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1.
Suman Dhami Garry Rumbles Alexander J. MacRobert David Phillips 《Photochemistry and photobiology》1997,65(1):85-90
Abstract— The photophysical properties of cis -disulfonated aluminum phthalocyanine (AlPcS2 ) in unilamellar vesicles (liposomes) of DL-a-dipalmitoyl-phosphatidylcholine have been measured. Both the fluorescence and triplet quantum yields decreased with increasing sensitizer concentration. The time-resolved fluorescence decays, analyzed by both the sum of exponentials and decay time distribution analyses, are compared with those reported for AlPcS2 in leukemic K562 cells. Information on the pho-todynamic transport and localization mechanism has been obtained by drawing correlations between the two systems, indicating active transport of the phthalocyanine into tumor cells involving lysosomal accumulation. 相似文献
2.
A single-crystal neutron diffraction analysis of the cluster complex [H(4)Co(4)(C(5)Me(4)Et)(4)] was carried out on the new quasi-Laue diffractometer VIVALDI at the Institut Laue-Langevin. The structure consists of four face-bridging hydrides attached to a tetrahedral cobalt metal core. Average distances and angles in the core of the molecule are as follows: Co-Co = 2.571(8), Co-C = 2.158(6), Co-H = 1.749(7), H.H = 2.366(9) A; Co-H-Co = 94.6(3), H-Co-H = 85.1(3) degrees. The hydride ligands are located off the Co-Co-Co planes by an average distance of 0.923(8) A. It is suggested that the dimensions of the HCo(3) fragments found in this molecule provide reasonable estimates for analogous distances and angles associated with chemisorbed H atoms situated on the 3-fold hollows of a cobalt surface. Crystallographic details: space group P2(1)/a (monoclinic); a = 21.979(2), b = 10.924(1), c = 34.406(2) A; beta = 90.81(1) degrees; Z = 8. Final agreement factor: R(F) = 0.099 for 3779 reflections [I > 2sigma(I)] collected at 20 K. 相似文献
3.
[reaction: see text] On treatment with samarium(II) iodide, gamma,delta-unsaturated ketones undergo very different processes depending upon the nature of the reaction conditions. Employing samarium(II) iodide and MeOH, functionalized syn-cyclopentanol products are obtained stereoselectively. Mechanistic studies suggest that this cyclization occurs via a sequential reduction/intramolecular aldol reaction. With samarium(II) iodide and HMPA, products of a 4-exo-trig cyclization and of an interesting fragmentation reaction are observed. 相似文献
4.
Results are presented for potentiometric ammonia gas-sensors which show that the response times increase significantly with age of the sensor when ammonium picrate is used as internal electrolyte and the samples have greater osmolarities than the internal electrolyte solution. A build-up of ammonium picrate crystals on the inner side of the gas-permeable membrane is responsible for this increasein response time. The use of ammonium chloride as internal electrolyte provides constant response times indepent of sample osmotic strength, and is recommended as a means of ensuring that optimal dynamic response characteristics are maintained. 相似文献
5.
Turner DR Henry M Wilkinson C McIntyre GJ Mason SA Goeta AE Steed JW 《Journal of the American Chemical Society》2005,127(31):11063-11074
Four isomorphous complexes of formula [M(L)(4)(H(2)O)(2)]SO(4).2H(2)O (M = Co, 1a; Ni, 1b; Cu, 1c; Zn, 1d) have been isolated and characterized by single-crystal X-ray diffraction and neutron diffraction using the quasi-Laue diffractometer VIVALDI at the Institut Laue-Langevin as well as by thermogravimetric analysis. The structures contain a discrete, strongly hydrogen-bonded water tetramer which causes a significant distortion of the metal coordination sphere in each case. Partial atomic charges and hardness analysis (PACHA) calculations reveal that the shortest hydrogen bonds are not the strongest in this constrained, cyclic solid-state structure and show that the distortion at the metal center is caused by the drive to maintain the integrity of the water tetramer. The system undergoes a disorder-order transition on slow cooling that provides insight into the nature of communication between water squares. 相似文献
6.
The use of grape tissue as a source of catalase for the determination of hydrogen peroxide is reported. A slice of grape tissue attached to the membrane of a Clark-type oxgen sensor was used to monitor the oxidation of hydrogen peroxide by catalase. At the steady state, the sensor responds linearly to hydrogen peroxide in the concentration range 1 × 10?5–5 × 10?4 M. The response time (T90) was of the order of 1 min for this sensor. No interference was observed from ethanol, amino acids, glucose and lactic acid. The long-term stability of the grape tissue sensor was much better than previously reported immobilized enzyme and liver tissue-based hydrogen peroxide sensors. 相似文献
7.
Although 7-methoxy- and 6,7-dimethoxy-2-methyl-4-vinyl-isocarbostyrils could not be isolated and characterised, they have been generated in situ and shown to undergo cyclo-addition reactions with typical dienophiles. The enol acetate of 2-methyl-4-acetylisocarbostyril has also been trapped as its adduct with maleic anhydride and with p-benzoquinone. 相似文献
8.
ULTRAVIOLET LIGHT-INDUCED FREE RADICAL FORMATION IN SKIN: AN ELECTRON PARAMAGNETIC RESONANCE STUDY 总被引:7,自引:0,他引:7
It has been suggested that ultraviolet light induces free radical formation in skin, leading to photoaging and cancer. We have demonstrated by electron paramagnetic resonance that the ascorbate free radical is naturally present in unexposed skin at a very low steady state level. When a section of SKH-1 hairless mouse skin in an EPR cavity is exposed to UV light (4,500 J m−2 −1, Xe lamp, 305 nm cutoff and IR filters), the ascorbate free radical signal intensity increases. These results indicate that UV light increases free radical oxidative stress, consistent with ascorbate's role as the terminal, small-molecule antioxidant. The initial radicals produced by UV light would have very short lifetimes at room temperature; thus, we have applied EPR spin trapping techniques to detect these radicals. Using α-[4-pyridyl 1-oxide]-N- tert -butyl nitrone (POBN), we have for the first time spin trapped a UV light-produced carbon-centered free radical from intact skin. The EPR spectra exhibited hyperfine splittings that are characteristic of POBN/alkyl radicals, aN = 15.56 G and aH = 2.70 G, possibly generated from membrane lipids as a result of β-scission of lipid alkoxyl radicals. Iron can act as a catalyst for free radical oxidative reactions; chronic exposure of skin to UV radiation causes increased iron deposition. Using our spin trapping system, we have shown that topical application of the iron-chelator, Desferal, to a section of skin reduces the UV light-induced POBN adduct radical signal. These results provide direct evidence for free radical generation and a role for iron in UV light-induced dermatopathology. We suggest that iron chelators can serve as photoprotective agents by preventing these oxidations. 相似文献
9.
Mund G Vidovic D Batchelor RJ Britten JF Sharma RD Jones CH Leznoff DB 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(19):4757-4763
Several iron(III) complexes incorporating diamidoether ligands are described. The reaction between [Li(2)[RN(SiMe(2))](2)O] and FeX(3) (X=Cl or Br; R=2,4,6-Me(3)Ph or 2,6-iPr(2)Ph) form unusual ate complexes, [FeX(2)Li[RN(SiMe(2))](2)O](2) (2, X=Cl, R=2,4,6-Me(3)Ph; 3, X=Br, R=2,4,6-Me(3)Ph; 4, X=Cl, R=2,6-iPr(2)Ph) which are stabilized by Li-pi interactions. These dimeric iron(III)-diamido complexes exhibit magnetic behaviour characteristic of uncoupled high spin (S= 5/2 ) iron(III) centres. They also undergo halide metathesis resulting in reduced iron(II) species. Thus, reaction of 2 with alkyllithium reagents leads to the formation of iron(II) dimer [Fe[Me(3)PhN(SiMe(2))](2)O](2) (6). Similarly, the previously reported iron(III)-diamido complex [FeCl[tBuN(SiMe(2))](2)O](2) (1) reacts with LiPPh(2) to yield the iron(II) dimer [Fe[tBuN(SiMe(2))](2)O](2) but reaction with LiNPh(2) gives the iron(II) product [Fe(2)(NPh(2))(2)[tBuN(SiMe(2))](2)O] (5). Some redox chemistry is also observed as side reactions in the syntheses of 2-4, yielding THF adducts of FeX(2): the one-dimensional chain [FeBr(2)(THF)(2)](n) (7) and the cluster [Fe(4)Cl(8)(THF)(6)]. The X-ray crystal structures of 3, 5 and 7 are described. 相似文献
10.