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91.
Charles L. Wilkins Milan Randić Sheldon M. Schuster Rodney S. Markin Steven Steiner Lonnie Dorgan 《Analytica chimica acta》1981,133(4):637-645
Characterization of molecular species based on the use of suitable graph invariants (graph paths, in particular) can provide a quantitative means of encoding structure; the technique is complementary to commoner approaches to studies of quantitative structure— activity relationships. Graph path encoding is here applied to quantitative studies of relationships between molecular structures and biological activity; the examples are the rates of various substrate reactions with hexoldnase, and the potential opiate-like activity of enkephalin analogs. 相似文献
92.
Ram S. Bhatt Nitya G. Kundu T. Ling Chwang Charles Heidelberger 《Journal of heterocyclic chemistry》1981,18(4):771-774
Condensation of 2,4-dimethoxy-5-iodo-6-carbomethoxypyrimidine ( 10 ) with copper (I) 3-tetrahydropyranyloxyprop-1-ynide ( 4 ) afforded 2,4-dimethoxy-5-(3′-tetrahydropyranyloxyprop-1′-yn)-6-carbomethoxypyrimidine ( 11 ), which was hydrolyzed to produce 2,4-dimethoxy-5-(3′-hydroxyprop-1′-yn)-6-carbomethoxypyrimidine ( 12 ). Oxidation of 12 with dimethyl sulfoxide-oxalyl chloride reagent gave the acetylenic aldehyde ( 13 ), which on treatment with sodium methoxide in dry tetrahydrofuran yielded 2,4-dimethoxy-5-ethynyl-6-carbomethoxypyrimidine ( 14 ). The trimethylsilyl derivative ( 15 ) was deprotected by sequential treatment with iodotrimethylsilane and aqueous sodium hydroxide, leading to the formation of 5-ethynylorotic acid ( 1 ). 相似文献
93.
Anita M. R. Fisher Angela Ferrario Charles J. Gomer 《Photochemistry and photobiology》1993,58(4):581-588
Photodynamic therapy (PDT) generates reactive oxygen species that are responsible for the initial cytotoxic events produced by this treatment. An extended (16 h) porphyrin incubation prior to light irradiation increased expression of the 75, 78 and 94 kDa glucose-regulated stress proteins (GRP), as well as the cognate form of the 70 kDa heat shock protein. However, these stress proteins were not induced following isoeffective PDT doses using a short (1 h) porphyrin incubation protocol. In the current study, Chinese hamster fibroblasts were used to examine sensitivity to adjunctive PDT and adriamycin as previous reports indicate a correlation between stress protein synthesis and a decrease in adriamycin cytotoxicity. Treatments that either induced GRP ( i.e . PDT with an extended porphyrin incubation or exposure to the calcium ionophore A23187) or did not induce GRP ( i.e . PDT with a short porphyrin incubation or UV irradiation) were followed at increasing time intervals with a 1 h adriamycin incubation. A time-dependent decrease in adriamycin cytotoxicity was observed when cells were first exposed to either of the PDT protocols or to A23187. Alterations in intracellular drug levels did not account for the change in adriamycin sensitivity. Likewise, intracellular glutathione concentrations and antioxidant enzyme activities were not significantly altered following PDT or A23187. Parameters associated with altered adriamycin sensitivity included a decrease in the percentage of S phase cells following PDT and A23187 as well as a depletion of intracellular ATP after PDT using the extended porphyrin incubation. These results demonstrate that PDT can be added to the growing list of diverse stresses producing transient resistance to adriamycin and that stress protein induction is not universally associated with all oxidative treatments inducing this resistance. 相似文献
94.
Charles M. Dozinel 《Fresenius' Journal of Analytical Chemistry》1957,157(6):401-405
Zusammenfassung Wir zeigen einen Weg zur Bestimmung von Antimon in Rein- bzw. Reinstkupfersorten. Die Erfassungsgrenze liegt bei 0,5 g Metalleinwaage in der Größenordnung zwischen 1 und 30 g Sb/Tonne (0,0001 und 0,0030%).Das Verfahren hat den Vorzug der Schnelligkeit gegenüber allen bisher üblichen Methoden. Die Reproduzierbarkeit der gefundenen Werte kann als befriedigend bezeichnet werden, obgleich die Extinktionskurve nicht ganz geradlinig verläuft.Wenn die oben erwähnte Kupferstammlösung vorliegt, läßt sich die Bestimmung innerhalb von 30 min durchführen. 相似文献
95.
Herein we report a surprisingly facile and clean synthesis of base-stabilised phosphorus(I) and arsenic(I) iodide salts, which are reagents that provide convenient access to new low oxidation state main group compounds. 相似文献
96.
M.Mark Midland Ronald L. Halterman Charles A. Brown Angela Yamaichi 《Tetrahedron letters》1981,22(42):4171-4172
The isomerization of optically-active secondary propargyl alcohols, RCHOHCC(CH2)nCH3, to terminal acetylenic alcohols, RCHOH(CH2)n+1 C=CH, by potassium 3-aminopropylamide (KAPA) proceeds without loss of configuration at the hydroxy center. 相似文献
97.
The sine-wave polarographic determination of zirconium in aqueous media was investigated using solutions which were 0.55 – 5.5·10-3M in zirconyl chloride and 1 M in potassium chloride and had been adjusted to pH 2.0 with hydrochloric acid. It was possible to determine zirconium in the concentration range of 0.05 to 0.4 mg per ml. The sine-wave polarographic behavior of zirconium in aqueous solutions in the pH range 2–3 is discussed. The sine-wave polarographic determination of niobium in aqueous media was investigated using concentrated sulfuric acid containing 5 to 0.1 mg of niobium per ml in a supporting electrolyte of citric acid; the determination of niobium was possible down to 0.1 mg of niobium per ml of concentrated sulfuric acid although the D.C. polarographic method was impractical for the determination of less than 0.5 mg of niobium per ml. 相似文献
98.
Phosphoric acid anodizing solutions are routinely titrated to monitor their concentrations; however, after successive anodizations of aluminum metal, increasing amounts of dissolved aluminum interfere with the neutralization titration. The true concentration of phosphoric acid is determined by a correction factor based on the concentration of the dissolved aluminum, which is determined industrially by flame atomic absorption spectrometry. The academic determination of a correction factor for aluminum as well as copper can be designed as a traditional or a problem-based learning exercise. 相似文献
99.
The 13C spectra of 5,6,9,10-tetradehydrocyclodeca[1,2,3,4-def]-benzo [7,8]biphenylene, 1, and 5,6,9,10-tetradehydrocyclodeca [1,2,3,4-def]-naphtho [2,3-7,8]biphenylene, 2, are reported as are those of a number of simpler acetylenic hydrocarbons used as spectral references. Most of the shifts can be assigned unambiguously. The acetylenic shift assignments were verified by ortho-proton, sp-carbon (1H(1)-13Csp(3)) decoupling experiments. A simple additive shift correlation is found for the hydrocarbons containing unstrained acetylenic groups. However, significant discrepencies are found for the 13C shifts for the strained hydrocarbons 1, 2, 1,2-bis(phenylethynyl)-benzene, 12, and 2,3-bis(phenylethynyl)-naphthalene, 13. The discrepencies are particularily large for carbons near the triple bonds and are attributed to a combination of strain, rehybridization, and other proximity effects related to the interaction between the ortho-substituted acetylenic carbons. 相似文献
100.
ACUTE SKIN RESPONSE IN ALBINO MICE FOLLOWING PORPHYRIN PHOTOSENSITIZATION UNDER OXIC AND ANOXIC CONDITIONS 总被引:4,自引:0,他引:4
Abstract Acute normal skin toxicity induced by porphyrin photosensitization has been examined using albino mice. Oxic and anoxic (clamped) skin was exposed to red light (630 nm) 24 h following administration of hematoporphyrin derivative (HpD) or Photofrin II (the active component of HpD). Experiments were also performed to determine the effect of sodium pentobarbital anesthesia on HpD and Photofrin II photosensitization of normal skin. Results from this study demonstrated that comparable levels of acute skin damage were induced by HpD and Photofrin II under oxic conditions but neither porphyrin produced any apparent phototoxicity under anoxic conditions. In addition, the level of skin damage induced by porphyrin photosensitization was not affected by sodium pentobarbital anesthesia. 相似文献