 with Priestia species improved significantly (p < 0.05) the antagonistic activity (10.41 mm) against S. agalactiae compared to mono-culture (7.70 mm). Our results suggested that was possible to produce a potential multistrain preparation in a lab bioreactor with high viability of L. lactis A12 (9.33 Log10 CFU/mL), high survival to gastric conditions (> 85%), and with antagonistic activity against fish pathogen. This preparation could be used as a feed additive intended for fish nutrition.

Waste newspaper activation by sodium phosphate for adsorption dynamics of methylene blue

Abstract This study investigates the potential of using waste newspaper (WN) as an adsorbent for removing methylene blue (MB) dye from water, emphasizing the environmental benefits of repurposing waste materials. Activated carbon (AC) was synthesized from WN using sodium phosphate (NaH2PO4) as the activating agent, which is known for producing high mesopore content and requiring relatively low activation temperatures. The activated carbon’s physicochemical properties were thoroughly characterized using techniques such as FTIR, SEM, and surface area analysis based on the Brunner-Emmett-Teller (BET) theory. The specific surface area of AC was 917 m2/g. Continuous adsorption experiments were conducted to evaluate the efficiency of the synthesized activated carbon in a dynamic flow system. Various operating conditions, including initial dye concentration, influent flow rate, and bed height, were explored to optimize the adsorption process. This study applied the Yoon-Nelson, Thomas, Adams-Bohart and modified Logistic models to analyze the breakthrough curves and predict adsorption capacities. Results demonstrated that the AC exhibited high adsorption capacity (14.7 mg/g), particularly at lower flow rates and higher bed heights. This work offers valuable insights into sustainable wastewater treatment methods, showcasing the effectiveness of using low-cost, waste-derived activated carbon for dye removal in industrial applications.

A disodium hydrogen phosphate dodecahydrate / expanded graphite composite phase change material suitable for use in the roofing of buildings

A disodium hydrogen phosphate dodecahydrate / expanded graphite composite phase change material suitable for use in the roofing of buildings

Unique Research for Developing a Full Factorial Design Evaluated Liquid Chromatography Technique for Estimating Budesonide and Formoterol Fumarate Dihydrate in the Presence of Specified and Degradation Impurities in Dry Powder Inhalation.

A simple LC method has been developed and validated for estimating budesonide (epimer B + A) and formoterol fumarate dihydrate in dry powder inhalation. The development results of this study make it very significant. The degradation and process impurities in EP and ChP were identified in addition to budesonide and formoterol fumarate. As of yet, no one has reported all impurities using a single method. It is a unique research because it analyzes APSD (Aerodynamic Particle Size Distribution), DDU (Delivered Dose Uniformity), BU (Blend Uniformity), Assay, and cleaning test samples. It enhances the quality of medicine and separates all organic impurities and isomers through a suitable stationary phase (YMC-Pack Pro C18, 150 × 4.6 mm × 3 μm). We optimized the chromatographic conditions: Injection volume was 20 μL, and flow rate was 1.0 mL/min. The wavelength was optimized at 220 nm. After experimental and validation results. An example is A, which contains sodium dihydrogen orthophosphate monohydrate, sodium 1-decane sulfonate, adjusted pH 3.0, and acetonitrile at a ratio of 80:20 (v/v), and B, which contains pH 3.0 buffer and acetonitrile at a ratio of 20:80 (v/v) respectively. In addition to being optimized, the test method was validated according to ICH Q2(R2).

Disodium hydrogen phosphate facilitates the gold enhancement reaction of nanogold in the pre-embedding immunoelectron microscopy.

Immunoelectron microscopy is a technique for analyzing molecular localization at the ultrastructural level. In the pre-embedding immunoelectron microscopy, samples are immunolabeled with extremely small gold particles. Gold enhancement then enlarges the gold particles to an easily visible size. During the examination of the optimal conditions, we found that phosphate buffer accelerates the enhancement reaction. Furthermore, disodium hydrogen phosphate was identified as responsible for this effect. Disodium hydrogen phosphate enabled the gold labeling of deep regions within thick tissue samples. In conclusion, our method is useful for increasing the sensitivity, especially in the deeper region of the sample.

Locally administered liposomal drug depot enhances rheumatoid arthritis treatment by inhibiting inflammation and promoting cartilage repair

Rheumatoid arthritis (RA) is a chronic autoimmune condition characterized by synovial hyperplasia, where inflammatory macrophages within the joint synovium produce multiple inflammatory cytokines, leading to cartilage damage. The development of therapeutic strategies that combine anti-inflammatory effects and cartilage repair mechanisms holds great promise for effective RA treatment. To address the limitations associated with the off-target effects of intravenous administration and the risk of synovial cavity infection with repeated local injections, we have innovatively developed a liposomal drug depot through hyaluronic acid (HA)-modified liposomes encapsulating dexamethasone sodium phosphate (DSP)-loaded nanogels, termed HA-Lipo@G/D. The nanogels were prepared by ionic cross-linking of chondroitin sulfate and gelatin, both of which have notable cartilage repair properties. In vitro studies demonstrated that this formulation exhibited sustained drug release, enhanced uptake by inflammatory macrophages, reduced secretion of inflammatory factors (TNF-α, IL-1β), and significantly decreased chondrocyte apoptosis induced by inflammatory factors. Moreover, in vivo assessments in a rat model of collagen-induced arthritis revealed effective accumulation of the liposomal drug depot at the inflamed joint site, resulting in macrophage repolarization and cartilage tissue repair. Our findings provide a synergistic strategy for inhibiting inflammation and mitigating cartilage damage through local joint cavity injection, thereby enhancing the therapeutic efficacy of RA.Graphical

The concurrent use of 2.5% polyacrylamide hydrogel and betamethasone esters for intra-articular injection is well tolerated in 10 healthy horses.

This study assessed the safety and tolerability of concurrent intra-articular (IA) injection of 2.5% polyacrylamide hydrogel (2.5% iPAAG) and betamethasone sodium phosphate and betamethasone acetate esters (BME) in the metacarpophalangeal joints (MCPJs) of healthy horses. 10 healthy therapeutic riding horses were enrolled in this open-label safety study from August 1 to September 14, 2023. Inclusion criteria required normal physical examinations, insulin level, hematology, biochemistry, soundness at all gaits, and negative forelimb flexion tests. Screening occurred from days -14 to -0. Each horse received a single IA injection of 1 mL of 2.5% iPAAG and 1 mL of BME (6 mg/mL) into the right MCPJ on day 0. Posttreatment veterinary assessments (days 0, 1, 2, 3, 7, 14, and 30) included physical examinations, joint-specific evaluations (skin temperature, fetlock circumference at the level of the MCPJ), soundness assessments, and adverse event monitoring. Caretaker observation diaries (days 0 through 30) were also reviewed. No adverse events occurred, and all horses remained clinically sound. Joint circumference remained stable without evidence of effusion. Transient increases in skin temperature on days 2, 3, 7, and 14 correlated with ambient temperature changes, returning to baseline by day 30. Caretaker observations supported clinical findings. Concurrent IA administration of 2.5% iPAAG and BME was safe and well tolerated in the right MCPJ of healthy horses, with no evidence of local or systemic adverse effects. This therapy combines BME's short-term anti-inflammatory effects with 2.5% iPAAG's long-term synovial integration, warranting further evaluation in diseased joints.

Tuning Magnesium-Air Fuel Cell Performance and Corrosion Behavior through Electrode and Electrolyte Configuration

Magnesium-air fuel cell (MAFC) is a hybrid system that combines the design of a fuel cell and a battery, requiring a constant replacement of anode and electrolyte to operate. MAFC application is limited for short-term high-power applications like emergency and portable power supplies because of severe corrosion problems impairing the performance of MAFC. Hence, this study focuses on performance by investigating the effect of electrolyte volume, electrodes position, and electrolyte concentration on performance of Mg–air fuel cell. Three sets of experiments were conducted starting with variation in volume of electrolyte. Then, it is applied in the cell configuration to test the MAFC performance with different electrode position. Lastly, the best electrode position is applied to the new modified MAFC together with the chosen electrolyte to investigate the effect of electrolyte concentration on MAFC performance. Finding shows that electrolyte volume not really significant to the performance while higher NaCl concentration can increase the performance of MAFC significantly. 10 wt% of NaCl produce the highest power density of 38.95 mW.cm&lt;sup&gt;-2&lt;/sup&gt; and operating voltage of 1.67 V. Unfortunately, higher corrosion rate was observed in higher NaCl concentration. Finally, adding sodium phosphate act as corrosion inhibitor manage to suppress the corrosion reaction and lowers the corrosion rate.

Molecularly imprinted hydrogels embedded with two-dimensional photonic crystals for the detection of dexamethasone/betamethasone sodium phosphate.

Dexamethasone sodium phosphate (DSP) and betamethasone sodium phosphate (BSP) imprinted hydrogels embedded with two-dimensional photonic crystals (2DPC) were developed as hormones-sensitive photonic hydrogel sensors with highly sensitive, selective, anti-interference and reproducible recognition capability. The DSP/BSP molecularly imprinted photonic hydrogels (denoted as DSP-MIPH and BSP-MIPH) can specifically recognize DSP/BSP by rebinding the DSP/BET molecules to nanocavities in the hydrogel network. This recognition is enabled by the similar shape, size, and binding sites of the nanocavities to the target molecules. The rebinding of hormones molecules causes the hydrogel to swell, resulting in a particle spacing increase of the embedded 2DPC of the hydrogel. The particle spacing increase can be used as sensing signal and can be acquired by simply measuring the Debye diffraction diameters of the photonic hydrogel sensor before and after exposure with a laser pointer and a ruler. The particle spacing increments of the DSP-MIPH and BSP-MIPH sensors linearly change when DSP and BSP concentrations changes within the ranges 0.025-1μM, 10-100μM, and 100-500μM, and the limits of detection (LoD) are 21.8nM for DSP and 12.6nM for BSP, respectively. These photonic hydrogel sensors were successfully applied tothe determination of DSP/BSP contents in the real pharmaceutical injections, providing an ideal strategy for the development of portable hormones sensors.

Elucidating the Unique J-Shaped Protomer Structure of Amyloid-β(1-40) Fibril with Cryo-Electron Microscopy

Although the structural diversity of amyloid-β (Aβ) fibrils plays a critical role in the pathology of Alzheimer’s disease (AD), the mechanisms underlying this diversity remain poorly understood. In this study, we report the discovery of a novel J-shaped protomer structure of Aβ40 fibrils, resolved at 3.3 Å resolution using cryo-electron microscopy. Under controlled conditions (20 mM sodium phosphate buffer, pH 8.0) designed to emphasize intra-protomer interactions and slow fibril elongation, the J-shaped structure revealed distinct salt bridges (e.g., D1-K28, R5-E22) that stabilize the fibril core. These findings expand our understanding of the free energy landscape of fibril formation, shedding light on how specific environmental factors, such as pH and ionic strength, may influence fibril polymorphism. Importantly, the unique features of the J-shaped protomer provide insights into the structural basis of amyloid plaque diversity in AD and suggest potential therapeutic strategies targeting intra-protomer interactions. This study underscores the importance of fibril polymorphism in AD pathology and offers a foundation for future research into fibril-targeted therapies.

Manufacturing of Liposomes Using a Stainless-Steel Microfluidic Device: An Investigation into Design of Experiments.

Liposomes are highly beneficial nanocarrier systems due to their biocompatibility, low toxicity, and exceptional inclusiveness, which lead to improved drug bioavailability. For biological applications, accurate control over these nanoparticles' mean size and size distribution is essential. Micromixers facilitate the continuous production of liposomes, enhancing the precision of size regulation and reproducibility. In this research, the performance of a stainless steel 316L micromixer was evaluated by using COMSOL Multiphysics simulations. The liposomes were precisely optimized using design of experiments techniques in a microfluidic setup, and then dexamethasone sodium phosphate (DSP) was successfully encapsulated in liposome nanoparticles. The physicochemical characteristics of liposomes, such as their ζ-potential, size, DSP loading capacity, encapsulation efficiency, and drug release, were assessed. Transmission electron microscopy and dynamic light scattering analysis were used to examine the structures of the liposomes. The drug release kinetics study was conducted to analyze the drug delivery system, and the Higuchi equation was determined to be the most suitable equation. The microfluidic chip was shown to be capable of creating small-sized liposomes with a size as small as 130 nm, exhibiting monodispersed characteristics and low polydispersity liposome populations.

RETRACTED: Di Paola et al. Environmental Risk Assessment of Dexamethasone Sodium Phosphate and Tocilizumab Mixture in Zebrafish Early Life Stage (Danio rerio). Toxics 2022, 10, 279.

The journal retracts the article "Environmental risk assessment of mixture of COVID-19 treating pharmaceutical drugs in zebrafish early life stage (Danio rerio)" [...].

Retrospective evaluation of dexamethasone for treatment of suspected critical illness-related corticosteroid insufficiency in dogs with septic shock (2017-2022): 60 cases.

To retrospectively compare and report vasopressor duration and mortality of septic dogs with hypotension refractory to vasopressor administration (presumed critical illness-related corticosteroid insufficiency [CIRCI]) treated with or without dexamethasone sodium phosphate (DxSP). Retrospective study (2017-2022). Tertiary referral and teaching hospitals. Sixty client-owned dogs with confirmed or presumed sepsis and vasopressor-resistant hypotension. Hypotension was defined as systolic arterial pressure < 90mmHg or MAP < 65mmHg. Vasopressor resistance was defined as hypotension despite therapy with moderate- to high-dose vasopressors (> 0.5µg/kg/min of norepinephrine IV). None. Twenty-six dogs received DxSP (DxSP group, 0.002-0.39mg/kg IV, variable frequency), and 34 dogs did not receive a glucocorticoid (non-DxSP group). The median time to vasopressor discontinuation was 20hours (interquartile range [IQR]: 21; n=6) in the DxSP group and 27 hours (IQR: 11; n=5) in the non-DxSP group. In the DxSP group, 23% (6/26) of dogs survived to discharge compared with 15% (5/34) of dogs in the non-DxSP group, which was not significantly different (relative risk: 0.90, 95% confidence interval: 0.70-1.16; P=0.41). There was no significant difference between the 2 groups in time from vasopressor administration to weaning in dogs that survived to discharge (P=0.43). The median time from steroid administration to vasopressor wean was 15 hours (IQR: 19; n=6), and the median time from steroid administration to sustained normotension (a systolic blood pressure > 90mmHg or a MAP>65mmHg for at least 4h) was 1 hour (IQR: 5; n=11). There was no association between DxSP therapy and survival, duration of vasopressor therapy, or time between steroid administration and discontinuation of vasopressor therapy in dogs being treated for sepsis, vasopressor resistance, and suspected CIRCI.

Smart core-shell microneedles for psoriasis therapy: In situ self-assembly of calcium ion-coordinated dexamethasone hydrogel.

Psoriasis is a prevalent relapsing dermatological condition that often necessitates lifelong treatment. The distinctive thickening of the stratum corneum presents a challenge to drug penetration. The employment of microneedles has been demonstrated to enhance the transdermal drug delivery efficacy by creating multiple microchannels in the skin. Nevertheless, polymeric microneedles often encounter difficulties in meeting the requirements for sustained drug release. It is imperative to acknowledge that sustained-release hydrogel microneedles are invariably fabricated under harsh crosslinking conditions. In addressing these challenges, a core-shell microneedles (CSMNs) system was customized at a facile, accessible process, enabling the in situ formation of supramolecular microhydrogels within the skin. This concept was realized by leveraging the interaction between the therapeutic drug dexamethasone sodium phosphate (DexP) and calcium chloride (CaCl2), combined with the differential biphasic release technology (DexP HMNs). Upon insertion into the skin, the core of the microneedles rapidly released CaCl2, which diffused to the shell and formed a hydrogel with DexP, creating multiple reservoirs for the sustained release of DexP. In vitro transdermal permeation experiments demonstrated that DexP HMNs greatly prolonged the skin retention time of DexP. In the context of psoriasis treatment, DexP HMNs were demonstrated to be more effective than DexP CSMNs in inhibiting keratinocyte proliferation and significantly reducing the levels of inflammatory factors and immune cell infiltration at the lesion site. This study provides a new direction for the development of intelligent microneedle drug delivery systems for sustained drug release and enhanced management of chronic skin diseases.

Accelerating Tumor Immunotherapy Through a Synergistic Strategy of Increasing Throttle and Relaxing Brake.

Tumor immunotherapy has been widely used clinically, but it is still hindered by weak antitumor immunity and immunosuppressive tumor microenvironment (TME). Here, a kind of simple disodium hydrogen phosphate nanoparticle (Na2HPO4 NP) is prepared to "accelerate" tumor immunotherapy by "increasing throttle" and "relaxing brake" simultaneously. The obtained Na2HPO4 NPs release a large amount of Na+ and HPO42- ions within tumor cells, thereby activating the caspase 1/GSDMD-mediated pyroptosis pathway to achieve immune activation. Meanwhile, alkalescent Na2HPO4 NPs can further consume lactic acid through acid-base neutralization, and regulate adenosine (Ado) metabolism via nanomaterial-induced biocatalytic process to relieve two-tier immunosuppression. Collectively, Na2HPO4 NPs effectively activate the antitumor immune process in vivo, and dramatically inhibit primary and distal tumor growth. This work will provide unique inspiration and strategy for the regulation of both positive and negative directions in immunotherapy.

Accelerating Tumor Immunotherapy Through a Synergistic Strategy of Increasing Throttle and Relaxing Brake

Tumor immunotherapy has been widely used clinically, but it is still hindered by weak antitumor immunity and immunosuppressive tumor microenvironment (TME). Here, a kind of simple disodium hydrogen phosphate nanoparticle (Na2HPO4 NP) is prepared to "accelerate" tumor immunotherapy by "increasing throttle" and "relaxing brake" simultaneously. The obtained Na2HPO4 NPs release a large amount of Na+ and HPO42‐ ions within tumor cells, thereby activating the caspase 1/GSDMD‐mediated pyroptosis pathway to achieve immune activation. Meanwhile, alkalescent Na2HPO4 NPs can further consume lactic acid through acid‐base neutralization, and regulate adenosine (Ado) metabolism via nanomaterial‐induced biocatalytic process to relieve two‐tier immunosuppression. Collectively, Na2HPO4 NPs effectively activate the antitumor immune process in vivo, and dramatically inhibit primary and distal tumor growth. This work will provide unique inspiration and strategy for the regulation of both positive and negative directions in immunotherapy.

Development and Evaluation of in situ eye gel for delivery of gatifloxacin and betamethasone sodium phosphate

التحدي الرئيسي الذي يواجه العلماء في مجال النقل البصري هو التخلص السريع من المواد الموجودة قبل القرنية في العديد من التطبيقات، وخاصة في المضادات الحيوية. فقط 5% من قطرات العين تدخل إلى القرنية. تم تصميم هذه التقنية لحل المشكلة عن طريق زيادة وقت الاتصال بالقرنية. بمجرد تطبيقه على العين، يتحول المحلول على الفور إلى مادة هلامية. الهدف من هذه الدراسة هو تحضير قطرة عين موضعية باستخدام بوليمر بولوكسامير 407 وصمغ جيلان حساس للأيونات ودراسة تأثير إضافة بوليمرات مخاطية لاصقة ميثيل السليلوز (MC) لتطوير عيون فعالة وطويلة المفعول. أنظمة توصيل الأدوية المضادة للبكتيريا والمضادة للالتهابات ) GTNوBSP (لعلاج التهاب الملتحمة الحاد. تم تحضير المستحضرات التي تحتوي على 17% بولوكسامير 407 و 0.5% صمغ جيلان بنسب مختلفة من MC ومقارنتها فيما يتعلق بدرجة حرارة التبلور، وقدرة التبلور، وزمن التبلور، ودراسة التحرر والالتصاق المخاطي. أدت زيادة تركيز MC إلى تعزيز جميع الخواص الفيزيائية لجيل صمغ البولوكسامير جيلان. الصيغة المثالية (F3) التي تحتوي على 0.3% MC كان لها 5 ثواني من وقت التبلور عند 31 درجة مئوية وبقيت على شكل هلام لمدة 24 ساعة. تم تمديد إطلاق كلا العقارين ولم يلاحظ أي تهيج في عين الأرنب عند اختباره على الحيوانات . من خلال تحسين فترة الإقامة قبل القرنية والتوافر البيولوجي للعين نتيجة للتناول الأقل تكرارًا، قد يُنظر إلى تركيبة الجل الجديدة في الموقع كبديل متفوق لقطرات العين التقليدية من جاتيفلوكساسين وبيتاميثازون لعلاج التهابات العين.

Improving natural red pigment production by Streptomyces phaeolivaceus strain GH27 for functionalization of textiles with in silico ADME prediction

The red pigment was recovered from the S. phaeolivaceus GH27 isolate, which was molecularly identified using 16S rRNA gene sequencing and submitted to GenBank as OQ145635.1. The ideal growth conditions included 1% (w/v) starch, diammonium citrate, dibasic sodium phosphate, 5% (v/v) inoculum, pH 8, a rotation speed of 150 rpm, a temperature of 37 °C, and an incubation period of 9 days. Using ethanol as a solvent, the red pigment was effectively recovered. Data indicates that pigment content remained steady at 40 and 50 °C. Heating the pigment extract to 60, 70, 80, 90, and 100 °C for one hour results in pigment retention of 98%, 96.5%, 95.5%, 94.6%, and 92.6% of its pigment density, respectively. Studies indicate that the pigment extracts exhibited optimal stability at alkaline pH levels. The findings demonstrate that the red pigment extract has a peak absorbance range of 280–340 nm, with a λmax of 300 nm. GC/MS analysis revealed that the primary components of the pigment extract were linolenic acid methyl ester and oleic acid methyl ester, constituting 26.41% and 25.25%, respectively. Fabrics dyed with extracted red pigment exhibit excellent fastness when using the comprehensive green method. In comparison to conventional and nanotechnological attributes, printed samples exhibit significant color strength without environmental repercussions. The treatment of cotton, wool, and polyester samples suppressed pathogen growth to differing extents. Polyester had the most important inhibitory effects on Staphylococcus aureus (50.03%) and Bacillus cereus (39.49%). The ADME physicochemical properties of the predominant medication were assessed, together with its bioavailability. The radar plot demonstrated ideal parameters for size, polarity, lipophilicity, solubility, and saturation, excluding flexibility. It exhibited intermediate synthetic accessibility, exceptional permeability and absorption, elevated gastrointestinal absorption, and blood–brain barrier penetration; nonetheless, it did not adhere to the medicinal chemistry rule of three.Graphical

Optimization of Capillary Electrophoresis by Central Composite Design for Separation of Pharmaceutical Contaminants in Water Quality Testing

Many pharmaceutical active compounds are prepared as hydrochlorides for quick release in the gastrointestinal tract upon oral administration. Their inadvertent escape into the water environment requires efficient analytical separation for accurate quantitation to monitor their environmental fate. The purpose of this study is to demonstrate how best to optimize a capillary electrophoresis method for the separation of four model pharmaceutical hydrochlorides. Concentration of sodium dibasic phosphate in the background electrolyte solution, pH adjustment with HCl or NaOH, and applied voltage across the capillary were the three key factors chosen for optimization. The peak resolutions and total migration time were examined as the response indicators to complete a central composite design in response surface methodology. The examination revealed that CE separation was driven significantly by a linear regression model and minimally by a quadratic regression model, based on the coefficient of determination, the lack of fit, the total sum of squares, and the p values. Under optimal conditions of the background electrolyte concentration of 75 mM, pH 9, and the applied voltage of 10 kV, the model hydrochlorides were separated within five minutes in the migration order of metformin (first) &gt; phenformin &gt; mexiletine &gt; ranitidine (last). The limits of UV detection/quantification attained under optimal CE conditions were 0.015/0.045, 0.020/0.060, 0.142/0.426, and 0.017/0.051, respectively.

UBIQUITIN-CONJUGATING ENZYME34 mediates pyrophosphatase AVP1 turnover and regulates abiotic stress responses in Arabidopsis.

Understanding the molecular mechanisms of abiotic stress responses in plants is instrumental for the development of climate-resilient crops. Key factors in abiotic stress responses, such as the proton- pumping pyrophosphatase (AVP1), have been identified, but their function and regulation remain elusive. Here, we explored the post-translational regulation of AVP1 by the ubiquitin-conjugating enzyme UBC34 and its relevance in the salt stress and phosphate starvation responses of Arabidopsis (Arabidopsis thaliana). Through in vitro and in vivo assays, we established that UBC34 interacts with and ubiquitylates AVP1. Mutant lines in which UBC34 was downregulated showed higher tolerance to salt and low inorganic phosphate (Pi) stresses, while we observed the opposite for plants overexpressing UBC34. Our results showed that UBC34 co-localizes with AVP1, and AVP1 activity is enhanced in the plasma membrane fractions of ubc34 mutants, indicating that UBC34 mediates the turnover of plasma membrane-localized AVP1. We also observed that UBC34 affects the apoplastic pH, but not the vacuolar pH of root cells. Based on our results, we propose a mechanistic model in which UBC34 mediates AVP1 turnover at the plasma membrane of root epidermal cells. Downregulation of UBC34 under salt and phosphate starvation conditions enhances AVP1 activity, leading to a higher proton gradient available for sodium sequestration and phosphate uptake.