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21.
Rosenfeld A Morgan J Goswami LN Ohulchanskyy T Zheng X Prasad PN Oseroff A Pandey RK 《Photochemistry and photobiology》2006,82(3):626-634
The effects of an additional keto group on absorption wavelength and the corresponding metal complexes Zn(II), Cu(II) In(III) on singlet oxygen production and photodynamic efficacy were examined among the alkyl ether analogs of pyropheophorbide-a. For the preparation of the desired photosensitizers, the methyl 13(2)-oxo-pyropheophorbide-a obtained by reacting methyl pyropheophorbide-a with aqueous LiOH-THF was converted into a series of alkyl ether analogs. These compounds were evaluated for photophysical properties and in vitro (by means of the MTT assay and intracellular localization in RIF cells) and in vivo (in C3H mice implanted with RIF tumors) photosensitizing efficacy. Among the alkyl ether derivatives, the methyl 3-decyloxyethyl-3-devinyl-13(2)-oxo-pyropheophorbide-a was found to be most effective and the insertion of In(III) into this analog further enhanced its in vitro and in vivo photosensitizing efficacy. Fluorescence microscopy showed that, in contrast to the hexyl and dodecyl ether derivatives of HPPH (which localize in mitochondria and lysosomes, respectively), the diketo-analogs and their In(III) complexes localized in Golgi bodies. The preliminary in vitro and in vivo results suggest that, in both free-base and metalated analogs, the introduction of an additional keto group at the five-member exocyclic ring in pyropheophorbide-a diminishes its photosensitizing efficacy. This may be due to a shift in subcellular localization from mitochondria to the Golgi bodies. The further introduction of In(III) enhances photoactivity, but not by shifting the localization of the photosensitizer. 相似文献
22.
Ibon Alkorta Janet E. Del Bene José Elguero Otilia Mó Manuel Yáñez 《Theoretical chemistry accounts》2009,124(3-4):187-195
Ab initio calculations were carried out to investigate the structures, binding energies, bonding, and NMR spin–spin coupling constants of complexes HLB=BLH, for L=CO, NH3, OH2, PH3, SH2, and ClH. Both B–B and B–H bonds lengthen on complex formation relative to singlet HBBH, and except for L=CO, the B–B bonds are double bonds. The order of stability of the trans isomers correlates with the ordering of ligands in the spectrochemical series of ligand field theory. The trans isomer is always more stable than the corresponding cis. Inverse correlations are found between 1 J(B–B) and 1 J(B–H) and the corresponding B–B and B–H distances. For the trans isomers, 1 J(B–B) appears to be related to the ordering of ligands in the spectrochemical series, while 1 J(B–H) is related to the protonation energy of the ligand L. 相似文献
23.
Jizhong Zhou Anthony V. Palumbo Janet M. Strong 《Applied biochemistry and biotechnology》1999,80(3):243-253
Two bacterial communities (NO92 and GBS) capable of degrading carbon tetrachloride (CT) were enriched from in-house CT-contaminated
water. These communities are able to degrade CT in the presence of toluene. To characterize the community structure and diversity,
one enrichment (NO92) was subjected to 16S ribosomal RNA (rRNA) gene-based molecular analysis. The 16S rRNA genes were amplified
from the bulk genomic community DNA and cloned into plasmid vectors. Unique 16S rRNA gene clones, i.e., phylotypes, were detected
by four tetrameric restriction enzymes. Together, 123 16S rRNA gene clones were obtained; thirty-one showed different restriction
fragment length polymorphism (RFLP) patterns. About 73% of the clones belong to two dominant RFLP patterns. Phylogenetic analysis
based on the partial 16S rRNA gene sequences of 10 major phylotypes showed that all the phylotypes that were sequenced were
affiliated with the high G+C Gram-positive bacteria. Whereas seven of the phylotypes (∼80% of the clones) were closely related
to Rhodococcus, the other three (∼5% of the clones) were related to Curtobacterium. These results suggest that this CT-degrading community is diverse but is predominated by closely related bacterial groups. 相似文献
24.
Del Bene JE Elguero J Alkorta I Yañez M Mó O 《The journal of physical chemistry. A》2006,110(32):9959-9966
Ab initio equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) calculations have been performed to investigate substituent effects on coupling constants for borazine and selected substituted borazines. For molecules in which F atoms are not bonded to adjacent atoms in the ring, F substitution increases the one-bond (11)B-(15)N coupling constants involving the atom at which substitution occurs but leaves the remaining one-bond B-N coupling constants essentially unchanged. For these molecules, the magnitudes of one-bond B-N coupling constants are only slightly dependent on the number of F atoms present. Fluorine substitution at adjacent B and N atoms in the borazine ring further increases the one-bond B-N coupling constant involving the substituted atoms and has the same effect on the other one-bond coupling constants as observed for corresponding molecules in which substitution occurs at alternate sites. In contrast to the effect of F substitution, substitution of Li at either N or B decreases one-bond B-N coupling constants relative to borazine. The effects of F and Li substitution on one-bond B-N coupling constants for borazine are similar to F and Li substitution effects on (13)C-(13)C coupling constants for benzene. 相似文献
25.
Andrews KW Schweitzer A Zhao C Holden JM Roseland JM Brandt M Dwyer JT Picciano MF Saldanha LG Fisher KD Yetley E Betz JM Douglass L 《Analytical and bioanalytical chemistry》2007,389(1):231-239
As part of a study initiating the development of an analytically validated Dietary Supplement Ingredient Database (DSID) in
the United States (US), a selection of dietary supplement products were analyzed for their caffeine content. Products sold
as tablets, caplets, or capsules and listing at least one caffeine-containing ingredient (including botanicals such as guarana,
yerba mate, kola nut, and green tea extract) on the label were selected for analysis based on market share information. Two
or three lots of each product were purchased and analyzed using high-pressure liquid chromatography (HPLC). Each analytical
run included one or two National Institute of Standards and Technology (NIST) Standard Reference Materials (SRMs) and two
products in duplicate. Caffeine intake per serving and per day was calculated using the maximum recommendations on each product
label. Laboratory analysis for 53 products showed product means ranging from 1 to 829 mg caffeine/day. For products with a
label amount for comparison (n = 28), 89% (n = 25) of the products had analytically based caffeine levels/day of between −16% and +16% of the claimed levels. Lot-to-lot
variability (n = 2 or 3) for caffeine in most products (72%) was less than 10%. 相似文献
26.
The pyridinium bisretinoid A2E, an autofluorescent pigment that accumulates in retinal pigment epithelial cells with age and in some retinal disorders, can mediate a detergent-like perturbation of cell membranes and light-induced damage to the cell. The photodynamic events initiated by the sensitization of A2E include the generation of singlet oxygen and the oxidation of A2E at carbon-carbon double bonds. To assess the ability of plant-derived anthocyanins to modulate adverse effects of A2E accumulation on retinal pigment epithelium (RPE) cells, these flavylium salts were isolated from extracts of bilberry. Nine anthocyanin fractions reflecting monoglycosides of delphinidin, cyanidin, petunidin and malvidin were obtained and all were shown to suppress the photooxidation of A2E at least in part by quenching singlet oxygen. The anthocyanins tested exhibited antioxidant activity of variable efficiency. The structural characteristics relevant to this variability likely included the ability to form a stable quinonoidal anhydro base at neutral pH, a conjugated diene structure in the C (pyrane) ring, the presence of hydroxyl groups on the B (benzene) ring and the relative hydrophobicity conferred by the arrangement of substituents on the B ring. Cells that had taken up anthocyanins also exhibited a resistance to the membrane permeabilization that occurs as a result of the detergent-like action of A2E. 相似文献
27.
28.
Previous studies of the photochemical reaction of 1-methylthymine (MeT) in frozen aqueous solution have indicated that four cyclobutane type dimers are formed. We have restudied this system and have found that, in addition to cyclobutane dimers, both a (5-4) adduct and a (6-4) adduct of MeT are formed in significant amounts. Upon standing in aqueous solution, the (5-4) adduct is susceptible to reaction to form an isomeric form of the parent adduct, possibly via ring-opening and closure reactions at C-6 of the saturated pyrimidine ring component of the adduct. Irradiation of each of these three adducts with UVB light produces a pair of Dewar-type adducts. The nine products were individually characterized by mass spectrometry, proton NMR spectroscopy and UV spectroscopy. A less comprehensive study showed that irradiation of thymidine in frozen aqueous solution produces a diastereomeric pair of (5-4) adducts, along with the previously known diastereomeric pair of (6-4) adducts. 相似文献
29.
Marym Lashanizadehgan Mehdi Rashidi Janet E. Hux Richard J. Puddephatt Samson S.M. Ling 《Journal of organometallic chemistry》1984,269(3):317-322
Reaction of excess MeLi and MeI with [PtCl2SMe2)2] gives the first binuclear tetramethylplatinum(IV) complex [Pt2Me8(μ-SMe2)2]. The characterization of this complex, and its reactions with donor ligands to give cis-[PtMe4L2] (L2 = Ph2PCH2PPh2, Ph2PCH2CH2PPh2, 2,2′-bipyridyl, 1,10-phenanthroline or L = PMe2Ph, PMePh2) are described. 相似文献
30.
Wolfgang A. Herrmann Roland M. Kratzer Janet Blümel Holger B. Friedrich Richard W. Fischer David C. Apperley Janos Mink Otto Berkesi 《Journal of molecular catalysis. A, Chemical》1997,120(1-3):197-205
Polymer-supported oxidic osmium catalysts based on cross-linked poly(4-vinyl pyridine) were synthesized by various routes and characterized by a number of physical techniques (Raman, IR, XPS, 13C and 15N solid-state NMR spectroscopy). Model compounds of type Os2O6L4 (L = pyridine, 4-iso-propyl pyridine, and 4-tert-butyl pyridine) were obtained under the conditions of the catalyst synthesis. The catalytic systems were successful in the dihydroxylation of alkenes. 相似文献