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141.
John F. Callan A. P. De Silva R. C. Mulrooney B. Mc Caughan 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(3-4):257-262
Summary This review highlights recent advances in the use of quantum dots (QD’s) as luminescent sensors. The bulk of the study concentrates
on systems that possess organic ligands bound to the surface of QD’s. These ligands vary from low molecular weight thiols
to larger molecules such as maltose binding protein. All have one thing in common: when a target analyte binds to the ligand/receptor,
a perturbation of the system occurs, that registers itself as a change in the luminescence intensity of the QD. Two main mechanisms
are prevalent in controlling the luminescent intensity in such systems. The first is Photoinduced Electron Transfer (PET)
and the second energy transfer. This review looks at current sensors that operate by using these mechanisms. Two component
systems are also investigated where a quencher is first added to a solution of the QD, followed by addition of the target
analyte that interacts with the quencher to influence the luminescence intensity. 相似文献
142.
The uncatalyzed 1,4-addition of phenylmagnesium bromide and furylmagnesium iodide to methyl 5-methoxy-1,5-cyclohexadienylcarboxylate (), directly followed by alkylation and hydrolysis leads to the corresponding cyclohexanones of type (R1 and R2 trans) in moderate to high yield. 相似文献
143.
A novel generally applicable synthesis of coumarins from phenolic substrates utilizing ring-closing metathesis is described. This sequence involves O-allylation of phenols followed by ortho-Claisen rearrangement, subsequent based-induced isomerization affording 2-(1-propenyl)phenols, acylation with acryloyl chloride, and finally ring-closing metathesis (RCM) with Grubbs’ second generation catalyst. 相似文献
144.
Résumé Les auteurs ont étudié le comportement chromatographique sur plusieurs phases stationnaires polaires et non polaires de composés cyclopropaniques stéréoisomêres: où R=H ou CH3 et X=CH, COOCH3 ou CH2OH. Les résultats sont interprétés en fonction de la configuration de X par rapport à , de la nature électronique de X et de l'orientation du phényle par rapport au plan du cyclopropane.
Relationship between chemical structure and retention. VII. Cyclopropane compounds
Summary The chromatographic behaviour, on several polar and non polar phases, of stereoisomeric cyclopropanes has been studied R=H or CH3 and X=CN, COOCH3, CH2OH. The results are interpreted in terms of the X versus configuration, the electronic nature of X and the orientation of the phenyl ring in relation to plane of the cyclopropane ring.相似文献
145.
F. De Meester J. M. Frre J. L. Piette P. Jacquemin L. Grooters G. Llabres S. Defays 《Journal of heterocyclic chemistry》1992,29(2):535-541
In an attempt to rationalize a synthesis of penicillin analogs modified at C(3), we have isolated the 3R(β)-carbinolamide derivative 4a. The trityl substituent on N(6′) seems to be responsible for the inversion of configuration which occurs at C(3) during the acid hydrolysis of the isocyanate intermediate. An hydrogen bond is formed on the β-face of the bell-shaped bicyclic skeleton between the N(6′)-nitrogen lone pair and the C(3) hydroxyl group. On standing, the carbinolamide analog slowly isomerizes to its expanded bicyclic isomer 4b , but the starting material may be easily recovered by treatment with acid. The postulated intermediate during isomerization, i.e., the open aldehyde form, does not accumulate. Substitutions of the hydroxyl group at C(3) lead to a variety of compounds with the biologically active 3S(α) configuration. These may be used to study the importance of the carboxyl group of penicillins in their interaction with β-lactamases at the molecular level. 相似文献
146.
The isolation of (2S,1'S,2'S)-2-(2'-carboxycyclopropyl)glycine (CCG I, 2) from Blighia sapida (Akee) was achieved through column chromatography on deactivated silica gel followed by ion-exchange chromatography. A HPLC method has also been devised in order to assess the purity of the isolated product. 相似文献
147.
Bergquist Peter L. Te’o V. S. Junior Gibbs Moreland D. Cziferszky Angela C. E. De Faria Fabricia P. Azevedo Maristela O. Nevalainen K. M. Helena 《Applied biochemistry and biotechnology》2002,98(1-9):165-176
Cost-effective production of enzymes for industrial processes makes the appropriate selection of the host-vector expression
system critical. We have developed two systems for the bulk production of bleaching enzymes from thermophiles. Kluyveromyces lactis has been developed as a secretion host employing expression vectors based on the 2μ-like plasmid pKD1 of Kluyveromyces drosophilarium. Our second system involves the filamentous fungus Trichoderma reesei. Fusion and nonfusion vectors have been constructed using the strong cellobiohydrolase 1 (cbh1) promoter. The KEX2 protease cleavage site and a 6 × HIS-tag have been incorporated to facilitate both cleavage and purification
of the mature foreign proteins. 相似文献
148.
Cyclization of suitable enamino ketones can produce hydroxyphthalides. 相似文献
149.
Concetta?De?Stefano Antonio?Gianguzza Daniela?Piazzese Silvio?SammartanoEmail author 《Analytical and bioanalytical chemistry》2003,375(7):956-967
The binding ability of diethylene triamine pentaacetate (dtpa(5-)) and triethylene tetraamine hexaacetate (ttha(6-)) ligands towards major components, H(+), Na(+), Mg(2+) and Ca(2+), of natural waters was studied in both single and mixed ionic media at different ionic strengths and at T=25 degrees C. Some measurements, performed in Mg(2+)-Ca(2+) mixtures, allowed us to find the formation of new mixed species MgCa(dtpa), MgCa(ttha) and MgCaH(ttha), here reported for the first time. All the complexes formed in the various systems were characterized in terms of both stoichiometry and stability, and an attempt was made to find general rules for the stability of mixed metal complexes in comparison with that of simple species. To obtain quantitative information on the complexing ability of dtpa and ttha in seawater, measurements have been carried out in artificial seawater ionic medium (Na(+), K(+), Ca(2+), Mg(2+), Cl(-) and SO(4)(2-)). Calculations, performed by considering the salt mixture as single salt BA, allowed us to find some quite stable B(i)H(j)L species. Under the natural seawater conditions [S(salinity)=35], we found for the most important species logbeta( B(dtpa))=9.64 and. Literature data comparison is also reported. 相似文献
150.
C.P. Boekel A. Jelsma J.H. Teuben H.J. De Liefde Meijer 《Journal of organometallic chemistry》1977,136(2):211-218
The thermolysis of compounds of the type Cp2VR (R = aryl) in the solid state has been studied. A distinct increase in thermal stability is observed upon substitution of the ortho-position of the aryl group. Thermal decomposition occurs with formation of RH, Cp2 V, a vanadocene homologue with the group R substituted in one of the Cp rings and, probably, a vanadocene homologue with two substituted Cp rings. It is shown that the abstraction of the hydrogen atom from the cyclopentadienyl ring, necessary for the formation of RH, is an intermolecular process, whereas the substitution of the aryl group in the Cp ring is intramolecular. A decomposition mechanism is proposed in which the group R is transferred from the vanadium atom to the C5H5 ring of the same molecule by interaction with an aryl group of another molecule. The thermal decomposition of Cp2VR is compared with that of the analogous titanium compounds. 相似文献