摘要:

Abstract—The induction and removal of DNA interstrand cross‐links (CL) was studied in normal human fibroblasts (1BR/3) using the highly photoreactive furocoumarin 4,5′,8‐trimethylpsoralen (TMP) in combination with monochromatic 365 nm and/or 405 nm radiation. We report that the presence of large amount of furan‐side monoadducts (MAf) induced by TMP plus 365 nm radiation blocks CL incision. When the amount of MAfis reduced by their conversion into even more CL, incision of the cross‐links is mor

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02733.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Upon UV‐A irradiation(320–400 nm), the photorcaction of psoralens either with a solvent molecule or with a second psoralen molecule competes with the well‐known photoaddition of psoralens to DNA. In the present study, a structural assignment of the 3‐carbethoxypsoralen (3‐CPs) photolysis products is proposed on the basis of their chromatographic (high performance liquid chromatography) and of their spectroscopic (absorption, fluorescence, mass spectrometry and1H Nuclear Magnetic Resonance) properties. Four photolysis products have been isolated and identified. The first one results from a water molecule addition on the 4′,5′ double bond of 3‐CPs, the second from an ethanol molecule addition on the 4′,5′ double bond. Two cyclobutane type dimers of 3‐CPs have also been characterized. These results confirm that, in protic solvents, the furan(4′,5′) double bond of 3‐CPs is more photoreactive tha

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02734.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—The photochemical behaviour of amiodarone was examinedin vitroin order to get more insight on the chemical reactions involved in the cutaneousphototoxicity processes.Irradiationat 300 nm of amiodarone degassed in ethanol solution leads to a photodehalogenation followed by a much slower α‐cleavage reaction. Desethylamiodarone, the main metabolite of AD was found to undergo the same reaction as AD. Results of photosensitization and quenching experiments together with phosphorescence spectra indicated that the reaction proceedsviathe triplet excited stateof amiodarone. Radical species formed during photolysis were identified by ESR spectroscopy. CH3CHOH, HO2and an unidentified radical were detected using 5,5‐dimethyl‐1‐pyrroline‐1‐oxide as spin trap. In aerated solutions, photosensitization of oxygen by amiodarone was demonstrated by adding singlet oxygen scavengers such as dimethylfuran and cholesterol. Overall, these results suggest that Type I and Type II mechanisms may take place in the phototoxicity of amiodarone and

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02735.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Human plasma apolipoprotein A‐I (apoA‐I) and apolipoprotein C‐I (apoC‐I) were investigated by time‐resolved fluorescence decay and depolarization. The tryptophyl fluorescence of apoA‐I undergoes a double‐exponential decay with lifetimes of 1.07 and 3.43 ns which remain unchanged over the range of apoA‐I concentration studied.The time‐resolved fluorescence of both native and denatured forms of apoC‐I exhibits an unusual tryptophyl fluorescence decay that was best fit to a triexponential function with lifetimes at 3.7 ± 0.2, 1.1 ± 0.1 and 0.1 ns at 2°C. The native and denatured forms of apoC‐I had rotational correlation times of 1.42 and 1.19 ns at 20°C respectively. A shorter rotational correlation time associated with the internal tryptophan motions was not observed or resolved.The decay of tryptophyl fluorescence in apoC‐I/DPPC/cholesterol complex at 20°C is also triexponential with lifetimes at 4.94, 1.28 and 0.21 ns, which are longer than those of the uncomplexed forms. Two rotational correlation times of 28.32 and 0.59 ns at 20°C were resolved by fluorescence depolarization measurements. The long rotational time remained constant with temperatures above 30°C. Also, the temperature dependence of the order parameter, S2, resembled a lipid phase transition curve with a transition midpoint at 38°C. The tryptophan and thus apoC‐I are found to be affect

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02736.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—We have compared the relative abilities of some putative biological protectors to block oxidation of 2,5‐bis(hydroxymethyl)furan (BHMF)† in illuminated solutions containing the photosensitizer rose bengal and in the separated‐surface‐sensitizer (S‐S‐S) system involving pure singlet oxygen (1ΔAgO2). While L‐histidine is a well‐known quencher of singlet oxygen, free L‐histidine is not commonly found in high concentrations in nature. L‐Carnosine (β‐alanyl‐L‐histidine), however, is present in the striated muscles of many organisms, most notably mammals, in concentrations up to 40 mM. At neutral pH, carnosine quenched singlet oxygen more effectively than did equimolar histidine, both in solubilized sensitizer studies and in the S‐S‐S system. In the pure singlet oxygen system, 1 mMcarnosine reduced the rate of BHMF oxidation as effectively as 3 mMhistidine alone, or a mixture of 3 mM histidine and 3 mMβ‐alanine. The fungal product L‐ergothioneine (2‐thiol‐L.‐histidine betaine) and its synthetic analogue, 2‐thiolhistidine, at 1 mMblocked photosensitized BHMF oxidation using solubilized rose bengal, as did urate at 0.5 mM. All three compounds failed to reduce the rate of BHMF oxidation by singlet oxygen in the S‐S‐S system, however. Homocarnosine (‐γ‐aminobutyryl‐L‐histidine) gave levels of protection against BHMF oxidation identical to histidine, but is present in the central nervous system only at micromolar concentrations. Neither 1 mMimidazole nor 5 mMurea reduced BHMF oxidation in either system. We conclude that some prevalent biomolecules may afford protection either by preventing singlet oxygen production (urate, L‐ergothioneine) or by intercepting singlet oxygen once formed (L‐carnosine).

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02737.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Human cells of the line NHIK 3025 were incubated with Photofrin II (PII) and exposed to light. Fluorescence‐ and absorption spectra of PII in the cells were measured. Light exposure resulted in a degradation of PII in the cells and changes in the shape of the fluorescence spectra. These changes are probably partly due to a photochemical modification of PII and to a relocalization of PII in the cells. Notably, a destruction of binding sites for PII on or close to proteins was caused by the light exposure. The rate of the light‐induced decay of the porphyrin fluorescence intensity was only slightly increasing with the PII concentration, indicating that each porphyrin molecule is mainly degraded by photoproducts originating from itself. On the other hand, the rate of the degradation of porphyrin binding sites on the proteins increased with increasing PII concentrations.The excitation spectrum of PII in cells has a peak at285–290 nm attributed to energy transfer from proteins to porphyrins located close to the proteins. The intensity of this peak relative to the intensity of the Soret band increases with decreasing porphyrin concentrations. This might indicate that some of the binding sites close to proteins have a higher affinity for the porphyrin than binding sites at longer distances from the p

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02738.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Anion permeability was studied in normal and photomodified erythrocytes and the role of anion species in photomodification and singlet oxygen generation was evaluated. Relative permeability to halides and nitrate was assessed using lysis rates in valinomycin‐treated cells to make anion permeation rate‐limiting. In non‐photomodified cells the normal high temperature dependence (E:, = 67 kJ/mol; 16 kcalhol), selectivity sequence (NO,>I>Br>F>Cl) and sensitivity to block by the stilbene derivative HzDIDS were confirmed. In cells photomodified by illumination in the presence of phloxine B the anion permeability was severely perturbed. The temperature dependence was strongly reduced, the permeability to ions other than fluoride increased, leading to a reversal of the F/CI selectivity, and the capacity to be blocked by HIDIDS was lost. Pretreatment with NEM and posttreatment with DTE did not affect rates of photohemolysis. The amount of photomodification varied with species of anion present in the reaction medium, being greatest for F and smallest for I. Rates of singlet oxygen generation in aqueous solution measured by the RNO bleaching method followed the same anion sequence, suggesting a strong external heavy atom

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02739.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Five eudistomins, β‐carboline derivatives isolated from a Caribbean tunicate, were tested for phototoxicity against several viruses, bacteria, yeast, and mammalian cells. The five compounds showed varying degrees of UVA dependant phototoxicity (i.e. long wavelength UV dependant) against murine cytomegalovirus (MCMV), Sindbis virus (SV) and mouse 3T3 cells, although the relative order of potency was the same for these three organisms. Eudistomin N was the most active (approximately the same as the β‐carboline, harmine), while eudistomins M and O were moderately phototoxic, and H and I had little activity. To some degree the relative phototoxicity was correlated with fewer side chain substituents. A similar relative order of phototoxic potency was seen against phage T4, but in this case the magnitude of the effect was considerably reduced, in contrast to harmine. The antibacterial and antifungal activities were not correlated with antiviral effects, and some UVA‐independent activities were seen. Thus the eudistomins may possess different mechanisms of action against different organisms, depending upon the presence or absen

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02740.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Longwave ultraviolet radiation(UVA–320–400nm) is known to induce inflammation, pigmentation and tumor production in mammalian skin. The mechanisms by which such radiation induces these biologic phenomena are poorly defined. In an effort to broaden our knowledge in this area, we examined the effect of UVA on DNA biosynthesis in Hartley strain albino guinea pig skin. The animals were irradiated with selected doses of solar simulated UVA, and DNA was assayed by [3H]thymidine incorporation into epidermal DNA by autoradiography. These studies revealed that UVA inhibited DNA synthesis in a dose dependent manner between 40 and 80 J cm‐2at 3 h post‐irradiation. This inhibition was followed by a stimulation of synthesis at 5 h and a second inhibition/ stimulation at 8 and 24 h, respectively. Although the mechanism of alteration is undefined, our data suggest that UVA has profound effects on DNA biosynthesis in mammalian

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02741.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—The growth delay induced by near‐UV radiation has been largely attributed to injured tRNA's and to the stringent response. We report an associated membrane perturbation whose recovery determines substantial modifications in the behavior of log phaseEscherichia coliK–12 exposed to sublethal doses of near‐UV radiation (366 nm). When incubated at 37°C in plain nutrient broth, cells suffered a growth delay of about 100 min with parallel inhibition of several membrane functions. Conversely, when grown in conditions known to influence membrane activities, these were slightly inhibited and the growth delay lasted about 50 min. All the above conditions triggered the stringent response, characterized by an equivalent post‐irradiation burst of intracellular guanosine 5′3′ tetra and pentaphosphate and by a similar decay rate of the nucleotides accumulated at time 0 of the growth lag. According to our data the polyphosphates' half decay time in irradiated cells remains practically constant and close to 15 min. But, while cells from unsupplemented broth at 37°C resumed normal growth in around 100 min those with recovered membranes were rescued from growth inhibition in about one ha

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02742.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY