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91.
Photoactivation of pheophorbide a induces a mitochondrial-mediated apoptosis in Jurkat leukaemia cells 总被引:5,自引:0,他引:5
Lee WY Lim DS Ko SH Park YJ Ryu KS Ahn MY Kim YR Lee DW Cho CW 《Journal of photochemistry and photobiology. B, Biology》2004,75(3):119-126
The mechanism of cell death by pheophorbide a (Pba) which has been established to be a potential photosensitizer was examined in experimental photodynamic therapy (PDT) on Jurkat cells, a human lymphoid tumor cell line. In 30-60 min after irradiation, Pba treated cells exhibited apoptotic features including membrane blebbing and DNA fragmentation. Pba/PDT caused a rapid release of cytochrome c from mitochondria into the cytosol. Sequentially, activation of caspase-3 and the cleavage of poly ADP-ribose polymerase (PARP) were followed. Meanwhile, no evidence of activation of caspase-8 was indicated in the cells. In experiments with caspase inhibitors, it was found that caspase-3 alone was sufficient initiator for the Pba-induced apoptosis of the cells. Pba specific emission spectra were confirmed in the mitochondrial fraction and the light irradiation caused a rapid change in its membrane potential. Thus, mitochondria were entailed as the crucial targets for Pba as well as a responsible component for the cytochrome c release to initiate apoptotic pathways. Taken together, it was concluded that the mode of Jurkat cell death by Pba/PDT is an apoptosis, which is initiated by mitochondrial cytochrome c release and caspase-3-pathways. 相似文献
92.
Transformation of arctiin to estrogenic and antiestrogenic substances by human intestinal bacteria 总被引:2,自引:0,他引:2
Xie LH Ahn EM Akao T Abdel-Hafez AA Nakamura N Hattori M 《Chemical & pharmaceutical bulletin》2003,51(4):378-384
After anaerobic incubation of arctiin (1) from the seeds of Arctium lappa with a human fecal suspension, six metabolites were formed, and their structures were identified as (-)-arctigenin (2), (2R,3R)-2-(3',4'-dihydroxybenzyl)-3-(3",4"-dimethoxybenzyl)butyrolactone (3), (2R,3R)-2-(3'-hydroxybenzyl)-3-(3",4"-dimethoxybenzyl)butyrolactone (4), (2R,3R)-2-(3'-hydroxybenzyl)-3-(3"-hydroxy-4"-methoxybenzyl)butyrolactone (5), (2R,3R)-2-(3'-hydroxybenzyl)-3-(3",4"-dihydroxybenzyl)butyrolactone (6), and (-)-enterolactone (7) by various spectroscopic means including two dimensional (2D)-NMR, mass spectrometry, and circular dichroism. A possible metabolic pathway was proposed on the basis of their structures and the time course of the transformation. Enterolactones obtained from the biotransformation of arctiin and secoisolariciresinol diglucoside (SDG, from the seeds of Linum usitatissium) by human intestinal bacteria were proved to be enantiomers, with the (-)-(2R,3R) and (+)-(2S,3S) configurations, respectively. Compound 6 showed the most potent proliferative effect on the growth of MCF-7 human breast cancer cells in culture among 1 and six metabolites, while it showed inhibitory activity on estradiol-mediated proliferation of MCF-7 cells at a concentration of 10 microM. These results indicate that the transformation of 1 by intestinal flora might be essential for the manifestation of the estrogenic and antiestrogenic activity of 1. 相似文献
93.
Four new heterometallic glutarate coordination polymers, [Eu2M(H2O)4][O2C(CH2)3CO2]4.2H2O (M = Mn (1), Fe (2), Co (3) and Ni (4)) have been obtained under hydrothermal synthesis. The single-crystal X-ray diffraction analyses showed that they have two-dimensional frameworks based on the linear polyhedral chains consisting of two nine-coordinated Eu(III)O9 and a six-coordinated M(II)O6. These 1-D MO6-Eu2O16 chains are cross-linked by glutarate ligands as an interchain pillared architecture, whose conformations vary depending upon the transition metals. The magnetic behavior of the compounds show a weak antiferromagnetic interaction, in which shielding of the 4f electrons by the outer shell electrons effectively precludes significant coupling interactions between the Eu-4f electrons and transition metal (M)-3d electrons. 相似文献
94.
This paper describes an efficient synthetic route for various types of novel carbocyclic nucleosides. The required stereochemistry of the targeted nucleosides was successfully obtained with use of Grubbs cyclization and Trost allylic alkylation from the carbohydrate chiral template "D-lactose". 相似文献
95.
The 13C-NMR spectra of the synthetic membrane modifying nonadecapeptide Boc-(Aib-l-Ala)5-Gly-Ala-Aib-Pro-Ala- Aib-Aib-Glu(OBz)-Gln-OMe (Aib = α-aminoisobutyric acid), and of synthetic intermediates were used for conformational analysis in solution. The assignments of the 13C-NMR signals of Aib are based on the magnetic nonequivalence (MNE) of the geminal Cβ-signals in asymmetric environment resulting in a shift difference of 0.2–0.5 ppm due to neighbouring chiral residues. More than 4 ppm MNE are observed due to α-helical conformation and about 2.5 ppm for Aib situated in the corners of a rigid β-turn. The Ala-Cα signal is also sensitive to different secondary structures. The Cα signal for C-terminal alanine is found at 49–50 ppm, and for alanine within unordered oligopeptides it absorbs at 50–51 ppm. α-Helical environment shifts the Ala-Cα signal to lower field down to 54 ppm. In methanolic solution the nonadecapeptide shows a α-helical N-terminal region. For the C-terminus beginning with proline-14 no periodically ordered conformation is observed, and we suggest a sequence of β-turns. Furthermore the typical E/Z isomerism of the prolyl-peptide bond can be observed on proline itself and on its neighbour alanine. 相似文献
96.
Hyoung Sik Kim Min Kang Min Woo Song Jin Won Park Byoung Ryul Min 《Reaction Kinetics and Catalysis Letters》2004,81(2):251-257
Pt-Pd bimetallic catalysts were prepared in order to develop and investigate catalysts having excellent activity and stability
for benzene destruction. The effect of Pt addition to Pd catalysts is studied by XPS analysis.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
97.
Reaction of 1,6-enynes with a hydrosilane in the presence of immobilized cobalt/rhodium bimetallic nanoparticles gives 2-methyl-1-silylmethylidene-2-cyclopentanes in the absence of carbon monoxide and 2-formylmethyl-1-silylmethylidene-2-cyclopentanes under 1 atm of carbon monoxide, respectively. [reaction: see text] 相似文献
98.
Jin Ho Lee Heoung Woo Kim Pyong Ki Pak Hai Bang Lee 《Journal of polymer science. Part A, Polymer chemistry》1994,32(8):1569-1579
Functional group gradient surfaces where the density of functional groups changes gradually along the sample length were prepared. The functional group (? COOH, ? CONH2, and ? OH group) gradient surfaces were produced by the treatment of low-density PE sheets using a corona with gradually increasing power, followed by the graft copolymerization of acrylic acid and subsequent substitution reaction of carboxylic acid groups to amide or hydroxyl groups. The prepared gradient surfaces were characterized by the measurement of water contact angle, FTIR-ATR, and ESCA. The gradient surfaces prepared can be used to systematically investigate the interactions of biological or other species in terms of the surface functional groups and their density of polymeric materials. © 1994 John Wiley & Sons, Inc. 相似文献
99.
A high-performance liquid chromatographic (HPLC) procedure has been evaluated to establish a routine test in the clinical laboratory for measuring the profiles of estrogen and progestin receptor isoforms in human breast and endometrial tumors. This procedure will be used to determine if there is a relationship between particular isoform profiles and response to various endocrine therapies. Evaluation of various HPLC modes has shown that high-performance ion-exchange chromatography (HPIEC) with silica-based anion exchangers offers a promising approach. In this paper, we have compared HPIEC columns of different lengths (10 and 25 cm) and pore sizes (300, 500 and 1,000 A) in order to obtain an optimal separation procedure. Because of receptor lability, all investigations were performed at 4 degrees C. The mobile phase consisted of 10-500 mM phosphate buffer, supplemented with the stabilizing agent, sodium molybdate at pH 7.4. Recoveries from each of the columns were between 70-100%. The length of the column did not influence significantly the retention time and salt concentration required for elution of receptor proteins. However, pore sizes appeared to alter these parameters. With a larger pore size (1,000 A), the retention of proteins was lower (elution with 50 mM phosphate) than that observed with the 500-A pore size column (elution with 100 mM phosphate) or of the 300-A pore size column (elution with 150 mM phosphate). Based solely on recovery patterns and peak shape, we conclude that separation of receptor isoforms on a 1,000-A, 25-cm column is best suited for clinical analysis. 相似文献
100.
Using reaction rate data collected in aprotic solvents, we have determined that the Baylis-Hillman rate-determining step is second order in aldehyde and first order in DABCO and acrylate. On the basis of these data, we have proposed a new mechanism involving a hemiacetal intermediate. The proposed mechanism was then supported using two different kinetic isotope experiments. 相似文献