Presence Of Potassium Ions Research Articles

Novel Supramolecular Hydrogel for Infected Diabetic Foot Ulcer Treatment.

Multifunctional responsive hydrogels hold significant promise for diabetic foot ulcer (DFU) treatment, though their complex design and manufacturing present challenges. This study introduces a novel supramolecular guanosine-phenylboronic-chlorogenic acid (GBC) hydrogel developed using a dynamic covalent strategy. The hydrogel forms through guanosine quadruplex assembly in the presence of potassium ions and chlorogenic acid (CA) linkage via dynamic borate bonds. GBC hydrogels exhibit pH and glucose responsiveness, releasing more chlorogenic acid under acidic and high glucose conditions due to borate bond dissociation and G-quadruplex (G4)hydrogel disintegration. Experimental results indicate that GBC hydrogels exhibit good self-healing, shear-thinning, injectability, and swelling properties. Both in vitro and in vivo studies demonstrate the GBC hydrogel's good biocompatibility, ability to eliminate bacteria and reactive oxygen species (ROS), facilitate macrophage polarization from the M1 phenotype to the M2 phenotype (decreasing CD86 expression and increasing CD206 expression), exhibit anti-inflammatory effects (reducing TNF-α expression and increasing IL-10 expression), and promote angiogenesis (increasing VEGF, CD31, and α-SMA expression). Thus, GBC hydrogels accelerate DFU healing and enhance tissue remodeling and collagen deposition. This work provides a new approach to developing responsive hydrogels to expedite DFU healing.

The Influence of Ionic Environment on Nucleosome-Mica Interactions Revealed via Molecular Dynamics Simulations.

Mica serves as a crucial substrate in Atomic Force Microscopy (AFM) studies for visualizing and characterizing nucleosomes. Nucleosomes interact with the negatively charged mica surface via adsorbed cations. However, the specific influences of monovalent and divalent cations on nucleosome adsorption to the mica surface remain unclear. In this study, we investigated the binding of nucleosomes to the mica surface in the presence of monovalent potassium ions and divalent magnesium ions using molecular dynamics simulations. We also explored the impact of pre-treated mica surfaces on nucleosome binding and structure. Our findings reveal that nucleosome-mica interactions vary depending on the cations present, resulting in distinct effects on nucleosome structure. Notably, nucleosomes bind effectively to a mica surface in the presence of potassium ions with minimal structural perturbations.

Capparis spinosa L waste activated carbon as an efficient adsorbent for crystal violet toxic dye removal: Modeling, optimization by experimental design, and ecological analysis

Textile dyes are dramatic sources of pollution and non-aesthetic disturbance of aquatic life and therefore represent a potential risk of bioaccumulation that can affect living species. It is imperative to reduce or eliminate these dyes from liquid effluents with innovative biomaterials and methods. Therefore, this research aims to highlight the performance of Capparis spinosa L waste-activated carbon (CSLW-AC) adsorbent to remove Crystal Violet (CV) from an aqueous solution. The mechanism of CV adsorption on CSLW-AC was evaluated based on the coupling of experimental data and different characterization techniques. The efficiency of the CSLW-AC material reflected by the equilibrium adsorption capacity of CV could reach more than 195.671 mg·g–1 when 0.5 g·L–1 of CSLW-AC (Particle size ≤250 μm) is introduced into the CV of initial concentration of 100 mg·L–1 at pH 6 and temperature 65° C and in the presence of potassium ions after 60 min of contact time according to the one parameter at a time studies. The adsorption behavior of CV on CSLW-AC was found to be consistent with the pseudo-second-order kinetic model and Frumkin's linear isothermal model. The thermodynamic aspects indicate that the process is physical, spontaneous, and endothermic. The optimization of the process by the Box Behnken design of experiments resulted in an adsorption capacity approaching 183.544 mg·g–1 ([CV]=100 mg·L–1 and [CSLW-AC]=0.5 g·L–1 at 35 min). The results of the Lactuca sativa seeds germination in treated CV (70%), adsorbent solvent and thermal regeneration (more than 5 cycles), and process cost analysis (1.0484 $ L–1) tests are encouraging and promising for future exploitations of the CSLW-AC material in different industrial fields.

Effect of Concomitant Drugs on Sodium Zirconium Cyclosilicate Hydrate in Artificial Intestinal Juice.

To explore drug interactions involving sodium zirconium cyclosilicate hydrate (SZC) and concomitant drugs like calcium antagonists (amlodipine and nifedipine) and β-blockers (carvedilol and bisoprolol), we investigate how these concomitant drugs influenced the administration of SZC in an artificial intestinal juice. Initially, we assessed the potassium ion adsorption capacity, ranking it as follows: calcium polystyrene sulfonate (CPS, 54.9 mg/g) < sodium polystyrene sulfonate (SPS, 62.1 mg/g) < SZC (90.8 mg/g). However, the adsorption equilibrium was achieved in the order of CPS ≒ SPS (within 1 min) < SZC (within 1 h). Subsequently, we determined the residual percentages of amlodipine, nifedipine, carvedilol, and bisoprolol, finding them to be 79.0-91.9% for SZC, 0.38-38.4% for SPS, and 0.57-29.0% for CPS. These results suggest the efficacy of SZC in managing hyperkalemia alongside concomitant drugs in an artificial intestinal juice, with particular emphasis on amlodipine (calcium antagonist) and carvedilol (β-blocker). Additionally, we identified the presence of carbon, nitrogen, and oxygen components from both drugs on the SZC surface following interaction. We also evaluated how amlodipine, nifedipine, carvedilol, and bisoprolol affected the administration of SZC in the presence of potassium ions. Our results indicate that potassium ions and concomitant drugs did not interfere with each other in the artificial intestinal juice. These results offer valuable insights into the administration of SZC in conjunction with concomitant drugs. Lastly, the presented data shows qualitative results in this study.

Diversity and salinity adaptations of ammonia oxidizing archaea in three estuaries of China.

Ammonia-oxidizing archaea (AOA) are ubiquitously found in diverse habitats and play pivotal roles in the nitrogen and carbon cycle, especially in estuarine and coastal environments. Despite the fact that the diversity and distribution of AOA are thought to be tightly linked to habitats, little is known about the relationship that underpins their genomic traits, adaptive potentials, and ecological niches. Here, we have characterized and compared the AOA community in three estuaries of China using metagenomics. AOA were the dominant ammonia oxidizers in the three estuaries. Through phylogenetic analyses, five major AOA groups were identified, including the Nitrosomarinus-like, Nitrosopumilus-like, Aestuariumsis-like, Nitrosarchaeum-like, and Nitrosopelagicus-like groups. Statistical analyses showed that the aquatic and sedimentary AOA communities were mainly influenced by spatial factors (latitude and water depth) and environmental factors (salinity, pH, and dissolved oxygen) in estuaries, respectively. Compared to AOA dwelling in terrestrial and marine habitats, estuarine AOA encoded more genes involved in glucose and amino acid metabolism, transport systems, osmotic control, and cell motility. The low proteome isoelectric points (pI), high content of acidic amino acids, and the presence of potassium ion and mechanosensitive channels suggest a "salt-in" strategy for estuarine AOA to counteract high osmolarity in their surroundings. Our findings have indicated potential adaptation strategies and highlighted their importance in the estuarine nitrogen and carbon cycles. KEY POINTS: • Spatial and environmental factors influence water and sediment AOA respectively. • Estuarine AOA share low proteome isoelectric value and high acid amino acids content. • AOA adaptation to estuaries is likely resulted from their unique genomic features.

Rolling Circle Amplification/G‐Quadruplex‐Based Dual‐Signal Ratiometric Electrochemical Aptasensor for Ultrasensitive Detection of Pathogenic Bacteria

AbstractAccurate and efficient detection of pathogenic bacteria plays a crucial role in the diagnosis of infectious diseases. However, rapid and highly sensitive detection of specific bacteria in clinical samples remains challenging. In this study, we developed a ratiometric dual‐signal electrochemical biosensor for ultrasensitive detection of pathogenic bacteria, based on an aptamer recognition‐induced rolling circle amplification (RCA)/G‐quadruplex strategy. On the surface of a gold electrode chip, we used an aptamer sequence (P1) conjugated to ferrocene (Fc) to capture the target bacterium. This capture released a different, previously bound sequence (P2) sequence that initiated the RCA/G‐quadruplex cascade, which, in the presence of potassium ions, was able to bind the electrochemical indicator methylene blue (MB). We integrated the signals from the loss of Fc and the appearance of MB (IMB/IFC ratio) to quantify the target bacteria concentration. This biosensor showed excellent detection performance and specificity, with a detection limit of 10 CFU/mL. Notably, it showed great diagnostic potential for clinical infectious diseases caused by pathogenic bacteria in precise/personalized medicine applications.

G-Quadruplexes Formation by the C9orf72 Nucleotide Repeat Expansion d(GGGGCC)n and Conformation Regulation by Fangchinoline.

The G-quadruplex (GQ)-forming hexanucleotide repeat expansion (HRE) in the C9orf72 (C9) gene has been found to be the most common cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) (collectively, C9ALS/FTD), implying the great significance of modulating C9-HRE GQ structures in C9ALS/FTD therapeutic treatment strategies. In this study, we investigated the GQ structures formed by varied lengths of C9-HRE DNA sequences d(GGGGCC)4 (C9-24mer) and d(GGGGCC)8 (C9-48mer), and found that the C9-24mer forms anti-parallel GQ (AP-GQ) in the presence of potassium ions, while the long C9-48mer bearing eight guanine tracts forms unstacked tandem GQ consisting of two C9-24mer unimolecular AP-GQs. Moreover, the natural small molecule Fangchinoline was screened out in order to be able to stabilize and alter the C9-HRE DNA to parallel GQ topology. Further study of the interaction of Fangchinoline with the C9-HRE RNA GQ unit r(GGGGCC)4 (C9-RNA) revealed that it can also recognize and improve the thermal stability of C9-HRE RNA GQ. Finally, use of AutoDock simulation results indicated that Fangchinoline binds to the groove regions of the parallel C9-HRE GQs. These findings pave the way for further studies of GQ structures formed by pathologically related long C9-HRE sequences, and also provide a natural small-molecule ligand that modulates the structure and stability of C9-HRE GQ, both in DNA and RNA levels. Altogether, this work may contribute to therapeutic approaches of C9ALS/FTD which take the upstream C9-HRE DNA region, as well as the toxic C9-HRE RNA, as targets.

Dynamic Multicomponent Reactions-Directed Self-Assembled G-quadruplex Inherent Antibacterial Hydrogel.

Nowadays, inherent antibacterial hydrogels have gained significant attention due to their utilization against infectious bacteria. Herein, we focus on the development of an injectable, self-healable, dynamic, and G-quadruplex hydrogel with inherent antibacterial activity. The dynamic self-assembled hydrogel is constructed upon multicomponent reactions (MCR) among guanosine, 2-formylphenylboronic acid, and amino acid/peptides in the presence of potassium ions. The role of amino acid/peptides in the formation of the G-quadruplex hydrogel is studied in detail. The G-quadruplex structure is formed via the π-π stacking of G-quartets. The formation of G-quadruplex is investigated by thioflavin T binding assay, CD spectroscopy, and PXRD. The formation of the dynamic imino-boronate bond in the hydrogels is well characterized by temperature-dependent 11B NMR (VT-NMR) and FT-IR spectroscopy. Furthermore, HR-TEM images and rheological experiments reveal the fibrillar networks and viscoelastic property of the hydrogels. The presence of the dynamic imino-boronate ester bonds makes the hydrogel injectable and self-healable in nature. These dynamic G-quadruplex hydrogels show potential antibacterial activity against a series of Gram-positive and Gram-negative bacteria. The hydrogels have been used for the entrapment and sustained release of an anticancer drug doxorubicin over 48 h at different pHs (4.8, 7.4, and 8.5) and temperature without the influence of any external stimuli. Such injectable and self-healable hydrogels could be used in various applications in the field of biomedical science.

A supramolecular gel with unique rheological properties for treating corneal virus infection

Herpes simplex keratitis (HSK) caused by herpes simplex virus-1 infection of the cornea has taken a significant toll on the visual health of people worldwide. Anti-viral hydrogels are preferred in the treatment of HSK due to enhanced topical drug retention and reduced side effects, however, current polymer-based gelling systems usually generate clumpy or uneven gel layers on ocular surface, and are easily cleared by eyelid blinking. This study proposes a supramolecular gel co-assembled by all-small-molecule building blocks including ganciclovir and 2′-deoxyguanosine in the presence of potassium ions. The developed gel performs fascinating rheological and texture properties including high viscoelastic, good spread ability, and deformation recovery behavior, enabling the formation of a uniform and thin gel layer on ocular surface to resist the clearance by eyelid blinking and tear washing. The gel shows similar ocular convenience, but much longer drug retention in ocular tissues and higher therapeutic efficacy compared to the clinical ganciclovir gel on the primary and recurrent mouse HSK models, rabbit HSK models, and also efficiently inhibited the HSV-1 replication in ex vivo human corneal tissues. The results suggest that this all-small-molecule supramolecular gel could be a promising drug formulation for treating HSK. Data and materials availabilityThe main data supporting the results in this study are available within the paper and its Supplementary Information. The associated raw data and analyzed datasets are too large to be readily shared publicly, but they are available from the corresponding author on reasonable request.

Taq-Polymerase Stop Assay to Determine Target Selectivity of G4 Ligands in Native Promoter Sequences of MYC, TERT, and KIT Oncogenes.

Computational and high-throughput experimental methods predict thousands of potential quadruplex sequences (PQSs) in the human genome. Often these PQSs contain more than four G-runs, which introduce additional uncertainty into the conformational polymorphism of the G4 DNA. G4-specific ligands, which are currently being actively developed as potential anticancer agents or tools for studying G4 structures in genomes, may preferentially bind to specific G4 structures over the others that can be potentially formed in the extended G-rich genomic region. We propose a simple technique that identifies the sequences that tend to form G4 in the presence of potassium ions or a specific ligand. Thermostable DNA Taq-polymerase stop assay can detect the preferential position of the G4 -ligand binging within a long PQS-rich genomic DNA fragment. This technique was tested for four G4 binders PDS, PhenDC3, Braco-19, and TMPyP4 at three promoter sequences of MYC, KIT, and TERT that contain several PQSs each. We demonstrate that the intensity of polymerase pausing reveals the preferential binding of a ligand to particular G4 structures within the promoter. However, the strength of the polymerase stop at a specific site does not always correlate with the ligand-induced thermodynamic stabilization of the corresponding G4 structure.

DNA aptamer-based affinity chromatography system for purification of recombinant proteins tagged with lysine tag

Affinity chromatography (AC) is one of the techniques widely used for the purification of recombinant proteins. In our previous study, we presented a successful application of the Argi system [1] for the purification of recombinant proteins, based on the specific interaction between an arginine tag and a DNA aptamer. Exploring the possible application of positively charged peptide tags in the purification of recombinant proteins, in this study we developed and characterized an AC system based on the specific and reversible interaction between a DNA aptamer and a lysine tag (Lys-tag) comprising five lysine residues (5 K). We optimized the length of both the selected DNA aptamer and Lys-tag which were named B5K aptamer and 5K-tag, respectively. The results showed that the stability of the B5K aptamer and 5K-tag was dependent on the presence of potassium ions. The conditions for mild elution of 5K-tagged protein from B5K aptamer were determined. Our study proved that the developed system can be used for the purification of recombinant proteins from Escherichia coli total protein extracts.

(Invited) Unravelling Water-Ion Dynamics in Reverse Osmosis Membranes with Nuclear Magnetic Resonance Spectroscopy

Fundamental understanding of the charge (ions and water) transport in polymeric membranes used at the forefront of the water-energy nexus challenge is yet uncertain and depends on the complex interplay between polymer structure and dynamics that facilitate transport. Herein, we investigated the dynamics-transport of proton and ion transport in a rather neutrally charged organic membrane (i.e., polyamide) using solid-state NMR spectroscopy. Specifically, the role of competing ions' effect in complex ionic mixtures at the membrane interface has been explored on a molecular level. Proton and sodium ion diffusion measurements are made using pulsed-field gradient NMR diffusometry. The energy barriers for proton and ion transport within the active layer of the reverse osmosis (RO) membrane are assessed using magic angle spinning (MAS) and static NMR spectral line shape analysis. We have investigated the dynamics-transport of water and sodium ions in complex ionic mixtures of polyamide polymeric media using solid-state NMR spectroscopy. Through monitoring 13C, 23Na, and 1H NMR nuclei, quantitative insights into the diffusion of water (1H), sodium mobile ion (Na+), and polymer membrane dynamics (13C) are extrapolated. Furthermore, the spin-lattice (T1) relaxation time of sodium and water ions is investigated to obtain quantitative insight into how sodium and water ions’ rotational movements occur in the absence and presence of other competing seawater cations such as potassium. Room temperature spectra and spin-lattice relaxation times indicated the presence of both mobile and rigidly held ionic species in the membrane at different levels of relative humidity. The concentration and temperature dependence of relaxation times and chemical shifts have been investigated. NMR relaxation measurements detect how the water rotation is modified by sodium and potassium cations in the membrane. Results show that at low relative humidity and in the presence of competing ions, there are sodium ion resonances for crystalline sodium ions and rigidly held sodium ions on the surface. With increasing relative humidity and decreasing competing ions, the resonance suggests solution-like dynamic rotational movements of sodium ions in polyamide. The results confirm the change in activation energy barrier for sodium and hydrogen ion permeation in polyamide upon the presence of potassium ions.

Amplified and label-free electrochemical detection of a protease biomarker by integrating proteolysis-triggered transcription

Cell-free synthetic biology provides a promising strategy for developing high-performance biosensors by integrating with advanced testing technologies. However, the combination of synthetic biology with electrochemical testing techniques is still underdeveloped. Here, we proposed an electrochemical biosensor for the label-free and ultrasensitive detection of target protease biomarker by coupling a protease-responsive RNA polymerase (PR) for signal amplification. Taking tumor biomarker matrix metalloprotease-2 (MMP-2) as a model protease, we employed PR to transduce each proteolysis reaction mediated by MMP-2 into multiple programmable RNA outputs that can be captured by the DNA probes immobilized on a gold electrode. Moreover, the captured RNAs are designed to contain a guanine-rich sequence that can form G-quadruplex and bind to hemin in the presence of potassium ions. In this scenario, the activity of MMP-2 is converted and amplified into the electrochemical signals of hemin. Under the optimal conditions, this PR-based electrochemical biosensor enabled the sensitive detection of MMP-2 in a wide linear dynamic range from 10 fM to 1.0 nM, with a limit of detection of 7.1 fM. Moreover, the proposed biosensor was further applied in evaluating MMP-2 activities in different cell cultures and human tissue samples, demonstrating its potential in the analysis of protease biomarkers in complex clinical samples.

Recurrent Potential G-Quadruplex Sequences in Archaeal Genomes.

Evolutionary conservation or over-representation of the potential G-quadruplex sequences (PQS) in genomes are usually considered as a sign of the functional relevance of these sequences. However, uneven base distribution (GC-content) along the genome may along the genome may result in seeming abundance of PQSs over average in the genome. Apart from this, a number of other conserved functional signals that are encoded in the GC-rich genomic regions may inadvertently result in emergence of G-quadruplex compatible sequences. Here, we analyze the genomes of archaea focusing our search to repetitive PQS (rPQS) motifs within each organism. The probability of occurrence of several identical PQSs within a relatively short archaeal genome is low and, thus, the structure and genomic location of such rPQSs may become a direct indication of their functionality. We have found that the majority of the genomes of Methanomicrobiaceae family of archaea contained multiple copies of the interspersed highly similar PQSs. Short oligonucleotides corresponding to the rPQS formed the G-quadruplex (G4) structure in presence of potassium ions as demonstrated by circular dichroism (CD) and enzymatic probing. However, further analysis of the genomic context for the rPQS revealed a 10–12 nt cytosine-rich track adjacent to 3'-end of each rPQS. Synthetic DNA fragments that included the C-rich track tended to fold into alternative structures such as hairpin structure and antiparallel triplex that were in equilibrium with G4 structure depending on the presence of potassium ions in solution. Structural properties of the found repetitive sequences, their location in the genomes of archaea, and possible functions are discussed.

Negative volume changes of human G-quadruplexes at unfolding

G-quadruplexes are tetrahelical structures. They are important targets for anti-cancer drugs, since they are situated at crucial positions within the genome. We studied the volumetric properties of the unfolding of three G-quadruplexes in the presence of potassium ion. The unfolding volume changes were determined using high-pressure fluorescence spectroscopy. The c-MYC, KIT, and VEGF sequences unfold with the transition volume of -17, -6 and -18 cm3/mol, respectively. The small magnitude of the unfolding volume of KIT could be explained by its unique structure and the lower amount of void volume. Since the cell interior is highly crowded, the available volume is restricted. Therefore the volumetric changes during the conformational transformations gain biological importance.

UV shielding and transparency of K+-doped Li3VO4 nanostructured superionic conductors

A potassium (K)-doped lithium vanadate (Li3VO4) sample was synthesised by using the conventional solid-state reaction technique. X-ray diffraction results showed the polycrystalline behaviour of potassium-doped lithium vanadate. It was also observed that the lithium (Li+) ion did not show its presence in the diffraction pattern, which indicates that potassium (K+) ions were well substituted in the interstitials and did not disturb the planes of the lithium vanadate matrix. The presence of potassium ions in the lithium vanadate matrix was also confirmed through molecular fingerprint (Fourier transform infrared) spectroscopy. The optical absorption study (ultraviolet (UV)–visible) showed that the materials absorbed in the UV region only and remained transparent for the visible region. With an increase in the potassium-ion doping concentration, the absorbance peaks shifted slightly towards higher wavelengths, suggesting an enhancement of the particle size. Furthermore, the emission spectroscopy studies (photoluminescence) showed an increase in the emission intensity towards the blue region of the visible spectrum. From the electrical conductivity study, it was found that the materials exhibited a supersonic phase above 800 K with predominantly ionic conductivity in the range 91.954–6.100 Ω−1 m−1. The ionic conductivity and transparency indicate the feasibility of designing transparent batteries with good UV-shielding properties.

Formation of an RNA Quadruplex-Duplex Hybrid in Living Cells between mRNA of the Epidermal Growth Factor Receptor (EGFR) and a G-Rich Antisense Oligoribonucleotide.

Antisense DNA oligonucleotides, short interfering RNAs (siRNAs), and CRISPR/Cas9 genetic tools are the most useful therapeutic nucleic acids regulating gene expression based on the antisense specificity towards messenger RNA. Here, we present an effective novel strategy for inhibiting translation based on the antisense-controlled formation of an RNA quadruplex-duplex hybrid (QDH) between a G-rich RNA antisense oligoribonucleotide (Q-ASO) and specific mRNA, comprising two distant G-tracts. We selected epidermal growth factor receptor (EGFR) as a well-established target protein in anticancer therapy. The chemically modified, bi-functional anti-EGFR Q-ASO and a 56-nt long EGFR mRNA fragment, in the presence of potassium ions, were shown to form in vitro very stable parallel G-quadruplex containing a 28-nt long external loop folding to two duplex-stem structure. Besides, the Q-ASOs effectively reduced EGFR mRNA levels compared to the non-modified RNA and DNA antisense oligonucleotides (rASO, dASO). In addition, the hybridization specificity of Q-ASO comprising a covalently attached fluorescent tag was confirmed in living cells by visualization of the G4 green fluorescent species in the presence of other antisense inhibitors under competitive conditions. The results presented here offer novel insights into the potential application of Q-ASOs for the detection and/or alteration of (patho)biological processes through RNA:RNA quadruplex-duplex formation in cellular systems.

Electrochemical and electrocatalytic stability of Prussian blue/Berlin green redox transformation in Prussian blue-polypyrrole composite films

Redox transformation of Prussian blue to Berlin green (PB/BG) in Prussian blue-polypyrrole (PB-PPy) composites synthesized via original one-step method has been studied. It was shown that the nature of anion and composition of background electrolyte play an important role for both the stability and the shape of electrochemical response of composite film during redox transfer of Prussian blue to Berlin green. Nitric acid, phosphoric acid, malic acid and citric acid 0.05 N (eq/L) solutions and the same acids partially neutralized with 0.01 N KOH were used as electrolyte to study the role of potassium ions presence in solution. The most stable electrochemical response of PB/BG redox transfer was obtained for the nitrate anions containing solutions in the presence of potassium ions. Nevertheless, the stability of the electrochemical transformation PB/BG in composite films in other media is enough to detect the sulphite ions content in wine samples via electrocatalytic reaction at the potentials of PB/BG redox transformation.

Inhibition of Influenza A virus propagation by benzoselenoxanthenes stabilizing TMPRSS2 Gene G-quadruplex and hence down-regulating TMPRSS2 expression

Proteolytic cleavage of influenza A virus (IAV) hemagglutinin by host proteases is crucial for virus infectivity and spread. The transmembrane serine protease TMPRSS2 was previously identified as the essential protease that can cleave hemagglutinin of many subtypes of influenza virus and spike protein of coronavirus. Herein, we found that a guanine rich tract, capable of forming intramolecular G-quadruplex in the presence of potassium ions, in the promoter region of human TMPRSS2 gene was quite important for gene transcriptional activity, hence affecting its function. Furthermore, 7 new synthesized benzoselenoxanthene analogues were found to enable stabilizing such G-quadruplex. More importantly, compounds can down-regulate TMPRSS2 gene expression, especially endogenous TMPRSS2 protein levels, and consequently suppress influenza A virus propagation in vitro. Our results provide a new strategy for anti-influenza A virus infection by small molecules targeting the TMPRSS2 gene G-quadruplex and thus inhibiting TMPRSS2 expression, which is valuable for developing small molecule drugs against influenza A virus and also may be a potential candidate as anti- SARS-CoV-2 (Severe Acute Respiratory Syndrome CoV 2) lead molecules.

Formate and potassium ions affect Escherichia coli proton ATPase activity at low pH during mixed carbon fermentation

Escherichia coli is able to ferment not only single but also mixtures of carbon sources. The formate metabolism and effect of formate on various enzymes have been extensively studied during sole glucose but not mixed carbon sources utilization. It was revealed that in membrane vesicles (MV) of wild type cells grown at pH 7.5 during fermentation of the mixture of glucose (2 g/L), glycerol (10 g/L), and formate (0.68 g/L), in the assays, the addition of formate (10 mM) increased the N,N'-dicyclohexylcarbodiimide (DCCD)-inhibited ATPase activity on ~30% but no effect of potassium ions (100 mM) had been detected. In selC (coding formate dehydrogenases) and fdhF (coding formate dehydrogenase H) single mutants, formate increased DCCD-inhibited ATPase activity on ~40 and ~70%, respectively. At pH 5.5, in wild type cells MV, formate decreased the DCCD-inhibited ATPase activity ~60% but unexpectedly in the presence of potassium ions, it was stimulated ~5.8 fold. The accessible SH or thiol groups number in fdhF mutant was less by 28% compared with wild type. In formate assays, the available SH groups number was less ~10% in wild type but not in fdhF mutant. Taken together, the data suggest that proton ATPase activity depends on externally added formate in the presence of potassium ions at low pH. This effect might be regulated by the changes in the number of redox-active thiol groups via formate dehydrogenase H, which might be directly related to proton ATPase FO subunit.