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Chemistry (Weinheim An Der Bergstrasse,... May 2022In a leap toward anion separation that uses only energy input for binding and release cycles, we report herein a new class of photoswitchable anion receptors featuring a...
In a leap toward anion separation that uses only energy input for binding and release cycles, we report herein a new class of photoswitchable anion receptors featuring a diiminoguanidinium functionality that displays a change of more than five orders of magnitude in switched-off binding strength towards sulfate, a representative oxyanion, upon photoirradiation with UV light. The (E,E)-2-pyridyl-diiminoguanidinium cation, synthesized as the triflate salt, binds sulfate with extraordinary strength in [D ]DMSO owing to its bidentate guanidinium hydrogen bonding, which can chelate the O-S-O edge of sulfate. Upon photoisomerization to the Z,Z isomer, the anion-binding site is essentially shut off by intramolecular hydrogen bonds to the 2-pyridyl substituents, as shown by anion-binding titrations, theoretical calculations, and X-ray structural analysis. This approach will allow the development of advanced anion-separation cycles that use only energy input and generate no chemical waste, and thus address challenging chemical separation problems in a more sustainable way.
Topics: Anions; Binding Sites; Cations; Hydrogen Bonding; Sulfates
PubMed: 35319796
DOI: 10.1002/chem.202200719 -
ACS Sensors Feb 2020Potentiometric probes used in direct potentiometry are attractive sensing tools. They give information on ion activities, which is often uniquely useful. If, instead,...
Potentiometric probes used in direct potentiometry are attractive sensing tools. They give information on ion activities, which is often uniquely useful. If, instead, concentrations are desired as sensor output, the ionic strength of the sample must be precisely known, which is often not possible. Here, for the first time, direct potentiometry can be made to report concentrations, rather than activities. It is demonstrated for the detection of monovalent anionic species by using a self-referencing Ag/AgI pulstrode as the reference element instead of a traditional reference electrode. This reference pulstrode releases a discrete quantity of iodide ions from the electrode and the resulting reference potential varies with the activity coefficient of iodide. The effects of activity coefficient on the indicator and reference electrode are therefore compensated and the observed cell potential may now be described in a Nernstian manner against anion concentration, rather than activity. Theoretical simulations and experimental results support the validity of this approach. For most monovalent anions of practical relevance, the potential difference between this approach and from a traditional activity coefficient calculation is less than 0.5 mV. The concept is validated with an all-solid-state nitrate sensor as well as a commercial fluoride-selective electrode, giving Nernstian responses in different ionic strength backgrounds against concentration without the need for correcting activity coefficients or liquid junction potentials.
Topics: Anions; Potentiometry
PubMed: 32050757
DOI: 10.1021/acssensors.9b02523 -
Biophysical Journal Jul 1998We have examined whether the anionic amino acids, glutamate and aspartate, permeate through the same volume-regulated conductance permeant to Cl- ions. Cell swelling was...
We have examined whether the anionic amino acids, glutamate and aspartate, permeate through the same volume-regulated conductance permeant to Cl- ions. Cell swelling was initiated in response to establishing a whole-cell configuration in the presence of a hyposmotic gradient. Volume-regulated anion currents carried by Cl-, glutamate, or aspartate developed with similar time courses and showed similar voltage-dependent inactivation. Permeability ratios (Paa/PCl) calculated from measured reversal potentials were dependent on the mole fraction ratio (MFR) of the permeant anions ([aa]/([aa] + [Cl-])). MFR was varied from 0.00 to 0.97. As the fraction of amino acid increased, Paa/PCl decreased. Current amplitude was similarly dependent on MFR. These results show that the permeation of anionic amino acids and that of Cl- ions are not independent of each other, indicating that the ion channel underlying the volume-regulated conductance can be occupied by more than one ion at a time. Application of Eyring rate theory indicated that the major barrier to Cl- ion permeation is at the intracellular side of the membrane, and that the major barrier to amino acid permeation is at the extracellular side of the membrane. The interactions between these permeant ions may have a physiological modulatory role in volume regulation through a volume-regulated anion conductance.
Topics: Anions; Aspartic Acid; Biophysical Phenomena; Biophysics; Cell Membrane Permeability; Cell Size; Chlorides; Electric Conductivity; Glutamic Acid; Humans; Ion Transport; Kinetics; Membrane Potentials; Models, Biological; Thermodynamics; Tumor Cells, Cultured
PubMed: 9649382
DOI: 10.1016/S0006-3495(98)77509-5 -
Archives of Biochemistry and Biophysics Jan 2005Enzymes that function on membrane surfaces offer many challenges to understanding structural and functional details due to the difficulties of obtaining relevant... (Review)
Review
Enzymes that function on membrane surfaces offer many challenges to understanding structural and functional details due to the difficulties of obtaining relevant information of the protein in a physiological environment. Focusing on this aspect of structural biology, it is important to develop conditions that mimic the interaction of membrane proteins with their binding surface and ultimately the mechanisms of action. This approach has been used to characterize the allosteric nature of secreted phospholipase A2 (PLA2) to its substrate interface. The breakthrough here was to crystallize the pancreatic group-IB PLA2 in an anion-assisted dimer with five coplanar phosphate anions bound. In the anion-assisted dimer structure one molecule of a tetrahedral mimic inhibitor and five anions are shared between the two subunits of the dimer. The sn-2-phosphate of the inhibitor, which mimics the tetrahedral intermediate of the esterolysis reaction, is bound in the active site of one subunit, and the alkyl chain extends into the active site slot of the second subunit across the subunit-subunit interface. This interface-bound structural mimic provided insight into the active site environment and specific anionic interactions to the i-face of the protein. The presence or absence of a single critical active site water, corresponds to the difference between the activated or inactivated form of the enzyme. The anion-assisted dimer structure supports a calcium coordinated nucleophilic water mechanism, with its pK(a) modulated by this assisting water. This working model has been further strengthened with an enzyme-product complex structure solved with the hydrolysis products of the substrate PAF also bound to the anion-assisted dimer form of PLA2. Additional confirmation of the assisting-water mechanism comes from a structure of the inactive zymogen proPLA2 also crystallized in an anion-assisted dimer. Remarkably, the assisting water present in the activated complex is absent in this proPLA2 structure.
Topics: Allosteric Site; Amino Acid Substitution; Anions; Binding Sites; Crystallography, X-Ray; Dimerization; Enzyme Activation; Enzyme Precursors; Glycine; Group II Phospholipases A2; Humans; Hydrogen Bonding; Hydrolysis; Kinetics; Ligands; Membrane Proteins; Models, Chemical; Models, Molecular; Models, Structural; Molecular Conformation; Molecular Structure; Molecular Weight; Pancreas; Phosphates; Phospholipases A; Phospholipases A2; Protein Binding; Protein Structure, Secondary; Protein Subunits; Quantum Theory; Substrate Specificity; Sulfates; Water
PubMed: 15581569
DOI: 10.1016/j.abb.2004.08.013 -
ACS Applied Materials & Interfaces Jul 2020Brain-inspired synaptic transistors have been considered as a promising device for next-generation electronics. To mimic the behavior of a biological synapse, both data...
Brain-inspired synaptic transistors have been considered as a promising device for next-generation electronics. To mimic the behavior of a biological synapse, both data processing and nonvolatile memory capability are simultaneously required for a single electronic device. In this work, a simple approach to realize a synaptic transistor with improved memory characteristics is demonstrated by doping an ionic additive, tetrabutylammonium perchlorate (TBAP), into an active polymer semiconductor without using any extra charge storage layer. TBAP doping is first revealed to improve the memory window of a derived transistor memory device from 19 to 32 V (∼68% enhancement) with an on/off current ratio over 10 at = -10 V. Through morphological analysis and theoretical calculations, it is revealed that the association of anion with polymers enhances the charge retention capability of the polymer and facilitates the interchain interactions to result in improved memory characteristics. More critically, the doped device is shown to successfully mimic the synaptic behaviors, such as paired-pulse facilitation (PPF), excitatory and inhibitory postsynaptic currents, and spike-rate dependent plasticity. Notably, the TBAP-doped device is shown to deliver a PPF index of up to 204% in contrast to the negligible value of an undoped device. This study describes a novel approach to prepare a synaptic transistor by doping conjugated polymers, which can promote the future development of artificial neuromorphic systems.
Topics: Anions; Density Functional Theory; Polymers; Quaternary Ammonium Compounds; Semiconductors; Silicon Dioxide; Synapses
PubMed: 32608231
DOI: 10.1021/acsami.0c06109 -
Rapid Communications in Mass... Jun 2022Sugars are key molecules of life but challenging to detect via electrospray ionization mass spectrometry (ESI-MS). Unfortunately, sugars are challenging analytes for...
RATIONALE
Sugars are key molecules of life but challenging to detect via electrospray ionization mass spectrometry (ESI-MS). Unfortunately, sugars are challenging analytes for mass spectrometric methods due to their high gas-phase deprotonation energies and low gas-phase proton affinities which make them difficult to ionize in high abundance for MS detection.
METHODS
Hydrogen-bond interactions in H PO -saccharide anionic systems were studied both experimentally (via electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry, ESI-FT-ICR-MS) and computationally by several sophisticated density-functional theoretical methods (DFT and DFT-D3).
RESULTS
The H PO dopant boosts the detection of sugars up to 51-times in the case of sucrose and up to 263-times for glucose (at 0.1 ppm concentration level). H PO binds toward sugar molecules with noticeably more hydrogen bonds than the established dopant chloride Cl does, with increasing binding energies in the order: Monosaccharides < Trisaccharides < Disaccharides. Analysis of a complex oak plant sample revealed that NH H PO specifically labeled a diverse set of sugar-type plant metabolites in the form of [M + H PO ] complexes.
CONCLUSIONS
We reveal the mechanism of interaction of H PO with different sugars and glycosylated organic compounds, which significantly enhances their ionization in mass spectrometry. A computational and experimental investigation is presented. A strong correlation between the MS signal intensities of detected [M + H PO ] anions of different saccharides and their calculated dissociation enthalpies was revealed. Thus, the variation in MS signal intensities can be very well described to a large extent by the variation in calculated saccharide affinities toward the H PO dopant anion, showing that DFT-D3 can very well describe experimental FT-ICR-MS observations.
Topics: Anions; Carbohydrates; Chlorides; Hydrogen; Phosphates; Spectrometry, Mass, Electrospray Ionization; Sugars
PubMed: 35229909
DOI: 10.1002/rcm.9283 -
Organic Letters Jul 2005[reaction: see text] Tyrosine-derived Zn(2+) coordination complexes and their fluorescent NBD conjugates are synthesized in a short, high-yielding procedure. The Zn(2+)...
[reaction: see text] Tyrosine-derived Zn(2+) coordination complexes and their fluorescent NBD conjugates are synthesized in a short, high-yielding procedure. The Zn(2+) complexes are highly water soluble, but in the presence of sodium laurate they readily transfer into an octanol layer. Furthermore, the NBD-labeled bis-Zn(2+) complex can partition into vesicle membranes containing anionic phospholipids.
Topics: Anions; Lipid Bilayers; Organometallic Compounds; Tyrosine; Zinc
PubMed: 15987193
DOI: 10.1021/ol0510421 -
Journal of the American Chemical Society Jan 2017The cell internalization of designed oligoarginine peptides equipped with six glutamic acid residues and an anionic pyranine at the N-terminus is triggered upon addition...
The cell internalization of designed oligoarginine peptides equipped with six glutamic acid residues and an anionic pyranine at the N-terminus is triggered upon addition of a supramolecular host. This host binds specifically to the pyranine moiety, enabling the complex to traverse the cell membrane. Interestingly, none of the components, neither the host nor the guest, are able to cross the cell membrane on their own.
Topics: Animals; Anions; Cell Membrane; Chlorocebus aethiops; Macromolecular Substances; Molecular Structure; Vero Cells
PubMed: 27984855
DOI: 10.1021/jacs.6b11103 -
Analytical Chemistry Aug 2015We present here anion-exchange nanospheres as novel titration reagents for anions. The nanospheres contain a lipophilic cation for which the counterion is initially...
We present here anion-exchange nanospheres as novel titration reagents for anions. The nanospheres contain a lipophilic cation for which the counterion is initially Cl(-). Ion exchange takes place between Cl(-) in the nanospheres and a more lipophilic anion in the sample, such as ClO4(-) and NO3(-). Consecutive titration in the same sample solution for ClO4(-) and NO3(-) were demonstrated. As an application, the concentration of NO3(-) in spinach was successfully determined using this method.
Topics: Anions; Chemistry Techniques, Analytical; Nanospheres; Spinacia oleracea; Titrimetry
PubMed: 26201018
DOI: 10.1021/acs.analchem.5b01530 -
Dalton Transactions (Cambridge, England... Nov 2022Rotaxanes, which are composed of ring and axle components, are important interlocked molecules with wide applications such as molecular machines and switchable...
Rotaxanes, which are composed of ring and axle components, are important interlocked molecules with wide applications such as molecular machines and switchable catalysts. The construction of interlocked structures targeting anions is an important issue, as evidenced by the fact that anionic groups are usually abundant in many biomacromolecules. We now report an allosteric pseudomacrocyclic anion receptor as a ring that spontaneously generates a rotaxane in an auto-clipping way, which does not require the successive ring forming reaction like usual clipping, in the presence of an axle with an anionic station. We designed a linear ligand 1 bearing three anion recognition moieties, , one thiourea group at the centre and two urea groups near the 2,2'-bipyridine ends of 1. The complexation of 1 with Cu proceeded in an intramolecular manner that quantitatively led to a macrocyclic structure [1·Cu]. Compared to 1, the anion binding ability of [1·Cu] was significantly larger (positive allosteric effect) due to the macrocyclization arrangement of the three anion recognition moieties in a cyclic fashion and electrostatic interaction. In addition, the kinetically labile but thermodynamically stable coordination properties of the pseudomacrocyclic ring unit promoted the spontaneous rotaxane formation with a phosphate axle at room temperature.
Topics: Rotaxanes; Copper; Models, Molecular; Anions; Ligands
PubMed: 36317492
DOI: 10.1039/d2dt03331c