The development of genetic reporters for magnetic resonance imaging (MRI) is essential for investigating biological functions in vivo. However, current MRI reporters have low sensitivity, making it challenging to create significant contrast against the tissue background, especially when only a small fraction of cells express the reporter. To overcome this limitation, we developed an approach for amplifying the sensitivity of molecular MRI by combining a chemogenetic contrast mechanism with a biophysical approach to increase water diffusion through the co-expression of a dual-gene construct comprising an organic anion transporting polypeptide, Oatp1b3, and a water channel, Aqp1. We first show that the expression of Aqp1 amplifies MRI contrast in cultured cells engineered to express Oatp1b3. We demonstrate that the contrast amplification is caused by Aqp1-driven increase in water exchange, which provides the gadolinium ions internalized by Oatp1b3-expressing cells with access to a larger water pool compared with exchange-limited conditions. We further show that our methodology allows cells to be detected using approximately 10-fold lower concentrations of gadolinium than that in the Aqp1-free scenario. Finally, we show that our approach enables the imaging of mixed-cell cultures containing a low fraction of Oatp1b3labeled cells that are undetectable on the basis of Oatp1b3 expression alone.
Monthly Archives: March 2024
Synthesis, Optical, Dielectric, SHG, Magnetic and Visible Light Driven Catalytic Studies on Compounds Belonging to the Swedenborgite Structure
New members of swedenborgite mineral structure were prepared and characterized. The material, InBaZn2.75Cu0.25GaO7, exhibits visible light assisted photocatalysis for the aerobic oxidation of styrenes. The substitution of transition elements in these oxides gives rise to new colored materials, which may be attractive candidates as new inorganic pigments.
Abstract
A new compound, InBaZn3GaO7, with swedenborgite structure along with transition metal (TM) substituted variants have also been prepared. The structure contains layers of tetrahedral ions (Zn2+/Ga3+) connected by octahedrally coordinated In3+ ion forming the three-dimensional structure with voids where the Ba2+ ions occupy. The TM substituted compounds form with new colors. The origin of the color was understood based on the ligand-field transitions. The near IR reflectivity studies indicate that the Ni – substituted compounds exhibit good near – IR reflectivity behavior, making them possible candidates for ‘cool pigments’. The temperature dependent dielectric studies indicate that the InBaZn3GaO7 compound undergoes a phase transition at ~360 °C. The compounds are active towards second harmonic generation (SHG). Magnetic studies show the compounds, InBaZn2CoFeO7 and InBaZn2CuFeO7 to be anti-ferromagnetic in nature. The copper containing compounds were found to be good catalysts, under visible light, for the oxidation of aromatic alkenes. The many properties observed in the swedenborgite structure-based compounds suggests that the mineral structure offers a fertile ground to investigate newer compounds and properties.
A dual‐function Cd‐based coordination polymer for the detection of moxifloxacin and SiO32− ions
H2L (L=1-(4-carboxyphenyl)-1H-pyrazole-3-carboxylic acid) and Cd2+ ions were self-assembled by solvothermal method to prepare the coordination polymer 1 with 1D chain structure. 1 has dual-channel specific recognition ability for moxifloxacin (MXF) and silicate (SiO3 2−), which can be used as the turn-off sensing material for their detection. 1 is currently the second CP-based fluorescent sensor for MXF detection, and has the best sensing performance, with a sensitivity increase of more than three times. At the same time, as the first CP-based sensor material for detecting SiO3 2−, 1 shows excellent sensing properties and the limit of detection (LOD) is 0.68 μM.
Abstract
A 1D coordination polymer (CP) [Cd2L2(H2O)4] ⋅ 3H2O (1) was prepared by solvothermal method using 1-(4-carboxyphenyl)-1H-pyrazole-3-carboxylic acid (H2L) as single ligand. Fluorescence sensing experiments show that 1 has dual-function specific recognition ability for moxifloxacin (MXF) and silicate (SiO3 2−), which can be used as the turn-off sensing material for their detection. When 1 specifically identifies MXF, the Ksv is as high as 6.46×105 M−1 (6–20 μM) and the limit of detection (LOD) is as low as 14 nM. 1 is the second example of a CP-based fluorescent probe for the detection of MXF, which has confirmed that the Ksv is the largest to date for the detection of MXF, with a detection sensitivity increase of more than three times. For SiO3 2− ions detection, the fluorescence intensity ratio has a good linear correlation with the concentration of SiO3 2− ions in the concentration range of 0–100 μM, with a slope of 1.33×104 M−1, and the LOD is as low as 0.68 μM. According to the reported literature, 1 is the only example of SiO3 2− ions sensing by CP-based fluorescence sensor so far. In order to better understand the sensing phenomenon, we also discussed the sensing mechanism for MXF and SiO3 2− ions.
Synthesis of Diaryl Tellurides with Sodium Aryltellurites under Mild Conditions
A highly efficient new protocol has been developed for the formation of C-Te bonds, leading to both symmetrical and unsymmetrical diaryl tellurides. This protocol utilizes sodium aryltellurites (4), which can be easily prepared from low-cost aryltelluride trichlorides and NaOH. The synthesis involves the use of 4 and arylazo sulfones as starting materials in the presence of (MeO)2P(O)H. A variety of diaryl tellurides are obtained in moderate to good yields using this method. Importantly, this innovative protocol eliminates the need for traditional, highly toxic aryltellurolating reagents such as diaryl ditellurides and elemental tellurium. This study will bring new vitality to the synthesis of tellurides.
Enhanced Catalytic Performance and Tolerance to Carbon Monoxide Poisoning of CoO/PtPd/r‐GO Nanocomposite Thin Film for Methanol Fuel Cells
An inexpensive and unique strategy of liquid/liquid interface was applied for the alloying of CoO/PtPd and CoO/PtPd/r-GO nanostructured thin films for efficient and accelerated oxidation of methanol in fuel cell anodes. Co (II) oxide facilitates the conversion of poisonous CO into CO2.
This study presents the facile synthesis of CoO/PtPd and CoO/PtPd/reduced-graphene oxide (r-GO) nanocomposites, highlighting their significant role in methanol fuel cells. To create a CoO/PtPd thin film at the toluene/water interface, we employed NaBH4 to effectively reduce PtCl2(COD), PdCl2(COD), and Co (acac)3 (COD = cis,cis-1,5- cyclooctadiene, acac = acetylacetonate). The two nanocomposites were analyzed using XRD, FE-SEM, AFM, XPS, BET, and TEM techniques. In the electrooxidation of methanol in the anodic part of fuel cell, cobalt (II) oxide can serve as an oxygen source in the catalytic oxidation of carbon monoxide (CO) or it can play a role in producing the HO-CoO intermediate to facilitate the oxidation of CO-PtPd to carbon dioxide (CO2). This reaction can help eliminate CO, which is a common poison for Pt-based catalysts in methanol oxidation. Our research reveals significant improvements in current densities and catalyst tolerance when using the CoO/PtPd/r-GO nanocomposite thin film. The observed current density for CoO/PtPd/r-GO is 263.33 mA.cm−2, surpassing the reported value of 30.00 mA.cm−2 for PtPd/r-GO. The j f /j b ratios, commonly used to evaluate catalyst tolerance, are approximately 2.80 for CoO/PtPd and 4.98 for CoO/PtPd/r-GO, in contrast to ratios larger than 0.99 for ETEK Pt and 0.58 for other types of commercial Pt/C. These findings indicate that the CoO/PtPd/r-GO thin film exhibits enhanced catalytic performance and improved tolerance to CO poisoning. Furthermore, the power output calculated for CoO/PtPd/r-GO is 104.5 mW·cm−2, which is comparable to the reported value of 48.03 mW·cm−2 for commercial Pt/C. These results demonstrate the potential of the CoO/PtPd/r-GO nanocomposite thin film as a promising alternative to traditional catalyst materials in methanol fuel cells.
Hydrodifluoromethylation of unactivated alkenes enabled by Visible‐Light Photocatalysis
Photocatalytic hydro-difluoromethylaton of unactivated alkenes has been developed using a commercially available difluoromethylating reagent (CF2HSO2Na). This methodology tolerates a variety of functional groups and allows late-stage modification of various alkenes derived from pharmaceutically relevant drugs.
Abstract
In the present manuscript, we have reported a general catalytic strategy that allows the synthesis of a variety of difluoro methylated alkanes from the corresponding unactivated alkenes using commercially available radical difluoromethylating reagent (CF2HSO2Na) under visible light photocatalysis. Further, this strategy allows the late-stage modification of various alkenes derived from pharmaceutically relevant drugs.
Expanding Rutinosidase Versatility: Acylated Quercetin Glucopyranosides as Substrates
Aspergillus niger rutinosidase (AnRut) efficiently cleaved a library of rutin glycomimetics - isoquercitrin acylated at C-6′ of its glucosyl moiety. The substrates tested included isoquercitrin substituted at glucosyl C-6′ with acetyl, benzoyl, phenylacetyl, phenylpropanoyl, cinnamyl, vanillyl, galloyl, 4-hydroxybenzoyl, and 3-(4-hydroxy-3-O-methylphenyl)propanoyl. AnRut showed the ability to transglycosylate with the substrates 6′-O-acetyl isoquercitrin and 6′-O-benzoyl isoquercitrin substrates, affording n-butyl 6-acetyl-β-d-glucopyranoside and n-butyl 6-benzoyl-β-d-glucopyranoside.
Abstract
Rutinosidase is a diglycosidase that catalyzes the cleavage of rutinose (α-l-Rhap-(1→6)-β-d-Glcp) from rutin or other rutinosides. It is also able to cleave β-glucopyranosides, e. g., isoquercitrin. This enzyme has a strong transglycosylation activity and a remarkable substrate specificity. We have shown that rutinosidase from Aspergillus niger (AnRut) is able to cleave β-glucopyranosides acylated at C-6 of glucose (6′-O-acylisoquercitrin) with acetyl, benzoyl, phenylacetyl, phenylpropanoyl, cinnamoyl, vanillyl, galloyl, 4-hydroxybenzoyl and 3-(4-hydroxy-3-methoxyphenyl)propanoyl. The release of the respective 6-acylglucopyranoses was confirmed by HPLC/MS and NMR methods. Selected compounds, i. e., 6′-O-acetyl, 6′-O-benzoyl, and 6′-O-cinnamyl derivatives of isoquercitrin, were also tested as transglycosylation substrates. Only 6′-acetylisoquercitrin and 6′-O-benzoylisoquercitrin underwent transglycosylations by AnRut to produce n-butyl 6-acetyl-β-d-glucopyranoside and n-butyl 6-benzoyl-β-d-glucopyranoside. Isoquercitrin 6′-O-cinnamate yielded on hydrolytic product. Molecular modeling based on the crystal structure of AnRut showed that large aromatic moieties at C-6′ of isoquercitrin block the side tunnel of AnRut leading into its active site and thus hinder the entry of the acceptor substrate for transglycosylation. This study demonstrates the great substrate flexibility of rutinosidase at the glycone site.
The use of silicon in the membrane electrode assembly of fuel cells
Silicon-based and silicon-containing materials have been used in polymer electrolyte membrane fuel cells (PEMFCs), solid oxide fuel cells (SOFCs) and phosphoric acid fuel cells (PAFCs). In this work the use of silicon in the membrane electrode assembly (MEA) of fuel cells is reviewed.
Abstract
Silicon, silicon-based and Si-containing materials are widely used and play different roles in fuel cells. These materials have been used overall in polymer electrolyte membrane fuel cells, but also in solid oxide fuel cells and phosphoric acid fuel cells. The most used Si compounds in fuel cells are SiO2 and SiC. In this work an overview of the use of Si-based and Si-containing materials in the membrane electrode assembly of fuel cells is presented.
Low‐Temperature CO Oxidation by the Pt/CeO2 Based Catalysts
This review analyzes the literature data and the results of studies of the Pt/CeO2 based catalysts which capable of providing the low-temperature CO oxidation. In this review the catalytic characteristics, local structure of active sites and charge state of platinum and ceria in catalysts, that is necessary for the low-temperature oxidation at T<50 °C, are summarized.
Abstract
This review analyzes the literature data and the results of studies of the Pt/CeO2-based catalysts that are capable of providing the low-temperature CO oxidation (LTO CO). The review summarizes the catalytic characteristics and the main properties of Pt/CeO2-based catalysts necessary for the low-temperature oxidation at T<50 °C. Analysis of the literature data on the use of physical methods of investigation and their correlation with the activity of Pt/CeO2 catalysts allowed us to conclude that the main active forms of platinum are small metallic clusters, single atoms Pt2+-SA and oxide clusters PtOx interacting with ceria nanoparticles. It has been established that the most active forms are PtOx clusters, which provide a high reaction rate in the temperature range from −50 to +50 °C. Forms of ionic Pt2+ with different coordination with oxygen ensure the activity of catalysts starting at temperatures above 100 °C. Finally, small metallic clusters occupy an intermediate position, providing activity above 0 °C, but their instability and gradual transition to the oxidized state Pt2+/PtOx are noted. At the conclusion of the review, the results of mathematical modeling demonstrate the correct kinetics description of the low-temperature CO oxidation based on the Mars-van Krevelen and associative mechanisms.
Nickel and Iron‐Doped Biocarbon Catalysts for Reverse Water‐Gas Shift Reaction
Biocarbon catalysts were prepared from iron and nickel impregnated pyrolyzed fern and willow to mimic plants issued from phytoremediation. Reverse water-gas shift (RWGS) catalyzed by these catalysts was studied at 400 °C and H2/CO2=3 as RWGS can partake in Fischer-Tropsch synthesis to form synthetic fuel. They were highly selective (>84 %) with fair conversion (<17 %) and showed no long-use (288 h) deactivation.
Abstract
Biocarbon catalysts for reverse water-gas shift reaction (RWGS) were produced from pyrolyzed fern and willow impregnated with iron and nickel nitrates. This reaction can partake during Fischer-Tropsch synthesis (FTS) by consuming CO2 and lowering both the H2/CO ratio and the efficiency in the production of fuels. RWGS has attracted much attention to widespread utilization of CO2 through the production of syngas. The catalysts were therefore tested in a fixed-bed reactor at 400 °C as it is the maximal temperature for FTS and high RWGS. They showed high selectivity towards CO (>84 %) and fair conversion (<17 %) compared to rust (81 %, 30 %, respectively) and Fe-impregnated alumina (100 %, 8 %). No loss in selectivity and conversion was observed for a longer residence time (288 h). Biomass inherent metals could provide reactive gas adsorption sites that improve conversion by dispersing electrons which reduces adsorption and dissociation energy barriers. K, Mg and Ca in fern biocarbon catalysts may be related to the higher CO2 uptake compared to willow catalysts. Electron deficient sites produced by reduction of biocarbon oxygen functional groups may facilitate CO2 uptake and activation. Ni-impregnated fern-based biocarbon showed the highest activity, due to the synergetic effect of the inherent metals, O vacancies and strong metal-carbon interactions.