摘要:

Abstract—Resonance Raman spectra of the Pr‐form of oat phytochrome have been obtained at 77 K. Interference from phytochrome fluorescence is avoided by employing far‐red 752 nm excitation. Vibrational assignments are suggested for the tetrapyrrole chromophore in phytochrome by comparison with previously published model compound spectra and by examining the characteristic shifts induced by deuteration of the pyrrole nitrogens. The lack of carbonyl intensity, the frequencies of the 1626 and 1644 cm‐1C=C stretching modes, and the presence of an intense mode at 1326 cm‐1are all consistent with a protonated structure for the tetrapyrrole chromophore in Pr. This suggests that the ‐50 nm red‐shift of the protein‐bound chromophore absorption compared to the chromophorein vitrois caused by protonation of the p

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02797.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—When incorporated into LDL, protoporphyrin and the porphyrin mixture constituting the trade mark Photofrin II photosensitize peroxidations of cholesterol and lipids. Not only 5a‐hydroperoxicholesterol, the specific product of cholesterol oxidation by1O2but also the epimeric 6‐hydroperoxicholesterols are produced as shown by HPLC. In addition to malonaldehyde‐like substances, the formation of 4‐hydroxynonenal, a highly reactive and toxic aldehyde resulting from lipid peroxide breakdown is detected. These products are also formed by dark radical chain reactions of lipid photoperoxides induced by photosensitization. The involvement of lipid photoperoxidation in LDL apoprotein modification is demonstrated by following the derivatization of e‐NH2groups of Lys residues which are necessary to binding to the LDL receptor. As a result, photosensitized LDL cannot bind to their receptors on fibroblasts. Lys residues are not sensitive to direct photodynamic reaction as confirmed by delipidation of LDL and solubilization of apoLDL in 1% SDS which totally inhibit Lys derivatization without affecting the degradation of Trp residues susceptible to the photodynamic attack. Another consequence of lipid peroxidation at the protein level is the formation of cross‐links between apoLDL and photooxidized lipids as shown using LDL loaded with radioactive arachidonic acid. On the other hand, cholesterol photoperoxidation does not lead to protein‐oxidized cholesterol cross‐links. These reactions between peroxidized lipids and LDL proteins are also responsible for the formation of lipofuscin‐like fluorescent pigments encountered in all aging processes. The biological and biomedical consequences of these re

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02798.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Photolyses at 485 or 490 nm of air saturated, H2I7O enriched, aqueous solutions of adriamycin (ADR) in the presence of 5,5‐dimethyl‐l‐pyrroline‐l‐oxide (DMPO) produce a mixture of hydroxyl radical spin‐adducts, i.e. DMPO‐16OH‐ and DMPO‐17OH‐, as detected by electron spin resonance (ESR). DMPO‐17OH‐ was also observed during the irradiation at these same wavelengths of aqueous solutions of ADR or daunomycin (DA) containing DMPO and17O enriched oxygen. Therefore, the observed hydroxyl radical spin‐adducts derive from both water and gaseous oxygen. It is concluded from the measured relative spin‐adduct concentrations and from the enrichment fractions that most of the DMPO‐OH adducts originate from water. However, if anaerobic diluted solutions of ADR (200μ M) or DA (600μM)in the presence of DMPO (13mMand 27 mMrespectively) are irradiated at these same wavelengths no spin adduct is detected, indicating that oxygen is needed for the adduct formation, at these drug and spin trap concentrations. DMPO‐OH‐ is always observed if relatively high concentrations of either the drug (1.1–2.9 mM) or the spin trap(100–150 mM) are used in argon saturated solutions. A water photooxidation mediated mechanism is proposed in order to account for these results, analogous to previous observations in the photochemistry of othe

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02799.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Photolysis of urocanic acid (UA) and nitro blue tetrazolium (NBT2+), under conditions wherein the NBT2+absorbs the light, leads to oxidation of the UA by the NBT2+excited state. When UA is itself photolyzed in the presence of oxygen and NBT2+, NBT2+reduction again occurs, but in this event via the intermediate formation of superoxid

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02800.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Measurement of singlet oxygen production by porphyrin‐type photosensitizers in simple buffer solutions show that TPPS is more efficient than PII (Photofrin II) or than hematoporphyrin. This behavior was observed using three independent analytical detection methods for1O2: RNO bleaching, tryptophan degradation, and oxygen consumption. Similar results were obtained when irradiating with a classical light source or with a pulsed dye laser. Addition of EPC liposomes to the buffer solution caused a decrease of efficiency for TPPS and an increase for PII. Addition of BSA shows the same relative pattern: a small increase of efficiency for TPPS and a tenfold increase for PII. These changes can be ascribed to specific interactions between the sensitizer molecules and the organized medium. Since changes in the fluorescence properties are also due to interactions with the medium, we monitored the emission of the sensitizers as a function of the environment. The fluorescence peak positions (at 648, 705 nm for TPPS and at 615, 677 nm for PII) were all red shifted. The intensities show an increase, particularly for PII in liposomes, due to a marked change in the microviscos

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02801.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Previous studies from our laboratories and elsewhere have shown that amides between fatty acids and the synthetic α, α, α, α ‐tetra (o‐aminophenyl)‐porphyrins exhibit good surfactant properties which facilitate their incorporation into structured assemblies characterized by hydrophobic‐hydrophilic compartmentalization. This paper will focus on a number of aspects of our studies of these porphyrins at different interfaces.The α, α, α, α (4,0) isomers are readily incorporated into Langmuir‐Blodgett films as either free base or metal complexes. Studies of assemblies containing free base and palladium (II) complexes have been carried out in which the porphyrin is irradiated in the presence of oxygen and nonexcited but oxidizable substrates. Much of the reactivity observed can be attributed to1O2* generation. These studies reveal the migration range and reactivity of activated oxygen in a structure related to biomem‐branes.Several of these synthetic porphyrins have also been examined in cell suspensions and in synthetic reversed micelle solutions. Studies in the former have shown that the porphyrins can mediate the photoinactivation of several enzymes located inside and within the mitochondrial membrane in tumor cells extracted from rats. They are found to compare favorably to hematoporphyrin derivative in effectiveness.Studies of the same porphyrins in their reactivity towards copper ion incorporation in anionic reversed micelles indicate striking rate differences which can be interpreted in part to structural variations between the porphyrins as well as to their orientation at the hydrophobic

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02802.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Porphyrin radical‐cations have been produced using laser flash photolysisviaoxidation of the porphyrin triplets by metronidazole. This radical‐cation reacts with OJ as shown by its increased half‐life in the presence of native superoxide dismutase. Comparable results are obtained when porphyrin radical‐cations are formed by Br2‐O2‐oxidation of porphyrins produced in pulse radiolysis of oxygen‐saturated aqueous solutions containing 20mMBr‐O‐. These results provide an explanation for the enhancement by superoxide dismutase of the photosensitizing capacity of porphyrins in the presence of electrophilic nitroimidazoles (Bazin and Santus, 1986). They may also apply to porphyrin radical‐cations formed by monophotonic or biphotonic phot

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02803.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—The weak and reversible binding of the antifungal drug, griseofulvin (GF), to calf thymus DNA has been demonstrated by difference spectroscopy and the quenching of the fluorescence of GF by DNA observed. The value ofKnwas determined to be 800M‐1by fluorescence quenching titration. Adenosine and guanosine also exhibit difference spectra with GF and quench GF fluorescence indicating that they may be the site of both binding and energy transfer. Thein vitrophotosensitization of DNA by griseofulvin is shown to occur. It is proposed that the clinically observedin vivophotosensitizing action of griseofulvin may result from binding followed by excitation energy transfer and that this may also be important in the antifungal activity of the d

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02804.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Absorption and fluorescence emission spectra, fluorescence lifetimes, fluorescence quantum yields, photoisomerization quantum yields and triplet quantum yields were measured for Merocyanine 540 (MC540) in ethanol and in large unilamellar dimyristoyl phosphatidylcholine vesicles. The major differences in the photophysics between the two media are the increase of the fluorescence quantum yield from 0.15 in ethanol to 0.6 in vesicles at 25° C, and the appearance of a second fluorescence decay with a lifetime of 1.87 ns in the latter medium. Upper and lower limits for the photoisomerization quantum yields were determined by combining the data from laser flash photolysis and optoacoustic spectroscopy. The decrease in photoisomerization quantum yield upon incorporation of the dye into the lipid bilayer by a factor 2 suggests that this process competes directly with fluorescence. The temperature dependence of the fluorescence and photoisomerization quantum yields in solution supports this model. In both media MC540 has a very low triplet quantum yield with values 0.002>(>øT>0.02 in ethanol and 0.01>øT‐>0.09 in liposomes Our data are consistent with the model whereby the dye is incorporated into the lipid bilayer as a monomer with two different orientations and this model is adopted on the basis of the biexponential behaviour of the fluorescence and photoisomer

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02805.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Quercetin(20–100 μM) suppressed photohemolysis sensitized by hematoporphyrin, while ascorbate(10–100 μM) stimulated it. However, in the presence of 40 μMquercetin, ascorbate promoted the suppression. The suppression by quercetin was due to scavenging of both singlet oxygen generated by a photosensitized reaction and radicals generated by decomposition of lipid peroxides formed by a singlet oxygen‐dependent reaction. In scavenging, quercetin was oxidized and the oxidation was suppressed by ascorbate. Ascorbate was oxidized by illumination in the presence of quercetin. It is suggested that the cooperation of quercetin with ascorbate in photohemolysis is due to reduction of oxidized quercetin by ascorbate regenerating th

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02806.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY