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Molecules (Basel, Switzerland) Oct 2020The synthesis, isolation and full characterization of ion pairs between alkaline metal ions (Li, Na, K) and mono-anions and dianions obtained from...
Synthesis and Characterization of Ion Pairs between Alkaline Metal Ions and Anionic Anti-Aromatic and Aromatic Hydrocarbons with π-Conjugated Central Seven- and Eight-Membered Rings.
The synthesis, isolation and full characterization of ion pairs between alkaline metal ions (Li, Na, K) and mono-anions and dianions obtained from -dibenzo[,]cycloheptenyl (CH = trop) is reported. According to Nuclear Magnetic Resonance (NMR) spectroscopy, single crystal X-ray analysis and Density Functional Theory (DFT) calculations, the trop and trop anions show anti-aromatic properties which are dependent on the counter cation M and solvent molecules serving as co-ligands. For comparison, the disodium and dipotassium salt of the dianion of dibenzo[]cyclooctatetraene (CH = dbcot) were prepared, which show classical aromatic character. A d-Rh(I) complex of trop was prepared and the structure shows a distortion of the CH ligand into a conjugated 10π -benzo pentadienide unit-to which the Rh(I) center is coordinated-and an aromatic 6π electron benzo group which is non-coordinated. Electron transfer reactions between neutral and anionic trop and dbcot species show that the anti-aromatic compounds obtained from trop are significantly stronger reductants.
Topics: Alkalies; Anions; Crystallography, X-Ray; Electrons; Heterocyclic Compounds; Hydrocarbons, Aromatic; Ions; Ligands; Metals; Molecular Structure
PubMed: 33076581
DOI: 10.3390/molecules25204742 -
PloS One 2013Glutathione (GSH) is a negatively charged tripeptide, which is a major determinant of the cellular redox state and defense against oxidative stress. It is assembled...
Glutathione (GSH) is a negatively charged tripeptide, which is a major determinant of the cellular redox state and defense against oxidative stress. It is assembled inside and degraded outside the cells and is released under various physiological and pathophysiological conditions. The GSH release mechanism is poorly understood at present. In our experiments, freshly isolated rat thymocytes were found to release GSH under normal isotonic conditions at a low rate of 0.82±0.07 attomol/cell/min and that was greatly enhanced under hypoosomotic stimulation to reach a level of 6.1±0.4 attomol/cell/min. The swelling-induced GSH release was proportional to the cell density in the suspension and was temperature-dependent with relatively low activation energy of 5.4±0.6 kcal/mol indicating a predominant diffusion mechanism of GSH translocation. The osmosensitive release of GSH was significantly inhibited by blockers of volume-sensitive outwardly rectifying (VSOR) anion channel, DCPIB and phloretin. In patch-clamp experiments, osmotic swelling activated large anionic conductance with the VSOR channel phenotype. Anion replacement studies suggested that the thymic VSOR anion channel is permeable to GSH(-) with the permeability ratio P(GSH)/P(Cl) of 0.32 for influx and 0.10 for efflux of GSH. The osmosensitive GSH release was trans-stimulated by SLCO/OATP substrates, probenecid, taurocholic acid and estrone sulfate, and inhibited by an SLC22A/OAT blocker, p-aminohippuric acid (PAH). The inhibition by PAH was additive to the effect of DCPIB or phloretin implying that PAH and DCPIB/phloretin affected separate pathways. We suggest that the VSOR anion channel constitutes a major part of the γ-glutamyl cycle in thymocytes and, in cooperation with OATP-like and OAT-like transporters, provides a pathway for the GSH efflux from osmotically swollen cells.
Topics: Animals; Anions; Cell Size; Glutathione; Ion Channels; Organic Anion Transporters; Osmolar Concentration; Permeability; Rats; Stress, Physiological; Temperature; Thymocytes
PubMed: 23383255
DOI: 10.1371/journal.pone.0055646 -
Molecules (Basel, Switzerland) Apr 2019A series of symmetrical and unsymmetrical alkyl tren based tris-thiourea anion transporters were synthesised and their anion binding and transport properties studied....
A series of symmetrical and unsymmetrical alkyl tren based tris-thiourea anion transporters were synthesised and their anion binding and transport properties studied. Overall, increasing the steric bulk of the substituents resulted in improved chloride binding and transport abilities. Including a macrocycle in the scaffold enhanced the selectivity of chloride transport in the presence of fatty acids, by reducing the undesired H⁺ flux facilitated by fatty acid flip-flop. This study demonstrates the benefit of including enforced steric hindrance and encapsulation in the design of more selective anion receptors.
Topics: Anions; Chlorides; Ion Transport; Lipid Bilayers; Magnetic Resonance Spectroscopy; Models, Molecular; Thiourea
PubMed: 30986928
DOI: 10.3390/molecules24071278 -
Journal of Korean Medical Science Aug 2000We have been studying CFTR channels in guinea pig pancreatic duct cells and rather surprisingly found that luminal HCO3- had a pronounced inhibitory effect on... (Review)
Review
We have been studying CFTR channels in guinea pig pancreatic duct cells and rather surprisingly found that luminal HCO3- had a pronounced inhibitory effect on cAMP-activated CFTR chloride currents. The block produced by HCO3- was rapid, voltage-independent and occurred over a physiological range of extracellular HCO3- concentrations. I- and ClO4- were also found to inhibit CFTR currents, but both were less effective than HCO3-. Although we have not identified how HCO3- is able to block CFTR our data suggests that an external anion-binding site on the channel itself is involved. Overall, our results show that luminal HCO3- acts as a potent inhibitor of CFTR channels (and by inference CFTR-mediated secretion), under normal physiological conditions. These data have implications not only for current models of pancreatic duct cell HCO3- transport, but also for other bicarbonate-secreting tissues, such as the liver, GI tract and lungs.
Topics: Animals; Anions; Bicarbonates; Cystic Fibrosis Transmembrane Conductance Regulator; Epithelial Cells; Pancreatic Ducts
PubMed: 10981498
DOI: 10.3346/jkms.2000.15.S.S12 -
Inorganic Chemistry Feb 2022Silver-indium-sulfide quantum dots (AIS QDs) have potential applications in many areas, including biomedicine. Their lack of regulated heavy metals, unlike many...
Silver-indium-sulfide quantum dots (AIS QDs) have potential applications in many areas, including biomedicine. Their lack of regulated heavy metals, unlike many commercialized QDs, stands out as an advantage, but the necessity for alloyed or core-shell structures and related costly and sophisticated processes for the production of stable and high quantum yield aqueous AIS QDs are the current challenges. The present study demonstrates the one-step aqueous synthesis of simple AgInS QD compositions utilizing for the first time either a polyethyleneimine/2-mercaptopropionic acid (AIS-PEI/2MPA) mixture or only 2-mercaptopropionic acid (AIS-2MPA) as the stabilizing molecules, providing a AgInS portfolio consisting of cationic and anionic AIS QDs, respectively, and tuneable emission. Small AIS QDs with long-term stability and high quantum yields (19-23%) were achieved at a molar ratio of Ag/In/S 1/10/10 in water without any dopant or a semiconductor shell. The theranostic potential of these cationic and anionic AIS QDs was also evaluated in vitro. Non-toxic doses were determined, and fluorescence imaging potential was demonstrated. More importantly, these QDs were electrostatically loaded with zwitterionic 5-aminolevulinic acid (ALA) as a prodrug to enhance the tumor availability of ALA and to improve ALA-induced porphyrin photodynamic therapy (PDT). This is the first study investigating the influence of nanoparticle charge on ALA binding, release, and therapeutic efficacy. Surface charge was found to be more critical in cellular internalization and dark toxicity rather than drug loading and release. Both QDs provided enhanced ALA release at acidic pH but protected the prodrug at physiological pH, which is critical for tumor delivery of ALA, which suffers from low bioavailability. The PDT efficacy of the ALA-loaded AIS QDs was tested in 2D monolayers and 3D constructs of HT29 and SW480 human colon adenocarcinoma cancer cell lines. The incorporation of ALA delivery by the AIS QDs, which on their own do not cause phototoxicity, elicited significant cell death due to enhanced light-induced ROS generation and apoptotic/necrotic cell death, reducing the IC50 for ALA dramatically to about 0.1 and 0.01 mM in anionic and cationic AIS QDs, respectively. Combined with simple synthetic methods, the strong intracellular photoluminescence of AIS QDs, good biocompatibility of especially the anionic AIS QDs, and the ability to act as drug carriers for effective PDT signify that the AIS QDs, in particular AIS-2MPA, are highly promising theranostic QDs.
Topics: Aminolevulinic Acid; Anions; Antineoplastic Agents; Cations; Cell Proliferation; Cell Survival; Drug Screening Assays, Antitumor; Humans; Indium; Optical Imaging; Photochemotherapy; Photosensitizing Agents; Quantum Dots; Silver; Sulfides; Tumor Cells, Cultured; Water
PubMed: 35104130
DOI: 10.1021/acs.inorgchem.1c03298 -
Chemphyschem : a European Journal of... Jul 2022The implementation of next-generation batteries requires the development of safe, compatible electrolytes that are stable and do not cause safety problems. The...
The implementation of next-generation batteries requires the development of safe, compatible electrolytes that are stable and do not cause safety problems. The difluoro(oxalato)borate ([DFOB] ) anion has been used as an electrolyte additive to aid with stability, but such an approach has most commonly been carried out using flammable solvent electrolytes. As an alternative approach, utilisation of the [DFOB] anion to make ionic liquids (ILs) or Organic Ionic Plastic Crystals (OIPCs) allows the advantageous properties of ILs or OIPCs, such as higher thermal stability and non-volatility, combined with the benefits of the [DFOB] anion. Here, we report the synthesis of new [DFOB] -based ILs paired with triethylmethylphosphonium [P ] , and diethylisobutylmethylphosphonium [P ] . We also report the first OIPCs containing the [DFOB] anion, formed by combination with the 1-ethyl-1-methylpyrrolidinium [C mpyr] cation, and the triethylmethylammonium [N ] cation. The traditional synthetic route using halide starting materials has been successfully replaced by a halide-free tosylate-based synthetic route that is advantageous for a purer, halide free product. The synthesised [DFOB] -based salts exhibit good thermal stability, while the ILs display relatively high ionic conductivity. Thus, the new [DFOB] -based electrolytes show promise for further investigation as battery electrolytes both in liquid and solid-state form.
Topics: Anions; Borates; Cations; Electrolytes; Ionic Liquids; Plastics
PubMed: 35451216
DOI: 10.1002/cphc.202200115 -
Inorganic Chemistry Jun 2011The Eu(III) complex of (1S,4S,7S,10S)-1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane (S-THP) is studied as a sensor for biologically relevant anions....
The Eu(III) complex of (1S,4S,7S,10S)-1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane (S-THP) is studied as a sensor for biologically relevant anions. Anion interactions produce changes in the luminescence emission spectrum of the Eu(III) complex, in the (1)H NMR spectrum, and correspondingly, in the PARACEST spectrum of the complex (PARACEST = paramagnetic chemical exchange saturation transfer). Direct excitation spectroscopy and luminescence lifetime studies of Eu(S-THP) give information about the speciation and nature of anion interactions including carbonate, acetate, lactate, citrate, phosphate, and methylphosphate at pH 7.2. Data is consistent with the formation of both innersphere and outersphere complexes of Eu(S-THP) with acetate, lactate, and carbonate. These anions have weak dissociation constants that range from 19 to 38 mM. Citrate binding to Eu(S-THP) is predominantly innersphere with a dissociation constant of 17 μM. Luminescence emission peak changes upon addition of anion to Eu(S-THP) show that there are two distinct binding events for phosphate and methylphosphate with dissociation constants of 0.3 mM and 3.0 mM for phosphate and 0.6 mM and 9.8 mM for methyl phosphate. Eu(THPC) contains an appended carbostyril derivative as an antenna to sensitize Eu(III) luminescence. Eu(THPC) binds phosphate and citrate with dissociation constants that are 10-fold less than that of the Eu(S-THP) parent, suggesting that functionalization through a pendent group disrupts the anion binding site. Eu(S-THP) functions as an anion responsive PARACEST agent through exchange of the alcohol protons with bulk water. The alcohol proton resonances of Eu(S-THP) shift downfield in the presence of acetate, lactate, citrate, and methylphosphate, giving rise to distinct PARACEST peaks. In contrast, phosphate binds to Eu(S-THP) to suppress the PARACEST alcohol OH peak and carbonate does not markedly change the alcohol peak at 5 mM Eu(S-THP), 15 mM carbonate at pH 6.5 or 7.2. This work shows that the Eu(S-THP) complex has unique selectivity toward binding of biologically relevant anions and that anion binding results in changes in both the luminescence and the PARACEST spectra of the complex.
Topics: Anions; Europium; Luminescent Agents; Luminescent Measurements; Magnetics; Molecular Structure; Organometallic Compounds; Stereoisomerism
PubMed: 21548563
DOI: 10.1021/ic200075w -
Molecules (Basel, Switzerland) Feb 2020A computational study of the iodide discrimination by different neutral and cationic iodotriazole halogen bonding hosts was carried out by means of Density Functional...
A computational study of the iodide discrimination by different neutral and cationic iodotriazole halogen bonding hosts was carried out by means of Density Functional Theory. The importance of the size of the scaffold was highlighted and its impact observed in the binding energies and intermolecular X···I distances. Larger scaffolds were found to reduce the electronic repulsion and increase the overlap between the halide electron lone pair and the corresponding I-C antibonding orbital, increasing the halogen bonding interactions. Additionally, the planarity plays an important role within the interaction, and can be tuned using hydroxyl to perform intramolecular hydrogen bonds (IMHB) between the scaffold and the halogen atoms. Structures with IMHB exhibit stronger halogen bond interactions, as evidenced by the shorter intramolecular distances, larger electron density values at the bond critical point and more negative binding energies.
Topics: Anions; Cations; Crystallography, X-Ray; Electrons; Halogens; Hydrogen Bonding; Iodine; Models, Chemical; Models, Molecular; Quantum Theory; Triazoles
PubMed: 32059506
DOI: 10.3390/molecules25040798 -
International Journal of Molecular... May 2023In order to improve the performance of the anion exchange membrane (AEM) used in acid recovery from industrial wastewater, this study adopted a new strategy in which...
In order to improve the performance of the anion exchange membrane (AEM) used in acid recovery from industrial wastewater, this study adopted a new strategy in which brominated poly (2,6-dimethyl-1,4-phenyleneoxide) (BPPO) and polyepichlorohydrin (PECH) were used as the polymer backbone of the prepared membrane. The new anion exchange membrane with a net structure was formed by quaternizing BPPO/PECH with N,N,N,N-tetramethyl-1,6-hexanediamine (TMHD). The application performance and physicochemical property of the membrane were adjusted by changing the content of PECH. The experimental study found that the prepared anion exchange membrane had good mechanical performance, thermostability, acid resistance and an appropriate water absorption and expansion ratio. The acid dialysis coefficient (U) of anion exchange membranes with different contents of PECH and BPPO was 0.0173-0.0262 m/h at 25 °C. The separation factors (S) of the anion exchange membranes were 24.6 to 27.0 at 25 °C. Compared with the commercial BPPO membrane (DF-120B), the prepared membrane had higher values of U and S in this paper. In conclusion, this work indicated that the prepared BPPO/PECH anion exchange membrane had the potential for acid recovery using the DD method.
Topics: Renal Dialysis; Anions; Polymers; Water; Diffusion
PubMed: 37239945
DOI: 10.3390/ijms24108596 -
The Journal of Physiology Sep 2022The volume-regulated anion channel (VRAC) is formed by LRRC8 subunits. Besides their role in the maintenance of cell homeostasis, VRACs are critically involved in...
The volume-regulated anion channel (VRAC) is formed by LRRC8 subunits. Besides their role in the maintenance of cell homeostasis, VRACs are critically involved in oxidative stress mechanisms: reactive oxygen species directly modulate VRACs in a subunit-dependent manner. It was reported that LRRC8A-LRRC8E heteromeric channels are activated by oxidation, whereas LRRC8A-LRRC8C heteromers are inhibited. Here we adopted chimeric- as well as concatemeric-based strategies to identify residues responsible for the divergent effect of oxidants. We identified two cysteines in the first two leucine rich repeats of LRRC8E, C424 and C448, as the targets of oxidation. Oxidation likely results in the formation of a disulfide bond between the two cysteines, which in turn induces a conformational change leading to channel activation. Additionally, we found that LRRC8C inhibition is caused by oxidation of the first methionine. We thus identified crucial molecular elements involved in channel activation, which are conceivably relevant in determining physiological ROS effects. KEY POINTS: Volume-regulated anion channels (VRACs) are heterohexameric complexes composed of an essential LRRC8A subunit and a variable number of LRRC8B-E subunits. VRACs are directly regulated by oxidation, with LRRC8A-LRRC8E heteromers being potentiated and LRRC8A-LRRC8C heteromers being inhibited by oxidation. We identified two LRRC8E specific intracellular cysteines that form a disulfide bond upon oxidation leading to LRRC8A-LRRC8E potentiation. Inhibition of LRRC8A-LRRC8C heteromers is mediated by the oxidation of the start methionine, being additionally dependent on the identity of the LRR domain. Besides providing physiological insights concerning the outcome of reactive oxygen species modulation, the results point to key structural elements involved in VRAC activation.
Topics: Anions; Disulfides; Membrane Proteins; Methionine; Reactive Oxygen Species
PubMed: 35861288
DOI: 10.1113/JP283321