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1.
Abstract 125 I- N 6 -(N-[6-N-{5-iodo-4-azidosalicyl}-aminohexyl]-aminocarbamoylmethyl)-nicotinamide adenine dinucleotide (125 I- N 6 -I-ASA-AH-NAD+ ) was synthesized by coupling N 6 -([6-aminohexyl]-carbamoylmethyl)-NAD+ with 4-azidosalicylic acid N-hydroxysuccinimide ester followed by radioiodination. The utility of 125 I-N 6 -I-ASA-AH-NAD+ as an effective site-directed photoprobe was demonstrated by the photolabeling of both glutamate dehydro-genase and 15-hydroxyprostaglandin dehydrogenase. Both enzymes can be saturated with labeled probe with apparent dissociation constants comparable to those reported for NAD+ . Photoincorporation of the probe into both enzymes was found to be protected specifically by NAD+ . These results indicate that 125 I- N 6 -I-ASA-AH-NAD+ can be a specific photoprobe for NAD+ -linked enzymes. 相似文献
2.
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
3.
B. D. Hirsch N. C. Walz B. E. Meeker M. R. Arnfield J. Tulip M. S. McPhee J. D. Chapman 《Photochemistry and photobiology》1987,46(5):847-852
Abstract The administration of misonidazole (MISO) to Fischer x Copenhagen rats whose R3327-H prostate tumors were treated with photodynamic therapy (PDT) produced enhanced tumor growth delays and cures. This potentiation of PDT by MISO was previously observed with R3327-AT tumors and was postulated to result from drug cytotoxicity of naturally-occurring and PDT-induced hypoxic cells. Radioactively-labelled MISO has been developed as a marker for tissue p02 at the cellular level and [3 H]MISO was administered to R3327-AT and R3327-H tumor-bearing rats before and after standard PDT treatments. The amount of 3 H in tissues 24 h after drug administration was a measure of'bound MISO'which reflects average tissue oxygenation. [3 H]MISO retained in R3327-AT tumors was ˜4x and in liver tissue ˜2x that retained in muscle, heart, brain and R3327-H tumors (1x). Tumors treated with Photofrin II and lased with 1000 J showed a 6-fold increase in retained [3 H]MISO in R3327-H tumors and a 2-fold increase in retained [3 H]MISO in R3327-AT tumors. The absolute levels of retained 3 H in both tumors after PDT were similar. These data provide direct evidence that PDT induces rapid hypoxia in both tumors. When the gastrocnemius muscle of the rat leg was similarly treated, the amount of [3 H]MISO retained was ˜4x greater than that in untreated muscle. This result suggests that PDT-induced hypoxia is not selective to just tumor tissue. These data suggest that the hypoxia-inducing property of PDT might be exploited in combination with hypoxic cell cytotoxins to produce improved tumor responses and cures. 相似文献
4.
The National Accelerator Centre (NAC) provides facilities for basic and applied research, radioisotope production and particle therapy. To date, 851 patients have been treated on the 66 MeV p + Be isocentric neutron therapy unit while 191 patients have been treated (mainly for intracranial conditions) on the 200 MeV horizontal proton beam facility. A variety of radioisotopes such as 67Ga, 81Rb/81Kr, 111In, 123I, and 201Tl are produced on a regular weekly basis, and more than 1000 consignments of radiopharmaceuticals prepared from these radioisotopes are supplied to more than 30 hospitals and private practices throughout South Africa each year. Some non-medical radioisotopes are also produced. 相似文献
5.
Abstract— A crude extract containing membrane components of Lemna paucicostata was treated with 1% Lubrol PX and fractionated by gel nitration. Binding activities to non-hydrolyzable analogues of ATP, [35 S]ATPγS (adenosine 5'[;γ-thio]triphosphate) and that of GTP, [35 S]GTPγS (guanosine 5'[γ-thiojtriphosphate) were detected in some fractions, and these activities were prevented in the presence of 0.1 mM ATP or GTP. ATP and GTP were 2 to 3 orders of magnitude more effective than CTP or UTP in preventing this binding activity. These fractions showed ATPase and GTPase activities with 1 nM [γ-32 P]ATP or [γ–32 P]GTP substrate. Analyses by sodium dodecyl sulfate polyacrylamide gel electrophoresis of these fractions after binding with [35 S]ATPγS or [35 S]GTP-γ S revealed that these fractions contained [35 S]ATPγS and [35 S]GTPγS binding proteins with molecular weights of 53 000 and 60 000, respectively. Both of these proteins were [32 P]ADP-ribosylated by endogenous ADP-ribosyl transferase. Three proteins with molecular weights of 11 000, 12 000 and 13 000 which could bind [35 S]ATP7S or [-35 S]GTP-γ S were ADP-ribosylated by endogenous ADP-ribosyl transferase. Pertussis toxin stimulated ADP-ribosylation of these proteins. Four proteins with molecular weight of 37 000, 50 000, 80 000 and 115 000 with PS S]ATP7S and [,3 S]GTP7S binding activities were also detected. The signal transduction of light to underlying clock mechanism in Lemna may be controlled by ATP-GTP-binding proteins and by the ADP-ribosylation of these proteins. 相似文献
6.
Tadashi Mizoguchi Shun Sakamoto Yasushi Koyama Kenji Ogura Fuyuhiko Inagaki 《Photochemistry and photobiology》1998,67(2):239-248
7.
Taras K. Antal Wayne Lo William H. Armstrong Esa Tyystjärvi 《Photochemistry and photobiology》2009,85(3):663-668
We measured the photosensitivity of an artificial tetranuclear oxo–Mn(IV) complex, [Mn4 O6 (bpea)4 ]Br4 , which has an adamantane-shaped {Mn4 O6 }4+ core. Illumination caused changes in the absorption spectrum of the compound consistent with a one-electron reduction in the compound. Bromide appears to be the most probable electron donor in the reaction system. Chemical modification of the cluster appears to destabilize it, predisposing it to reductive degradation. UV light was more efficient than visible light in causing the changes. The data support the suggestion that the natural oxygen-evolving Mn complex is photosensitive and can oxidize components of the oxygen-evolving complex in its excited state causing photoinhibition, and that photostability is an important issue in designing Mn complexes for artificial photosynthesis. Furthermore, light-induced oxidation of bromide by [Mn4 O6 (bpea)4 ]4+ may suggest that oxidation of chloride is involved in natural water splitting or has been involved during the evolution of the water-splitting enzyme. 相似文献
8.
Abstract— Various nitrogen containing compounds have previously been shown to quench singlet oxygen (10z). When measuring the dimol 1 O2 light emission arising from the H 2 O2 /OCI- reaction, we found that certain cyclic diamines increase the emission of light, while other amines were inhibitory. This increase of light emission was seen with both 1, 4diazabicyclo[2.2.2]octane and N, N'-dimethylpi-perazine but not with acyclic analogues. Sodium azide inhibited both the normal and enhanced light emission. The enhanced light emission shows spectral properties characteristic of l O2 dimol emission. 相似文献
9.
Yuki Hirai Hitoshi Tamiaki Shigenori Kashimura Yoshitaka Saga 《Photochemistry and photobiology》2009,85(5):1140-1146
Demetalation kinetics of bacteriochlorophylls (BChls) c, d and e from green sulfur photosynthetic bacteria were studied under weakly acidic conditions. Demetalation rate constants of BChl e possessing a formyl group at the 7-position were significantly smaller than those of BChls c and d , which had a methyl group at this position. The activation energy of demetalation of 31 R -8,12-diethyl([E,E])-BChl e was 1.5-times larger than that of 31 R -[E,E]-BChl c . 15 N-labeled 31 R -[E,E]-BChls c and e were purified from cells of green sulfur bacteria grown in a medium containing 15 NH4 Cl, and their 15 N NMR spectra were measured. The chemical shifts of N21 , N22 and N23 atoms of 31 R -[E,E]-BChl e were lower-field shifted than those of 31 R -[E,E]-BChl c , respectively, and especially the difference in chemical shifts of N22 was significantly large. These results suggest that the electron-withdrawing formyl group at the 7-position of BChl e affected an electronic state of the chlorin macrocycle and caused BChl e to be more tolerant for removal of the central magnesium compared with BChls c and d . 相似文献
10.
Abstract— Recent studies have shown that ultraviolet (UV) irradiation induces a systemic effect which enhances subsequent tumor induction by benzo[a]pyrene in a manner which is dependent on the dose of benzo[a]pyrene. The present study was designed to test whether UV-B irradiation renders mice susceptible to subcutaneous or intravenous injection of a regressor tumor induced by benzo[a]pyrene. The sources of UV-B irradiation were banks of 6 Westinghouse FS-40 sunlamps, situated 20 cm above the mouse cages. Female BALB/cAnNHsd received five 30-min dorsal UV-B radiation treatments per week for 12 weeks, resulting in a total dose of approx. 6.4 × 105 J m-2 . Two to seven days after termination of UV treatments, syngeneic regressor tumor cells (BP2) induced by benzo[a]pyrene were injected subcutaneously or intravenously into irradiated mice and unirradiated controls. By 38 days post subcutaneous implantation, 24/30 and 3/30 BP2 implants were detectable in the irradiated and unirradiated mice, respectively. Ultraviolet irradiated mice were also unable to reject lung colonies resulting from intravenous administration of BP2 cells, although they were rejected by unirradiated mice. The mean number of lung colonies per mouse was 16- to 35-fold greater in UV irradiated mice than in unirradiated controls, at 14 to 17 days post injection. Thus, UV irradiation rendered mice, with no known exposure to benzo[a]pyrene, susceptible to a subcutaneous or intravenous injection of a regressor tumor induced by benzo[a]pyrene. 相似文献
11.
Piotr J. Bilski M. A. Wolak V. Zhang D. E. Moore C. F. Chignell 《Photochemistry and photobiology》2009,85(6):1327-1335
Lamotrigine (LTG) [3,5-diamino-6-(2,3-dichlorophenyl)-1,2,4-triazine], an anticonvulsant and antidepressant drug Lamictal® , produces a (photo)toxic response in some patients. LTG absorbs UV light, generating singlet oxygen (1 O2 ) with a quantum yield of 0.22 in CH2 Cl2 , 0.11 in MeCN and 0.01 in D2 O. A small production of superoxide radical anion was also detected in acetonitrile. Thus, LTG is a moderate photosensitizer producing phototoxicity and oxidizing linoleic acid. LTG is a weak 1 O2 quencher ( k q = 3.2 × 105 m −1 s−1 in MeCN), but its photodecomposition products in dimethyl sulfoxide (DMSO) quenched 1 O2 very efficiently. Upon intense UV irradiation from a xenon lamp, LTG was photobleached rapidly in DMSO and slowly in acetonitrile, alcohol and water. The rate increased significantly when laser pulses at 266 nm were employed. The photobleaching products generated 1 O2 twice as strongly as LTG. Photobleaching was usually accompanied by the release of chloride anions, which increased in the presence of ascorbic acid. This suggests the formation of aryl radicals via dechlorination, a process which may be responsible for the photoallergic response observed in some patients. Our results demonstrate that LTG is a moderate generator of 1 O2 prone to photodechlorination, especially in a reducing environment, which can contribute to the reported phototoxicity of LTG. 相似文献
12.
Jean Louis Bec Pascal Delrieu Gérard Abravanel Nicole Paillous 《Photochemistry and photobiology》1986,44(1):41-45
Abstract— Photobinding of sulfanilamide to bovine serum albumin (BSA) was investigated by irradiating BSA and buffered BSA/drug solutions with UV light (Λ= 300 nm) under anaerobic conditions. The protein solutions were then denatured and the unbound sulfanilamide removed. Marked differences in the UV and fluorescence spectra of the solutions before and after irradiation were observed, suggesting covalent binding of the drug to BSA. This was confirmed using [14 C]labelled sulfanilamide. The extent of photobinding of sulfanilamide determined using the radiolabeled drug, was concentration dependent. The binding ratio varied from 3 mol drug per mol BSA for a 10-4 M drug concentration, to 10 mol drug per mol BSA for 10-2 M drug concentration.
The protein solutions were hydrolysed under acid conditions and the amino acids obtained were analysed by ion exchange chromatography. The hydrolysate of irradiated BSA (10-4 M ) -sulfanilamide (10-2 M ) mixture lost about 10 mol of cystine per mol of BSA. This loss was not observed after hydrolysis of irradiated alone or non-irradiated BSA. Irradiation of cystine with [14 C]sulfanilamide in HC1 solutions produced the same compound as was found after hydrolysis of irradiated BSA/sulfanilamide mixtures. This was demonstrated by autoradiography of paper chromatograms. The same compound was also detected in an irradiated [35 S]cystine non-labelled sulfanilamide mixture. It was not detected, however, after irradiation of a mixture of all amino acids of BSA excluding cystine. These data suggest that cystine residues are involved in the photobinding of sulfanilamide (or its photoproducts) to BSA. 相似文献
The protein solutions were hydrolysed under acid conditions and the amino acids obtained were analysed by ion exchange chromatography. The hydrolysate of irradiated BSA (10
13.
Abstract— From spectroscopic data and rate constants in the literature, equilibrium constants and rates of thermal formation of singlet oxygen (1 Δg and 1 Σg + ) were calculated for a number of conditions. For the gas phase we estimate K eq (1 Δg 3 Σg - ) = 1.67 exp(-94.31 KJ/RT) and K eq (1 Σg + /3 Σg - ) = 0.33 exp(-157.0 KJ/RT). The calculated rate constants for the 3 Σg + →1 Δg transition of O2 at 25°C varied from 2.5 × 10-11 s-1 in water to 4.8 × 10-16 s-1 in air, assuming equal solvent interactions with the ground and excited states. Physical quenchers for singlet oxygen are expected to be catalysts for its thermal formation. Equations are presented which allow one to estimate whether such catalysis by quenchers will result in a pro-oxidant effect. 相似文献
14.
Abstract— Semiquinone free radicals have been generated by the UV photolysis of aqueous solutions of melanin precursors (catechols and catecholamines) and characterized by electron spin resonance (ESR) spectroscopy. Hyperfine parameters of the semiquinones are sensitive to the nature of the substituents on the aromatic ring, reflecting (i) the ionization state of the substituent; (ii) restricted rotation of methylene protons; and (iii) the presence of a chiral carbon center. In the presence of complexing metal ions (Zn2+ , Cd2+ ) the semiquinones form chelate complexes whose ESR spectra differ from those of the uncomplexed radicals. Satellite peaks demonstrating hyperfine coupling to metal isotopes (67 Zn, 111 Cd and 113 Cd) present in natural abundance were detected in several instances. Concentrations of metal complexes are much higher than those of the uncomplexed radicals, suggesting that diamagnetic metal ions may be useful in identifying the presence of semiquinone radicals of this kind in various systems. 相似文献
15.
G. Schermann R. Schmidt A. Völcker H.-D. Brauer H. Mertes B. Franck 《Photochemistry and photobiology》1990,52(4):741-744
Abstract— –Photophysical properties of [26] porphyrin (26 P) were investigated in chloroform. The quantum yields of fluorescence, of S1 → T1 intersystem crossing and singlet oxygen formation were measured. The purity, stability, the strong absorption in the red (δmax = 783 nm; εmax = 28 000 M 1 cm-1 ) and the ability of singlet oxygen formation recommend 26 P as potential photosensitizer for tumor therapy. 相似文献
16.
EXCITED STATES AND REACTIVITY OF CARCINOGENIC BENZPYRENE; A COMPARISON WITH SKIN-SENSITIZING COUMARINS* 总被引:1,自引:0,他引:1
Thomas A. Moore ‡ William W. Mantulin ‡ Pill-Soon Song 《Photochemistry and photobiology》1973,18(3):185-194
Abstract— Significant spectroscopic difference was found between the 3 (π, π*) state of coumarins and the 3 La state of benzpyrene. No analogy of the partially localized triplet state associated with the coumarin chromophore was revealed in the case of the potent carcinogen, benzo[a]pyrene. Instead, the 3 La state of benzo[a]pyrene is characterized by more derealization than that of the non–carcinogenic benzo[e]pyrene. Therefore, the predominant photoreaction between benzo[a]pyrene and DNA bases does not seem to involve cycloaddition in contrast to the coumarin-pyrimidine system. Reactivity indices have been calculated, and results are consistent with recent experimental findings. In addition, spectroscopic properties of benzo[a]pyrene and benzo[e]pyrene have been comparatively described in terms of relatively high-resolution spectra, polarization measurements, and molecular orbital calculations. 相似文献
17.
Richard G. Brereton Ali Rahmani Yi-zeng Liang Olav M. Kvalheim 《Photochemistry and photobiology》1994,59(1):99-110
Abstract –The products of chlorophyll allomerization in methanol were isolated and analyzed by open column sucrose chromatography, liquid chromatography mass spectrometry (LCMS) and DAD-HPLC (diode-array high-performance liquid chromatography). Four main bands were found with molecular ions of (a) 908, (b) 938, (c) 938 and (d) 938, consistent with the structures (a) 132 -hydroxy-chlorophyll a (II), (b) and (c) Mg(II)-31 ,32 -didehydro-151 -hydroxy-151 -methoxy-rhodochlorin-15 acetic acid δ-lactone 152 -methyl 173 -phytyl ester and its epimer (III) and (d) Mg(II)-31 ,32 -didehydro-rhodochlorin-15-glyoxylic acid 131 ,152 -dimethyl 173 -phytyl ester (IV), evidence enhanced by UV/visible spectroscopy, chromatographic coelutions and chemometrics. Chlorophyll a was degraded both in the dark and light, under O2 and N2 . DAD-HPLC of the resultant degradation mixtures were analyzed using the chemometric heuristic-evolving latent projection method for resolution. Ultraviolet/visible spectra of II and III are reproducibly extracted from the mixtures after a short degradation time, whereas III and IV are the dominant compounds after longer degradation times. Changes in relative elution order of IV using open column chromatography and reverse-phase HPLC are established. A possible allomerization pathway is proposed. 相似文献
18.
Abstract— In experiments on the interception of reactive intermediates of strongly oxidizing character in dye (S) sensitized photooxidations using p -nitrosodimethylaniline (RNO) as a selective scavenger, it has been observed that some substrates (A) or 1 O2 acceptors (like imidazole derivatives) induce the bleaching of RNO as followed spectrophotometrically at 440 nm. Since singlet oxygen (1 O2 ) does not react chemically with RNO, this bleaching is a consequence of 1 O2 capture by the imidazole ring which results in the formation of a trans-annular peroxide intermediate [1 O2 ] capable of inducing the bleaching of RNO (-RNO). In the absence of RNO, [1 O2 ] decomposes or rearranges into the final oxygenation product 1 O2 : 1 Δg Thus, the system imidazole plus RNO can be used as a sensitive and selective test for the presence of 1 O2 in aqueous solutions. The method can also be applied in the presence of sensitizing dyes which, under visible irradiation, can partially bleach RNO even in the absence of imidazole derivatives. In such a case, the bleaching of RNO is strongly increased by the presence of imidazoles with a characteristic dependence on their concentration. The separation of the product of RNO bleaching by thin layer chromatography can serve as additional proof of the presence of 1 O2 in the system. The imidazole plus RNO method has been applied to a number of sensitizing and non-sensitizing dyes. 相似文献
19.
Abstract— Stationary phase cultures of a DNA repair proficient Escherichia coli K-12 strain showed a release of intracellular material as assessed by three different methods (260 nm absorption; [methyl-3 H]thymidine leakage and 86 Rb+ leakage) after broad-band (Black-Light Blue) near-UV radiation but not after far-UV (254 nm) radiation. As a control response for membrane damage to cells, this leakage of intracellular material was also determined by each method after mild-heat (52°C) treatment of E. coli K-12. An action spectrum for the release of 86 Rb+ from E. coli K-12 after irradiation with monochromatic wavelengths, from 254 to 405 nm, is also presented. The action spectrum for lethality (F37 values) obtained for this strain, shows that leakage of 86 Rb+ occurs at fluences equivalent to or slightly less than fluences causing inactivation at wavelengths above 305 nm. In contrast, at wavelengths below 305 nm, leakage of 86 Rb+ from irradiated cells can be induced but only at fluences significantly greater than was required to cause cell inactivation. These results indicate, therefore, that near-UV radiation can induce a damaging effect on the cell's permeability barrier which may be significant in causing the death of the cell, whereas the effect is not significant in causing the death of cells by far-UV radiation where DNA damage is known to be the main cause of lethality. 相似文献
20.
The steady-state UVA (350 nm) photolysis of ( E )-β-ionone ( 1 ) in aerated toluene solutions was studied by 1 H NMR spectroscopy. The formation of the 1,2,4-trioxane ( 2 ) and 5,8-endoperoxide ( 5 ) derivatives in the ratio of 4:1 was observed. Time-resolved laser induced experiments at 355 nm, such as laser-flash photolysis, photoacoustic and singlet oxygen 1 O2 phosphorescence detection, confirmed the formation of the excited triplet state of 1 with a quantum yield Φ T = 0.50 as the precursor for the generation of singlet oxygen 1 O2 ( Φ Δ = 0.16) and the isomeric α-pyran derivative ( 3 ), which was a reaction intermediate detected by NMR. In turn, the reaction of 1 O2 with 1 and 3 occurred with rate constants of 1.0 × 106 and 2.5 × 108 m −1 s−1 to yield the oxygenated products 5 and 2 , respectively, indicating the relevance of the fixed s-cis configuration in the α-pyran ring in the concerted [2+4] cycloaddition of 1 O2 . 相似文献