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1.
James Elver Johnson Mohammad Arfan Richard Hodzi Lyman R. Caswell Susan Rasmussen 《Photochemistry and photobiology》1990,51(2):139-144
Abstract— Photolysis at 254 nm of alkyl benzohydroxamates [C, H, CONHOR: R = CH3 H2 CH3 CH(CH3 )2 , CH2 C6 H5 CH(CH3 )C2 H5 CH(CH3 )- n -C6 H13 ] in acetonitrile or hydrocarbon solvents gives benzamide. These reactions can be sensitized by benzophenone (at ca. 350 nm) and are quenched by cis-piperylene. Racemization occurred when 2-octyl (+)-benzohydroxamate was irradiated in cyclohexane. These results are consistent with a mechanism involving a triplet biradical. Photolysis of phenyl benzohydroxamate [C6 H5 CONHOC6 H5 ] and benzyl N -methylbenzohydroxamate [C6 H5 CON-(CH3 )OCH2 Q6 H5 ] cannot be quenched with ris-piperylene and appear to be singlet reactions. 相似文献
2.
Paul A. J. Link Henk C. Van Der Plas Franz Müller 《Journal of heterocyclic chemistry》1988,25(2):375-380
Prolonged illumination of 8-X-5-deazaflavins (X = C1, N(CH3)2, NH2, p-NH2-C6H4) in the presence of an electron donor leads to the formation of a 5,5′-dimer and/or a 6,7-dihydro compound. The course and rate of these photoreductions were established and discussed in terms of electronic and steric effects, exerted by the substituent at position 8 and the electron donor. Pseudo first-order kinetics were found to apply to the photoreduction of 8-X-5-deazaflavins (X = Cl, NH2, p-NH2-C6H4) while the rate of the photoreduction of 8-X-5-deazaflavin (X = N(CH3)2) appeared to contain an autocatalytic element. The catalytic effect of 8-X-5-deazaflavins in the photoreduction of methyl viologen by EDTA was investigated. The substituent effect on the rate of the 8-X-5-deazaflavin mediated photoreduction of methyl viologen by EDTA was found to be comparable with that on the photoreduction rate of 8-X-5-deazaflavin in the presence of EDTA with the exception of 8-X-5-deazaflavin (X = N(CH3)2), which showed a remarkable relative enhancement of the reactivity towards methyl viologen photoreduction. 相似文献
3.
MIGUEL G. NEUMANN J. IOAN MATTHEWS† SILVIA E. BRASLAVSKYdR† 《Photochemistry and photobiology》1984,39(1):31-36
Abstract— The photoreduction of methylene blue in the presence of arylaminomethanesulfonates (RAMS = RC6 H4 NHCH2 SO3 Na) was studied by laser and conventional flash photolysis. These compounds quenched the methylene blue triplet deviating from a normal Stern-Volmer behaviour. For low quencher concentrations, a Rehm-Weller relationship was found between the k q 's and the DL G 's obtained for the electron transfer reactions. The lack of further quenching at higher [RAMS] is ascribed to the formation of a ground state ion pair between the dye and the anionic quencher which, on excitation, forms a triplet state unable to under go electron transfer for steric reasons. A second order decay rate constant was found for the semireduced species (MB') ( ca. 5 × 109 M -1 s-1 , independent of the RAMS used) and is attributed to a proton transfer from the radical zwitterion (RC6 H4 NH CH2 SO3 − ) to MB. The overall dependence on the substituent of the bleaching observed by continuous irradiation follows the triplet behaviour. 相似文献
4.
Abstract— Results on the photolysis of ethyl chloroacetate, CICH2 COOC2 H5 , at A°≅ 254 nm in liquid phase are presented. GLC and i.r. methods revealed as products: hydrogen chloride and ethyl acetate; in smaller quantities–ethyl succinate and ethyl oxalate; in traces–ethyl malonate, CO2 , CO and CH3 CI; yet other, unidentified products with higher boiling points. Quantum yields are determined for some products. Similar studies were performed in the presence of I2 as a radical scavenger. In the present case, ethyl iodoacetate I – CH2 COOC2 H5 was found to arise in the system. The following primary process may be written on the basis of the experimental data:
CICH2 COOC2 H5 ← CI + CH2 COOC2 H5
Attempts to explain the production of these compounds are based mainly on the properties of the CH2 COOC2 H5 radical. 相似文献
CICH
Attempts to explain the production of these compounds are based mainly on the properties of the CH
5.
Abstract— An investigation has been made of the reaction between methylene, formed by the photolysis of ketene, and hydrogen. Ethane, ethylene and methane are the major hydrocarbon products, and it has been shown that the formation of these products may be adequately described by the sequence of processes
CH2 CO + hv → CH2 + CO (1)
CH2 + H2 → CH3 +H (2)
2CH3 → C2 H6 (3)
CH3 + H2 + CH4 + H (4)
CH2 + CH2 CO → C2 H4 + CO (7)
In particular, the relative rates of ethane and methane formation are consistent with the known rate constants for reactions (3) and (4), and it is not therefore necessary to postulate the participation of an 'insertion' process
CH2 + H2 → CH4 (6) to account for the formation of methane.
Decrease of the energy possessed by the methylene, either by increase of the wavelength of ketene photolysis, or by increase of gas pressure, is shown to result in an increase in the reactivity of the methylene towards ketene relative to its reactivity towards hydrogen (i.e. the ratio k2 /k2 increases). 相似文献
CH
CH
2CH
CH
CH
In particular, the relative rates of ethane and methane formation are consistent with the known rate constants for reactions (3) and (4), and it is not therefore necessary to postulate the participation of an 'insertion' process
CH
Decrease of the energy possessed by the methylene, either by increase of the wavelength of ketene photolysis, or by increase of gas pressure, is shown to result in an increase in the reactivity of the methylene towards ketene relative to its reactivity towards hydrogen (i.e. the ratio k
6.
Paul Gottlieb Li-Gang Shen Eleanor Chimezie Soon Bahng Malcolm E. Kenney Bernard Horowitz Ehud Ben-Hur 《Photochemistry and photobiology》1995,62(5):869-874
Abstract— -Three phthalocyanine dyes HOSiPcOSi(CH3 )2 (CH2 )3 N(CH3 )2 (Pc 4), HOSiPc-OSi(CH3 )2 (CH2 )3 N+(CH3 )3I- (Pc 5) and aluminum tetrasulfophthalocyanine hydroxide (AlOHPcS4 ) were evaluated for their ability to inactivate the trypomastigote form of Trypanosoma cruzi in fresh frozen plasma (FFP) and red blood cell concentrates (RBCC). The compound Pc 4 was found to be highly effective in killing T. cruzi, Pc 5 less effective and AlOHPcS4 ineffective. With FFP as the medium, a complete loss of parasite infectivity in vitro (≥5 log10 ) was found to occur with 2 μ M Pc 4 after irradiation with red light (>600 nm) at a fiuence of 7.5 J/cm2 , while with RBCC as the medium, a complete loss was found to occur at a fiuence of 15 J/cm2 . Even without illumination, Pc 4 at 2 μ M also killed about 3.7-4.1 log10 of T. cruzi in FFP during 30 min. Observed differences in T. cruzi killing by the various phthalocyanines may relate to differences in binding; Pc 4 binds to the parasites about twice as much as Pc 5. Ultrastructural analysis of treated parasites suggests that mitochondria are a primary target of this photodynamic treatment. The data indicate that Pc 4 combined with exposure to red light could be used to eliminate bloodborne T. cruzi parasites from blood components intended for transfusion. The inactivation of T. cruzi by Pc 4 in the dark suggests a possible therapeutic application. 相似文献
7.
Abstract— Laser flash photolysis of trans -[Rh(dppe)2 X2 ][PF6 ] (X=Br and I; dppe=bis(diphenylphosphino)ethane) in CH2 Cl2 or CH3 CN produces the d7 Rh(II) radicals, [Rh(dppe)2 X]+ , and halogen atoms. The kinetics of the disappearance of [Rh(dppe)2 X]+ radicals in CH2 Cl2 or CH3 CN were mixed order: H-atom abstraction from solvent to produce the rhodium hydrides, [RhH(dppe)2 X][PF6 ], and Rh/X recombination. In the poor H-atom donor solvent, benzonitrile, Rh/Br recombination was observed to be uncomplicated by competing H-atom abstraction. The hydride complexes [RhH(dppe)2 X][PF6 ], formed by H-atom abstraction were completely characterized by 31 P{1 H}-NMR, 1 H-NMR, and mass specrometry. Cyclohexene was used as an effective trap for photogenerated Br atoms and yielded bromocyclohexane and 3-bromocyclohexene in a relative yield, 1:9. The photochemical mechanism is discussed in light of the transient absorbance and trapping studies. 相似文献
8.
L. S. Lussier C. Sandorfy H. OA L E-Thanh D. Vocelle 《Photochemistry and photobiology》1987,45(S1):801-808
Abstract— The Fourier-transform infrared spectra of chloroform-d solutions of conjugated imines CH3 CH=CHCH=NCH(CH3 )2 and CH3 CH2 CH=CHCH=CHCH=NCH(CH3 )2 and the related protonated species with HCl, HBr, HI, trichloro, dichloro, monobromo and monochloroacetic acids or propionic acid are presented. The effects of conjugation and protonation are examined. The results show that conjugation slightly increases the basicity of the Schiff bases. HCl, HBr and HI protonate the Schiff bases completely. The carboxylic acids protonate partially depending on their p K a , values. When the Schiff base contains two (or more) C=C bonds conjugated with C=N, the main C=C stretching band undergoes a strong intensification showing that sizeable dipole moment variations occur along the conjugated chain. 相似文献
9.
Syed I. A. Zaidi Rajesh Agarwal Guido Eichler Boris D. Rihter Malcolm E. Kenney Hasan Mukhtar 《Photochemistry and photobiology》1993,58(2):204-210
Abstract— Photodynamic therapy (PDT) of cancer is a modality that relies upon the irradiation of tumors with visible light following selective uptake of a photosensitizer by the tumor tissue. There is considerable emphasis to define new photosensitizers suitable for PDT of cancer. In this study we evaluated six phthalocyanines (Pc) for their photodynamic effects utilizing rat hepatic microsomes and human erythrocyte ghosts as model membrane sources. Of the newly synthesized Pc, two showed significant destruction of cytochrome P-450 and monooxygenase activities, and enhancement of lipid peroxidation, when added to microsomal suspension followed by irradiation with ∼ 675 nm light. These two Pc named SiPc IV (HOSiPcOSi[CH3 ]2 [CH2 ]3 N[CH3 ]2 ) and SiPc V (HOSiPcOSi[CH3 ]2 [CH2 ]3 N[CH3 ]3 1 I) showed dose-dependent photodestruction of cytochrome P-450 and monooxygenase activities in liver microsomes, and photoenhancement of lipid peroxidation, lipid hydroperoxide formation and lipid fluorescence in rnicrosomes and erythrocyte ghosts. Compared to chloroaluminum phthalocyanine tetrasulfonate, SiPc IV and SiPc V produced far more pronounced photodynamic effects. Sodium azide, histidine, and 2,5-dimethylfuran, the quenchers of singlet oxygen, afforded highly significant protection against SiPc IV- and SiPc V-mediated photodynamic effects. However, to a lesser extent, the quenchers of superoxide anion, hydrogen peroxide and hydroxyl radical also showed some protective effects. These results suggest that SiPc IV and SiPc V may be promising photosensitizers for the PDT of cancer. 相似文献
10.
P. F. HEELIS B. J. PARSONS G. O. PHILLIPS A. J. SWALLOW 《Photochemistry and photobiology》1991,53(1):21-23
Abstract— The one-electron reduction and oxidation of 5,10-methenyltetrahydrofolate has been studied in aqueous solution in the acidity range H0 = -1 to pH = 7 using the reducing species CO- 2 and (CH3 )2 -COH and oxidising species Br- 2 , and H2 SeO+3 . The spectral and other properties of the radicals so formed were found to be indcpendent of the reductant/oxidant used. Two protolytic forms of both the oxidised and reduced radicals were observed with approximate p K , values of 0.5 ± 0.3 being determined. Both the bridged form (5.10-methenyltetrahydrofolate) and the unbridged form (5- formyltetrahydrofolate) were found to be easily oxidised, whereas only the former could be reduced. 相似文献
11.
Abstract— Polymer rose bengal derivatives are converted to their C-6 ammonium salts. The φ1 O2 derived in CH2 C12 is a function of the K B of the neutralizing amine. 相似文献
12.
E. Ben-Hur N. E. Geacintov B. Studamire M. E. Kenney B. Horowitz 《Photochemistry and photobiology》1995,61(2):190-195
Abstract— Phthalocyanines are being studied as photosensitizers for virus sterilization of red blood cells (RBC). During optimization of the reaction conditions, we observed a marked effect of the irradiance on production of RBC damage. Using a broad-band light source (600–700 nm) between 5 and 80 mW/ cm2 , there was an inverse relationship between irradiance and rate of photohemolysis. This effect was observed with aluminum sulfonated phthalocyanine (AlPcSn ) and cationic silicon (HOSiPc-OSi[CH3 ]2 [CH2 ]3 N+ [CH3 ]3 I- phthalocyanine (Pc5) photosensitizers. The same effect occurred when the reduction of RBC negative surface charges was used as an endpoint. Under the same treatment conditions, vesicular stomatitis virus inactivation rate was unaffected by changes in the irradiance. Reduction in oxygen availability for the photochemical reaction at high irradiance could explain the effect. However, theoretical estimates suggest that oxygen depletion is minimal under our conditions. In addition, because the rate of photohemolysis at 80 mW/cm2 was not increased when irradiations were carried out under an oxygen atmosphere this seems unlikely. Likewise, formation of singlet oxygen dimoles at high irradiances does not appear to be involved because the effect was unchanged when light exposure was in D2 O. While there is no ready explanation for this irradiance effect, it could be used to increase the safety margin of RBC virucidal treatment by employing exposure at high irradiance, thus minimizing the damage to RBC. 相似文献
13.
Nicholas J. Turro Kou-Chang Lru Ming-Fea Chow Plato Lee 《Photochemistry and photobiology》1978,27(5):523-529
Abstract— Phosphorescence of organic molecules in fluid solutions may be conveniently and readily observed under certain conditions. If k p (radiative phosphorescence rate constant) is 10s-1 , then (in the absence of photoreaction) phosphorescence is observable upon N2 purging. For example, nitrogen purged, acetonitrile solutions of bromo and dibromonaphthalene display readily observable phosphorescence as a result of internal heavy atom enhancement of πS , and k p . External heavy atom enhancement of k, (CH2 BrCH2 Br solvent) of aromatic hydrocarbons even allows observation of phosphorescence from these compounds in N2 purged fluid solutions. Although bromonaphthalenes are not significantly phosphorescent in N2 purged aqueous solution, phosphorescence is readily observed in N2 purged detergent (HDTBr, HDTCl, and SDS) solutions above the critical micelle concentration. The general factors which determine whether phosphorescence is "readily" obervable in fluid solution are briefly discussed and the results are interpreted in light of these factors. 相似文献
14.
Abstract— The photolysis (Δ < 220 nm) of thymidine-5'-monophosphate was studied by electron-spin resonance (ESR) in acidic and alkaline phases. In both cases, the H–addition radical at the C6 position is detected at 77°K. At 225°K, a triplet 1:2:1 is observed, which suggests a H abstraction radical from the CH3 group. When oxygen is present during irradiation, a peroxide–type radical is observed, which results partly from a reaction like R + O2 → ROO and partly from an energy transfer from thymidine-5'-monophosphate to oxygen, probably in the 1 π0 state. 相似文献
15.
Abstract— The influence of chloride ion on the rate of decay of triplet methylene blue in 0.01 M acid in the absence and presence of ferrous ions was investigated by means of laser flash-photolysis monitored by kinetic spectrophotometry. Chloride weakly accelerates decay of 3 MBH2± in aqueous solution in the absence of Fe(II). Quenching of 3 MBH2+ by Fe(II) is more strongly catalyzed by Cl- in both water and 50 v/v% aq. CH3 CN. The uncatalyzed quenching constant, k 5 , is of the order of 1 × 106 M -1 s-1 while in 4.8 M aqueous chloride ( μ – 7.2 M ) k 5 = (37.2 ± 1.8) × 106 M -1 s-1 . A possible role of chloride is as a bridging species in quenching via electron transfer between 3 MBH2+ and Fe(II). 相似文献
16.
Colin F. Chignell B. Kalyanaraman Robert H. Sik Ronald P. Mason 《Photochemistry and photobiology》1981,34(2):147-156
Abstract— The photodecomposition of sulfanilamide, 4-aminobenzoic acid and related analogs in aqueous solution has been studied with the aid of spin traps 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) and CH3 NO2 as well as by direct electron spin resonance techniques. The NH2 radical was trapped by DMPO during the photolysis of aqueous solutions of sulfanilamide with a Xe arc lamp. Studies with [15 N1 ]-sulfanilamide indicated that the NH2 radical was generated by homolytic fission of the sulfur-nitrogen bond. Under the same conditions DMPO trapped the H and SO− 3 radicals during photolysis of sulfanic acid. Direct photolysis of sulfanilamide, sulfanilic acid and Na2 SO3 in the absence of any spin trap yielded the SO− 3 radical. Photolysis of 4-aminobenzoic acid at pH 7 gave the H radical which was trapped by DMPO. At low pH values OH and C6 H4 COOH radicals were generated during the photolysis of 4-aminobenzoic acid. No e− aq were trapped by CH3 NO2 when acid (pH 4) and neutral aqueous solutions of sulfanilamide or 4-aminobenzoic acid were photoirradiated. The mechanism of formation of known photoproducts from the free radicals generated by sulfanilamide and 4-aminobenzoic acid during irradiation are discussed. The free radicals generated by these agents may play an important role in their phototoxic and photoallergic effects. 相似文献
17.
Abstract— Ceramide, a stress-induced second messenger, has been associated with apoptosis in several malignant and non-malignant cell lines. We have shown that photodynamic treatment (PDT), using the phthalocyanine photosensitiz-er Pc 4 (HOSiPcOSi[CH3 ]2 [CH2 ]3 N[CH3 ]2 ), causes increased ceramide generation and subsequent induction of apoptosis in L5178Y-R (LY-R) mouse lymphoma cells. To test further if ceramide generation accompanies photocytotoxicity, we treated various cell lines with a PDT dose producing a 99-99.9% loss of clonogenicity. Like LY-R cells, human leukemia (U937) cells underwent rapid DNA fragmentation initiating within 1 h after PDT. Similarly, Chinese hamster ovary (CHO) cells showed rapid DNA laddering, beginning 1 h following the treatment. In contrast, mouse radiation-induced fibrosarcoma (RIF-1) cells showed no apoptosis within 24 h post-PDT, as judged by the absence of 50 kbp and oligonucleosome-size DNA fragments, as well as no annexin V binding to cells with preserved membrane integrity. Using the same doses of PDT, we observed a time-dependent ceramide accumulation in all three cell lines. While a significant increase in ceramide levels was reached within 1 and 10 min in U937 and CHO cells, respectively, elevated ceramide production was measured only after 30 min in RIF-1 cells. In addition, exogenous N-acetyl-sphingosine was able to mimic PDT-induced apoptosis in U937 and CHO cells. We suggest that ceramide accumulation is associated with PDT-induced apoptosis and photocytotox-icity. 相似文献
18.
Abstract The crystal and molecular structure of the title compound 4 have been determined by single crystal X-ray crystallography. The structure shows the typical S,-ruffled conformation observed for Ni(II) tetrapyrroles. Compared to the structure of the methyl ester of (132 -demethoxycarbonyl-pheophorbidato a)nickel(II), 4 shows a smaller Ca -Cm -Cm angle and a higher degree of conformational distortion at the methyl-substituted C20 position. This local distortion of the macrocycle might account for the bathochromic shifted absorption spectra of the bacteriochlorophylls c compared to the d-series. Crystal data: C35 H38 N4 NiO3 ; tetragonal, P43 21 2, a = 15.335(7) Å, c = 25.11(2) Å, V = 5904, Z = 8, λ(Mo Kα) = 0.71069 Å, μ= 0.701 mm−1 , P(000) = 2624, 130 K, R = 0.058 for 5700 reflections with F > 4.0σ(F). 相似文献
19.
Abstract— The concentration dependence of the lifetimes of the charge transfer excited states of Cu(dmp)+ 2 and Cu(dpp) + 2 has been investigated in CH2 C12 solution at 20° C. (dmp denotes 2,9-dimethyf-1,10-phenanthroline, and dpp denotes 2,9-diphenyl-l,10-phenanthroline.) In dilute solution (< 30 μM) the lifetime of Cu(dmp)+ 2 , is 95 ± 5 ns, independent of the anion. At higher concentrations the lifetime decreases, in most cases, to a limiting value that depends upon the counterion. The measured limiting lifetimes range from 38 ± 3 ns for CIO- 4 to 78 ± 5 ns for PF- 6 . The anion-induced quenching is attributed to exciplex quenching which is mediated by an ion pair which exists in the ground state. The results imply that the quenching ability of the anions follows the order BPh-4 < PF -6 , < BF-4 < CIO -4 < NO-3 which is consistent with previous estimates of donor strength. The lifetime of Cu(dpp)+ 2 is also concentration dependent, but the effect is much smaller because the phenyl substituents impede attack by the anion. 相似文献
20.
Eberhard Bothe Man Nien Schuchmann Dietrich Schulte-Frohlinde Clemens von Sonntag 《Photochemistry and photobiology》1978,28(4-5):639-643
Abstract— In aqueous solutions α-hydroxyalkylperoxyl radicals undergo a spontaneous and a base catalysed HO2 elimination. From kinetic deuterium isotope effects, temperature dependence, and the influence of solvent polarity it was concluded that the spontaneous reaction occurs via an HO2 elimination followed by the dissociation of the latter into H+ and O2 - . The rate constant of the spontaneous HO2 elimination increases with increasing methyl substitution in α-position ( k (CH2 (OH)O2 ) < 10s-1 k (CH3 CH(OH)O2 ) = 52s-1 k ((CH3 )2 C(OH)O2 ) = 665 s-1 ). The OH- catalysed reaction is somewhat below diffusion controlled. The mixture of peroxyl radicals derived from polyhydric alcohols eliminate HO2 at two different rates. Possible reasons for this behaviour are discussed. The mixture of the six peroxyl radicals derived from d -glucose are observed to eliminate HO2 with at least three different rates. The fastest rate is attributed to the HO2 elimination from the peroxyl radical at C-l ( k > 7000s-1 ). Because of the HO2 eliminations the peroxyl radicals derived from d -glucose do not undergo a chain reaction in contrast to peroxyl radicals not containing an α-OH group. In competition with the first order elimination reactions the α-hydroxylalkylperoxyl radicals undergo a bimolecular decay. These reactions are briefly discussed. 相似文献