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International Journal of Environmental... May 2023Dichloromethane (DCM) is recognized as a very harmful air pollutant because of its strong volatility and difficulty to degrade. Ionic liquids (ILs) are considered as...
Dichloromethane (DCM) is recognized as a very harmful air pollutant because of its strong volatility and difficulty to degrade. Ionic liquids (ILs) are considered as potential solvents for absorbing DCM, while it is still a challenge to develop ILs with high absorption performances. In this study, four carboxyl-functionalized ILs-trioctylmethylammonium acetate [N][Ac], trioctylmethylammonium formate [N][FA], trioctylmethylammonium glycinate [N][Gly], and trihexyl(tetradecyl)phosphonium glycinate [P][Gly]-were synthesized for DCM capture. The absorption capacity follows the order of [P][Gly] > [N][Gly] > [N][FA] > [N][Ac], and [P][Gly] showed the best absorption capacity, 130 mg DCM/g IL at 313.15 K and a DCM concentration of 6.1%, which was two times higher than the reported ILs [Beim][EtSO] and [Emim][Ac]. Moreover, the vapor-liquid equilibrium (VLE) of the DCM + IL binary system was experimentally measured. The NRTL (non-random two-liquid) model was developed to predict the VLE data, and a relative root mean square deviation (rRMSD) of 0.8467 was obtained. The absorption mechanism was explored via FT-IR spectra, H-NMR, and quantum chemistry calculations. It showed a nonpolar affinity between the cation and the DCM, while the interaction between the anion and the DCM was a hydrogen bond. Based on the results of the study of the interaction energy, it was found that the hydrogen bond between the anion and the DCM had the greatest influence on the absorption process.
Topics: Ionic Liquids; Methylene Chloride; Spectroscopy, Fourier Transform Infrared; Anions
PubMed: 37239516
DOI: 10.3390/ijerph20105787 -
Nucleic Acids Research Nov 2022We present a systematic structural and energetic characterization of phosphate(OP)-nucleobase anion…π stacking interactions in RNAs. We observed OP-nucleobase...
We present a systematic structural and energetic characterization of phosphate(OP)-nucleobase anion…π stacking interactions in RNAs. We observed OP-nucleobase stacking contacts in a variety of structural motifs other than regular helices and spanning broadly diverse sequence distances. Apart from the stacking between a phosphate and a guanine or a uracil two-residue upstream in specific U-turns, such interactions in RNA have been scarcely characterized to date. Our QM calculations showed an energy minimum at a distance between the OP atom and the nucleobase plane centroid slightly below 3 Å for all the nucleobases. By sliding the OP atom over the nucleobase plane we localized the optimal mutual positioning of the stacked moieties, corresponding to an energy minimum below -6 kcal•mol-1, for all the nucleobases, consistently with the projections of the OP atoms over the different π-rings we observed in experimental occurrences. We also found that the strength of the interaction clearly correlates with its electrostatic component, pointing to it as the most relevant contribution. Finally, as OP-uracil and OP-guanine interactions represent together 86% of the instances we detected, we also proved their stability under dynamic conditions in model systems simulated by state-of-the art DFT-MD calculations.
Topics: Thermodynamics; Phosphates; RNA; Guanine; Uracil; Anions; RNA, Untranslated
PubMed: 36416268
DOI: 10.1093/nar/gkac1081 -
Scientific Reports Apr 2021Ion channel proteins are physiologically important molecules in living organisms. Their molecular functions have been investigated using electrophysiological methods,...
Ion channel proteins are physiologically important molecules in living organisms. Their molecular functions have been investigated using electrophysiological methods, which enable quantitative, precise and advanced measurements and thus require complex instruments and experienced operators. For simpler and easier measurements, we measured the anion transport activity of light-gated anion channelrhodopsins (ACRs) using a pH electrode method, which has already been established for ion pump rhodopsins. Using that method, we successfully measured the anion transport activity and its dependence on the wavelength of light, i.e. its action spectra, and on the anion species, i.e. its selectivity or preference, of several ACRs expressed in yeast cells. In addition, we identified the strong anion transport activity and the preference for NO of an ACR from a marine cryptophyte algae Proteomonas sulcata, named PsuACR_353. Such a preference was discovered for the first time in microbial pump- or channel-type rhodopsins. Nitrate is one of the most stable forms of nitrogen and is used as a nitrogen source by most organisms including plants. Therefore, PsuACR_353 may play a role in NO transport and might take part in NO-related cellular functions in nature. Measurements of a mutant protein revealed that a Thr residue in the 3 transmembrane helix, which corresponds to Cys102 in GtACR1, contributed to the preference for NO. These findings will be helpful to understand the mechanisms of anion transport, selectivity and preference of PsuACR_353.
Topics: Anions; Biological Transport; Channelrhodopsins; Cryptophyta; Electrodes; Hydrogen-Ion Concentration; Mutation; Nitrates; Pichia
PubMed: 33846397
DOI: 10.1038/s41598-021-86812-z -
Physiological Reports May 2021Models of acid-base balance include acid production from (1) oxidation of sulfur atoms on amino acids and (2) metabolically produced organic acid anions. Acid load is...
Models of acid-base balance include acid production from (1) oxidation of sulfur atoms on amino acids and (2) metabolically produced organic acid anions. Acid load is balanced by alkali from metabolism of GI anions; thus, net acid production is equivalent to the sum of urine sulfate and organic anion (measured by titration in urine), minus GI anion. However, the relative contributions of these three sources of acid production in people eating free choice diets, and presumably in acid-base balance, have not been well studied. We collected 26 urines from 18 normal subjects (10 male) and 43 urine samples from 34 stone formers (17 male) and measured sulfate, organic anion, and components of GI anion and acid excretion in each; values were expressed as mEq/mmol creatinine. Mean values of the urine components, except creatinine and pH, did not differ between the sexes or groups. Urine organic acid and acid production varied directly with age (p ≤ 0.03). In a general linear model of acid excretion, the coefficients for sulfate, organic anion, and GI anion were 0.34 ± 0.09, 0.49 ± 0.12, and -0.51 ± 0.06, respectively, p ≤ 0.005, and the model accounted for 54% of the variance. A model for urine ammonia gave similar results. Urine organic anion is a significant contributor to total acid production and may be responsible for an increase in acid production with age.
Topics: Acid-Base Equilibrium; Adult; Aging; Anions; Female; Humans; Kidney; Kidney Calculi; Male; Middle Aged; Sulfates
PubMed: 34042292
DOI: 10.14814/phy2.14870 -
Accounts of Chemical Research Aug 2022The interactions of hydrated ions with molecular and macromolecular solution and interface partners are strong on a chemical energy scale. Here, we recount the foremost...
The interactions of hydrated ions with molecular and macromolecular solution and interface partners are strong on a chemical energy scale. Here, we recount the foremost ab initio theory for the evaluation of the hydration free energies of ions, namely, quasi-chemical theory (QCT). We focus on anions, particularly halides but also the hydroxide anion, because they have been outstanding challenges for all theories. For example, this work supports understanding the high selectivity for F over Cl in fluoride-selective ion channels despite the identical charge and the size similarity of these ions. QCT is built by the identification of inner-shell clusters, separate treatment of those clusters, and then the integration of those results into the broader-scale solution environment. Recent work has focused on a close comparison with mass-spectrometric measurements of ion-hydration equilibria. We delineate how ab initio molecular dynamics (AIMD) calculations on ion-hydration clusters, elementary statistical thermodynamics, and electronic structure calculations on cluster structures sampled from the AIMD calculations obtain just the free energies extracted from the cluster experiments. That theory-experiment comparison has not been attempted before the work discussed here, but the agreement is excellent with moderate computational effort. This agreement reinforces both theory and experiment and provides a numerically accurate inner-shell contribution to QCT. The inner-shell complexes involving heavier halides display strikingly asymmetric hydration clusters. Asymmetric hydration structures can be problematic for the evaluation of the QCT outer-shell contribution with the polarizable continuum model (PCM). Nevertheless, QCT provides a favorable setting for the exploitation of PCM when the inner-shell material shields the ion from the outer solution environment. For the more asymmetrically hydrated, and thus less effectively shielded, heavier halide ions clustered with waters, the PCM is less satisfactory. We therefore investigate an inverse procedure in which the inner-shell structures are sampled from readily available AIMD calculations on the bulk solutions. This inverse procedure is a remarkable improvement; our final results are in close agreement with a standard tabulation of hydration free energies, and the final composite results are independent of the coordination number on the chemical energy scale of relevance, as they should be. Finally, a comparison of anion hydration structure in clusters and bulk solutions from AIMD simulations emphasize some differences: the asymmetries of bulk solution inner-shell structures are moderated compared with clusters but are still present, and inner hydration shells fill to slightly higher average coordination numbers in bulk solution than in clusters.
Topics: Molecular Dynamics Simulation; Thermodynamics; Water
PubMed: 35829622
DOI: 10.1021/acs.accounts.2c00078 -
The FEBS Journal Mar 2022The divalent anion sodium symporter (DASS) family contains both sodium-driven anion cotransporters and anion/anion exchangers. The family belongs to a broader ion...
The divalent anion sodium symporter (DASS) family contains both sodium-driven anion cotransporters and anion/anion exchangers. The family belongs to a broader ion transporter superfamily (ITS), which comprises 24 families of transporters, including those of AbgT antibiotic efflux transporters. The human proteins in the DASS family play major physiological roles and are drug targets. We recently determined multiple structures of the human sodium-dependent citrate transporter (NaCT) and the succinate/dicarboxylate transporter from Lactobacillus acidophilus (LaINDY). Structures of both proteins show high degrees of structural similarity to the previously determined VcINDY fold. Conservation between these DASS protein structures and those from the AbgT family indicates that the VcINDY fold represents the overall protein structure for the entire ITS. The new structures of NaCT and LaINDY are captured in the inward- or outward-facing conformations, respectively. The domain arrangements in these structures agree with a rigid body elevator-type transport mechanism for substrate translocation across the membrane. Two separate NaCT structures in complex with a substrate or an inhibitor allowed us to explain the inhibition mechanism and propose a detailed classification scheme for grouping disease-causing mutations in the human protein. Structural understanding of multiple kinetic states of DASS proteins is a first step toward the detailed characterization of their entire transport cycle.
Topics: Anions; Dicarboxylic Acid Transporters; Humans; Membrane Transport Proteins; Sodium; Symporters
PubMed: 34403567
DOI: 10.1111/febs.16158 -
Spectrochimica Acta. Part A, Molecular... Mar 2023The UV-vis and ECD spectroelectrochemistry (SEC) of a chiral binaphthalenylamine derivative of the N-butyl naphthalenediimide (NDIB-NH) enantiomers were applied to...
The UV-vis and ECD spectroelectrochemistry (SEC) of a chiral binaphthalenylamine derivative of the N-butyl naphthalenediimide (NDIB-NH) enantiomers were applied to measure UV-vis and ECD spectra of NDIB-NH radicals and dianion formed in the reduction and oxidation processes observed in cyclic voltammetry (CV). The CV curves and EPR spectroelectrochemistry enabled us to establish conditions at which a radical-anion [NDIB-NH]̇, a dianion [NDIB-NH], and a radical-cation [NDIB-NH]̇ are formed. The DFT restricted open-shell CAM-B3LYP-D3/def2TZVP/PCM calculations demonstrated that in the radical-anion [NDIB-NH]̇, spin is spread over the NDI system while in the radical-cation [NDIB-NH]̇ it is spread over the aminonaphthalene moiety. The UV-vis spectra of radical-anion and dianion show the most significant changes in the 400-800 nm range. In that range, the ECD spectra varied with the change of electrode potential more than the UV-vis did and enabled the identification of a new ECD band of [NDIB-NH]̇ at ca. 400 nm hidden in the background in the UV spectra at -1000 mV. A broad structured ECD pattern with a maximum at ca. 530 nm was observed for [NDIB-NH]̇ (-1000 mV), while a single smooth ECD band of [NDIB-NH] was located at 520 nm (-1750 mV). For the first time, an isosbestic point (455 nm) was found in ECD spectroelectrochemical measurements for the radical-cation [NDIB-NH]̇ in equilibrium with the NDIB-NH neutral form. The TD-DFT CAM-B3LYP-D3/6-31G** calculations combined with the hybrid (explicit combined with implicit) solvation model fairly well reproduced the UV-vis and ECD SEC of neutral and redox forms of NDIB-NH but the ECD spectrum of [NDIB-NH]̇ above 390 nm.
Topics: Density Functional Theory; Oxidation-Reduction; Anions; Cations
PubMed: 36436264
DOI: 10.1016/j.saa.2022.122089 -
ACS Sensors Aug 2023We report here a small library of a new type of acyclic squaramide receptors (-) as selective ionophores for the detection of ketoprofen and naproxen anions (KF and NS,...
We report here a small library of a new type of acyclic squaramide receptors (-) as selective ionophores for the detection of ketoprofen and naproxen anions (KF and NS, respectively) in aqueous media. H NMR binding studies show a high affinity of these squaramide receptors toward KF and NS, suggesting the formation of H-bonds between the two guests and the receptors through indole and -NH groups. Compounds - have been tested as ionophores for the detection of KF and NS inside solvent PVC-based polymeric membranes. The optimal membrane compositions were established through the careful variation of the ligand/tridodecylmethylammonium chloride (TDMACl) anion-exchanger ratio. All of the tested acyclic squaramide receptors - have high affinity toward KF and NS and anti-Hofmeister selectivity, with and showing the highest sensitivity and selectivity to NS. The utility of the developed sensors for a high precision detection of KF in pharmaceutical compositions with low relative errors of analysis (RSD, 0.99-1.4%) and recoveries, %, in the range 95.1-111.8% has been demonstrated. Additionally, the chemometric approach has been involved to effectively discriminate between the structurally very similar KF and NS, and the possibility of detecting these analytes at concentrations as low as 0.07 μM with of 0.947 and at 0.15 μM with of 0.919 for NS and KF, respectively, was shown.
Topics: Ionophores; Anions; Quinine
PubMed: 37530141
DOI: 10.1021/acssensors.3c00981 -
Cells Jun 2023We assessed interactions between the astrocytic volume-regulated anion channel (VRAC) and aquaporin 4 (AQP4) in the supraoptic nucleus (SON). Acute SON slices and...
We assessed interactions between the astrocytic volume-regulated anion channel (VRAC) and aquaporin 4 (AQP4) in the supraoptic nucleus (SON). Acute SON slices and cultures of hypothalamic astrocytes prepared from rats received hyposmotic challenge (HOC) with/without VRAC or AQP4 blockers. In acute slices, HOC caused an early decrease with a late rebound in the neuronal firing rate of vasopressin neurons, which required activity of astrocytic AQP4 and VRAC. HOC also caused a persistent decrease in the excitatory postsynaptic current frequency, supported by VRAC and AQP4 activity in early HOC; late HOC required only VRAC activity. These events were associated with the dynamics of glial fibrillary acidic protein (GFAP) filaments, the late retraction of which was mediated by VRAC activity; this activity also mediated an HOC-evoked early increase in AQP4 expression and late subside in GFAP-AQP4 colocalization. AQP4 activity supported an early HOC-evoked increase in VRAC levels and its colocalization with GFAP. In cultured astrocytes, late HOC augmented VRAC currents, the activation of which depended on AQP4 pre-HOC/HOC activity. HOC caused an early increase in VRAC expression followed by a late rebound, requiring AQP4 and VRAC, or only AQP4 activity, respectively. Astrocytic swelling in early HOC depended on AQP4 activity, and so did the early extension of GFAP filaments. VRAC and AQP4 activity supported late regulatory volume decrease, the retraction of GFAP filaments, and subside in GFAP-VRAC colocalization. Taken together, astrocytic morphological plasticity relies on the coordinated activities of VRAC and AQP4, which are mutually regulated in the astrocytic mediation of HOC-evoked modulation of vasopressin neuronal activity.
Topics: Rats; Animals; Aquaporin 4; Supraoptic Nucleus; Astrocytes; Vasopressins; Anions; Neurons
PubMed: 37443757
DOI: 10.3390/cells12131723 -
Microbiology (Reading, England) Oct 2022During enterobacterial mixed-acid fermentation, formate is generated from pyruvate by the glycyl-radical enzyme pyruvate formate-lyase (PflB). In , especially at low pH,... (Review)
Review
During enterobacterial mixed-acid fermentation, formate is generated from pyruvate by the glycyl-radical enzyme pyruvate formate-lyase (PflB). In , especially at low pH, formate is then disproportionated to CO and H by the cytoplasmically oriented, membrane-associated formate hydrogenlyase (FHL) complex. If electron acceptors are available, however, formate is oxidized by periplasmically oriented, respiratory formate dehydrogenases. Formate translocation across the cytoplasmic membrane is controlled by the formate channel, FocA, a member of the formate-nitrite transporter (FNT) family of homopentameric anion channels. This review highlights recent advances in our understanding of how FocA helps to maintain intracellular formate and pH homeostasis during fermentation. Efflux and influx of formate/formic acid are distinct processes performed by FocA and both are controlled through protein interaction between FocA's N-terminal domain with PflB. Formic acid efflux by FocA helps to maintain cytoplasmic pH balance during exponential-phase growth. Uptake of formate against the electrochemical gradient (inside negative) is energetically and mechanistically challenging for a fermenting bacterium unless coupled with proton/cation symport. Translocation of formate/formic acid into the cytoplasm necessitates an active FHL complex, whose synthesis also depends on formate. Thus, FocA, FHL and PflB function together to govern formate homeostasis. We explain how FocA achieves efflux of formic acid and propose mechanisms for pH-dependent uptake of formate both with and without proton symport. We propose that FocA displays both channel- and transporter-like behaviour. Whether this translocation behaviour is shared by other members of the FNT family is also discussed.
Topics: Anions; Carbon Dioxide; Enterobacteriaceae; Escherichia coli; Escherichia coli Proteins; Formate Dehydrogenases; Formates; Homeostasis; Hydrogen-Ion Concentration; Hydrogenase; Membrane Transport Proteins; Nitrites; Protons; Pyruvates
PubMed: 36197793
DOI: 10.1099/mic.0.001253