摘要:

Abstract—Absorption, fluorescence and phosphorescence spectra as well as fluorescence and phosphorescence quantum yields of 8‐X‐5‐deazaflavins (X = C1, NO2,p‐NO2‐C6H4, N(CH3)2, NH2,p‐NH2‐C6H4,p‐N(CH3)2‐C6H4‐N=N) were determined. It was found that all these data are highly influenced by the substituent at position 8 of the 5‐deazaisoalloxazine skeleton. Also the photoreduction of 8‐X‐5‐deazaflavins in the presence of electron donors was studied. It was established that the photoreduction leads to the formation of a 5,5‘‐dimer and/or a 6,7‐dihydro compound. Reduction of the C(6)‐C(7) bond is promoted by strong electron‐donating substituents and bulky electron donors. 5‐Deazaftavins with a reducible substituent at position 8 exhibit reduction of the substituent prior to the reduc

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1987.tb07380.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract—Irradiation of daunomycin (or adriamycin) and the spin trap 5,5‐dimethyl‐l‐pyrroline‐1‐oxide (DMPO) at 490 nm in the presence or in the absence of air generated the hydroxyl radical adduct (DMPO‐OH). The observed DMPO‐OH signal was not affected by the addition of hydroxyl radical scavengers (ethanol, formate), suggesting that direct trapping of the hydroxyl radical was not involved. The DMPO‐OH signal was insensitive to superoxide dismutase and catalase, which ruled out the possibility of superoxide or H2O2involvement. These findings demonstrate that daunomycin (or adriamycin) does not generate hydroxyl radicals or superoxide radical anions when subjected to 490‐nm excitation. However, when daunomycin (or adriamycin) was irradiated at 310 nm DMPO adducts derived from two carbon‐centered radicals, superoxide and the hydroxyl radical were detected. The superoxide adduct of DMPO was abolished by the addition of SOD, providing unequivocal evidence for the generation of the superoxide anion radical. The daunomycin semiquinone radical, observed upon 310‐nm irradiation of daunomycin in the absence of DMPO, appears to be the precursor of the superoxide radical anion. One of the carbon‐centered radicals trapped by DMPO exhibited a unique set of hyperfine parameters and was identified as an acyl radical. This suggests that the known photochemical deacylation of daunomycin occursviaa homolytic cleavage mechanism. The free radicals generated photolytically from adriamycin and daunomycin may be involved in the etiology of the skin ulceration and inflammation caused by these drugs. A knowledge of the dependence of these photogenerated radicals on the wavelength of excitation may be important in the development of adriamycin and daunomycin

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1987.tb07381.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract—A reversed‐phase HPLC system has been developed which separates the common nucleo‐bases from the 6‐methylimidazo[4,5‐b]pyridin‐5‐one (6‐MIP) produced on acid hydrolysis of a thymine‐adenine photoadduct (TA*) that is formed between adjacent thymine and adenine bases in UV‐irradiated polydeoxyribonucleotides. By measuring the relative amounts of adenine and 6‐MIP in acid hydrolysates, this system has been used to investigate how polynucleotide conformation affects the yield of TA* in poly(dA‐dT) irradiated at 254 nm. The photoreactivity of other pyrimidine‐purine sequences has been examined with the deoxydinucleoside monophosphates d(TpI) and d(m5CpA) and with the alternating DNA copolymers poly(dA‐dU), poly(dI‐dC), poly(dG‐dC) and poly(dA‐dC).poly(dG‐dT). Samples were irradiated at 254 nm in aqueous solution and in ice, and at wavelengths>290 nm with acetone as photosensitizer. A photoproduct resembling TA*, and giving 6‐MIP on acid hydrolysis, was isolated from d(TpI) irradiated at 254 nm in solution or in ice; d(m5CpA) was comparatively unreactive. Acid hydrolysates of the irradiated DNA copolymers were screened by HPLC and by TLC and paper electrophoresis, for the presence of imidazo[4,5‐b]pyridin‐5‐one, 6‐MIP, or other species attributable to specific photoproduct formation. By this criterion, however, none of the copolymers showed evidence of significant photoreactivity in either their single‐ or double‐stranded conformational states. The formation of mixed pyrimidine‐purine photoadducts in D

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1987.tb07382.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract—We tested water‐soluble sulfonated phthalocyanine and three metal chelate derivatives for their tumoricidal effect on the EMT‐6 mammary tumor in mice exposed to red light. The metal‐free sulfophthalocyanine had little effect, whereas the aluminum complex and the lower sulfonated fraction of the gallium complex exhibited tumoricidal activity similar to hematoporphyrin‐based photosensitizer (Photofrin II). The higher sulfonated fractions of the gallium complex were less active as compared to the lower sulfonated fraction. The cerium complex was the most active sensitizer in terms of dye and light doses required to induce tumor necrosis and cure but also showed the highest phototoxicity towards healthy skin. These results suggest that sulfonated phthalocyanines will offer a new alternative in photodynamic therapy of light‐accessibl

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1987.tb07383.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract—The photosensitized oxidation of L‐tryptophan by gallium phthalocyanines sulfonated to different degrees is studied as a function of both substrate and sensitizer concentrations in water and 50% MeOH‐H2O solutions. The maximum quantum yield of singlet oxygen was found to be nearly 0.5 for all sulfonated gallium complexes. The effect of adding sulfonate groups in the phthalocyanine backbone is to change the tendency of dye molecules to dimerize or aggregate in a particular solvent. A shift in the chemical equilibrium away from the monomeric state, which occurs at high dye concentrations and at lower degrees of dye sulfonation, results in a reduced photochemical yield. The variation of quantum yields in different solvent systems and at several wavelengths is similarly accounted for by the fraction of light absorbed by the productive monomer

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1987.tb07384.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract—An introduction to the fundamental characteristics of synthetic melanin fluorescence is presented. The particular difficulties associated with the detection and reduction of the relatively weak signal are discussed and a technique is described for correcting the fluorescence spectra for attenuation of the excitation and emission beams. Spectra are reported for the excitation wavelength range 340–400 nm and an emission range of 360–560 nm. The concentration dependence of the corrected fluorescence signal is examined and is shown to be linear. The variation of the fluorescence spectra with excitation wavelength suggests a two‐component fluorescence, for the wavelength range studied. The presence of an isosbestic point in the spectra is used to identify the fluorophores as components of a reaction equilibrium. The possible relationship of this equilibrium to that associated with the melanin photo ESR is d

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1987.tb07385.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract—The flow linear dichroism properties of covalent adducts derived from the photochemical binding of various psoralen derivatives to salmon sperm DNA were investigated. The psoralens studied include bifunctional derivatives (8‐methoxypsoralen,5‐methoxypsoralen, tetrahydropyrido [3,4: 4‘,5’] psoralen) and monofunctional derivatives (pyrido [3,4‐c]psoralen, 7‐methylpyrido [3,4‐c] psoralen, 3‐carbethoxypsoralen). The orientation of the psoralen moieties (furan‐side monoadducts) relative to the orientation of the DNA bases was determined. All of the furan‐side monoadducts are characterized by a similar orientation, with mean angles between the psoralen moiety and the normals of the planes of the DNA bases ranging between 70° and values close—but not equal—to 90°. The results are consistent with a pseudo‐intercalative adduct geometry, most probably involving stacking in

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1987.tb07386.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract—Variously pigmented strains ofUstilago violaceawere exposed to monochromatic light from 400 to 650 nm in 50‐nm increments to determine which wavelengths were most effective for photo‐killing. In addition, liquid nitrogen temperature absorption spectra were determined for intact cells of the fungal strains. The high cytochromeccontaining pink strains 1.C429, AB278a‐1, 1.C425 and 2.C427 were more sensitive to cytochrome absorption wavelengths than were their low cytochromeccounterparts 15.10, 1.C2y, 1.C2wand 1.C427, while the carotene accumulating strains 1.C2yand AB278a‐1 were more resistant to photo‐killing than their carotene lacking counterparts 15.10, 1.C2w, 1.C427 and 1.C429, 1.C415, 2.C428 even at wavelengths not absorbed by carotenes. The results suggest that cytochromecand other cytochromes are photosensitizers and that carotene‐related protection is through the quenching of the photosensitizers as well as

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1987.tb07387.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract—Power absorption by aqueous solutions of methylene blue containing high concentrations of polystyrene microspheres was measured at 650 nm, using the photosensitized inactivation of subtilisin Carlsberg as an internal actinometer. The results were analyzed with the one‐dimensional diffusion approximation for a finite slab. It is shown that the power absorption is determined by two macroscopic parameters, the optical penetration depth and the linear absorption coefficient. The optical penetration depth was determined independently by measuring flux profiles with an inserted fiber‐optic method. The results are in satisfactory agreement with the predictions of the diffusion model, with microsphere diameters from 0.5 to 5 μm and a wide range of scatterer and dye concentrations. The presence of the scatterers diminished the power absorbed by the dye in all cases. The predictions of one‐dimensional diffusion model are compared to Kubelka‐Munk theory, and shown to be equivalent for optically de

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1987.tb07388.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract—With accumulating evidence that the membrane is an important site for near‐UV inactivating events, we have investigated the effects of near‐UV radiation on the unsaturated fatty acid auxotrophE. coliK1060 following incorporation into the membrane phospholipids of fatty acids with varying degrees of unsaturation. Sensitivity, lipid peroxidation and membrane damage, as determined by86Rb+leakage, have been found to increase with increasing unsaturation in log‐phase cells. Similar experiments carried out in D2O also show an increase in sensitivity, lipid peroxidation and membrane damage, indicating that singlet oxygen may be responsible for such near‐UV‐radiation‐

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1987.tb07389.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY