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Given its pivotal role in modulating various pathological processes, precise measurement of nitric oxide (âNO) levels in physiological solutions is imperative. The key techniques include the ozone-based chemiluminescence (CL) reactions, amperometric âNO sensing, and Griess assay, each with its advantages and drawbacks. In this study, a hemin/H2O2/luminol CL reaction was employed for accurately detecting âNO in diverse solutions. We investigated how the luminescence kinetics was influenced by âNO from two donors, nitrite and peroxynitrite, while also assessing the impact of culture medium components and reactive species quenchers. Furthermore, we experimentally and theoretically explored the mechanism of hemin oxidation responsible for the initiation of light generation. Although both hemin and âNO enhanced the H2O2/luminol-based luminescence reactions with distinct kinetics, hemin's interference with âNO/peroxynitrite- modulated their individual effects. Leveraging the propagated signal due to hemin, the âNO levels in solution were estimated, observing parallel changes to those detected via amperometric detection in response to varying concentrations of the âNO-donor. The examined reactions aid in comprehending the mechanism of âNO/hemin/H2O2/luminol interactions and how these can be used for detecting âNO in solution with minimal sample size demands. Moreover, the selectivity across different solutions can be improved by incorporating certain quenchers for reactive species into the reaction.
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Hemina , Sondas Moleculares , Óxido Nítrico , Hemina/química , Peróxido de Hidrógeno/química , Peróxido de Hidrógeno/análisis , Cinética , Mediciones Luminiscentes , Luminol/química , Sondas Moleculares/química , Óxido Nítrico/análisis , Oxidación-Reducción , Ácido Peroxinitroso/análisis , Ácido Peroxinitroso/química , SolucionesRESUMEN
Graphitic carbon nitride (g-CN) is a transition metal free semiconductor that mediates a variety of photocatalytic reactions. Although photoinduced electron transfer is often postulated in the mechanism, proton-coupled electron transfer (PCET) is a more favorable pathway for substrates possessing X-H bonds. Upon excitation of an (sp2 )N-rich structure of g-CN with visible light, it behaves as a photobase-it undergoes reductive quenching accompanied by abstraction of a proton from a substrate. The results of modeling allowed us to identify active sites for PCET-the 'triangular pockets' on the edge facets of g-CN. We employ excited state PCET from the substrate to g-CN to selectively cleavethe endo-(sp3 )C-H bond in oxazolidine-2-ones followed by trapping the radical with O2 . This reaction affords 1,3-oxazolidine-2,4-diones. Measurement of the apparent pKa value and modeling suggest that g-CN excited state can cleave X-H bonds that are characterized by bond dissociation free energy (BDFE) ≈100â kcal mol-1 .
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Multiplex optical detection in live cells is challenging due to overlapping signals and poor signal-to-noise associated with some chemical reporters. To address this, the application of spectral phasor analysis to stimulated Raman scattering (SRS) microscopy for unmixing three bioorthogonal Raman probes within cells is reported. Triplex detection of a metallacarborane using the B-H stretch at 2480-2650â cm-1 , together with a bis-alkyne and deuterated fatty acid can be achieved within the cell-silent region of the Raman spectrum. When coupled to imaging in the high-wavenumber region of the cellular Raman spectrum, nine discrete regions of interest can be spectrally unmixed from the hyperspectral SRS dataset, demonstrating a new capability in the toolkit of multiplexed Raman imaging of live cells.
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Ácidos Grasos , Microscopía Óptica no Lineal , Microscopía Óptica no Lineal/métodos , Microscopía , Espectrometría Raman/métodosRESUMEN
Hemin and heme-peroxidases have been considered essential catalysts for the nitrite/hydrogen peroxide (H2O2)-mediated protein nitration in vitro, understood as one of the main pathways for protein modification in biological systems. However, the role of nitric oxide (âNO) in the heme/hemin-induced protein nitration has not been studied in-depth. This is despite its reductive nitrosylating effects following binding to hemin and the possible involvement of the reactive nitrogen species in the nitration of various functional proteins. Here, the âNO-binding affinity of hemin has been studied along with the influence of âNO on the internalization of hemin into MDA-MB-231 cells and the accompanying changes in the profile of intracellular nitrated proteins. Moreover, to further understand the mechanism involved, bovine serum albumin (BSA) nitration was studied after treatment with hemin and âNO, with an investigation of the effects of pH of the reaction medium, generation of H2O2, and the oxidation of the tyrosine residues as the primary sites for the nitration. We demonstrated that hemin nitrosylation enhanced its cellular uptake and induced the one-electron oxidation and nitration of different intracellular proteins along with its âNO-scavenging efficiency. Moreover, the hemin/NO-mediated BSA nitration was proved to be dependent on the concentration of âNO and the pH of the reaction medium, with a vital role being played by the scavenging effects of protein for the free hemin molecules. Collectively, our results reaffirm the involvement of hemin and âNO in the nitration mechanism, where the nitrosylation products can induce protein nitration while promoting the effects of the components of the nitrite/H2O2-mediated pathway.
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Hemina , Nitritos , Hemina/química , Hemina/metabolismo , Peróxido de Hidrógeno/metabolismo , Óxido Nítrico , Nitritos/metabolismo , Albúmina Sérica Bovina/química , Tirosina/químicaRESUMEN
Nitric oxide (â¢NO) is one of the prominent free radicals, playing a pivotal role in breast cancer progression. Hyaluronic acid (HA) plays an essential role in neutralizing free radicals in tumor tissues. However, its interactions with nitric oxide have not been thoroughly investigated. Hence, this study attempts to understand the mechanism of these interactions and the different effects on the intracellular â¢NO levels and migration of breast cancer cells. The affinity of HA to scavenge â¢NO was investigated alongside the accompanying changes in specific physico-chemical properties and the further effects on the â¢NO-induced attachment and migration of the breast cancer cell lines, MDA-MB-231 and HCC1806. The reaction of the nitrogen dioxide radical, formed via â¢NO/O2 interactions, with HA initiated a series of oxidative reactions, which, in the presence of â¢NO, induce the fragmentation of the polymeric chains. Furthermore, these interactions were found to hinder the NO-induced migration of cancer cells. However, the NO-induced HA modification/fragmentation was inhibited in the presence of hemin, a NO-scavenging compound. Collectively, these results help toward understanding the involvement of HA in the â¢NO-induced cell migration and suggest the possible modification of HA, used as one of the main materials in different biomedical applications.
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Neoplasias de la Mama , Ácido Hialurónico , Línea Celular Tumoral , Movimiento Celular , Femenino , Humanos , Receptores de Hialuranos/metabolismo , Ácido Hialurónico/química , Óxido NítricoRESUMEN
Ring-fused benzimidazolequinones are well-known anti-tumour agents, but dimeric ring-fused adducts are new. The alicyclic [1,2-a] ring-fused dimethoxybenzimidazole-benzimidazolequinone (DMBBQ) intermediate allows late-stage functionalization of bis-p-benzimidazolequinones. DMBBQs are chlorinated and brominated at the p-dimethoxybenzene site using nontoxic sodium halide and Oxone in HFIP/water. X-ray crystallography is used to rationalize site preference in terms of the discontinuity in conjugation in the DMBBQ system. Quinone formation occurs by increasing in situ halogen generation and water. Conversely, radical trifluoromethylation occurs at the quinone of the DMBBQ.
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The complex [Ru(bpy)2 L](2+) , where bpy=2,2'-bipyridine, L=4-(phenylethynyl)-2,2'-bipyridine, was prepared in its racemic and resolved forms (Δ and Λ). The phenylethynyl unit on the bipyridine for the complex acts as a binding site for α-cyclodextrin in water (1:1 complex, K=3390â L mol(-1) ) or ß-cyclodextrin (2:1 complex, K1 =887â L mol(-1) , K2 =8070â L mol(-1) ). The presence of the cyclodextrin provides partial protection to the complex under light-activated water oxidation conditions.
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A fine control of the pirouetting motion of rotaxanes was achieved by using a series of metallabisdicarbollides. The latter were used as anions in the protonated form of benzylic amide macrocycle-containing fumaramide rotaxanes. The present paper discusses the synthesis and the structural and dynamic characterizations of the first examples of anionic boron cluster-containing rotaxanes. To study the dynamic properties of such molecules, the pirouetting rate of the weakly coordinating boron cluster-containing rotaxanes with the more strongly coordinating trifluoroacetate anion (TFA(-)), which would form a close ion pair with the macrocycle, was measured using the exchange spectroscopy NMR technique. Our hypothesis was that the stronger the ion pair the lower the rate of rotation due to the presence of a bigger volume of solvent to be moved. The anion would act as an anchor for the pirouetting motion. Indeed, the results show the expected trend: the rotaxane with the closely coordinating TFA(-) anion pirouettes most slowly, and the most weakly coordinating hexabromoderivative of cobaltabisdicarbollide pirouettes the fastest.
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The compounds [N(CH3)4][3,3'-Co(8-(p-C6H4C2H3)-1,2-C2B9H10)(1',2'-C2B9H11)], [N(CH3)4][3,3'-Co(8-(p-C6H4CHO)-1,2-C2B9H10)(1',2'-C2B9H11)], and [N(CH3)4][3,3'-Co(8-(m-C6H4CHO)-1,2-C2B9H10)(1',2'-C2B9H11)] were synthesized using an easy methodology, in very good yields and large quantities, which are important requisites to be employed as starting reagents. They have been fully characterized by elemental analysis, IR, NMR, and MALDI-TOF-MS, and the crystal structures of [N(CH3)4][3,3'-Co(8-(p-C6H4C2H3)-1,2-C2B9H10)(1',2'-C2B9H11)] and [N(CH3)4][3,3'-Co(8-(p-C6H4CHO)-1,2-C2B9H10)(1',2'-C2B9H11)] were elucidated by single-crystal X-ray diffraction. These compounds, having terminal formyl and vinyl functional groups, are suitable platforms to involve the aromatic cobaltabisdicarbollide unit into extended π-conjugated systems. It is expected that these synthons will facilitate the applicability of metallacarboranes in a wide variety of different fields, where π-conjugated systems are needed to keep electronic communication.
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Due to its role as a free radical signal-transducing agent with a short lifespan, precise measurement of nitric oxide (âNO) levels presents significant challenges. Various analytical techniques offer distinct advantages and disadvantages for âNO detection. This research aims to simplify the detection process by developing a hydrogel system using iron(III)-protoporphyrin IX (hemin)-loaded hyaluronan for the detection of âNO in solution. Various hydrogel formulations were created, and the effects of their components on hydrogel-supported luminol chemiluminescence (CL) kinetics, radical scavenging, and physicochemical properties were analysed through factorial analysis. The candidate formulations were then evaluated using two âNO donors. An increase in the degree of crosslinking in unloaded formulations enhanced interactions with the CL reaction components, hydrogen peroxide (H2O2) and luminol, thereby affecting light generation. However, hemin loading negated these effects, resulting in more prominent luminescence kinetics in formulations with lower crosslinking degrees. Similarly, âNO influenced the kinetics differently, interacting with both the CL reaction and hydrogel components. Hemin-loaded formulations exhibited enhanced signal propagation when exposed to âNO, followed by H2O2 and luminol, whereas reversing the order of addition inhibited this propagation. The magnitude of these luminescence changes depended on the type and concentration of the âNO donor, demonstrating greater sensitivity to âNO levels compared to amperometric sensing. These findings suggest that the studied hydrogel platform has potential for the facile and accurate detection of âNO in solution, requiring minimal sample sizes.
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Ácido Hialurónico , Hidrogeles , Mediciones Luminiscentes , Luminol , Óxido Nítrico , Protoporfirinas , Luminol/química , Óxido Nítrico/análisis , Óxido Nítrico/química , Protoporfirinas/química , Ácido Hialurónico/química , Hidrogeles/química , Mediciones Luminiscentes/métodos , Peróxido de Hidrógeno/química , Peróxido de Hidrógeno/análisis , Luminiscencia , Soluciones , CinéticaRESUMEN
Hemin triggers intracellular reactive oxygen species (ROS) accumulation and enhances heme oxygenase-1 (HOX-1) activity, indicating its potential as an anticancer agent, though precise control of its intracellular levels is crucial. The study explores the impact of hemin and its derivatives, hemin-tyrosine, and hemin-styrene (H-Styr) conjugates on migration, HOX-1 expression, specific apoptosis markers, mitochondrial functions, and ROS generation in breast cancer cells. Molecular docking and dynamics simulations were used to understand the interactions among HOX-1, heme, and the compounds. Hemin outperforms its derivatives in inducing HOX-1 expression, exhibiting pro-oxidative effects and reducing cell migration. Molecular simulations show that heme binds favorably to HOX-1, followed by the other compounds, primarily through van der Waals and electrostatic forces. However, only van der Waals forces determine the H-Styr complexation. These interactions, influenced by metalloporphyrin characteristics, provide insights into HOX-1 regulation and ROS generation, potentially guiding the development of breast cancer therapies targeting oxidative stress.
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Recentstudies toward finding more efficient ruthenium metalloligands for photocatalysis applications have shown that the derivatives of the linear [Ru(dqp)2]2+ (dqp: 2,6-di(quinolin-8-yl)-pyridine) complexes hold significant promise due to their extended emission lifetime in the µs time scale while retaining comparable redox potential, extinction coefficients, and absorption profile in the visible region to [Ru(bpy)3]2+ (bpy: 2,2'-bipyridine) and [Ru(tpy)2]2+ (tpy: 2,2':6',2â³-terpyridine) complexes. Nevertheless, its photostability in aqueous solution needs to be improved for its widespread use in photocatalysis. Carbon-based supports have arisen as potential solutions for improving photostability and photocatalytic activity, yet their effect greatly depends on the interaction of the metal complex with the support. Herein, we present a strategy for obtaining Ru-polypyridyl complexes covalently linked to aminated reduced graphene oxide (rGO) to generate novel materials with long-term photostability and increased photoactivity. Specifically, the hybrid Ru(dqp)@rGO system has shown excellent photostable behavior during 24 h of continual irradiation, with an enhancement of 10 and 15% of photocatalytic dye degradation in comparison with [Ru(dqp)2]2+ and Ru(tpy)@rGO, respectively, as well as remarkable recyclability. The presented strategy corroborates the potential of [Ru(dqp)2]2+ as an interesting photoactive molecule to produce more advantageous light-active materials by covalent attachment onto carbon-based supports.
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Dyad molecules containing the 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz) ligand with general formula [(tpy)Ru(µ-tppz)Ru(X)(L-L)](n+) (X=Cl, CF3COO, or H2O; L-L=2,2'-bipyridine (bpy) or 3,5-bis(2-pyridyl)pyrazole (Hbpp); tpy=2,2':6',2"-terpyridine) have been prepared, purified, and isolated. The complexes have been characterized by analytical and spectroscopic techniques and by X-ray diffraction analysis for two of them. Additionally, full electrochemical characterization based on cyclic voltammetry, differential pulse voltammetry, and square wave voltammetry has been also performed. The pH dependence of the redox couples for the aqua complexes have also been studied and their corresponding Pourbaix diagrams drawn. Furthermore, their capacity to catalytically oxidize organic substrates, such as alcohols, alkenes, and sulfides, has been carried out chemically, electrochemically, and photochemically. Finally, their capacity to behave as water oxidation catalysts has also been tested.
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This tutorial review will deal with the study of metallacarboranes and their interactions with other molecules from a theoretical point of view. This contribution is devoted to guide experimental chemists through calculations that some years ago were reserved to theoretical specialists. The widespread availability of fast computers enables nowadays studies of complex compounds (e.g. metallacarboranes) from different perspectives including simulation of NMR, infrared or Raman spectra and calculation of other properties such as atomic charges or inter-/intramolecular interactions. The insights gained on the basis of theoretical calculations are crucial for either finding novel or improving existing applications of metallacarboranes. For example, in the case of enzyme inhibitors, the interactions of the metallacarboranes with the surrounding protein and how the interaction affects the efficiency are difficult problems to study experimentally. The use of theoretical tools can provide a detailed understanding of the physico-chemical basis of the interactions and thus offers a chance to control the overall process.
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The enhanced expression of nitric oxide (â¢NO) synthase predicts triple-negative breast cancer outcome and its resistance to different therapeutics. Our earlier work demonstrated the efficiency of hemin to scavenge the intra- and extracellular â¢NO, proposing its potency as a therapeutic agent for inhibiting cancer cell migration. In continuation, the present work evaluates the effects of â¢NO on the migration of MDA-MB-231 cells and how hemin modulates the accompanied cellular behavior, focusing on the corresponding expression of cellular glycoproteins, migration-associated markers, and mitochondrial functions. We demonstrated for the first time that while â¢NO induced cell migration, hemin contradicted that by â¢NO-scavenging. This was in combination with modulation of the â¢NO-enhanced glycosylation patterns of cellular proteins with inhibition of the expression of specific proteins involved in the epithelial-mesenchymal transition. These effects were in conjunction with changes in the mitochondrial functions related to both â¢NO, hemin, and its nitrosylated product. Together, these results suggest that hemin can be employed as a potential anti-migrating agent targeting â¢NO-scavenging and regulating the expression of migration-associated proteins.
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The industrial adoption of microbial electrosynthesis (MES) is hindered by high overpotentials deriving from low electrolyte conductivity and inefficient cell designs. In this study, a mixed microbial consortium originating from an anaerobic digester operated under saline conditions (â¼13 g L-1 NaCl) was adapted for acetate production from bicarbonate in galvanostatic (0.25 mA cm-2) H-type cells at 5, 10, 15, or 20 g L-1 NaCl concentration. The acetogenic communities were successfully enriched only at 5 and 10 g L-1 NaCl, revealing an inhibitory threshold of about 6 g L-1 Na+. The enriched planktonic communities were then used as inoculum for 3D printed, three-chamber cells equipped with a gas diffusion biocathode. The cells were fed with CO2 gas and operated galvanostatically (0.25 or 1.00 mA cm-2). The highest production rate of 55.4 g m-2 d-1 (0.89 g L-1 d-1), with 82.4% Coulombic efficiency, was obtained at 5 g L-1 NaCl concentration and 1 mA cm-2 applied current, achieving an average acetate production of 44.7 kg MWh-1. Scanning electron microscopy and 16S rRNA sequencing analysis confirmed the formation of a cathodic biofilm dominated by Acetobacterium sp. Finally, three 3D printed cells were hydraulically connected in series to simulate an MES stack, achieving three-fold production rates than with the single cell at 0.25 mA cm-2. This confirms that three-chamber MES cells are an efficient and scalable technology for CO2 bio-electro recycling to acetate and that moderate saline conditions (5 g L-1 NaCl) can help reduce their power demand while preserving the activity of acetogens.
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It has been shown by electrospray ionization-ion-trap mass spectrometry that B(12)I(12)(2-) converts to an intact B(12) cluster as a result of successive stripping of single iodine radicals or ions. Herein, the structure and stability of all intermediate B(12)I(n)(-) species (n=11 to 1) determined by means of first-principles calculations are reported. The initial predominant loss of an iodine radical occurs most probably via the triplet state of B(12)I(12)(2-), and the reaction path for loss of an iodide ion from the singlet state crosses that from the triplet state. Experimentally, the boron clusters resulting from B(12)I(12)(2-) through loss of either iodide or iodine occur at the same excitation energy in the ion trap. It is shown that the icosahedral B(12) unit commonly observed in dodecaborate compounds is destabilized while losing iodine. The boron framework opens to nonicosahedral structures with five to seven iodine atoms left. The temperature of the ions has a considerable influence on the relative stability near the opening of the clusters. The most stable structures with five to seven iodine atoms are neither planar nor icosahedral.
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With photovoltaics becoming a mature, commercially feasible technology, society is willing to allocate resources for developing and deploying new technologies based on using solar light. Analysis of projects supported by the European Commission in the past decade indicates exponential growth of funding to photocatalytic (PC) and photoelectrocatalytic (PEC) technologies that aim either at technology readiness levels (TRLs) TRL 1-3 or TRL > 3, with more than 75 Mio allocated from the year 2019 onward. This review provides a summary of PC and PEC processes for the synthesis of bulk commodities such as solvents and fuels, as well as chemicals for niche applications. An overview of photoreactors for photocatalysis on a larger scale is provided. The review rounds off with the summary of reactions performed at lab scale under natural outdoor solar light to illustrate conceptual opportunities offered by solar-driven chemistry beyond the reduction of CO2 and water splitting. The authors offer their vision of the impact of this area of research on society and the economy.
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A meta-analysis approach was used, to study the microbiomes of biofilms and planktonic communities underpinning microbial electrosynthesis (MES) cells. High-throughput DNA sequencing of 16S rRNA gene amplicons has been increasingly applied to understand MES systems. In this meta-analysis of 22 studies, we find that acetogenic and methanogenic MES cells share 80% of a cathodic core microbiome, and that different inoculum pre-treatments strongly affect community composition. Oxygen scavengers were more abundant in planktonic communities, and several key organisms were associated with operating parameters and good cell performance. We suggest Desulfovibrio sp. play a role in initiating early biofilm development and shaping microbial communities by catalysing H2 production, to sustain either Acetobacterium sp. or Methanobacterium sp. Microbial community assembly became more stochastic over time, causing diversification of the biofilm (cathodic) community in acetogenic cells and leading to re-establishment of methanogens, despite inoculum pre-treatments. This suggests that repeated interventions may be required to suppress methanogenesis.
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Metano , Microbiota , Methanobacterium/genética , Oxígeno , ARN Ribosómico 16S/genéticaRESUMEN
Metal-organic frameworks (MOFs) are promising multifunctional porous materials for biomedical and environmental applications. Here, we report synthesis and characterization of a new MOF based on the tetrahedral secondary building unit [Zn4O(CBAB)3]n (NUIG4), where CBABH2 = 4-((4-carboxybenzylidene)amino)benzoic acid. NUIG4 belongs to the family of MOFs with primitive cubic pcu topology, being a rare example with 4-fold interpenetration. The pore architecture enables unprecedentedly high doxorubicin (DOX) loading capacity (1955 mg DOX/g NUIG4) with pH-controlled release. Solid-state NMR and ab initio modeling confirmed formation of aromatic π-π stacking interactions between DOX and the framework. Preliminary cell-line experiments suggested a protective effect of NUIG4 on healthy HDF cells against DOX toxicity. NUIG4 also displays potential for adsorptive small-molecule gas separation, with a BET surface area of 1358 m2 g-1 and high selectivity of 2.75 for C2H2 over CO2.