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The Journal of Organic Chemistry May 2024Anions have a profound effect on the properties of soluble proteins. Such Hofmeister effects have implications in biologics stability, protein aggregation,...
Anions have a profound effect on the properties of soluble proteins. Such Hofmeister effects have implications in biologics stability, protein aggregation, amyloidogenesis, and crystallization. However, the interplay between the important noncovalent interactions (NCIs) responsible for Hofmeister effects is poorly understood. To contribute to improving this state of affairs, we report on the NCIs between anions and ammonium and guanidinium hosts and , and the consequences of these. Specifically, we investigate the properties of cavitands designed to mimic two prime residues for anion-protein NCIs─lysines and arginines─and the solubility consequences of complex formation. Thus, we report NMR and ITC affinity studies, X-ray analysis, MD simulations, and anion-induced critical precipitation concentrations. Our findings emphasize the multitude of NCIs that guanidiniums can form and how this repertoire qualitatively surpasses that of ammoniums. Additionally, our studies demonstrate the ease by which anions can dispense with a fraction of their hydration-shell waters, rearrange those that remain, and form direct NCIs with the hosts. This raises many questions concerning how solvent shell plasticity varies as a function of anion, how the energetics of this impact the different NCIs between anions and ammoniums/guanidiniums, and how this affects the aggregation of solutes at high anion concentrations.
Topics: Guanidine; Anions; Arginine; Ammonium Compounds; Lysine; Molecular Dynamics Simulation
PubMed: 38662908
DOI: 10.1021/acs.joc.4c00242 -
The FEBS Journal Nov 2011Plant anion channels allow the efflux of anions from cells. They are involved in turgor pressure control, changes in membrane potential, organic acid excretion,... (Review)
Review
Plant anion channels allow the efflux of anions from cells. They are involved in turgor pressure control, changes in membrane potential, organic acid excretion, tolerance to salinity and inorganic anion nutrition. The recent molecular identification of anion channel genes in guard cells and in roots allows a better understanding of their function and of the mechanisms that control their activation.
Topics: Anions; Ion Channels; Membrane Potentials; Plant Cells; Signal Transduction
PubMed: 21955597
DOI: 10.1111/j.1742-4658.2011.08370.x -
Molecules (Basel, Switzerland) May 2022Fluorescent receptors (-) based on (thio)ureido-functionalized hexahomotrioxacalix[3]arenes were synthesised and obtained in the partial cone conformation in solution....
Fluorescent receptors (-) based on (thio)ureido-functionalized hexahomotrioxacalix[3]arenes were synthesised and obtained in the partial cone conformation in solution. Naphthyl or pyrenyl fluorogenic units were introduced at the lower rim of the calixarene skeleton via a butyl spacer. The binding of biologically and environmentally relevant anions was studied with NMR, UV-vis absorption, and fluorescence titrations. Fluorescence of the pyrenyl receptor displays both monomer and excimer fluorescence. The thermodynamics of complexation was determined in acetonitrile and was entropy-driven. Computational studies were also performed to bring further insight into the binding process. The data showed that association constants increase with the anion basicity, and AcO, BzO and F were the best bound anions for all receptors. Pyrenylurea is a slightly better receptor than naphthylurea , and both are more efficient than naphthyl thiourea . In addition, ureas and were also tested as ditopic receptors in the recognition of alkylammonium salts.
Topics: Anions; Calixarenes; Coloring Agents; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Molecular Conformation
PubMed: 35630730
DOI: 10.3390/molecules27103247 -
Critical Care (London, England) 2008Evidence is emerging that elevated concentrations of the intermediates of the citric acid cycle may contribute to unmeasured anions in critical illness. Both the anion...
Evidence is emerging that elevated concentrations of the intermediates of the citric acid cycle may contribute to unmeasured anions in critical illness. Both the anion gap and the strong ion gap are used as scanning tools for recognition of these anions. The mechanisms underlying these elevations and their significance require further clarification.
Topics: Acid-Base Equilibrium; Acidosis; Animals; Anions; Humans; Shock, Hemorrhagic
PubMed: 18304373
DOI: 10.1186/cc6768 -
Current Opinion in Structural Biology Jun 2022Members of the LRRC8 family participate in the response of vertebrate cells to osmotic changes in their environment. These proteins form heteromeric assemblies composed... (Review)
Review
Members of the LRRC8 family participate in the response of vertebrate cells to osmotic changes in their environment. These proteins form heteromeric assemblies composed of the obligatory subunit LRRC8A and at least one of the other four homologs, which together function as anion-selective channels with distinct properties that are activated upon cell-swelling. The hexameric complexes share a conserved architecture consisting of a membrane-inserted pore domain with an ion permeation path located at the axis of symmetry and cytoplasmic leucine-rich repeat domains that regulate the open probability of the channel. In this review, we summarize the current understanding of structure-function relationships of these unusual ion channels whose mechanisms are, despite their large physiological importance, still poorly understood.
Topics: Anions; Cell Size; Ion Channels; Membrane Proteins; Protein Domains
PubMed: 35504105
DOI: 10.1016/j.sbi.2022.102382 -
Biochimica Et Biophysica Acta Apr 2016All ion channels are able to discriminate between substrate ions to some extent, a process that involves specific interactions between permeant anions and the so-called...
All ion channels are able to discriminate between substrate ions to some extent, a process that involves specific interactions between permeant anions and the so-called selectivity filter within the channel pore. In the cystic fibrosis transmembrane conductance regulator (CFTR) anion-selective channel, both anion relative permeability and anion relative conductance are dependent on anion free energy of hydration--anions that are relatively easily dehydrated tend to show both high permeability and low conductance. In the present work, patch clamp recording was used to investigate the relative conductance of different anions in CFTR, and the effect of mutations within the channel pore. In constitutively-active E1371Q-CFTR channels, the anion conductance sequence was Cl(-) > NO3(-) > Br(-) > formate > SCN(-) > I(-). A mutation that disrupts anion binding in the inner vestibule of the pore (K95Q) disrupted anion conductance selectivity, such that anions with different permeabilities showed almost indistinguishable conductances. Conversely, a mutation at the putative narrowest pore region that is known to disrupt anion permeability selectivity (F337A) had minimal effects on anion relative conductance. Ion competition experiments confirmed that relatively tight binding of permeant anions resulted in relatively low conductance. These results suggest that the relative affinity of ion binding in the inner vestibule of the pore controls the relative conductance of different permeant anions in CFTR, and that the pore has two physically distinct anion selectivity filters that act in series to control anion conductance selectivity and anion permeability selectivity respectively.
Topics: Animals; Anions; Cell Membrane Permeability; Chloride Channels; Cricetinae; Cystic Fibrosis Transmembrane Conductance Regulator; Kidney; Mutation; Patch-Clamp Techniques
PubMed: 26779604
DOI: 10.1016/j.bbamem.2016.01.009 -
Journal of the American Chemical Society Jan 2023When high-energy radiation passes through aqueous material, low-energy electrons are produced which cause DNA damage. Electronic states of anionic nucleobases have been...
When high-energy radiation passes through aqueous material, low-energy electrons are produced which cause DNA damage. Electronic states of anionic nucleobases have been suggested as an entrance channel to capture the electron. However, identifying these electronic resonances have been restricted to gas-phase electron-nucleobase studies and offer limited insight into the resonances available within the aqueous environment of DNA. Here, resonance and detachment energies of the micro-hydrated uracil pyrimidine nucleobase anion are determined by two-dimensional photoelectron spectroscopy and are shown to extrapolate linearly with cluster size. This extrapolation allows the corresponding resonance and detachment energies to be determined for uracil in aqueous solution as well as the reorganization energy associated with electron capture. Two shape resonances are clearly identified that can capture low-energy electrons and subsequently form the radical anion by solvent stabilization and internal conversion to the ground electronic state. The resonances and their dynamics probed here are the nucleobase-centered doorway states for low-energy electron capture and damage in DNA.
Topics: Water; Uracil; Anions; Solvents; DNA
PubMed: 36584340
DOI: 10.1021/jacs.2c11440 -
Molecules (Basel, Switzerland) Feb 2021Biodegradable and antimicrobial waterborne polyurethane dispersions (PUDs) and their casted solid films have recently emerged as important alternatives to their... (Review)
Review
Biodegradable and antimicrobial waterborne polyurethane dispersions (PUDs) and their casted solid films have recently emerged as important alternatives to their solvent-based and non-biodegradable counterparts for various applications due to their versatility, health, and environmental friendliness. The nanoscale morphology of the PUDs, dispersion stability, and the thermomechanical properties of the solid films obtained from the solvent cast process are strongly dependent on several important parameters, such as the preparation method, polyols, diisocyanates, solid content, chain extension, and temperature. The biodegradability, biocompatibility, antimicrobial properties and biomedical applications can be tailored based on the nature of the polyols, polarity, as well as structure and concentration of the internal surfactants (anionic or cationic). This review article provides an important quantitative experimental basis and structure evolution for the development and synthesis of biodegradable waterborne PUDs and their solid films, with prescribed macromolecular properties and new functions, with the aim of understanding the relationships between polymer structure, properties, and performance. The review article will also summarize the important variables that control the thermomechanical properties and biodegradation kinetics, as well as antimicrobial and biocompatibility behaviors of aqueous PUDs and their films, for certain industrial and biomedical applications.
Topics: Anions; Anti-Infective Agents; Biodegradable Plastics; Humans; Polymers; Polyurethanes; Solvents; Surface-Active Agents; Water
PubMed: 33670378
DOI: 10.3390/molecules26040961 -
Pharmacology Research & Perspectives Jun 2023Syringin is a natural chemical compound first isolated from the bark of lilac and is known to have neuroprotective effects in middle cerebral artery occlusion (MCAO)....
Syringin is a natural chemical compound first isolated from the bark of lilac and is known to have neuroprotective effects in middle cerebral artery occlusion (MCAO). Volume regulated anion channel (VRAC) is a cell swelling-activated anion channel, which is implicated in brain ischemia. However, the mechanism underlying the syringin protecting the neuron from damage in MCAO is still unclear. We hypothesized that syringin has an inhibitory effect on the opening of VRAC channels. To access the effect of syringin on VRAC currents and predict how syringin interacts with VRAC proteins, we performed whole-cell patch-clamp experiments using HEK293 cells. Initially, HEK293 cells were perfused with isotonic extracellular solution, followed by hypotonic extracellular solution to stimulate endogenous VRAC currents. Once the VRAC currents reached a steady state, the hypotonic solution containing syringin was perfused to study the effect of syringin on VRAC currents. The potential interaction between syringin and the VRAC protein was investigated using molecular docking as a predictive model. In this study, we found that syringin moderately inhibited VRAC currents in a dose-dependent manner. The potential binding of syringin to LRRC8 protein was predicted through in silico molecular docking, which suggests an affinity of -6.6 kcal/mol and potential binding sites of arginine 103 and leucine 101. Our results herein characterize syringin as an inhibitor of the VRAC channels, which provides valuable insights for the future development of VRAC channel inhibitors.
Topics: Humans; HEK293 Cells; Membrane Proteins; Molecular Docking Simulation; Anions
PubMed: 37278329
DOI: 10.1002/prp2.1105 -
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