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81.
Alena Rudolph Dino AlbericoRobert Jordan Ming PanFabio E.S. Souza Boris Gorin 《Tetrahedron letters》2013
A new synthetic strategy towards the C27–C35 subunit of Eribulin (1) has been devised to include a protected 1,2-amino alcohol at C34–C35. Early introduction of the C35 amino group in the synthesis of 1 increases the efficiency of the route. This new approach can be accomplished on a multi-gram scale and allows for the successful synthesis of Eribulin. 相似文献
82.
Superparamagnetic particles have been attractive for molecular diagnostics and analytical chemistry applications due to their unique magnetic properties and their ability to interact with various biomolecules of interest. This paper presents a critical overview of magnetic nano ‐ and microparticles used as a solid phase for extraction and purification of DNAs. The mechanisms of DNA binding to the surface of functionalised magnetic particles are described. The most widely used materials including silica supports, organic polymers and other materials, mostly containing magnetite or paramagnetic metallic elements are reviewed. The main application areas of magnetic particles for DNA separation are briefly described. 相似文献
83.
Tomáš Řezanka Irena Kolouchová Alena Čejková Tomáš Cajthaml Karel Sigler 《Journal of separation science》2013,36(20):3310-3320
LC with atmospheric pressure chemical ionization (ACPI) MS with RP and chiral phase was used for separation of triacylglycerols (TAGs) from yeasts of the genera Candida, Kluyveromyces, Rhodotorula, Saccharomyces, Torulospora, Trichosporon, and Yarrowia. Chiral LC–APCI‐MS is based on using two columns in series packed with a 3,5‐dimethylphenyl carbamate modified β‐cyclodextrin chiral phase. All regioisomers and enantiomers of TAGs containing one to five double bonds were separated. Molecular species of TAGs, i.e. regioisomers and enantiomers, were identified and quantified by MS/MS. Among the 94 identified TAGs, the most abundant were triolein, oleopalmitoleoolein, and dipalmitoleoolein. In strains producing palmitoleic acid in amounts >25% of total fatty acids (FAs), this acid, or unsaturated FA is bound in sn‐1. In strains containing palmitoleic acid at 10–25% total FAs this acid is mainly bound in sn‐3, saturated FA being bound in sn‐1. Strains containing <10% palmitoleic acid form preferentially symmetrical TAGs. 相似文献
84.
Roza R. Alieva Nadezhda V. Belogurova Alena S. Petrova Nadezhda S. Kudryasheva 《Analytical and bioanalytical chemistry》2014,406(12):2965-2974
Photoproteins are responsible for bioluminescence of marine coelenterates; bioluminescent and fluorescent biomarkers based on photoproteins are useful for monitoring of calcium-dependent processes in medical investigations. Here, we present the analysis of intensity and color of light-induced fluorescence of Ca2+-discharged photoprotein obelin in the presence of alcohols (ethanol and glycerol). Complex obelin spectra obtained at different concentrations of the alcohols at 350- and 280-nm excitation (corresponding to polypeptide-bound coelenteramide and tryptophan absorption regions) were deconvoluted into Gaussian components; fluorescent intensity and contributions of the components to experimental spectra were analyzed. Five Gaussian components were found in different spectral regions—ultraviolet (tryptophan emission), blue-green (coelenteramide emission), and red (hypothetical indole-coelenteramide exciplex emission). Inhibition coefficients and contributions of the components to experimental fluorescent spectra showed that presence of alcohols increased contributions of ultraviolet, violet, and red components, but decreased contributions of components in the blue-green region. The effects were related to (1) changes of proton transfer efficiency in fluorescent S*1 state of coelenteramide in the obelin active center and (2) formation of indole-coelenteramide exciplex at 280-nm photoexcitation. The data show that variation of fluorescence color and intensity in the presence of alcohols and dependence of emission spectra on excitation wavelength should be considered while applying the discharged obelin as a fluorescence biomarker. 相似文献
85.
Lenka Soukupová Alena Komersová Karel Komers árka tpánková Alexander egan 《Reaction Kinetics and Catalysis Letters》2008,95(2):205-211
Mechanism and kinetics of in vitro hydrolysis of acetyl-β-methylcholine by acetylcholinesterase from electric eel in a mixed batch reactor at 25 and 37°C, pH
8, ionic strength 0.11 M and catalytic activity of the enzyme preparat of 3.5 U mL−1 were studied. The optimal kinetic parameters were determined. 相似文献
86.
Data of experiments with single-path and multipath reception of broadband continuous pseudonoise acoustic signals (0.8–1.3 kHz) in a deep ocean are discussed. The experiments were carried out on tracks from ~ 60 to ~ 420 km in length, which corresponds to the first seven convergence zones. The data on the cross-correlation coefficients and arrival time differences are presented (for the first, second, and seventh zones) for signals received by one highly directional (~2°) vertical array or by two such arrays simultaneously at depths of 200 and 450 m. The correlation characteristics of signals propagating over purely water paths, i.e., without reflections from the waveguide boundaries, and arriving under different angles in the vertical plane are compared. It is found that the origin of the decorrelation of signals received from various directions or at different depths (all other factors being the same) is the incomplete resolution of the received multipath signals in the arrival angle in the vertical plane. 相似文献
87.
Trouillas P Marsal P Svobodová A Vostálová J Gazák R Hrbác J Sedmera P Kren V Lazzaroni R Duroux JL Walterová D 《The journal of physical chemistry. A》2008,112(5):1054-1063
Flavonolignans from silymarin, the standardized plant extract obtained from thistle, exhibit various antioxidant activities, which correlate with the other biological and therapeutic properties of that extract. To highlight the mode of action of flavonolignans as free radical scavengers and antioxidants, 10 flavonolignans, selectively methylated at different positions, were tested in vitro for their capacity to scavenge radicals (DPPH and superoxide) and to inhibit the lipid peroxidation induced on microsome membranes. The results are rationalized on the basis of (i) the oxidation potentials experimentally obtained by cyclic voltammetry and (ii) the theoretical redox properties obtained by quantum-chemical calculations (using a polarizable continuum model (PCM)-density functional theory (DFT) approach) of the ionization potentials and the O-H bond dissociation enthalpies (BDEs) of each OH group of the 10 compounds. We clearly establish the importance of the 3-OH and 20-OH groups as H donors, in the presence of the 2,3 double bond and the catechol moiety in the E-ring, respectively. For silybin derivatives (i.e., in the absence of the 2,3 double bond), secondary mechanisms (i.e., electron transfer (ET) mechanism and adduct formation with radicals) could become more important (or predominant) as the active sites for H atom transfer (HAT) mechanism are much less effective (high BDEs). 相似文献
88.
Alena A. Volgusheva Daria A. Todorenko Ivan V. Konyukhov Elena N. Voronova Sergey I. Pogosyan Tatyana Yu Plyusnina Sergey S. Khruschev Taras K. Antal 《Photochemistry and photobiology》2023,99(4):1106-1114
The effect of the toxicant 2,3′,4,4′,6-pentachlorobiphenyl (PCB-119) on the growth, chlorophyll content, and PSII activity of C. sorokiniana cells was investigated. A strong negative effect of the toxicant was observed at PCB concentration of 0.05 μg mL−1, when culture growth ceased, chlorophyll strongly bleached, and cell death occurred. The use of original highly sensitive fluorimeter to measure three types of high-resolution chlorophyll fluorescence kinetics allowed us to detect an initial dramatic decrease in the activity of primary photosynthetic reactions, followed by their almost complete recovery at the end of the incubation period when most cells were dead. The study of the distribution of individual cells in culture in terms of Fv/Fm parameter, which reflects the quantum yield of PSII photochemistry, revealed the existence of 2–3% of cells retaining high Fv/Fm (>0.7) in the presence of the toxicant. The treated cultures were able to resume growth after prolonged incubation in fresh medium. The high sensitivity fluorescence methods used made it possible to identify stress-resistant cells which maintain high photosynthetic activity in the presence of lethal doses of toxic substances; these cells provide recovery of the population after stress. 相似文献
89.
Biospecimens with nearly flat surfaces on a flat stage are typically required for laser-based mass spectrometry imaging (MSI) techniques. However, sampling stages are rarely perfectly level, and accounting for this and the need to accommodate non-flat samples requires a deeper understanding of the laser beam depth of focus. In ablation-based MSI methods, a laser is focused on top of the sample surface, ensuring that the sample is at the focal point or remains within depth of focus. In general, the depth of focus of a given laser is related to the beam quality (M2) and the wavelength (λ). However, because laser is applied on a biological sample, other variables can also impact the depth of focus, which could affect the robustness of the MSI techniques for diverse sample types. When the height of a sample ranges outside of the depth of focus, ablated area and the corresponding ion abundances may vary as well, increasing the variability of results. In this tutorial, we examine the parameters and equations that describe the depth of focus of a Gaussian laser beam. Additionally, we describe several approaches that account for surface roughness exceeding the depth of focus of the laser. 相似文献
90.
Dr. Zi Wang Dr. Alena M. Sheveleva Dr. Daniel Lee Yinlin Chen Dr. Dinu Iuga Dr. W. Trent Franks Dr. Yujie Ma Dr. Jiangnan Li Dr. Lei Li Dr. Yongqiang Cheng Dr. Luke L. Daemen Dr. Sarah J. Days Dr. Anibal J. Ramirez-Cuesta Bing Han Dr. Alexander S. Eggeman Prof. Eric J. L. McInnes Dr. Floriana Tuna Prof. Sihai Yang Prof. Martin Schröder 《Angewandte Chemie (International ed. in English)》2023,62(28):e202302602
We report the modulation of reactivity of nitrogen dioxide (NO2) in a charged metal–organic framework (MOF) material, MFM-305-CH3 in which unbound N-centres are methylated and the cationic charge counter-balanced by Cl− ions in the pores. Uptake of NO2 into MFM-305-CH3 leads to reaction between NO2 and Cl− to give nitrosyl chloride (NOCl) and NO3− anions. A high dynamic uptake of 6.58 mmol g−1 at 298 K is observed for MFM-305-CH3 as measured using a flow of 500 ppm NO2 in He. In contrast, the analogous neutral material, MFM-305, shows a much lower uptake of 2.38 mmol g−1. The binding domains and reactivity of adsorbed NO2 molecules within MFM-305-CH3 and MFM-305 have been probed using in situ synchrotron X-ray diffraction, inelastic neutron scattering and by electron paramagnetic resonance, high-field solid-state nuclear magnetic resonance and UV/Vis spectroscopies. The design of charged porous sorbents provides a new platform to control the reactivity of corrosive air pollutants. 相似文献