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Biophysical Journal Jun 2024The light-gated anion channelrhodopsin GtACR1 is an important optogenetic tool for neuronal silencing. Its photochemistry, including its photointermediates, is poorly...
The light-gated anion channelrhodopsin GtACR1 is an important optogenetic tool for neuronal silencing. Its photochemistry, including its photointermediates, is poorly understood. The current mechanistic view presumes BR-like kinetics and assigns the open channel to a blue-absorbing L intermediate. Based on time-resolved absorption and electrophysiological data, we recently proposed a red-absorbing spectral form for the open channel state. Here, we report the results of a comprehensive kinetic analysis of the spectroscopic data combined with channel current information. The time evolutions of the spectral forms derived from the spectroscopic data are inconsistent with the single chain mechanism and are analyzed within the concept of parallel photocycles. The spectral forms partitioned into conductive and nonconductive parallel cycles are assigned to intermediate states. Rejecting reversible connections between conductive and nonconductive channel states leads to kinetic schemes with two independent conductive states corresponding to the fast- and slow-decaying current components. The conductive cycle is discussed in terms of a single cycle and two parallel cycles. The reaction mechanisms and reaction rates for the wild-type protein, the A75E, and the low-conductance D234N and S97E protein variants are derived. The parallel cycles of channelrhodopsin kinetics, its relation to BR photocycle, and the role of the M intermediate in channel closure are discussed.
Topics: Kinetics; Ion Channel Gating; Rhodopsin; Animals; Anions; Light; Models, Biological; Channelrhodopsins
PubMed: 38762755
DOI: 10.1016/j.bpj.2024.05.016 -
Chemical Science May 2024Hydrogen bond (H-bond) network connectivity in electric double layers (EDLs) is of paramount importance for interfacial HER/HOR electrocatalytic processes. However, it...
Hydrogen bond (H-bond) network connectivity in electric double layers (EDLs) is of paramount importance for interfacial HER/HOR electrocatalytic processes. However, it remains unclear whether the cation-specific effect on H-bond network connectivity in EDLs exists. Herein, we report simulation evidence from molecular dynamics that cations at Pt(111)/water interfaces can tune the structure and the connectivity of H-bond networks in EDLs. As the surface charge density becomes more negative, we show that the connectivity of the H-bond networks in EDLs of the Na and Ca systems decreases markedly; in stark contrast, the connectivity of the H-bond networks in EDLs of the Mg system increases slightly. Further analysis revealed that the interplay between the hydration of cations and the interfacial water structure plays a key role in the connectivity of H-bond networks in EDLs. These findings highlight the key roles of cations in EDLs and electrocatalysis.
PubMed: 38756806
DOI: 10.1039/d3sc06904d -
Nature Communications May 2024Optical detection of magnetic field is appealing for integrated photonics; however, the light-matter interaction is usually weak at low field. Here we observe that the...
Optical detection of magnetic field is appealing for integrated photonics; however, the light-matter interaction is usually weak at low field. Here we observe that the photoluminescence (PL) decreases by > 40% at 10 mT in rubrene microcrystals (RMCs) prepared by a capillary-bridge assembly method. The giant magneto-PL (MPL) relies on the singlet-triplet conversion involving triplet-triplet pairs, through the processes of singlet fission (SF) and triplet fusion (TF) during radiative decay. Importantly, the size of RMCs is critical for maximizing MPL as it influences on the photophysical processes of spin state conversion. The SF/TF process is quantified by measuring the prompt/delayed PL with time-resolved spectroscopies, which shows that the geminate SF/TF associated with triplet-triplet pairs are responsible for the giant MPL. Furthermore, the RMC-based magnetometer is constructed on an optical chip, which takes advantages of remarkable low-field sensitivity over a broad range of frequencies, representing a prototype of emerging opto-spintronic molecular devices.
PubMed: 38734699
DOI: 10.1038/s41467-024-48464-1 -
Chemical Science May 2024Ligand-to-metal charge transfer (LMCT) excited states are capable of undergoing a wide array of photochemical reactions, yet receive minimal attention compared to other... (Review)
Review
Ligand-to-metal charge transfer (LMCT) excited states are capable of undergoing a wide array of photochemical reactions, yet receive minimal attention compared to other charge transfer excited states. This work provides general criteria for designing transition metal complexes that exhibit low energy LMCT excited states and routes to drive photochemistry from these excited states. General design principles regarding metal identity, oxidation state, geometry, and ligand sets are summarized. Fundamental photoreactions from these states including visible light-induced homolysis, excited state electron transfer, and other photoinduced chemical transformations are discussed and key design principles for enabling these photochemical reactions are further highlighted. Guided by these fundamentals, this review outlines critical considerations for the future design and application of coordination complexes with LMCT excited states.
PubMed: 38725519
DOI: 10.1039/d3sc05268k -
Chemical Science May 2024Ferrocene and its derivatives have fascinated chemists for more than 70 years, not least due to the analogies with the properties of benzene. Despite these similarities,...
Ferrocene and its derivatives have fascinated chemists for more than 70 years, not least due to the analogies with the properties of benzene. Despite these similarities, the obvious difference between benzene and ferrocene is the presence of an iron ion and hence the availability of d-orbitals for properties and reactivity. Phenylnitrene with its rich photochemistry can be considered an analogue of nitrenoferrocene. As with most organic and inorganic nitrenes, nitrenoferrocene can be obtained by irradiating the azide precursor. We study the photophysical and photochemical processes of dinitrogen release from 1,1'-diazidoferrocene to form 1-azido-1'-nitrenoferrocene with UV-pump-mid-IR-probe transient absorption spectroscopy and time-dependent density functional theory calculations including spin-orbit coupling. An intermediate with a bent azide moiety is identified that is pre-organised for dinitrogen release a low-lying transition state. The photochemical decay paths on the singlet and triplet surfaces including the importance of spin-orbit coupling are discussed. We compare our findings with the processes discussed for photochemical dinitrogen activation and highlight implications for the photochemistry of azides more generally.
PubMed: 38725494
DOI: 10.1039/d4sc00883a -
Chemical Science May 2024Designing molecules with donor-acceptor-donor (D-A-D) architecture plays an important role in obtaining second near-infrared region (NIR-II, 1000-1700 nm) fluorescent...
Designing molecules with donor-acceptor-donor (D-A-D) architecture plays an important role in obtaining second near-infrared region (NIR-II, 1000-1700 nm) fluorescent dyes for biomedical applications; however, this always comes with a challenge due to very limited electronic acceptors. On the other hand, to endow NIR-II fluorescent dyes with combined therapeutic applications, trivial molecular design is indispensable. Herein, we propose a pyrazine-based planar electronic acceptor with a strong electron affinity, which can be used to develop NIR-II fluorescent dyes. By structurally attaching two classical triphenylamine electronic donors to it, a basic D-A-D module, namely Py-NIR, can be generated. The planarity of the electronic acceptor is crucial to induce a distinct NIR-II emission peaking at ∼1100 nm. The unique construction of the electronic acceptor can cause a twisted and flexible molecular conformation by the repulsive effect between the donors, which is essential to the aggregation-induced emission (AIE) property. The tuned intramolecular motions and twisted D-A pair brought by the electronic acceptor can lead to a remarkable photothermal conversion with an efficiency of 56.1% and induce a type I photosensitization with a favorable hydroxyl radical (OH˙) formation. Note that no additional measures are adopted in the molecular design, providing an ideal platform to realize NIR-II fluorescent probes with synergetic functions based on such an acceptor. Besides, the nanoparticles of Py-NIR can exhibit excellent NIR-II fluorescence imaging towards orthotopic 4T1 breast tumors in living mice with a high sensitivity and contrast. Combined with photothermal imaging and photoacoustic imaging caused by the thermal effect, the imaging-guided photoablation of tumors can be well performed. Our work has created a new opportunity to develop NIR-II fluorescent probes for accelerating biomedical applications.
PubMed: 38725487
DOI: 10.1039/d3sc06886b -
Journal of Colloid and Interface Science Sep 2024The covalent bonding of a ruthenium bipyridine complex derivative with the aromatic network of single walled carbon nanotubes (SWNT) through a stepwise protocol is...
The covalent bonding of a ruthenium bipyridine complex derivative with the aromatic network of single walled carbon nanotubes (SWNT) through a stepwise protocol is presented, thus yielding the sample SWNT-Ru. To do that, an-amino decorated phenanthroline is bonded to the nanotube by means of the diazonium chemistry protocol, providing anchoring points for discrete organometallic units as depicted by the solid characterization techniques employed. The hybrid material, able to emit upon excitation, is active in the visible light-driven photocatalytic oxidation of organic sulfides to sulfoxides. SWNT-Ru presents a wide scope being able to convert more than 10 substrates with different characteristics, including added-value chemicals, with a stable performance over more than 6 cycles without metal leaching and enhanced activity compared to related homogeneous complexes. A versatile character is also demonstrated since this hybrid catalyst follows both possible photooxidation mechanisms.
PubMed: 38723538
DOI: 10.1016/j.jcis.2024.05.018 -
Frontiers in Chemistry 2024Since the dawn of photochemistry 150 years ago, photoreactions have been conducted under polychromatic light. However, despite the pivotal role that photokinetics should...
Since the dawn of photochemistry 150 years ago, photoreactions have been conducted under polychromatic light. However, despite the pivotal role that photokinetics should naturally play for such reactive photosystems, the literature lacks a comprehensive description of that area. Indeed, one fails to identify explicit model integrated rate laws for these reactions, a characteristic type for their kinetic behavior, or their kinetic order. In addition, there is no consensus in the community on standardized investigative tools to evaluate the reactivity of these photosystems, nor are there venues for the discussion of such photokinetic issues. The present work is a contribution addressing some of these knowledge gaps. It proposes an unprecedented general formula capable of mapping out the kinetic traces of photoreactions under polychromatic light irradiation. This article quantitatively discusses several reaction situations, including the effects of initial reactant concentration and the presence of spectator molecules. It also develops a methodology for standardizing actinometers and defines and describes both the spectral range of highest reactivity and the photonic yield. The validity of the model equation has been proven by comparing its results to both theoretical counterparts and those generated by fourth-order Runge-Kutta numerical calculations. For the first time, a confirmation of the -order character of the kinetics under polychromatic light was established.
PubMed: 38711947
DOI: 10.3389/fchem.2024.1367276 -
Inorganic Chemistry May 2024Photochemical ligand release from metal complexes may be exploited in the development of novel photoactivated chemotherapy agents for the treatment of cancer and other...
Photochemical ligand release from metal complexes may be exploited in the development of novel photoactivated chemotherapy agents for the treatment of cancer and other diseases. Highly intriguing photochemical behavior is reported for two ruthenium(II) complexes bearing conformationally flexible 1,2,3-triazole-based ligands incorporating a methylene spacer to form 6-membered chelate rings. [Ru(bpy)(pictz)] () and [Ru(bpy)(btzm)] () (bpy = 2,2'-bipyridyl; pictz = 1-(picolyl)-4-phenyl-1,2,3-triazole; btzm = bis(4-phenyl-1,2,3-triazol-4-yl)methane) exhibit coordination by the triazole ring through the less basic N2 atom as a consequence of chelation and readily undergo photochemical release of the pictz and btzm ligands (ϕ = 0.079 and 0.091, respectively) in acetonitrile solution to form -[Ru(bpy)(NCMe)] () in both cases. Ligand-loss intermediates of the form [Ru(bpy)(κ-pictz or κ-btzm)(NCCD)] are detected by H NMR spectroscopy and mass spectrometry. Photolysis of yields three ligand-loss intermediates with monodentate pictz ligands, two of which form through simple decoordination of either the pyridine or triazole donor with subsequent solvent coordination ( and , respectively). The third intermediate, shown to be able to form photochemically directly from , arises through linkage isomerism in which the monodentate pictz ligand is coordinated by the triazole N3 atom () with a comparable ligand-loss intermediate with an N3-bound κ-btzm ligand also observed for .
PubMed: 38701516
DOI: 10.1021/acs.inorgchem.4c00251 -
Pharmaceutics Mar 2024Leishmaniasis is a group of parasitic diseases with the potential to infect more than 1 billion people; however, its treatment is still old and inadequate. In order to...
Leishmaniasis is a group of parasitic diseases with the potential to infect more than 1 billion people; however, its treatment is still old and inadequate. In order to contribute to changing this view, this work consisted of the development of complexes derived from M metal ions with thioureas, aiming to obtain potential leishmanicidal agents. The thiourea ligands (HL) were obtained by reactions of -toluenesulfohydrazide with R-isothiocyanates and were used in complexation reactions with Ag and Au, leading to the formation of complexes of composition [M(HL)]X (M = Ag or Au; X = NO or Cl). All compounds were characterized by FTIR, H NMR, UV-vis, emission spectroscopy and elemental analysis. Some representatives were additionally studied by ESI-MS and single-crystal XRD. Their properties were further analyzed by DFT calculations. Their cytotoxicity on Vero cells and the extracellular leishmanicidal activity on and cells were evaluated. Additionally, the interaction of the complexes with the Old Yellow enzyme of the (LbOYE) was examined. The biological tests showed that some compounds present remarkable leishmanicidal activity, even higher than that of the standard drug Glucantime, with different selectivity for the two species of . Finally, the interaction studies with LbOYE revealed that this enzyme could be one of their biological targets.
PubMed: 38675113
DOI: 10.3390/pharmaceutics16040452