FLUORESCENCE SPECTROSCOPY OF BENZO[a]PYRENE DIOL EPOXIDE-DNA ADDUCTS. CONFORMATION-SPECIFIC EMISSION SPECTRA

The fluorescence characteristics of adducts derived from the covalent binding of the highly tumorigenic (+) and the non-tumorigenic (-) enantiomers of trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) to native calf thymus DNA are significantly different from one another both at room temperature and at 77 K. The ratio R of fluorescence intensities of the (0,0) band I (situated near 380 nm) and vibronic band V (near 400 nm) of the pyrene ring system in the BPDE-DNA adducts and of the tetraol (BPT) hydrolysis product of BPDE is very sensitive to the polarity of the solvent, thus mimicking the well known behavior of pyrene itself (A. Nakajima, 1971, Bull. Chem. Soc. Jpn. 44, 3272). The fluorescence excitation and emission spectra of the (+)-BPDE-DNA adducts are relatively sharp and only slightly red-shifted (2-3 nm) with respect to those of BPT in aqueous buffer solution, and R = 1.07 when the fluorescence is excited at the maximum of the absorption spectrum; this compares with R = 1.17 for BPT in water, R = 0.75 in ether, and R = 0.84 for noncovalently intercalated BPT. These results suggest that the pyrene ring system in the covalent (+)-BPDE-DNA adducts is located in an environment which is relatively exposed to the aqueous environment, while physically intercalated BPT molecules are located at hydrophobic binding sites. The fluorescence characteristics of the (-)-BPDE-DNA adducts are more heterogeneous and thus more complex than those of the (+)-adducts. The R ratio depends rather strongly on the wavelength of excitation; a minor, more highly fluorescent and relatively solvent-accessible form of adducts exhibits an R ratio of 1.01. The major, less solvent accessible form is characterized by a larger red shift in the absorption spectrum (approximately 10 nm) and emission spectrum (approximately 6 nm for the (0,0) band) relative to BPT, and an R ratio of 1.07. These characteristics suggest that the local environments of the pyrenyl residues in the (-)-BPDE-DNA adducts are significantly different from those of BPT bound noncovalently to DNA by the intercalation mechanism. Fluorescence methods, particularly at low temperatures where the bands are better resolved and the fluorescence yields are significantly greater than at room temperature, can also be used to distinguish covalent DNA adducts derived from the binding of (+)-BPDE and (-)-BPDE to native double-stranded DNA.     

MECHANISMS OF QUENCHING OF THE FLUORESCENCE OF A BENZO[a]PYRENE TETRAOL METABOLITE MODEL COMPOUND BY 2'-DEOXYNUCLEOSIDES

Abstract— The hydrophobic interactions of bulky polycyclic aromatic hydrocarbons with nucleic acid bases and the formation of noncovalent complexes with DNA are important in the expressions of the mutagenic and carcinogenic potentials of this class of compounds. The fluorescence of the polycyclic aromatic residues can be employed as a probe of these interactions. In this work, the interactions of the (+)-trans stereoisomer of the tetraol 7,8,9,10-tetrahydroxytetrahydrobenzo[a]pyrene (BPT), a hydrolysis product of a highly mutagenic and carcinogenic diol epoxide derivative of benzo[a]pyrene, were studied with 2′-deoxynucleosides in aqueous solution by fluorescence and UV spectroscopic techniques. Ground-state complexes between BPT and the purine derivatives 2′-deoxyguanosine (dG), 2′-deoxyadenosine (dA), and 2′-deoxyinosine (dI) are formed with association constants in the range of ～40–130 M^?1 Complex formation with the pyrimidine derivatives 2′-deoxythymidine (dT), 2′-deoxycytidine (dC), and 2′-deoxyuridine (dU) is significantly weaker. Whereas dG is a strong quencher of the fluorescence of BPT by both static and dynamic mechanisms (dynamic quenching rate constant k_dyn= [2.5 ± 0.41 × 10⁹M¹ s ¹, which is close to the estimated diffusion-controlled value of ～ 5 × 10⁹M^{? 1} s^?1), both dA and dI are weak quenchers and form fluorescenceemitting complexes with BPT. The pyrimidine derivatives dC, dU, and dT are efficient dynamic fluorescence quenchers (K_dyn～ [1.5–3.0] × 10⁹M^?1 s^?1), with a small static quenching component due to complex formation evident only in the case of dT. None of the four nucleosidcs dG, dA, dC and dT are dynamic quenchers of BPT in the triplet excited state; the observed lower yields of triplets are attributed to the quenching of single excited states of BPT by 2′-deoxynucleosides without passing through the triplet manifold of BPT. Possible fluorescence quenching mechanisms involving photoinduced electron transfer are discussed. The strong quenching of the fluorescence of BPT by dG, dC and dT accounts for the low fluorescence yields of BPT-native DNA and of pyrene-DNA complexes.     

FLUORESCENCE AND ELECTROGENERATED CHEMILUMINESCENCE STUDIES OF SEVERAL DIMETHYL-SUBSTITUTED BENZO[a]PYRENES

Abstract— Absorption spectra, molar absorptivities, fluorescence spectra and fluorescence quantum yields of five dimethylbenzo[a]pyrenes (DMBP) in benzene solutions at room temperature are reported. Electrogenerated chemiluminescence (ecl) spectra and the relative eel intensities of these compounds to that of 9,10-diphenylanthracene in the 1:1 acetonitrile-benzene mixed solvent with tetra- n -butyl-ammonium perchlorate as a supporting electrolyte are also reported. Both fluorescence quantum yield and ecl intensity studies show that the vicinal dimethyl substitution lowers the fluorescence and eel efficiency, and this effect is more pronounced in a compound whose K-region is blocked. The compounds in which the L-region is blocked showed much higher fluorescence and eel efficiency. The fluorescence of DMBP molecules is quenched by the donor molecule, tri- p -tolylamine with a diffusion controlled rate to form an emitting exciplex. The cation radical of TPTA and the radical anion of the DMBPs are shown to form an exciplex efficiently by the eel experiments. Both quenching and eel results indicate that all DMBPs studied here are good acceptors.     

QUENCHING OF PYRENE FLUORESCENCE BY TRYPTOPHAN IN MICELLAR SOLUTIONS

Deactivation of excited pyrene incorporated to cationic (cetyltrimethylammonium chloride), anionic (sodium dodecyl sulfate) and neutral (Triton X-100) micelles by tryptophan has been investigated over a wide pH range. Data obtained allow an estimation of the tryptophan association to the micelles, of the tryptophan apparent p K in the micellar solutions, and of the dynamics of tryptophan incorporation to the micellar pseudophase. In particular, the data obtained at pH 7 allow an estimation of the effect of the micellar charge upon the binding capacity of the tryptophan zwitterion.     

烷基苄基铵对芘的荧光猝灭行为研究

广义的荧光猝灭系指所有能使荧光强度降低的物理和化学过程,但通常涉及的主要有动态猝灭和静态猝灭,二者均遵从Stern-Volmer方程,但由于猝灭作用本质不同,它们在荧光寿命变化、温度效应及吸收光谱等方面表现出差异可资区别.本文通过稳态荧光强度变化和荧光衰减速率的比较研究了具有不同烷基链长的十四烷基苄基二甲基氯化铵(Zeph)和苄基三甲基溴化铵(TMBA)对芘的荧光猝灭,并基于电导实验结果以及猝灭剂全反式构象从理论上计算了Zeph和TMBA的猝灭速率常数,讨论了荧光猝灭的性质和长链分子的构型。     

FLUORESCENCE QUENCHING OF PYRENE DERIVATIVES BY NITROXIDES IN MICROHETEROGENEOUS SYSTEMS

Abstract Fluorescence quenching of pyrene derivatives by 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO), 4-oxo-2,2,6,6-tetramethylpiperidinyl-1-oxy and 4-hydroxy-2,2,6,6-tetramethylpiperidinyl-1-oxy has been measured in homogeneous solvents and microheterogeneous systems: cetyltrimethylammonium chloride micelles, large unilamellar vesicles of dioctadecyldimethylammonium chloride and dipalmitoylphosphatidylcholine (DPPC) and rat liver microsomes. The extent of intraaggregate quenching is mostly determined by the quencher incorporation to the micro-phases. In particular, it is observed that quenching by TEMPO in vesicles is considerably faster when the bilayer is in the liquid crystalline state. This significant increase in quenching rate with the melting of the bilayer is not observed for the other TEMPO derivatives, indicating that the effect of the lipid organization upon the solubility is related to the hydrophobicity of the solute. The data obtained in rat liver microsomes at 37°C show a pattern very similar to that observed in DPPC vesicles in the liquid crystalline state.     

PHOTOCHEMICAL COUPLING OF BENZO[a]PYRENE WITH 1-METHYLCYTOSINE; PHOTOENHANCEMENT OF CARCINOGENICITY

Abstract— Irradiation of the carcinogenic benzo[ a ]pyrene(I) with 1-methylcytosine hydro-chloride(II) (molar ratio 1:10) at 3500 Å in methanol-acetone produces the 6-(1-methylcytos-5-yl)-benzo[ a ]pyrene(III). The structure of the product shows the hydrocarbon bound through the most active 6-carbon atom to the nucleophilic 5-position of the base. In the second part, the possibility of observing carcinogenic effects on the mouse skin from non-carcinogenic hydrocarbons under the action of u.v. light is investigated. Both experiments provide evidence that the 4,5-double bond ( K region) of I presumably does not play a role in triggering the cancer process.     

芘在改性硅胶上的光物理研究——以芘为探针研究改性硅胶的表面特性

研究了芘在正十碳烷氧基和三甲基硅氧基改性硅腔表面上的荧光光谱和寿命。在这二种硅胶上,激基缔合物是由基态聚积体直接受光和受激发的单分子和基态的单分子所形成、在硅胶≡Si—O—C_(10)H_(21)-n上比在硅胶≡Si—O—SiMe_3上所形成的聚积体较少。化学改性与物理改性相结合可使芘在较大的浓度范围内主要以单分子分散。激基缔合物的形成主要是由动力学过程所控制。研究了温度对芘的荧光光谱和寿命的影响。激基缔合物形成过程的活化能约为7kcal mol~(-1)。讨论了环境对单分子荧光光谱结构的影响。     

KINETICS OF FLUORESCENCE FADING OF ACRIDINE ORANGE-HEPARIN COMPLEXES IN SOLUTION

Abstract— The irreversible photochemical fading of fluorescence of acridine orange-heparin complexes indicates that fading involves the reaction of a "reactive" excited bound dye dimer with one in the ground state. A kinetic parameter, r ", is derived, which has a constant value over a considerable range of conditions, and which is directly related to rate constants for photophysical and photochemical processes. This parameter appears to be characteristic for heparin and may serve to identify it in the presence of other glycosaminoglycans.     

芘为荧光探针研究SDS/H2O二元体系的热相变

以芘作为荧光探针, 对十二烷基硫酸钠(SDS)40 g%的水溶液在-20 ℃～30 ℃温区的相变进行了研究。该二元体系的主要相变是凝聚胶-液晶的转变, 测定其相变温度为20 ℃。自由水形成的冰层在0 ℃融化, 由此导致在化冰前后体系呈现出不同的凝聚胶相。在-17 ℃退火处理, 体系出现了新的凝聚胶相。以上出现的各相均可由I_E/I_M值清楚地表征, 从而首次证实了这种探针方法为一种成功的膜模拟体系相变的研究手段。     

SINGLET OXYGEN INDUCED MUTAGENESIS OF BENZO[α]PYRENE DERIVATIVES

Singlet oxygen activates the mutagenicity of several benzo[a]pyrene (BP) derivatives in the absence of mammalian metabolic action. This has been demonstrated using a separated-surface-sensitizer system for generating chemically pure singlet oxygen, eliminating most of the complications that arise with singlet oxygen generation by conventional photosensitization. Salmonella typhimurium bacteria were exposed to singlet oxygen in the presence of certain BP derivatives and the mutation frequency determined with an azaguanine forward mutation assay. The mutation frequency was increased by exposure to singlet oxygen compared to light-only controls for those BP derivatives that were saturated at either the 7,8 or 9,10 positions but not both. The increase in mutation frequency depends on both the concentration of BP derivative and on the dose of singlet oxygen. Mutation frequency was also significantly increased when bacteria were treated with a solution of trans-7,8-dihydrodiol-BP that had been separately exposed to singlet oxygen, unequivocally demonstrating that the mutagenicity is due to the formation of a product of BP derivative oxidation by singlet oxygen and that this product has a lifetime at least on the order of minutes in acetonitrile. The requirement for singlet oxygen rather than some other form of reactive oxygen was confirmed by determination of the gas phase lifetime of the intermediate responsible for activating mutagenicity. This was performed by measuring the dependence of the mutation frequency on the distance separating the sensitizer from the target. This gives a value of 88 +/- 35 ms, which is in excellent agreement with the mean value of 89 ms calculated from previous independent determinations of the gas phase lifetime of singlet oxygen reported in the literature.     

SYNTHESIS AND FLUORESCENCE STUDY OF St／DVB COPOLYMERS LABELLED WITH PYRENE GROUPS

ＳＹＮＴＨＥＳＩＳＡＮＤＦＬＵＯＲＥＳＣＥＮＣＥＳＴＵＤＹＯＦＳｔ／ＤＶＢＣＯＰＯＬＹＭＥＲＳＬＡＢＥＬＬＥＤＷＩＴＨＰＹＲＥＮＥＧＲＯＵＰＳＷａｎｇＧｕｏｃｈａｎｇ；ＬｉａｎｇＹｕａｎｆｏｎｇ；ＧａｏＨｕａｎ；ＬｉａｎｇＬｉｊｕｎ；ＨｅＢｉｎｇｌｉ...     

PHOTOPHYSICAL STUDIES OF PYRENE INCORPORATED IN NAFION MEMBRANES*

Abstract— High concentrations of organic chromophores, in particular pyrene, were found to incorporate into the cluster network of water swollen Nation. The vibrational structure of the fluorescent molecule and its fluorescence lifetime were used to probe the location of pyrene in this structure. Strong heavy-atom induced room temperature phosphorescence was observed from the chromophore in the water swollen membrane. Excimer formation in tm-butanol swollen Nation was observed and was utilized to estimate the micro viscosity in this system.     

FLUORESCENCE SPECTRA AND ZERO-FIELD MAGNETIC RESONANCE OF CHLOROPHYLL a-WATER COMPLEXES

Abstract. –Fluorescence detected magnetic resonance (FDMR) and fluorimetry have been used to study chlorophyll-water complexes at T = 4.2 K. By combining these methods, zero-field splitting (ZFS)-parameters can be assigned to the triplet state of the various species. It is found that these parameters decrease upon aggregation and/or complexation. These results can be rationalized by using a simple free-electron model for chlorophyll including excitonic interaction. Evidence is presented favouring a structure recently proposed by Shipman and Katz for a chlorophyll-dimer involving hydrogen-bonded water, present in non-polar solutions at low temperature with spectral properties similar to those of chlorophyll in vivo.     

不同组成的铕—噻吩甲酰基三氟丙酮络合物合成与荧光特性

本文合成与铕与ＴＴＡ及啉啡罗啉或表面活性剂Ｎ－氯代十六烷基吡啶两个三元络合物及铕－ＴＴＡ两元络合物。用元素分析，差热热重分析，红外与紫外光谱等方法表征了各化合物。测定了各络合物的固态及溶液荧光光谱，实验表明高对称八配位的Ｅｕ（ＴＴＡ）４ＣＰ络合物荧光强度最高。     

铕(Ⅲ)的双亚砜混配配合物的合成、表征及其荧光光谱

本文合成了１，３－双（苯基亚砜）丙烷，１，４双（苯基亚砜）丁烷与１，１０－菲罗啉，２，２’－联吡啶的铕（Ⅲ）配合物，并通过元素分析、红外光谱、紫外光谱、摩尔电导和热分析对该系列配合物进行了表征，并测量和分析了有关五个配合物的荧光光谱．     

苯甲酸铽络合物发光性能的研究

本文应用紫外、红外吸收光谱、稳态和时间分辨的荧光光谱研究了苯甲酸及它的(邻、间、对)羟基衍生物与铽离子的络合物的发光性能和能量传递关系;探讨了羧酸的结构、络合物的形成,以及溶剂、pH值对发光强度和能量传递的影响。     

A COMPARISON OF FLUORESCENCE QUENCHING AND FLUORESCENCE DECAY STUDIES WITH TRYPTOPHAN

Abstract— The quenching of the fluorescence of aqueous tryptophan solutions has been studied as a function of emission wavelength using acrylamide as a collisional quencher. Our quenching studies are consistent with recent observations of the heterogeneity of tryptophan fluorescence, but they show a slight discrepancy when compared to certain analyses of the decay of tryptophan fluorescence in terms of two components.     

芘—苯甲醛COPNA树脂的合成及其磁性行为的研究

芘苯甲醛ＣＯＰＮＡ树脂的合成及其磁性行为的研究阮湘泉董奕郑嘉明郭崇涛（天津大学化学工程系，天津３０００７２）关键词三芳基甲烷，ＣＯＰＮＡ树脂，稳定自由基，铁磁性在有机磁体的研究中，Ｏｔａ等人曾研究了以次甲基交联的缩合多核芳香烃（ＣＯＰＮＡ）树脂经光...