ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1991.tb02071.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe 355 nm laser flash photolysis of nalidixic acid at pH 9.2 leads to the formation of the nalidixate anion triplet state (absorption Λmax= 620 nm; 5700 ≤εT≤ 9000 M−1cm−1; 0.6 ≤φT≤ 1). The first order triplet state decay(kT=7.7 times 10−3s−1) is accompanied by a diffusion controlled triplet‐triplet annihilation. Oxygen efficiently quenches the triplet state(k =3.2 times 109M−1s−1). The nalidixate radical dianion (absorption Λmilx= 650 nm; ε= 3000M−1cm−1) is produced by the diffusion controlled reductive quenching of the triplet state by tryptophan and tyrosine. The superoxide anion (O−2) is produced by diffusion controlled reaction of the radical dianion with oxygen. The O−2is characterized by its reactions with ferricytochrome c and superoxide dismutase. The physiological form of nalidixic acid is thus a good

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1991.tb02072.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractEvidence from a characteristic transient spectrum, its lifetime and quenching by N2O demonstrates that XeCl excimer laser excitation of the reduced form of pyridoxal 5′‐phosphate bound to lysine residues will produce the hydrated electron. The phenoxyltype radical coproduct was also observed. The results identify a useful label of protein structures for site‐specific electron generation which can occur outside the region of light absorption by aromatic residues of protein. The results also represent the first observation of hydrated electron formation from flash excitation of a vitamin B6 cof

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1991.tb02073.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractNanosecond (λcxc= 266, 355 and 532 nm) and picosecond (λcxc. = 355 nm) laser flash photolysis of hematoporphyrin (Hp) was performed in neutral (pH 7.4) and alkaline (pH 12) aqueous solution, as well as in the presence of 0.1% Triton X‐100. The dependence of the yield of photoproduced hydrated electrons (e−aq) on laser pulse energy was studied over a wide range of energies (0.2 to>1000 mJ cm−2). The results show that e˜, are predominantly formed in a two‐photon process at λexc= 266 and 355 nm. One‐photon quantum yields are higher at λexc= 266 nm than at λexc= 355 nm. Both one‐photon and two‐photon pathways are less efficient at higher Hp concentration, reflecting the influence of Hp self‐aggregation. Two‐photon eaqformation is more efficient when 30 ps pulses are used for excitation, as compared to 10 ns pulses. No e−aqcould be detected at λexc= 532 nm. Nanosecond pulse‐induced transient spectra obtained

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1991.tb02074.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe phosphorescence properties, especially the dynamic behavior of metal free and metal complexed porphyrins, have been studied in phosphate buffered saline (PBS) containing0–3% human serum albumin (HSA). 6,7‐Bisaspartyl‐2,4‐bis (l‐hexyloxyethyl)‐deutero‐porphyrin (DP) and its gallium(III), zinc(II), and indium(III) complexes are used as photosensitizers. Upon irradiation, a solution of porphyrins containing more than 0.1% HSA shows phosphorescence with a lifetime longer than 1 ms. With an increase in irradiation time, phosphorescence intensities and lifetimes of porphyrins increase, depending upon their concentrations and triplet lifetimes, and approach saturated values close to those under deaerated conditions. The experimental results may be interpreted in terms of hypoxia induced by photosensitization in a local environment surrounding the sensitizer. The hypoxia is caused by the reaction between proteins and singlet molecular oxygen generated by photosensitization of porphyrins. Phosphorescence behavior of sensitizers in HSA PBS solution gives significant information for classifying photosensitizers as to their efficacy for photody

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1991.tb02075.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractIncubation of methoxypsoralen (5‐MOP) in the presence of diploid yeast cells(Saccharomyces cerevisiae)before UV‐A exposure leads to an incubation‐time dependent decrease of photoinduced genotoxic effects. The reduction in photoinduced genotoxicity is stronger in cells grown in the presence of 20% glucose and containing high levels of cytochrome P‐450 than in cells grown in the presence of 0.5% glucose and containing undetectable levels of cytochrome P‐450. Inhibition of P‐450 activity by specific inhibitors, such as tetrahydrofuran and metyrapone, strongly affects the observed decrease in 5‐MOP genotoxicity, indicating the involvement of P‐450 in 5‐MOP metabolism. As demonstrated by spectrophotometric and chromatographic (HPLC) analysis during incubation of 5‐MOP with P‐450 containing yeast cells, 5‐MOP gradually disappears from the cell supernatant of the incubation mixture. The reduction in the chromatographic peak corresponding to 5‐MOP is accompanied by the appearance of a new peak that probably corresponds to a metabolite. As shown by the use of P‐450 specific inhibitors, the metabolite appears to be due to P‐450 mediated 5‐MOP metabolisation. Its UV absorption spectrum suggests an alteration of the pyro

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1991.tb02076.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe chemical structure of the 8‐methoxypsoralen oxidized product that inhibits the chemo‐tactic activity of anaphylatoxin C5a was determined to be 2,3‐dihydro‐2,9‐dimethoxy‐3‐hydroxy‐7‐oxo‐7H‐futo[3,2‐g][l]benzopyran. Its minimal concentration required to obtain the maximum inhibition of C5a des Arg (1 times 10−8M) chemotactic activity is 2.5 times 10−8M.Bioactivity of this substance was maintained for 2 weeks, stored in a dark room at room temperature under aerobic conditions. There is a possibility that this substance may be useful in the treatment

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1991.tb02077.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractFluoride inhibits chloroaluminum phthalocyanine tetrasulfonate (AIPcS)‐induced photo‐hemolysis when added to dye loaded cells prior to light exposure. The mechanism by which F˜ exerts this effect was studied by measuring the binding of phthalocyanine (Pc) to various proteins in the absence and presence of F−. Parallel measurements were made of the photodynamic action under these conditions. Fluoride reduced the binding to proteins of AIPcS and CoPcS. The binding of CuPcS, ZnPcS and H2PcS was not affected. When bound to bovine serum albumin and exposed to light, H2Pc, ZnPc and AIPcCI were bleached at a biphasic rate. Only the photobleaching of AIPcCI was affected by F−. The effect of F” was to inhibit the initial rapid phase without affecting the slower phase. In the presence of D2O only the second phase of photobleaching was enhanced, in the absence or presence of F−. No effect of F−was observed on tryptophan photooxidation or glyceraldehyde‐3‐phosphate dehydrogenase photoinactivation by AIPcS. Crosslinking of spectrin monomers photosensitized by AIPcS was inhibited by F−in parallel with the reduced binding of dye to the protein. It is concluded that F˜ exerts its effect by complexing with metal ligands of Pc. As a result, the dye may be released from the protein or the binding mode may be changed in such a way that effective photochemistry is prevented. Primary photophysical processes of Pc most probably

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1991.tb02078.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe influence of lipoprotein association onin vitrotumor cell killing andin vivotumor photosensitization with benzoporphyrin derivative (BPD) has been investigated in M‐1 tumor bearing mice. The association of benzoporphyrin mono acid ring A with either low or high density lipoprotein increased tumor cell killing in anin vivolin vitrocytotoxicity assay performed 3 h post intravenous drug administration. Eight hours following photosensitizer injection only low density lipoprotein (LDL) mixtures produced significant (P≤ 0.005) increases in tumor cell killing compared to BPD in unfractionated plasma. The efficacy ofin vivophotosensitization in the presence of lipoproteins correlated with thein vivolin vitrocytotoxicity. Association of BPD with low or high density lipoproteins resulted in delayed tumor regrowth and higher cure rates when light exposure (125J/cm2) was performed 3 h post drug administration. When light exposure was performed 8 h post‐injection only LDL‐BPD mixtures led to enhanced tumor eradication compared to BPD administered in aqueous solution or unfractionated

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1991.tb02079.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThis paper examines the relationship between lipid composition, plasma membrane fluidity, expression of dye binding sites, and susceptibility to merocyanine 540 (MC540)‐sensitized irradiation in L1210 leukemia cells. Reducing the cells' cholesterol content by exchange diffusion with phosphatidylcholine liposomes or by inhibiting its biosynthesis with 25‐hydroxycholesterol enhanced plasma membrane fluidity, the expression of dye binding sites, and the cells' susceptibility to MC540‐sensitized irradiation. Conversely, if the cholesterol content was enhanced by exchange diffusion with cholesterol:phosphatidylcholine liposomes, the cells' susceptibility to MC540‐sensitized irradiation was decreased. However, contrary to expectations, dye‐binding was slightly enhanced and plasma membrane fluidity remained unchanged. Growing the cells in fatty acid‐supplemented medium had profound effects on their lipid composition. Cells enriched in polyunsaturated fatty acids had more fluid plasma membranes. However, dye‐binding was not significantly affected and photosensitivity was slightly reduced. These results suggest that cholesterol is one, but probably not the only, determinant of the expression of cellular dye binding sites and, consequently, the cell's susceptibility to MC540‐sensitized irradiation. By contrast, plasma membrane fluidity does not appear to play a major role in the regulation of dye‐bindin

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1991.tb02080.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY