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101.
Younes Ghasemi Sara Rasoul-Amini Mohammad Hossein Morowvat Mohammad Bagher Ghoshoon Mohammad Javad Raee Soraya Khoubani Narges Negintaji Fatemeh Nouri Rezvan Parvizi 《Chemistry of Natural Compounds》2009,45(6):824-828
A unicellular microalga, Chlorella vulgaris, was isolated from rice field and applied in the biotransformation experiment
of hydrocortisone (1). This strain has not been previously tested for hydrocortisone bioconversion. Fermentation was carried out in BG-11 medium
supplemented with 0.05% substrate at 25°C for 14 days incubation. The products obtained were chromatographically purified
followed by their characterization using spectroscopic methods. 11β,17α,20β,21-Tetrahydroxypregn-4-en-3-one (2), 11β,17β-dihydroxyandrost-4-en-3-one (3), and 11β-hydroxyandrost-4-ene-3,17-dione (4) were the main bioproducts in the hydrocortisone bioconversion. Bioreaction characteristics observed were 20-ketone reduction
for accumulation of compound 2 and side chain degradation of the substrate to prepare compounds 3 and 4. Time course study showed the accumulation of the product 2 from the second day of the fermentation and 3 as well as 4 from the third day. All the metabolites reached their maximum concentration in seven days. Microalgal 18S rRNA gene was also
amplified by PCR. PCR products were sequenced to confirm their authenticity as 18S rRNA gene of microalgae. The result of
PCR blasted with other sequenced microalgae in NCBI showed 100% homology to the 18S small subunit rRNA of six strains of Chlorella
vulgaris. 相似文献
102.
Bound states of Dirac fermions in monolayer gapped graphene in the presence of local perturbations
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In graphene,conductance electrons behave as massless relativistic particles and obey an analogue of the Dirac equation in two dimensions with a chiral nature.For this reason,the bounding of electrons in graphene in the form of geometries of quantum dots is impossible.In gapless graphene,due to its unique electronic band structure,there is a minimal conductivity at Dirac points,that is,in the limit of zero doping.This creates a problem for using such a highly motivated new material in electronic devices.One of the ways to overcome this problem is the creation of a band gap in the graphene band structure,which is made by inversion symmetry breaking(symmetry of sublattices).We investigate the confined states of the massless Dirac fermions in an impured graphene by the short-range perturbations for "local chemical potential" and "local gap".The calculated energy spectrum exhibits quite different features with and without the perturbations.A characteristic equation for bound states(BSs) has been obtained.It is surprisingly found that the relation between the radial functions of sublattices wave functions,i.e.,f_m~+(r),g_m~+(r),and f_m~-(r),g_m~-(r),can be established by SO(2) group. 相似文献
103.
Seyed Sajad Sajadikhah Malek Taher Maghsoodlou Nourallah Hazeri Sayyed Mostafa Habibi-Khorassani Anthony C.Willis 《中国化学快报》2012,23(5):569-572
An efficient green protocol is described for the preparation of highly functionalized piperidines via a one-pot five-component reaction between aromatic aldehydes,anilines andβ-ketoesters in the presence of oxalic acid dihydrate as catalyst in ethanol at ambient temperature.The structure as well as the relative stereochemistry of these compounds was confirmed by single X-ray crystallographic analysis. 相似文献
104.
3‐(2,2′‐Bipyridyl)‐substituted iminocoumarin molecules (compounds 1 and 2 ) exhibit dual fluorescence. Each molecule has one electron donor and two electron acceptors that are in conjugation, which leads to fluorescence from two independent charge transfer (CT) states. To account for the dual fluorescence, we subscribe to a kinetic model in which both CT states form after rapid decays from the directly accessed S1 and S2 excited states. Due to the slow internal conversion from S2 to S1, or more likely the slow interconversion between the two subsequently formed CT states, dual emission is allowed to occur. This hypothesis is supported by the following evidence: 1) the emission at short and long ends of the spectrum originates from two different excitation spectra, which eliminates the possibility that dual emission occurs after an adiabatic reaction at the S1 level. 2) The fluorescence quantum yield of compound 2 grows with increasing excitation wavelength, which indicates that the high‐energy excitation elevates the molecule to a weakly emissive state that does not internally convert to the low‐energy, highly emissive state. The intensity of the two emission bands of 1 is tunable through the specific interactions between either of the two electron acceptors with another species, such as Zn2+ in the current demonstration. Therefore, the development of ratiometric fluorescent indicators based on the dual‐emitting iminocoumarin system is conceivable. Further fundamental studies on this series of compounds using time‐resolved spectroscopic techniques, and explorations of their applications will be carried out in the near future. 相似文献
105.
Taft F Harmrolfs K Nickeleit I Heutling A Kiene M Malek N Sasse F Kirschning A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(3):880-886
Access of four new tumor specific folic acid/ansamitocin conjugates is reported that relies on a synthetic strategy based on the combination of mutasynthesis and semisynthesis. Two bromo‐ansamitocin derivatives were prepared by mutasynthesis or by a modified fermentation protocol, respectively, that served as starting point for the semisynthetic introduction of an allyl amine linker under Stille conditions. A sequence of standard coupling steps introduced the pteroic acid/glutamic acid/cysteine unit to the modified ansamitocins. All new derivatives, including those that are expected to be generated after internalization of the folic acid/ansamitocin conjugates into the cancer cell and reductive cleavage of the disulfide linkage showed good to strong antiproliferative activity (IC50 <10 nM ) for different cancer cell lines. Finally, the four conjugates were exposed to two cancer cell lines [cervix carcinoma, KB‐3‐1 (FR+) and lung carcinoma, A‐459 (FR?)], the latter devoid of the membrane‐bound folic acid receptor (FR?). All four conjugates showed strong antiproliferative activity for the FR+ cancer cell line but were inactive against the FR? cell line. The synthetic strategy pursued is based on the combination of mutasynthesis and semisynthesis and proved to be powerful for accessing new ansamitocin derivatives that are difficult to prepare by total synthesis. 相似文献
106.
Soleyman Hosseinzadeh Younes Saadat Samira Abdolbaghi 《Colloid and polymer science》2012,290(9):847-853
In this study, the preparation of micron-sized polymer particles having a novel and unique nonspherical shape which we called almond-shell-like by dual-seeded dispersion polymerization (DSDP) of 2-ethylhexyl methacrylate (EHMA) with polystyrene (PS) and poly(methyl methacrylate) (PMMA) seed particles in the presence of decane droplets and evaporation of decane after the polymerization was discussed. The experimental results showed that mushroom-like morphology which is a precursor of the almond-shell-like shape was obtained from DSDP of EHMA. It was found that with changing the PS/PMMA seed particles' weight ratio, the size of the dents on the surface of the particles can be controlled. Furthermore, it was observed that various nonspherical particles can be produced using different methacrylic seed particles and initiators. 相似文献
107.
Soleyman Hosseinzadeh Younes Saadat Hormoz Eslami Faramarz Afshar-Taromi Alireza Hosseinzadeh Mehdi Rimaz Vahid Hooshangi 《Colloid and polymer science》2012,290(16):1713-1719
In this work, the preparation of micron-sized polymer particles with nonspherical shapes via seeded dispersion polymerization of 2-ethylhexyl methacrylate with polystyrene seed particles in the presence of hydrocarbon droplets and evaporation of hydrocarbon after the polymerization under various polymerization conditions was discussed. The effect of second monomer and initiator type, mixing method, and stabilizer content on the shape of the obtained particles was investigated. It was observed that particles with more nonspherical shapes were obtained with increasing the alkyl chain length of ester group of the methacrylate of the second monomer which is because of increasing the absorption amounts of hydrocarbon by second polymer domains. Moreover, the experimental results showed that shape of the particles which was produced by shaking is more nonspherical than the shape of the particles which was obtained from tumbling. Furthermore, particles with different nonspherical shapes were prepared by changing the initiator type and stabilizer content. 相似文献
108.
Silvia H. Santagneli Jinjun Ren Matthias T. Rinke Sidney J.L. Ribeiro Younes Messaddeq Hellmut Eckert 《Journal of Non》2012,358(6-7):985-992
Vitreous samples (1-x) AgPO3–x MoO3 (0 ≤ x ≤ 0.5) were prepared by conventional melt-quenching and characterized by Differential Scanning Calorimetry (DSC). The structural evolution of the vitreous network was monitored by 31P solid state nuclear magnetic resonance and Raman scattering, and assignments were aided by corresponding studies on the model compound AgMoO2PO4. The 31P MAS-NMR data differentiate between species having two, one, and zero P―O―P linkages (Q(2) Q(1), and Q(0) species), respectively. Interatomic connectivities involving these units are revealed by two-dimensional INADEQUATE data, utilizing the formation of double quantum coherences mediated by indirect 31P–31P spin–spin interactions via P―O―P linkages. As this method discriminates against isolated P atoms, it also serves as an important spectral editing tool for constraining lineshape fits. 95Mo NMR data and Raman spectra suggest that the Mo species are most likely six-coordinate, forming four P―O―Mo linkages and are otherwise invariant with composition, except at MoO3 contents ≥ 40 mole %, where some Mo―O―Mo bonding and/or clustering is observed. 相似文献
109.
Mondal S Nechab M Vanthuyne N Bertrand MP 《Chemical communications (Cambridge, England)》2012,48(19):2549-2551
The tandem Crabbé homologation-radical rearrangement of terminal enediynes leads, in a one-pot procedure, to the enantioselective synthesis of six- and seven-membered ring α-aminoesters bearing a quaternary stereocenter based on the phenomenon of memory of chirality. 相似文献
110.
Mohammadreza Kalaee Shahin Akhlaghi Saeedeh Mazinani Alireza Sharif Younes Charesaz Jarestani Mehrzad Mortezaei 《Journal of Thermal Analysis and Calorimetry》2012,110(3):1407-1414
The morphology, thermal degradation behavior in addition to static and dynamic mechanical properties of various ethylene?Cpropylene?Cdiene (EPDM) rubber compounds containing nano-zinc oxide (NZnO) were investigated compared to those of EPDM with ordinary-sized ZnO (OSZnO). The field-emission scanning electron microscopy studies showed that unlike the conventional system, the formation of large size ZnO agglomerates was discouraged for NZnO filled systems. Thermogravimetric analysis (TG) revealed that the thermal degradation of EPDM system was delayed upon the inclusion of NZnO instead of OSZnO in the compound. The kinetic analysis of TG data based on Friedman and Kissinger methods showed that the nanocomposite samples exhibited higher activation energy (E a ) and lower order of reaction (n) over the conventional system, suggesting the enhancement of thermal stability upon decreasing ZnO particle size. The results obtained from dynamic mechanical analysis and static mechanical characterizations in terms of hardness, resilience, and abrasion tests interestingly indicated that NZnO not merely could act as a thermal insulator, but also could perform as a nano-filler to improve the final performance of EPDM elastomers. 相似文献