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951.
Reece JS Miller MJ Arnold MA Waterhouse C Delaplaine T Cohn L Cannon T 《Applied biochemistry and biotechnology》2003,104(1):1-11
A compact, flow-through oxygen sensor device based on luminescence quenching was used to monitor dissolved oxygen levels during
mammalian cell growth on the STS-93 mission of the Columbia space shuttle. Excitation of an oxygen-sensitive ruthenium complex
was provided by a radiolumin escent light source (0.9 mm in diameter, 2.5 mm long), and the intensity of the resulting luminescence
was measured by a simple photodiode detector. The use of radiolum inescence for the excitation light source is a unique approach
that provides many features important for long-term and remote monitoring applications. For the spaceflight experiment, human
lung fibroblast cells (WI-38) were grown in hollow-fiber bioreactors. Oxygen concentration was measured in the flow path both
before and after the bioreactor cartridge in order to gain information about the metabolism of the cells. The sensor was found
to be nonperturbing to cell growth and withstood the challenging physical conditions of shuttle launch and landing while maintaining
a stable calibration function. In addition, the sensor provided physically meaningful oxygen predictions. 相似文献
952.
Acid Orange 7, a textile azo dye, has been partially mineralized and degraded using -radiolysis and sonolysis. These two different advanced oxidation processes (AOP) are effective in producing OH radicals and cause complete destruction of the chromophore. The reaction mechanism of dye degradation has been probed by analyzing the reaction products with HPLC. In both cases, the final end products of degradation are oxalate and formate ions. The intermediates observed are all similar. While hydroxybenzenesulfonic acid is the major observed reaction intermediate in the oxidation processes, the pulse radiolysis studies indicate that the OH radical initiated pathway for attack occurs via the initial formation of 1,2-naphthaquinone and subsequent breakdown into oxalic acid. 相似文献
953.
Guella G Skropeta D Mancini I Pietra F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(23):5770-5777
It is shown here that calenzanane sesquiterpenes (1 and 6) can be isolated from organic extracts from the red seaweed Laurencia microcladia Kützing from the Bay of Calenzana, Elba Island, provided contact with acidic media is minimized. Such contact induces rearrangements of 1 in dry solvents to indene-type 5 and the blue-colored guaiazulenium-type ion 17, via spectrometrically (NMR) characterized indene-type transient intermediates 10, 14, and 12. Addition of NEt(3) to the reaction mixture at appropriate stages allowed the isolation of 12 (and 8 on workup on SiO(2)), and guaiazulene (18). Prolonged contact with silica gel led to complete degradation of 1, giving calenzanane-type epimeric enones 20 a/20 b as well as indene-type epimeric carbinols 22 a/22 b and fulvene 7. The latter was also formed during silica-gel flash chromatography of the algal extracts. A unifying mechanistic view of these branching and cascade transformations may have both heuristic value, suggesting possible artefact origin of azulenoids, and synthetic applications. 相似文献
954.
Julie Pineau Dr. Luís M. P. Lima Prof. Carlos Platas-Iglesias Prof. Jan Rijn Zeevaart Dr. Cathryn H. S. Driver Dr. Nathalie Le Bris Prof. Raphaël Tripier 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(41):e202200942
The limited use of palladium-103 and -109 radionuclides for molecular radiotherapy is surely due to the lack of appropriate ligands capable of fulfilling all criteria required for application in nuclear medicine. Furthermore, the thermodynamic properties of these complexes in solution remain difficult to establish. The challenge is compounded when considering that radiolabeling of compounds for translation to clinical trials requires fast complexation. Thus, the coordination of Pd(II) and 103/109Pd-nuclides is a huge challenge in terms of molecular design and physicochemical characterization. Herein, we report a comprehensive study highlighting TE1PA , a monopicolinate cyclam – already established in nuclear imaging with 64Cu-PET (positron emission tomography) imaging tracers – as a highly relevant chelator for natural Pd and subsequently 109Pd-nuclide. The structural, thermodynamic, kinetic and radiolabeling studies of Pd(II) with TE1PA , as well as the comparison of this complex with three structurally related derivatives, support palladium- TE1PA radiopharmaceuticals as leading candidates for targeted nuclear medicine. 相似文献
955.
Jennifer G. Cromley Julie L. Booth Theodore W. Wills Briana L. Chang Nhi Tran Michael Madeja 《Mathematical Thinking and Learning》2017,19(1):55-68
Spatial skills have been shown in various longitudinal studies to be related to multiple science, technology, engineering, and math (STEM) achievement and retention. The specific nature of this relation has been probed in only a few domains, and has rarely been investigated for calculus, a critical topic in preparing students for and in STEM majors and careers. We gathered data on paper-and-pencil measures of spatial skills (mental rotation, paper folding, and hidden figures); calculus proficiency (conceptual knowledge and released Advanced Placement [AP] calculus items); coordinating graph, table, and algebraic representations (coordinating multiple representations); and basic graph/table skills. Regression analyses suggest that mental rotation is the best of the spatial predictors for scores on released AP calculus exam questions (β = 0.21), but that spatial skills are not a significant predictor of calculus conceptual knowledge. Proficiency in coordinating multiple representations is also a significant predictor of both released AP calculus questions (β = 0.37) and calculus conceptual knowledge (β = 0.47). The spatial skills tapped by the measure for mental rotation may be similar to those required to engage in mental animation of typical explanations in AP textbooks and in AP class teaching as tested on the AP exam questions. Our measure for calculus conceptual knowledge, by contrast, did not require coordinating representations. 相似文献
956.
Dr. Chia-Hsin Chen Dr. Frederic Mentink-Vigier Dr. Julien Trébosc Dr. Ieva Goldberga Dr. Philippe Gaveau Dr. Emilie Thomassot Dr. Dinu Iuga Prof. Mark E. Smith Dr. Kuizhi Chen Dr. Zhehong Gan Nicolas Fabregue Dr. Thomas-Xavier Métro Dr. Bruno Alonso Dr. Danielle Laurencin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(49):12574-12588
In recent years, there has been increasing interest in developing cost-efficient, fast, and user-friendly 17O enrichment protocols to help to understand the structure and reactivity of materials by using 17O NMR spectroscopy. Here, we show for the first time how ball milling (BM) can be used to selectively and efficiently enrich the surface of fumed silica, which is widely used at industrial scale. Short milling times (up to 15 min) allowed modulation of the enrichment level (up to ca. 5 %) without significantly changing the nature of the material. High-precision 17O compositions were measured at different milling times by using large-geometry secondary-ion mass spectrometry (LG-SIMS). High-resolution 17O NMR analyses (including at 35.2 T) allowed clear identification of the signals from siloxane (Si−O−Si) and silanols (Si−OH), while DNP analyses, performed by using direct 17O polarization and indirect 17O{1H} CP excitation, agreed with selective labeling of the surface. Information on the distribution of Si−OH environments at the surface was obtained from 2D 1H−17O D-HMQC correlations. Finally, the surface-labeled silica was reacted with titania and using 17O DNP, their common interface was probed and Si−O−Ti bonds identified. 相似文献
957.
John Rojas Sergio Cabrera Julie Benavides Yasmín Lopera Cristhian J. Yarce 《Molecules (Basel, Switzerland)》2021,26(9)
Clove essential oil (CEO) is known for having excellent antioxidant and antimicrobial properties, but the poor stability of its components to light and temperature compromise this activity. The aim of this study is to evaluate the textural, antioxidant, antimicrobial and microstructural properties of matrixes produced with representative natural waxes and CEO. Thus, waxy emulsifiers, such as beeswax, candelilla wax, carnauba wax, and ozokerite wax, were employed to create such matrixes. The thermal, microstructural, textural, wetting, antioxidant, antimicrobial and infrared characteristics of the matrixes were then studied. The diverse chemical composition (long-chain wax esters in carnauba wax and short-chain fatty acids and hydrocarbons in beeswax and ozokerite wax, respectively) explained the differences in wetting, texture, melting, and crystallization characteristics. Crystal forms of these matrix systems varied from grainy, oval, to needle-like shape, but keeping an orthorhombic allomorph. The alignment and reorganization of beeswax and ozokerite wax into needle-like crystals increased the matrix strength and adhesion force compared to those of carnauba and candelilla matrixes, which showed weak strength and grainy morphology. The former two waxes and their matrixes also showed the largest plasticity. These lipidic matrixes show potential use for topical applications having acceptable antioxidant and textural properties. 相似文献
958.
Jordi Borrs Julie Foster Roxana Kashani Laura Melndez-Alafort Jane Sosabowski Joan Suades Ramon Barnadas-Rodríguez 《Molecules (Basel, Switzerland)》2021,26(8)
The zinc dithiocarbamates functionalized with folic acid 2Zn and 3Zn were synthesized with a simple straightforward method, using an appropriated folic acid derivative and a functionalized zinc dithiocarbamate (1Zn). Zinc complexes 2Zn and 3Zn show very low solubilities in water, making them useful for preparing Tc-99m radiopharmaceuticals with a potentially high molar activity. Thus, the transmetallation reaction in water medium between the zinc complexes 2Zn or 3Zn and the cation fac-[99mTc(H2O)3(CO)3]+, in the presence of the monodentate ligand TPPTS, leads to the formation of the 2 + 1 complexes fac-[99mTc(CO)3(SS)(P)] bioconjugated to folic acid (2Tc and 3Tc). In spite of the low solubility of 2Zn and 3Zn in water, the reaction yield is higher than 95%, and the excess zinc reagent is easily removed by centrifugation. The Tc-99m complexes were characterized by comparing their HPLC with those of the homologous rhenium complexes (2Re and 3Re) previously synthesized and characterized by standard methods. Preliminary in vivo studies with 2Tc and 3Tc indicate low specific binding to folate receptors. In summary, Tc-99m folates 2Tc and 3Tc were prepared in high yields, using a one-pot transmetallation reaction with low soluble zinc dithiocarbamates (>1 ppm), at moderate temperature, without needing a subsequent purification step. 相似文献
959.
Julien Gravel Julie Kempf Prof. Dr. Andreea Schmitzer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(51):18642-18648
Herein, we report a reversible modular chloride transport process based on host–guest competitive interactions between an imidazolium‐based chloride carrier and beta‐cyclodextrin. We report evidence for the formation of the supramolecular complex between 1,3‐bis(2‐(adamantan‐1‐yl)ethyl)imidazolium bis(trifluorometyl‐sulfonyl)imide with two β‐cyclodextrins. Through fluorescence assays in liposomes and black lipid membrane experiments, we demonstrate that the formation of the supramolecular complex results in the inhibition of the chloride transport. We show that the chloride transport process can be entirely restored in the presence of competitive adamantyl‐functionalized guests. This is the first example of an entirely reversible modular chloride transport process in phospholipid bilayers involving a mobile carrier transporter and cyclodextrin supramolecular complex. 相似文献
960.
The development of molecularly imprinted chiral stationary phases has traditionally been limited by the need for a chiral pure template. Paradoxically, availability of a chiral pure template largely defeats the purpose of developing a chiral stationary phase. To solve this paradox, imprinting of scalemic and racemic template mixtures was investigated using both chiral (N-α-bismethacryloyl-l-alanine) and achiral (N,O-bisacrylamide ethanolamine) crosslinkers. Imprinting of scalemic mixtures provided polymers capable of partial separation of Boc-tyrosine enantiomers with virtually the same results when using either the chiral or achiral crosslinker. However, the chiral crosslinker was required for chiral differentiation by the racemic imprinted polymers which were evaluated in both batch rebinding and chromatographic modes. Batch rebinding analysis revealed intersecting binding isotherms for the L- and D-Boc-tyrosine, indicating bias for the D or L enantiomer is concentration dependent. Partial chromatographic separation was achieved by the racemic imprinted polymers providing variable D or L bias in equal probability over multiple replicates of polymer synthesis. Correlation of enantiomer bias with the batch rebinding results and optimization of HPLC parameters are discussed. 相似文献