-
Accounts of Chemical Research Dec 2022Knowledge of the electronic structure of an aqueous solution is a prerequisite to understanding its chemical and biological reactivity and its response to light. One of...
Knowledge of the electronic structure of an aqueous solution is a prerequisite to understanding its chemical and biological reactivity and its response to light. One of the most direct ways of determining electronic structure is to use photoelectron spectroscopy to measure electron binding energies. Initially, photoelectron spectroscopy was restricted to the gas or solid phases due to the requirement for high vacuum to minimize inelastic scattering of the emitted electrons. The introduction of liquid-jets and their combination with intense X-ray sources at synchrotrons in the late 1990s expanded the scope of photoelectron spectroscopy to include liquids. Liquid-jet photoelectron spectroscopy is now an active research field involving a growing number of research groups. A limitation of X-ray photoelectron spectroscopy of aqueous solutions is the requirement to use solutes with reasonably high concentrations in order to obtain photoelectron spectra with adequate signal-to-noise after subtracting the spectrum of water. This has excluded most studies of organic molecules, which tend to be only weakly soluble. A solution to this problem is to use resonance-enhanced photoelectron spectroscopy with ultraviolet (UV) light pulses ( ≲ 6 eV). However, the development of UV liquid-jet photoelectron spectroscopy has been hampered by a lack of quantitative understanding of inelastic scattering of low kinetic energy electrons (≲5 eV) and the impact on spectral lineshapes and positions.In this Account, we describe the key steps involved in the measurement of UV photoelectron spectra of aqueous solutions: photoionization/detachment, electron transport of low kinetic energy electrons through the conduction band, transmission through the water-vacuum interface, and transport through the spectrometer. We also explain the steps we take to record accurate UV photoelectron spectra of liquids with excellent signal-to-noise. We then describe how we have combined Monte Carlo simulations of electron scattering and spectral inversion with molecular dynamics simulations of depth profiles of organic solutes in aqueous solution to develop an efficient and widely applicable method for retrieving true UV photoelectron spectra of aqueous solutions. The huge potential of our experimental and spectral retrieval methods is illustrated using three examples. The first is a measurement of the vertical detachment energy of the green fluorescent protein chromophore, a sparingly soluble organic anion whose electronic structure underpins its fluorescence and photooxidation properties. The second is a measurement of the vertical ionization energy of liquid water, which has been the subject of discussion since the first X-ray photoelectron spectroscopy measurement in 1997. The third is a UV photoelectron spectroscopy study of the vertical ionization energy of aqueous phenol which demonstrates the possibility of retrieving true photoelectron spectra from measurements with contributions from components with different concentration profiles.
Topics: Photoelectron Spectroscopy; Molecular Dynamics Simulation; Anions; Water; Ultraviolet Rays
PubMed: 36442085
DOI: 10.1021/acs.accounts.2c00523 -
Pharmacological Research Apr 2023Organic anion transporting polypeptide 2B1 (OATP2B1/SLCO2B1) facilitates uptake transport of structurally diverse endogenous and exogenous compounds. To investigate the...
Organic anion transporting polypeptide 2B1 (OATP2B1/SLCO2B1) facilitates uptake transport of structurally diverse endogenous and exogenous compounds. To investigate the roles of OATP2B1 in physiology and pharmacology, we established and characterized Oatp2b1 knockout (single Slco2b1 and combination Slco1a/1b/2b1) and humanized hepatic and intestinal OATP2B1 transgenic mouse models. While viable and fertile, these strains exhibited a modestly increased body weight. In males, unconjugated bilirubin levels were markedly reduced in Slco2b1 compared to wild-type mice, whereas bilirubin monoglucuronide levels were modestly increased in Slco1a/1b/2b1 compared to Slco1a/1b mice. Single Slco2b1 mice showed no significant changes in oral pharmacokinetics of several tested drugs. However, markedly higher or lower plasma exposure of pravastatin and the erlotinib metabolite OSI-420, respectively, were found in Slco1a/1b/2b1 compared to Slco1a/1b mice, while oral rosuvastatin and fluvastatin behaved similarly between the strains. In males, humanized OATP2B1 strains showed lower conjugated and unconjugated bilirubin levels than control Slco1a/1b/2b1-deficient mice. Moreover, hepatic expression of human OATP2B1 partially or completely rescued the impaired hepatic uptake of OSI-420, rosuvastatin, pravastatin, and fluvastatin in Slco1a/1b/2b1 mice, establishing an important role in hepatic uptake. Expression of human OATP2B1 in the intestine was basolateral and markedly reduced the oral availability of rosuvastatin and pravastatin, but not of OSI-420 and fluvastatin. Neither lack of Oatp2b1, nor overexpression of human OATP2B1 had any effect on fexofenadine oral pharmacokinetics. While these mouse models still have limitations for human translation, with additional work we expect they will provide powerful tools to further understand the physiological and pharmacological roles of OATP2B1.
Topics: Male; Mice; Humans; Animals; Bilirubin; Rosuvastatin Calcium; Fluvastatin; Pravastatin; Organic Anion Transporters; Mice, Transgenic; Peptides; Anions; Mice, Knockout
PubMed: 36907287
DOI: 10.1016/j.phrs.2023.106724 -
Chemphyschem : a European Journal of... Jan 2023Modulation and fine-tuning of the strength of weak interactions to bind anions are described in a series of synthetic receptors. The general design of the receptors...
Modulation and fine-tuning of the strength of weak interactions to bind anions are described in a series of synthetic receptors. The general design of the receptors includes both a urea motif and a tetrazine motif. The synthetic sequence towards three receptors is detailed. Impacts of H-bond strength and linker length between urea and tetrazine on chloride complexation are studied. Binding properties of the chloride anion are examined in both the ground and excited states using a panel of analytical methods (NMR spectroscopy, mass spectrometry, UV/Visible spectroscopies, and fluorescence). A ranking of the receptors by complexation strength has been determined, allowing a better understanding of the structure-properties relationship on these compounds.
Topics: Urea; Chlorides; Hydrogen Bonding; Anions
PubMed: 36111796
DOI: 10.1002/cphc.202200524 -
Pflugers Archiv : European Journal of... Dec 2023Optogenetic actuators are rapidly advancing tools used to control physiology in excitable cells, such as neurons and cardiomyocytes. In neuroscience, these tools have...
Optogenetic actuators are rapidly advancing tools used to control physiology in excitable cells, such as neurons and cardiomyocytes. In neuroscience, these tools have been used to either excite or inhibit neuronal activity. Cell type-targeted actuators have allowed to study the function of distinct cell populations. Whereas the first described cation channelrhodopsins allowed to excite specific neuronal cell populations, anion channelrhodopsins were used to inhibit neuronal activity. To allow for simultaneous excitation and inhibition, opsin combinations with low spectral overlap were introduced. BiPOLES (Bidirectional Pair of Opsins for Light-induced Excitation and Silencing) is a bidirectional optogenetic tool consisting of the anion channel Guillardia theta anion-conducting channelrhodopsin 2 (GtACR2 with a blue excitation spectrum and the red-shifted cation channel Chrimson. Here, we studied the effects of BiPOLES activation in cardiomyocytes. For this, we knocked in BiPOLES into the adeno-associated virus integration site 1 (AAVS1) locus of human-induced pluripotent stem cells (hiPSC), subjected these to cardiac differentiation, and generated BiPOLES expressing engineered heart tissue (EHT) for physiological characterization. Continuous light application activating either GtACR2 or Chrimson resulted in cardiomyocyte depolarization and thus stopped EHT contractility. In contrast, short light pulses, with red as well as with blue light, triggered action potentials (AP) up to a rate of 240 bpm. In summary, we demonstrate that cation, as well as anion channelrhodopsins, can be used to activate stem cell-derived cardiomyocytes with pulsed photostimulation but also to silence cardiac contractility with prolonged photostimulation.
Topics: Humans; Optogenetics; Channelrhodopsins; Myocytes, Cardiac; Anions; Cations
PubMed: 37863976
DOI: 10.1007/s00424-023-02869-x -
Photochemistry and Photobiology Mar 2022Polymethine fluorophores have facilitated the advance of biological and material sciences, due to their advantageous photophysical properties. However, the need to...
Polymethine fluorophores have facilitated the advance of biological and material sciences, due to their advantageous photophysical properties. However, the need to maintain a monomeric state can severely limit the utility and processability of dyes. High concentrations of fluorophore can lead to aggregation and negate the beneficial photophysical properties of monomers. Another concern is "crossing the cyanine limit" in which delocalization within the polymethine scaffold is broken, producing the presence of an asymmetric state diminishing its photophysical behavior. Herein, we attempt to overcome these limitations by exploring anion exchange on a cationic flavylium heptamethine scaffold. By increasing the size and hydrophobicity of the anion, we can effectively tune the degree of ion pairing within the polymethine dye. Interestingly, we found that the effect of ion pairing on photophysical properties was subtle for the flavylium heptamethine scaffold in comparison to the more commonly used indolenine cyanine dye. Utilizing larger weakly coordinating anions enabled solubility of the flavylium heptamethine fluorophore in nonpolar solvents, which could otherwise not be achieved. Even with more subtle effects than classic cyanine dyes, anion exchange on flavylium polymethine dyes holds potential for further manipulation of the properties of these low energy dyes.
Topics: Anions; Carbocyanines; Fluorescent Dyes; Solubility; Solvents
PubMed: 34592003
DOI: 10.1111/php.13531 -
Journal of Chromatography. A Nov 2022Obtaining reliable speciation data for evaluating dietary exposure, and increasing understanding of arsenic biochemistry in algae, are hindered by the availability of...
Obtaining reliable speciation data for evaluating dietary exposure, and increasing understanding of arsenic biochemistry in algae, are hindered by the availability of suitable standards of arsenosugars, the major species in these types of samples. Moreover, chemical syntheses of such compounds have been reported to be complex and tedious. The aim of this work was to investigate the feasibility of the anionic exchange SPE cartridges (SAX and WAX) as an easy and quick alternative for the isolation and preconcentration of arsenosugars. Two commercial silica-based SPE cartridges strong anion exchange sorbent (DSC-SAX) and weak anion exchange sorbent (DSC-NH2) were compared for the SPE of three arsenosugars (PO-Sug, SO-Sug and SO-Sug). The effect of pH, ionic strength, type of salt and elution solvent on the elution protocols of these arsenosugars are studied. Eluted solutions from SPE were analyzed by ICP-MS for total arsenic content and IC-ICP-MS for the study of arsenic speciation. The developed SPE procedure allows to obtain a solution containing the three arsenosugars isolated from other arsenic species with recoveries over 75% for SO-Sug and SO-Sug, whereas for PO-Sug were around 45%.
Topics: Arsenic; Arsenates; Monosaccharides; Solid Phase Extraction
PubMed: 36252409
DOI: 10.1016/j.chroma.2022.463549 -
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 -
Scientific Reports Apr 2023Microbial rhodopsins, a family of photoreceptive membrane proteins containing the chromophore retinal, show a variety of light-dependent molecular functions....
Microbial rhodopsins, a family of photoreceptive membrane proteins containing the chromophore retinal, show a variety of light-dependent molecular functions. Channelrhodopsins work as light-gated ion channels and are widely utilized for optogenetics, which is a method for controlling neural activities by light. Since two cation channelrhodopsins were identified from the chlorophyte alga Chlamydomonas reinhardtii, recent advances in genomic research have revealed a wide variety of channelrhodopsins including anion channelrhodopsins (ACRs), describing their highly diversified molecular properties (e.g., spectral sensitivity, kinetics and ion selectivity). Here, we report two channelrhodopsin-like rhodopsins from the Colpodellida alga Vitrella brassicaformis, which are phylogenetically distinct from the known channelrhodopsins. Spectroscopic and electrophysiological analyses indicated that these rhodopsins are green- and blue-sensitive pigments (λ = ~ 550 and ~ 440 nm) that exhibit light-dependent ion channeling activities. Detailed electrophysiological analysis revealed that one of them works as a monovalent anion (Cl, Br and NO) channel and we named it V. brassicaformis anion channelrhodopsin-2, VbACR2. Importantly, the absorption maximum of VbACR2 (~ 440 nm) is blue-shifted among the known ACRs. Thus, we identified the new blue-shifted ACR, which leads to the expansion of the molecular diversity of ACRs.
Topics: Channelrhodopsins; Ion Channels; Anions; Ion Transport; Electrophysiological Phenomena
PubMed: 37117398
DOI: 10.1038/s41598-023-34125-8 -
Molecules (Basel, Switzerland) Jun 2020Polyhydroborate salts represent the important class of energy materials attracting significant recent attention. Some of these salts exhibit promising hydrogen storage... (Review)
Review
Polyhydroborate salts represent the important class of energy materials attracting significant recent attention. Some of these salts exhibit promising hydrogen storage properties and/or high ionic conductivities favorable for applications as solid electrolytes in batteries. Two basic types of thermally activated atomic jump motion are known to exist in these materials: the reorientational (rotational) motion of complex anions and the translational diffusion of cations or complex anions. The present paper reviews recent progress in nuclear magnetic resonance (NMR) studies of both reorientational and diffusive jump motion in polyhydroborate salts. The emphasis is put on sodium and lithium -borates exhibiting high ionic conductivity and on borohydride-based systems showing extremely fast reorientational motion down to low temperatures. For these systems, we discuss the effects of order-disorder phase transitions on the parameters of reorientations and diffusive jumps, as well as the mechanism of low-temperature rotational tunneling.
Topics: Anions; Bromates; Cations; Magnetic Resonance Spectroscopy; Models, Molecular; Molecular Conformation; Salts
PubMed: 32604750
DOI: 10.3390/molecules25122940 -
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