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Journal of Chromatography. A Jul 2022Aqueous microemulsions (MEs), where an oil coexists with water in the presence of the anionic surfactant sodium dodecyl sulphate (SDS), have been proposed as a solution...
Aqueous microemulsions (MEs), where an oil coexists with water in the presence of the anionic surfactant sodium dodecyl sulphate (SDS), have been proposed as a solution to decrease the amount of organic solvent in the mobile phase needed in reversed-phase liquid chromatography (RPLC). However, the oil phase of a typical ME is volatile, toxic and flammable, and although it is added in a small amount, it would be desirable to avoid it from an environmental perspective. This is the reason for the proposal of Peng et al. (J. Chromatogr. A 1499 (2017) 132‒139) to replace the oil in microemulsion liquid chromatography (MELC) by the apolar ionic liquid (IL) 1-hexyl-3-methylimidazolium hexafluorophosphate ([CCIM][PF]), to analyse neutral phenolic acids at acidic pH. Based on this report, an MELC procedure is here proposed for β-adrenoceptor antagonists, which are basic compounds where the dominant species is cationic. To verify the formation of MEs containing SDS and IL, and elucidate the interactions between the cationic basic compounds with the SDS anion, and the cation and anion in the IL, an extensive study was carried out with several methylimidazolium ILs containing the cations [CCIM], [CCIM], or [CCIM], combined with the anions Cl, BF, or PF, using 1-butanol as co-surfactant. The behaviour was compared with that observed in classical MELC with octane, micellar liquid chromatography with SDS and 1-propanol, and RPLC with mobile phases containing an IL and acetonitrile.
Topics: Anions; Chromatography, Liquid; Ionic Liquids; Oils; Surface-Active Agents; Water
PubMed: 35598540
DOI: 10.1016/j.chroma.2022.463142 -
International Journal of Molecular... Dec 2022A naphthalene imide () and a naphthalene () bearing two pyrrole units have been synthesized, respectively, as anion receptors. It was revealed by H NMR spectral studies...
A naphthalene imide () and a naphthalene () bearing two pyrrole units have been synthesized, respectively, as anion receptors. It was revealed by H NMR spectral studies carried out in CDCN that receptors and bind various anions via hydrogen bonds using both C-H and N-H donors. Compared with receptor , receptor shows higher affinity for the test anions because of the enhanced acidity of its pyrrole NH and naphthalene CH hydrogens by the electron-withdrawing imide substituent. Molecular mechanics computations demonstrate that the receptors contact the halide anions via only one of the two respective available N-H and C-H donors whereas they use all four donors for binding of the oxyanions such as dihydrogen phosphate and hydrogen pyrophosphate. Receptor , a push-pull conjugated system, displays a strong fluorescence centered at 625 nm, while receptor exhibits an emission with a maximum peak at 408 nm. In contrast, upon exposure of receptors and to the anions in question, their fluorescence was noticeably quenched particularly with relatively basic anions including F, HPO, HPO, and HCO.
Topics: Anions; Phosphates; Magnetic Resonance Spectroscopy; Hydrogen Bonding; Pyrroles
PubMed: 36613608
DOI: 10.3390/ijms24010163 -
Journal of Enzyme Inhibition and... Dec 2021Inorganic anions inhibit the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) generally by coordinating to the active site metal ion. Cyanate was reported as a... (Review)
Review
Inorganic anions inhibit the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) generally by coordinating to the active site metal ion. Cyanate was reported as a non-coordinating CA inhibitor but those erroneous results were subsequently corrected by another group. We review the anion CA inhibitors (CAIs) in the more general context of drug design studies and the discovery of a large number of inhibitor classes and inhibition mechanisms, including zinc binders (sulphonamides and isosteres, dithiocabamates and isosteres, thiols, selenols, benzoxaboroles, ninhydrins, etc.); inhibitors anchoring to the zinc-coordinated water molecule (phenols, polyamines, sulfocoumarins, thioxocoumarins, catechols); CAIs occluding the entrance to the active site (coumarins and derivatives, lacosamide), as well as compounds that bind outside the active site. All these new chemotypes integrated with a general procedure for obtaining isoform-selective compounds (the tail approach) has resulted, through the guidance of rigorous X-ray crystallography experiments, in the development of highly selective CAIs for all human CA isoforms with many pharmacological applications.
Topics: Anions; Carbonic Anhydrase Inhibitors; Carbonic Anhydrases; Coordination Complexes; Crystallography, X-Ray; Drug Design; Humans; Isoenzymes; Models, Molecular; Zinc
PubMed: 33615947
DOI: 10.1080/14756366.2021.1882453 -
Advances in Colloid and Interface... Jun 2014Most lipid components of cell membranes are either neutral, like cholesterol, or zwitterionic, like phosphatidylcholine and sphingomyelin. Very few lipids, such as... (Review)
Review
Most lipid components of cell membranes are either neutral, like cholesterol, or zwitterionic, like phosphatidylcholine and sphingomyelin. Very few lipids, such as sphingosine, are cationic at physiological pH. These generally interact only transiently with the lipid bilayer, and their synthetic analogs are often designed to destabilize the membrane for drug or DNA delivery. However, anionic lipids are common in both eukaryotic and prokaryotic cell membranes. The net charge per anionic phospholipid ranges from -1 for the most abundant anionic lipids such as phosphatidylserine, to near -7 for phosphatidylinositol 3,4,5 trisphosphate, although the effective charge depends on many environmental factors. Anionic phospholipids and other negatively charged lipids such as lipopolysaccharides are not randomly distributed in the lipid bilayer, but are highly restricted to specific leaflets of the bilayer and to regions near transmembrane proteins or other organized structures within the plane of the membrane. This review highlights some recent evidence that counterions, in the form of monovalent or divalent metal ions, polyamines, or cationic protein domains, have a large influence on the lateral distribution of anionic lipids within the membrane, and that lateral demixing of anionic lipids has effects on membrane curvature and protein function that are important for biological control.
Topics: Animals; Anions; Biophysical Phenomena; Humans; Lipid Bilayers; Membrane Microdomains; Membrane Proteins; Membranes, Artificial; Models, Biological; Phospholipids; Static Electricity; Surface Properties
PubMed: 24556233
DOI: 10.1016/j.cis.2014.01.016 -
International Journal of Molecular... Mar 2021We investigate dissociative electron attachment to tirapazamine through a crossed electron-molecule beam experiment and quantum chemical calculations. After the electron...
We investigate dissociative electron attachment to tirapazamine through a crossed electron-molecule beam experiment and quantum chemical calculations. After the electron is attached and the resulting anion reaches the first excited state, D, we suggest a fast transition into the ground electronic state through a conical intersection with a distorted triazine ring that almost coincides with the minimum in the D state. Through analysis of all observed dissociative pathways producing heavier ions (90-161 u), we consider the predissociation of an OH radical with possible roaming mechanism to be the common first step. This destabilizes the triazine ring and leads to dissociation of highly stable nitrogen-containing species. The benzene ring is not altered during the process. Dissociation of small anionic fragments (NO, CN, CN, NH, O) cannot be conclusively linked to the OH predissociation mechanism; however, they again do not require dissociation of the benzene ring.
Topics: Algorithms; Anions; Electrons; Models, Chemical; Radiation-Sensitizing Agents; Tirapazamine
PubMed: 33808887
DOI: 10.3390/ijms22063159 -
Molecules (Basel, Switzerland) May 2022In this article, we present fluorescent guanidiniocarbonyl-indoles as versatile oxo-anion binders. Herein, the guanidiniocarbonyl-indole (GCI) and...
In this article, we present fluorescent guanidiniocarbonyl-indoles as versatile oxo-anion binders. Herein, the guanidiniocarbonyl-indole (GCI) and methoxy-guanidiniocarbonyl-indole (MGCI) were investigated as ethylamides and compared with the well-known guanidiniocarbonyl-pyrrole (GCP) concerning their photophysical properties as well as their binding behavior towards oxo-anions. Hence, a variety of anionic species, such as carboxylates, phosphonates and sulfonates, have been studied regarding their binding properties with GCP, GCI and MGCI using UV-Vis titrations, in combination with the determination of the complex stoichiometry using the Job method. The emission properties were studied in relation to the pH value using fluorescence spectroscopy as well as the determination of the photoluminescence quantum yields (PLQY). Density functional theory (DFT) calculations were undertaken to obtain a better understanding of the ground-lying electronic properties of the investigated oxo-anion binders. Additionally, X-ray diffraction of GCP and GCI was conducted. We found that GCI and MGCI efficiently bind carboxylates, phosphonates and sulfonates in buffered aqueous solution and in a similar range as GCP (K ≈ 1000-18,000 M, in bis-tris buffer, pH = 6); thus, they could be regarded as promising emissive oxo-anion binders. They also exhibit a visible fluorescence with a sufficient PLQY. Additionally, the excitation and emission wavelength of MGCI was successfully shifted closer to the visible region of the electromagnetic spectrum by introducing a methoxy-group into the core structure, which makes them interesting for biological applications.
Topics: Anions; Arginine; Carboxylic Acids; Fluorescent Dyes; Indoles; Organophosphonates; Pyrroles
PubMed: 35566361
DOI: 10.3390/molecules27093005 -
Journal of the American Chemical Society Aug 2022Molecular photodynamics can be dramatically affected at the water/air interface. Probing such dynamics is challenging, with product formation often probed indirectly...
Molecular photodynamics can be dramatically affected at the water/air interface. Probing such dynamics is challenging, with product formation often probed indirectly through its interaction with interfacial water molecules using time-resolved and phase-sensitive vibrational sum-frequency generation (SFG). Here, the photoproduct formation of the phenolate anion at the water/air interface is probed directly using time-resolved electronic SFG and compared to transient absorption spectra in bulk water. The mechanisms are broadly similar, but 2 to 4 times faster at the surface. An additional decay is observed at the surface which can be assigned to either diffusion of hydrated electrons from the surface into the bulk or due to increased geminate recombination at the surface. These overall results are in stark contrast to phenol, where dynamics were observed to be 10 times faster and for which the hydrated electron was also a photoproduct. Our attempt to probe phenol showed no electron signal at the interface.
Topics: Anions; Phenols; Vibration; Water
PubMed: 35900260
DOI: 10.1021/jacs.2c04935 -
Sensors (Basel, Switzerland) Nov 2015The synthesis of four symmetrical compounds containing urea/thiourea and anthracene/nitrobenzene groups was optimized. N,N'-Di((anthracen-9-yl)-methylene)...
The synthesis of four symmetrical compounds containing urea/thiourea and anthracene/nitrobenzene groups was optimized. N,N'-Di((anthracen-9-yl)-methylene) thio-carbonohydrazide showed sensitive and selective binding ability for acetate ion among the studied anions. The presence of other competitive anions including F(-), H₂PO₄(-), Cl(-), Br(-) and I(-) did not interfere with the strong binding ability. The mechanism of the host-guest interaction was through multiple hydrogen bonds due to the conformational complementarity and higher basicity. A theoretical investigation explained that intra-molecular hydrogen bonds existed in the compound which could strengthen the anion binding ability. In addition, molecular frontier orbitals in molecular interplay were introduced in order to explain the red-shift phenomenon in the host-guest interaction process. Compounds based on thiourea and anthracene derivatives can thus be used as a chemosensor for detecting acetate ion in environmental and pharmaceutical samples.
Topics: Acetates; Anions; Anthracenes; Chemistry Techniques, Analytical; Models, Molecular; Thiourea
PubMed: 26561816
DOI: 10.3390/s151128166 -
International Journal of Molecular... Jun 2023Amyloid fibrils have immense potential to become the basis of modern biomaterials. The formation of amyloid fibrils in vitro strongly depends on the solvent properties....
Amyloid fibrils have immense potential to become the basis of modern biomaterials. The formation of amyloid fibrils in vitro strongly depends on the solvent properties. Ionic liquids (ILs), alternative solvents with tunable properties, have been shown to modulate amyloid fibrillization. In this work, we studied the impact of five ILs with 1-ethyl-3-methylimidazolium cation [EMIM] and anions of Hofmeisterseries hydrogen sulfate [HSO], acetate [AC], chloride [Cl], nitrate [NO], and tetrafluoroborate [BF] on the kinetics of insulin fibrillization and morphology, and the structure of insulin fibrils when applying fluorescence spectroscopy, AFM and ATR-FTIR spectroscopy. We found that the studied ILs were able to speed up the fibrillization process in an anion- and IL-concentration-dependent manner. At an IL concentration of 100 mM, the efficiency of the anions at promoting insulin amyloid fibrillization followed the reverse Hofmeister series, indicating the direct binding of ions with the protein surface. At a concentration of 25 mM, fibrils with different morphologies were formed, yet with similar secondary structure content. Moreover, no correlation with the Hofmeister ranking was detected for kinetics parameters. IL with the kosmotropic strongly hydrated [HSO] anion induced the formation of large amyloid fibril clusters, while the other kosmotropic anion [AC] along with [Cl] led to the formation of fibrils with similar needle-like morphologies to those formed in the IL-free solvent. The presence of the ILs with the chaotropic anions [NO] and [BF] resulted in longer laterally associated fibrils. The effect of the selected ILs was driven by a sensitive balance and interplay between specific protein-ion and ion-water interactions and non-specific long-range electrostatic shielding.
Topics: Ionic Liquids; Amyloid; Insulin; Anions; Solvents; Amyloidogenic Proteins; Insulin, Regular, Human; Cations
PubMed: 37298650
DOI: 10.3390/ijms24119699 -
Protein Science : a Publication of the... Jul 2002Data are reported for T(m), the temperature midpoint of the thermal unfolding curve, of ribonuclease A, versus pH (range 2-9) and salt concentration (range 0-1 M) for...
Data are reported for T(m), the temperature midpoint of the thermal unfolding curve, of ribonuclease A, versus pH (range 2-9) and salt concentration (range 0-1 M) for two salts, Na(2)SO(4) and NaCl. The results show stabilization by sulfate via anion-specific binding in the concentration range 0-0.1 M and via the Hofmeister effect in the concentration range 0.1-1.0 M. The increase in T(m) caused by anion binding at 0.1 M sulfate is 20 degrees at pH 2 but only 1 degree at pH 9, where the net proton charge on the protein is near 0. The 10 degrees increase in T(m) between 0.1 and 1.0 M Na(2)SO(4), caused by the Hofmeister effect, is independent of pH. A striking property of the NaCl results is the absence of any significant stabilization by 0.1 M NaCl, which indicates that any Debye screening is small. pH-dependent stabilization is produced by 1 M NaCl: the increase in T(m) between 0 and 1.0 M is 14 degrees at pH 2 but only 1 degree at pH 9. The 14 degree increase at pH 2 may result from anion binding or from both binding and Debye screening. Taken together, the results for Na(2)SO(4) and NaCl show that native ribonuclease A is stabilized at low pH in the same manner as molten globule forms of cytochrome c and apomyoglobin, which are stabilized at low pH by low concentrations of sulfate but only by high concentrations of chloride.
Topics: Anions; Chlorides; Enzyme Stability; Hot Temperature; Hydrogen-Ion Concentration; Protein Binding; Protein Denaturation; Ribonuclease, Pancreatic; Salts; Sulfates; Thermodynamics; Urea
PubMed: 12070329
DOI: 10.1110/ps.0205902