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41.
Takaaki Tsuchida Gang Zheng Ravindra K. Pandey William R. Potter David A. Bellnier Barbara W. Henderson Harubumi Kato Thomas J. Dougherty 《Photochemistry and photobiology》1997,66(2):224-228
Human serum albumin (HSA) is one of the key components in human blood that may influence drug distribution. As such, it is important to know the affinity of any drug for albumin. Previously, Photofrina mixture of monomeric, dimeric and oligomeric porphyrins, has been subjected to HSA binding studies. However, due to its complex nature, binding studies on Photofrin or other hematoporphyrin derivatives with HSA are inconclusive. In this report, the binding properties of some components (dimers and trimers) of Photofrin® and the relationship between murine photosensitizing efficacy and those binding properties were investigated. The interaction of these porphyrins with HSA was investigated by direct ultrafiltration and fluorescent titration techniques with fluorescent probes such as dansyl-L-proline (DP), which is known to interact selectively with site II on HSA. Porphyrins also were tested for antitumor activity in a mouse model following intravenous administration and exposure to laser light. Together, the results suggest that the photosensitizers that were preferentially bound to site II of HSA were most effective at controlling murine tumor regrowth 相似文献
42.
43.
The thermal decomposition of cadmium acetate dihydrate in helium and in air atmosphere has been investigated by means of a
coupled TG-DTA-MS method combined with X-ray diffraction analysis. Dehydration of Cd(CH3COO)2·2H2O is a two-stage process with Cd(CH3COO)2·H2O as intermediate. The way of Cd(CH3COO)2 decomposition strongly depends on the surrounding gas atmosphere and the rate of heating. CdO, acetone and CO2 are the primary products of decomposition in air. In helium decomposition goes by two parallel and consecutive reactions
in which intermediates, Cd and CdCO3, are formed. Metallic cadmium oxidizes and cadmium carbonate decomposes giving CdO. Some of the metallic cadmium, depending
on the heating rate and the concentration of oxygen, evaporates. Acetone is partially oxidized in secondary reactions with
oxygen.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
44.
Two equivalents of the thermally stable silylene Si[(NCH2But)2C6H4-1,2] (1) react with pyridine to yield the 1-aza-2,3-disilacyclobutane derivative (2), which is labile and slowly rearranges via a 1,3-H shift to the 2-pyridyldisilane (3). A similar reaction of 1 with quinoline gives 1-aza-2,3-disilacyclobutane derivative (4), which is stable. The X-ray structures of 2 and 3 are discussed. 相似文献
45.
Rüdiger O Abad JM Hatchikian EC Fernandez VM De Lacey AL 《Journal of the American Chemical Society》2005,127(46):16008-16009
The orientation of hydrogenase bound covalently to a pyrolytic graphite edge electrode modified with a 4-aminophenyl monolayer can be modulated via electrostatic interactions during the immobilization step. At low ionic strength and when the amino groups of the electrode surface are mostly protonated, the hydrogenase is immobilized with the negatively charged region that surrounds its 4Fe4S cluster nearer to the protein surface facing the electrode. This allows direct electron transfer between the immobilized hydrogenase and the electrode, which is observed by the strong catalytic currents measured in the presence of the H2 substrate. Therefore, a very stable enzymatic electrode is produced that catalyzes nonmediated H2 oxidation. 相似文献
46.
A study on the reactivity of 3,4-dihydro-2-pyridones 9, derived from (S)-phenylglycinol, toward different bases is presented. Using a catalytic amount of bases, the cis bicyclic lactams were obtained with excellent diastereoselectivities. 相似文献
47.
Alig Robin Karine Julienne Jean Claude Meslin David Deniaud 《Tetrahedron letters》2004,45(52):9557-9559
Substituted pyridones and pyridines have been synthesised efficiently by employing iminium salt as a key precursor. These compounds were prepared using tandem [4+2] cycloaddition/deamination between azabutadiene and dienophiles. 相似文献
48.
Thaler F Valsasina B Baldi R Xie J Stewart A Isacchi A Kalisz HM Rusconi L 《Analytical and bioanalytical chemistry》2003,376(3):366-373
beta-Elimination of the phosphate group on phosphoserine and phosphothreonine residues and addition of an alkyldithiol is a useful tool for analysis of the phosphorylation states of proteins and peptides. We have explored the influence of several conditions on the efficiency of this PO(4)(3-) elimination reaction upon addition of propanedithiol. In addition to the described influence of different bases, the solvent composition was also found to have a major effect on the yield of the reaction. In particular, an increase in the percentage of DMSO enhances the conversion rate, whereas a higher amount of protic polar solvents, such as water or isopropanol, induces the opposite effect. We have also developed a protocol for enrichment of the modified peptides, which is based on solid-phase covalent capture/release with a dithiopyridino-resin. The procedure for beta-elimination and isolation of phosphorylated peptides by solid-phase capture/release was developed with commercially available alpha-casein. Enriched peptide fragments were characterized by MALDI-TOF mass spectrometric analysis before and after alkylation with iodoacetamide, which allowed rapid confirmation of the purposely introduced thiol moiety. Sensitivity studies, carried out in order to determine the detection limit, demonstrated that samples could be detected even in the low picomolar range by mass spectrometry. The developed solid-phase enrichment procedure based on reversible covalent binding of the modified peptides is more effective and significantly simpler than methods based on the interaction between biotin and avidin, which require additional steps such as tagging the modified peptides and work-up of the samples prior to the affinity capture step. 相似文献
49.
Bérangère C Caussarieu N Morin P Morin-Allory L Lafosse M 《Journal of separation science》2004,27(12):964-970
An original system which uses Porous Graphitic Carbon as support and a mixture of organic solvents as mobile phase is proposed for the analysis of triterpenic acids by liquid chromatography. The separation of betulinic acid, ursolic acid, oleanolic acid, and 18alpha- and 18beta-glycyrrhetinic acids was carried out within a short time and monitored by evaporative light scattering detection as universal detection method. Molecular modelling studies show that the main contribution to the selectivity comes from the electrostatic interaction characterised by the dipole moment of the products. 相似文献
50.
The development of an amperometric biosensor for the determination of phenolic compounds is described, using quinoprotein glucose dehydrogenase. The enzyme is integrated into carbon paste and its ability to donate electrons to oxidized phenolic compounds during glucose oxidation is exploited. The sensor response is based on electrochemical oxidation of the phenolic compound followed by its enzymatic regeneration when the bulk solution contains glucose and the electrode is potentiostated at +500 mV (vs. Ag/AgCl/0.1 mol/L KCl). As the result of the catalytic analyte regeneration the electrodes offer very sensitive measurements of redox species like p-aminophenol and hydroquinone and catecholamines such as epinephrine, norepinephrine, and dopamine. The sensor performance is characterized for the different substrates. Highest sensitivity is achieved for p-aminophenol which could be determined at sub-nanomolar level. 相似文献