摘要:

Abstract—The photoproducts of the dinucleoside monophosphates, dTpdT, dTpdC and dTpdU, have been purified by high performance liquid chromatography and characterized by UV absorption spectroscopy, fast atom bombardment mass spectrometry and by secondary thermal and photoreactions. Four types of photoproducts were analyzed: (1) cyclobutane dimers includingcis‐synisomers and two diastereomers of thetrans‐synisomers; (2) 6‐4 photoadducts and the corresponding Dewar valence isomers; (3) photohydrates comprising two diastereomers and (4) a new photoproduct resembling nucleobase amine adducts, which occurs only for dTpdC. The quantum yields of formation of these photoproducts and for some secondary photoreactions were measured by kinetic analysis of the photoproduct yield as a function of photon fluence. These results indicate thatcis‐syncyclobutane dimers are the photoproducts formed with highest efficiency with dT[p]dC dimers being formed with 50–75% the efficiency of dT[p]dT dimers. The 6‐4 photoadducts are formed with 5–10% the efficiency ofcis‐syncyclobutane dimers and the 6‐4 photoadduct of dTpdC is formed two to three times more efficiently than that of dTpdT. Photohydrates are also formed efficiently due to an equilibrium between stacked and unstacked complexes of the dinucleoside monophosphates. It is shown that three of these photoproducts, namely the cyclobutane dimers of dTpdC, the 6‐4 photoadducts and the possible nucleobase amine adduct, undergo photolysis in the UV‐B region resulting in either photoreversion or

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1993.tb09207.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract—The photoproducts of the dinucleoside monophosphates, dTpdT, dTpdC and dTpdU, have been purified by high performance liquid chromatography and characterized by UV absorption spectroscopy, fast atom bombardment mass spectrometry and by secondary thermal and photoreactions. Four types of photoproducts were analyzed: (1) cyclobutane dimers includingcis‐synisomers and two diastereomers of thetrans‐synisomers; (2) 6‐4 photoadducts and the corresponding Dewar valence isomers; (3) photohydrates comprising two diastereomers and (4) a new photoproduct resembling nucleobase amine adducts, which occurs only for dTpdC. The quantum yields of formation of these photoproducts and for some secondary photoreactions were measured by kinetic analysis of the photoproduct yield as a function of photon fluence. These results indicate thatcis‐syncyclobutane dimers are the photoproducts formed with highest efficiency with dT[p]dC dimers being formed with 50–75% the efficiency of dT[p]dT dimers. The 6‐4 photoadducts are formed with 5–10% the efficiency ofcis‐syncyclobutane dimers and the 6‐4 photoadduct of dTpdC is formed two to three times more efficiently than that of dTpdT. Photohydrates are also formed efficiently due to an equilibrium between stacked and unstacked complexes of the dinucleoside monophosphates. It is shown that three of these photoproducts, namely the cyclobutane dimers of dTpdC, the 6‐4 photoadducts and the possible nucleobase amine adduct, undergo photolysis in the UV‐B region resulting in either photoreversion or

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1993.tb09208.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract—The acetone‐sensitized irradiation using UV‐B (ultraviolet light, 280–320 nm; sunlamps) of thymidyl‐yl(3′→5′)deoxyfluorouridine monophosphate produces two main photoproducts. The distribution of these photo‐products is dependent on the pH of the irradiation solution. At pH 6, thecis‐syncyclobutane‐type photodimer is the major product, whereas at high pH (8–10) a photoadduct is the major product. These photoproducts have been identified and structurally characterized by H‐1 and C‐13 NMR spectroscopy. The photoadduct arises from defluorination of the 5‐fluorouracil moiety. The structure of the photoadduct maintains the sugar‐phosphate backbone of the starting material (d‐TpF), and contains a saturated thymine moiety with an added Thy(C6‐hydroxyl)

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1993.tb09209.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract—The riboflavin‐sensitized photooxidation of ascorbate ion (HA‐) to ascorbate radical (A‐) was followed by electron spin resonance (ESR) spectroscopy in conjunction with oxygen depletion measurements. In air‐saturated aqueous media, steady‐state amounts of A‐are rapidly established upon irradiation. The ESR signal disappears within a few seconds after the light is extinguished–more slowly under constant irradiation as oxygen is depleted. No photooxidation was observed in deaerated media. Similar results were obtained with other flavins and when ascorbyl palmitate was substituted for HA‐. The effect of added superoxide dismutase, catalase, desferrioxamine, and singlet oxygen scavengers (NaN3and tryptophan) was studied, as was replacement of water by D2O and saturation with O2. The results are indicative of ascorbate free radical productionviadirect reaction between ascorbate ion and triplet riboflavin in the presence of O2. While the presence of superoxide ion tends to reduce the steady‐state concentration of A‐, competition from the reaction of HA‐with singlet oxygen is less apparent in this system (at HA‐≥ 1 mM) than in the previously studied aluminum phthalocyanine tetrasulfona

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1993.tb09210.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract—The interaction of biological carotenoids with 3‐hydroxymethyl‐3,4,4‐trimethyl‐1,2‐dioxetane (HTMD), a thermodissociable source of electronically excited ketones, was investigated using reversed‐phase high‐performance liquid chromatography. Incubation of the all‐transisomers of β‐carotene, lycopene and canthaxanthin with HTMD led to significanttrans‐to‐cisisomerization, withcisisomers accounting for 20–50% of products formed (the balance assigned as oxidation products). The isomers forming from all‐trans‐β‐carotene were identified as 9‐cis‐, 13‐cis‐ and 15‐cis‐β‐carotene by cochromatography ofcisisomer standards and by on‐line diode array absorbance spectroscopy. An HTMD‐dependentcis‐to‐transisomerization was observed in incubations started with 15‐cis‐β‐carotene, and it occurred more rapidly and to a greater extent than the isomerization of all‐trans‐β‐carotene. The isomer patterns generated from lycopene and β‐carotene are generally similar to those reported recently for var

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1993.tb09211.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract—Corrected emission spectra and fluorescence lifetimes of polycytidylic acid in ethylene glycol: water glass at low temperatures are reported. Luminescence properties observed exhibit a strong dependence on pH and temperature. At neutral pH a vibronic structure of a blue part of the fluorescence spectrum is revealed when temperature is changed from 77 to 10 K, confirming that a monomer component of fluorescence is present. There is also a strong difference in decay of a red‐shifted excimer fluorescence at 10 K at pH 7 and pH 3.9, reflecting a different protonation of cytosine residues and different conformations of polynucleotides in such conditi

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1993.tb09212.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract—Intracellular targets for the photosensitizer α‐terthienyl (αT) were examined by fluorescence microscopy and microfluorospectrometry using human nonkeratinized buccal cells. Intracellular distribution of αT was observed as fluorescent patches widely dispersed in the cytoplasm. The distribution of the fluorescent patches was compared with that of acid phosphatase activity visualized as an azo dye produced by the fast garnet 2‐methyl‐4‐[(2‐methyl‐phenyl)azo]benzenediasonium sulfate reaction. Because both the distribution sites coincided, lysosomes were the likely sites of intracellular affinity of αT. However, because acid phosphatase is not a specific lysosomal marker, we tried to detect another lysosomal enzyme, β‐galactosidase, to confirm if the fluorescent patches were lysosomes, using fluorescein‐di‐(β‐D‐galactopyranoside) (FDG) as a fluorogenic substrate. Without UV‐A (320–400 nm) irradiation of the cells after uptake of αT and FDG, no significant fluorescence was observed. In contrast, with prior UV‐A irradiation in the presence of αT and FDG, the bright yellow fluorescence of fluorescein, which is the digested product of FDG, was clearly detected in the cells by fluorescence microscopy. This observation implied that inflow of external FDG into the lysosomes is caused by lysosomal membrane damage on αT photosensitization. The present results indicated that lysosomes are the

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1993.tb09213.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract—5‐Aminolevulinic acid (ALA), a precursor of protoporphyrin IX (Pp IX), was administered into the rat uterine cavity in an attempt to selectively ablate the endometrium. Doses of ALA ranging from 4 to 50 mg were injected into one uterine horn of rats while the vehicle (saline) was injected into the contralateral horn. Animals were divided into three groups. In group one, the uterine horns were removed and processed for either fluorescent mi‐ croscopy or spectrophotofluorometry 3 h later. In group two, rats were allowed to survive for either 2 or 10 days, and then the uterine horns were harvested and processed histologically. In group three, both uterine horns were exposed to transmural light (approximately 150 J/cm*) 3 h after administration of ALA or saline and processed histologically either 2 or 10 days later.Fluorescent microscopy showed fluorescence in the endometrium and not in the myometrium. The maximum emission spectra of endometrial fluorescence occurred at 630 and 690 nm, characteristic of Pp IX. In contrast, no fluorescence was detected in saline‐treated uterine horns. Light exposure resulted in extensive damage only to the ALA‐treated endometrium. There was no indication of regeneration 10 days after treatment.We conclude from these studies that ALA administered into the lumen of the rat uterus is selectively converted into Pp IX within the endometrium. Furthermore, photoactivation of the Pp IX results in selective ablation of the en

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1993.tb09214.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract—Two new sensitizers are introduced for a potential use in photodynamic therapy: Zn2+‐ and MG2+‐tetrabenzoporphyrin (ZnTBP and MgTBP). A comparative study of the quantum yields of singlet oxygen generation (ΦΔ) of hematoporphyrin derivative (HpD), Photofrin II (PF‐II), Zn2+‐phthalocyanine tetrahydroxyl [ZnPC(OH)4] and the newly introduced sensitizers ZnTBP and MgTBP in liposomes, as well as the kinetics of a photochemical reaction sensitized by them, was made by employing the fluorescent membrane probe 9,10‐dimethylanthracene (DMA). We followed the photosensitization of DMA in real time by monitoring its fluorescence decrease at 457 nm and found that DMA's photosensitization is oxygen mediated. The kinetic traces of the photosensitization reactions were fitted to an analytical function, and the ΦΔvalues were evaluated. At 10 μMsensitizer in an aqueous suspension of 2 mg/mL egg phosphatidylcholine (EPC), HpD was found to have the largest value of ΦΔ(0.215), followed by PF‐II (0.191), ZnTBP (0.023), MgTBP (0.019) and ZnPC(OH)4(0.005). As a test of the method, ΦΔfor methylene blue in ethanol was measured and found to be 0.45 as compared to 0.52 reported in the literature. Due to difference in the sensitizers' absorbances at the laser's wavelength, the reaction photosensitized by ZnTBP was the fastest with a time constant of 6.7 min, followed by MgTBP (8.7), PF‐II (11.9), HpD (17.1) and ZnPC(OH)4(31.2), all at equal sensitizers' concentrations and laser intensities. The binding constants of the sensitizers to EPC lip

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1993.tb09215.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract—Methyl esters of hydroxycinnamic acids are photobiologically active.Cis(Z)and trans(E)p‐methoxymethyl‐cinnamate photosensitizeEscherichia coliand Chinese hamster ovary cells. They also produce sister chromatid exchanges. Photosensitization is oxygen independent, and the cinnamates are not genetically active in the absence of light in the AmesSalmonella typhimuriu

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1993.tb09216.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY