摘要:

Abstract—Rabbit erythrocyte cell ghosts were prepared containing tetrasodium meso‐tetra (4‐sulfona‐to‐phenyl) porphine (12‐hydrate), a water soluble porphyrin. Laser flash kinetic spectroscopy of the suspension revealed a difference spectrum consistent with the porphyrin T, state. The time profiles of the signal decay were bi‐exponential, and oxygen quenched each of the two components differently. Triplet‐triplet extinction coefficients and quantum yields were lower for the ghost suspension than for porphyrin in solution. Fluorescence lifetime studies of the suspension also showed the presence of two components. Singlet oxygen luminescence, as measured by germanium diode detection, was observed, with a lifetime of 46 (jls an

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02756.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—The conditions under which electronically‐excited 1: 1 complexes are expected to produce high yields of separated radical‐ions are presented with reference to the porphyrin‐quinonc system in terms of the symmetry properties of intermolecular orbitals (IMO). These conditions are translated into design properties of a 4‐center photoinduced charge separation unit DDAO in which post‐excitation energy and electron transfer processes result from diabatic internal conversions between singly‐excited configurations differentiated by the location of holes and electrons in valence and conduction IMO of the unit. It is suggested that a major role of the donor pair is the inhibition of diabatic charge recombination by the low intermolecular component of the vibrational overlap integral over isoenergetic ground (DD) and cationic (DD +) c

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02757.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Photosensitizing capabilities of anthracenedione anticancer agents to oxidize NADH in aqueous solutions have been studied by EPR and spin trapping techniques. It is demonstrated that 1,4‐diamino substituted anthraquinones, like mitoxantrone and ametantrone, do not photosensitize NADH oxidation while 1,5‐ and l,8‐bis[[(diethylamino)ethyl]amino]anthraquinones do, undergoing simultaneous one‐electron reduction to their semiquinone radical forms upon illumination with visible light. In aerated aqueous solutions the reaction leads to the production of superoxide ion and hydrogen

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02758.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Photooxidation reactions in ascorbate (AH)‐containing erythrocyte membrane suspensions have been studied in broad perspective by simultaneously monitoring lipid peroxidation in the membrane compartment and formation of hydrogen peroxide (H2O2) and hydroxyl radical (OH) in the aqueous compartment. Non‐bound uroporphyrin (UP) and membrane‐bound protoporphyrin (PP) were used as sensitizers. Photoreduction of UP to the radical anion (UP‐) was detected by electron spin resonance when UP/AH/membrane mixtures were irradiated anaerobically. Aerobic irradiation resulted in a strong AH‐‐stimulation of lipid peroxidation, H2O2formation, and OH‐generation (detected with 2‐deoxyribose (DOR) and the spin trap 5,5‐dimethyl‐l‐pyrroline‐N‐oxide). Use of diagnostic agents (e.g. catalase, desferrioxamine, mannitol) revealed that OH‐is involved in light‐stimulated DOR oxidation, but not in lipid peroxidation. Similar irradiation in the presence of PP resulted in far greater lipid peroxidation than observed with UP, but less DOR oxidation, and insignificant accumulation of H2O2. This suggests that photoreduction of membrane‐bound PP is less efficient, possi

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02759.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—The triplet state characteristics (spectrum, lifetime and quantum yield) for four dye sensi tisers [methylene blue (MB), erythrosin (ER), haematoporphyrin (HP) and riboflavin (RF)] were determined in methanol by laser flash photolysis and singlet oxygen yields (0.60 to 0.48) from time‐resolved measurements of the 1270 nm near infrared emission. The reaction of singlet oxygen with four long chain unsaturated phenyl esters [oleate (18: 1), linoleate (18: 2), linolenate (18: 3) and arachidonate (20: 4)]was followed quantitatively using the singlet oxygen luminescence technique and also, after continuous420–700 nm irradiation, by HPLC and other analysis of the isomeric product monohydroperoxides. The overall quantum yield of photooxidation (∼10‐2) was shown to be consistent with the observed singlet oxygen quenching constants(2–12 times 104dm3mol‐1s‐1) for the four esters studied and the singlet oxygen lifetime in methanol (τ∼ 9 μs). The isomer product distribution was interpreted in terms of a dual singlet oxygen and radical mechanism, the radical contribution increasing with sensitiser in the order ER = MB

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02760.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—In connection with the use of red light‐photosensitizers for photodynamic therapy, the redox reactivity of excited metallophthalocyanines (M = Al, Ga) was investigated by flash photolysis in order to establish whether photooxidations proceed by Foote's mechanisms I or II. Aminoacids (tryptophan, tyrosine) were seen to function as electron transfer quenchers of the excited phthalocyanines with rate constants 107k104M‐1s‐1. This was not the case of purines or ATP. The ability of the excited phthalocyanines to sensitize photooxidations by mechanisms I and II is discussed in terms of evaluated rate co

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02761.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—The lowest excited triplet T1states of the two alkaloids, morphine and codeine, have been investigated by ODMR and emission spectroscopy. The electronic character of their T1states could be determined by comparing the T1properties with those of the constituent parts guaiacol and veratrole. The T1properties, e.g. phosphorescence spectra, zero‐field splitting parameters and triplet sublevel selective decay rates are very similar for the constituent parts and the alkaloids. Thus, in analogy to veratrole and guaiacol, the T1state of codeine and morphine is assigned to a ππ* state mainly localized on the benzene ring and the attached alkoxy and hydroxy groups. There is no evidence for a contribution from the other subunits, trialkylamine and unsaturated alcohol, to the T1state of codeine and mor

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02762.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Photoacoustic (PA) spectroscopy reveals a new electronic transition in concentrated aqueous solutions of hematoporphyrin IX (Hp). This new band has a maximum near 440 nm. Its intensity is sensitive to pH, concentration, PA chopping frequency, and the presence of sodium dodecyl sulfate (SDS). Data presented support the assignment of this new band to a dimeric form of Hp. The pH effects on this new band are discussed in terms of their implications for the selective biodistribution of certain porphyrin‐based photochemotherapeutic age

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02763.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—The fluorescence properties of three ortho aminobenzoate local anesthetics have been determined in a variety of solvents. Results from these studies have been used to deduce how these drugs interact with phosphatidylcholine bilayers. The emission energy, fluorescence quantum yield and lifetime exhibited a biphasic dependence on solvent polarity. In aprotic solvents, alcohols and in ethanol‐water mixtures containing less than 40% water, quantum yields and lifetimes were high (approximately 0.55 and 8.5 ns respectively). In ethanol‐water mixtures containing>40% water, the strong fluorescence quenching was primarily due to an increase in the rate of non‐radiative deactivation of the excited state. Both the radiative (kr) and non‐radiative (knr) rate constants show a biphasic dependence on solvent polarity. These studies suggest the presence of two singlet excited states for these molecules, a polar singlet excited state, S1‐pand a charge transfer excited state, S1‐ctwith the latter predominating in ethanol‐water mixture containing>40% water. In egg phosphatidylcholine bilayers, the fluorescence, lifetime and quantum yield are consistent with the view that these drugs are localized within the lipid head group region where the charge‐transfer excited state can be stabilized by intermolecular

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02764.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—The absorption and fluorescence spectra, and the fluorescence lifetime of acridine orange (AO) were measured in a wide range of the sodium dodecyl sulfate (SDS) concentration below and above the critical micelle concentration (cmc). The fluorescence consisted of two components with different lifetimes; short (3 ns). The short and long lifetime components are attributed to the AO monomer and dimer associated with detergent, respectively. The lifetime of the dimer increased with increasing the SDS concentration just below the cmc. It decreased suddenly to a constant value just above the cmc. The lifetime of the monomer showed only a slight increase in the concentration range of SDS employe

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02765.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY