THE CATALYTIC EFFECTS OF OXYGEN AND AMINES IN THE REDOX-INITIATED DIMERIZATION OF N-VINYLCARBAZOLE*

The redox reaction between N-vinylcarbazole (NVC) and various oxidants including Ce(Ⅳ), Fe(Ⅲ)and benzoylperoxide in methanol proceeds via the initial formation of the NVC N-cation radical which in turn leads to the formation of the NVC cyclic dimer, trans-1,2-dicarbazylcyclobutane. Molecular oxygen and a few arylamines are able to accelerate the rate of the formation and increase the yield of the dimer. The mechanism of this process and the functions of oxygen and arylamines are presented as follows: The participation of molecular oxygen is to facilitate the dissociation of the resulting reduced metal ion and the NVC N-cation radical ion pair or charge transfer complex, thereby releasing the free NVC N-cation radical and increase the rate of the formation and yield of the dimer. The arylamine in this reaction between NVC and oxidants can be viewed as electron transfer agent between NVC and the oxidant. Because the amines are present in small amount relative to the oxidants and can be regenerated in pr     

FURTHER IN VIVO STUDIES ON THE PARTICIPATION OF SINGLET OXYGEN IN THE PHOTODYNAMIC INACTIVATION AND INDUCTION OF GENETIC CHANGES IN SACCHAROMYCES CEREVISIAE

Abstract —In vivo participation of singlet excited oxygen (¹O₂, ¹Δ9) in the photodynamic inactivation and induction of genetic changes (gene conversion) in acridine orange-sensitized yeast cells was investigated by using N₃^-, an efficient ¹O₂ quencher, and D²O, a known agent for the enhancement of the lifetime of ¹O₂. The addition of N₃^- protected the cells from both photodynamic actions. From an analysis of the concentration-dependent protection, about 80% of the induction of the genetic change is explainable on the basis of ¹O₂ mechanism. The quantitative estimation of the N₃^- protection in the inactivation was not possible because of the sigmoidal nature of the inactivation curve. The replacement of H₂O with D₂O during illumination was effective in enhancing the photodynamic inactivation but almost completely ineffective for the gene conversion induction. The deuterium effect with the cell system was clearly not as large as would be expected from in vitro experiments. This, however, could be explained from the kinetic consideration that natural quenchers of ^lO₂ in the cell would mask the deuterium effect. By experiments with different cell stages it was demonstrated that these two modifying effects were dependent on the intracellular reaction environment. The conclusion is that ¹O₂ must be the major intermediate responsible for the photodynamic actions in acridine orangesensitized yeast cells.     

ON THE ACRIDINE AND THIAZINE DYE SENSITIZED PHOTODYNAMIC INACTIVATION OF LYSOZYME—SINGLET OXYGEN SELF-QUENCHING BY THE SENSITIZERS

Abstract— The quantum yield of the photodynamic inactivation of lysozyme increases in the sequence acridine orange, methylene blue, proflavine and acriflavine (1:5:6:12). At least up to protein concentrations of 0.1 m M , singlet oxygen is exclusively responsible for the inactivation of the enzyme. For methylene blue, acriflavine and proflavine the quantum yields decrease considerably with increasing dye concentrations. From measurements in H₂O and D₂O buffer solutions it was concluded that in the case of methylene blue the effect is mainly caused by the quenching of singlet oxygen [rate constant (3–4) × 10⁸ M ⁻¹ s⁻¹]. For the acridine sensitizers both singlet oxygen and dye triplet quenching processes have to be taken into consideration. It has been found that all sensitizers act as competitive inhibitors of the enzymatic reaction of lysozyme. However, the dye-protein interaction near the active center cannot be responsible for the observed dye self-quenching effect.     

FORMATION OF 5-HYDROXYMETHYLCYTOSINE-CONTAINING PYRIMIDINE DIMERS IN UV-IRRADIATED BACTERIOPHAGE T4 DNA

Cyclobutyl pyrimidine dimers composed of 5-hydroxymethylcytosine and thymine (5HMC>T dimer for a mutant of T4 ( denV ) that is unable to excise pyrimidine dimers from its DNA. The ability of 5HMC to form dimers suggests that other modified pyrimidines such as 5-methylcytosine can participate in dimer formation, particularly at the UV wavelengths in sunlight likely to be responsible for the induction of skin cancer.     

REPAIR OF PSORALEN PLUS NEAR ULTRAVIOLET LIGHT DAMAGE IN BACTERIOPHAGE T4

Abstract— The sensitivity of bacteriophage T4 to psoralen plus NUV was investigated using a series of T4 repair defective mutants. The recombinational repair deficient mutants T4x, T4y and T4w were more sensitive than wild-type; while T4v, an endonuclease V mutant, exhibited the same sensitivity as wild-type. However, endonuclease V appears to initiate abortive repair in the absence of the x and presumably y gene products. Host repair gene products were shown not to be involved in the repair of psoralen plus NUV damages in T4.     

PHOTOINITIATION OF SPORANGIOPHORES IN PHYCOMYCES MUTANTS DEFICIENT IN PHOTOTROPISM AND IN MUTANTS LACKING β-CAROTENE

Abstract—The formation of sporangiophores from mature Phycomyces mycelium is inhibited in a closed system. Irradiation of the mycelium with blue light reverses the inhibition of spordngiophore formation. Dose response curves for this reaction are established for wild type. β-caroteneless mutants and for mutants that are deficient in phototropism.
Phototropic-negative mutants. altered in genes madA and madB , have a raised threshold in this light reaction. whereas mutants deficient in genes madD to madG are unaffected. β-caroteneless mutants deficient in genes carA, carB , or carR have a threshold raised by a factor of 100–2000 depending on the amount of residual synthesis of β-carotene.     

不同制法镁铝尖晶石在环己酮双聚中的应用

用共沉淀法，溶胶－凝胶法，超临界干燥技术和脲燃烧法制备了一系列镁铝尖晶石，并将其用于环己酮双聚合成环己烯环己酮（ＣＨＣＨ）的反应中。借助于ＴＥＭ、ＸＲＤ、ＢＥＴ和ＣＯ＿２－ＴＰＤ等手段考察了不同制备方法对催化剂性质及性能的影响。     

COMPARISON OF THE LETHAL EFFECT OF 5-IODOURACIL INCORPORATED INTO BACTERIOPHAGE T4 IN THE PRESENCE AND ABSENCE OF NEAR-VISIBLE LIGHT

Abstract— Bacteriophages T2 or T4 containing 5-iodouracil (IUra) substituted for thymine in their DNA are inactivated by near-visible light, with fluorescent lamps as the source of near-visible light. Inactivation increases with the dose of near-visible light and follows first order kinetics. Relative inactivation rates are linearly proportional to percent substitution. Equivalent per cent substitution by IUra or 5-iodo-2'-deoxyuridine (IdUrd) results in equivalent sensitization to inactivation with both T2 and T4. However, incorporation of IUra into T4 and T2 also is lethal in the absence of light. The lethal effect of IUra substitution differs from the lethal effect of IUra substitution plus near-visible light irradiation in at least three respects: (1) IUra substitution is lethal for T4 under conditions where the residual viability is stable and where environmental light cannot account for the inactivation. (2) The hit curve for IUra lethality, as a function of per cent IUra substitution, has a large shoulder while the hit curve for sensitization to inactivation by near-visible light, as a function of per cent IUra substitution, has no shoulder. (3) At equivalent extents of inactivation. IdUrd substitution in the absence of light has a greater effect on phenotypic expression of T4 than either near-visible light irradiation alone or IUra substitution plus near-visible light irradiation, as measured by either delay in appearance or decrease in total amount of two induced enzyme activities (dihydrofolate reductase and deoxycytidylate hydroxymethylase).     

ACTION SPECTRA FOR THE APPEARANCE OF DIFFERENCE ABSORPTION BANDS AT 480 AND 520 mμ IN ILLUMINATED CHLORELLA CELLS AND THEIR POSSIBLE SIGNIFICANCE TO A TWO-STEP MECHANISM OF PHOTOSYNTHESIS

Abstract— In the difference absorption spectrum of thin, actively growing* aerobic suspensions of Chlorella pyrenoidosa , both the 480 mμ (negative) and the 520 mμ (positive) bands are produced by light absorbed in chlorophyll b and chlorophyll a; the ratio of absorption changes caused by equal number of incident quanta of 650 mμ light and those of 680 mμ light, is about 1.2. Both effects are partially inhibited by DCMU. Upon replacing air with argon, the effects are increased several fold and become relatively insensitive to DCMU. The increase is stronger in the absorption region of chlorophyll a , than in that of chlorophyll b ; the ratio of the absorption changes, caused by equal numbers of 650 mμ and 680 mμ quanta decreases to about 0.8, for both effects. Variable (as regards the exact ratios of absorption changes), but parallel results for 480 and 520 mμ bands were obtained with cultures having low quantum yield of photosynthesis. This parallelism in the behavior of the 480 mμ and the 520 mμ band suggests that at least part of these two bands have a common origin. However, many observations suggest that both difference bands may have a multiple origin; as a working hypothesis, this origin is discussed in terms of three reactions: Reaction A—Photoreduction of chlorophyll a in system II; Reaction B—Photooxidation of chlorophyll b in system II; and Reaction C—Photooxidation (perhaps of a carotenoid) in system I.     

INDUCTION OF FREE RADICALS IN DNA BY PROFLAVINE AND VISIBLE LIGHT: INFLUENCE OF OXYGEN AND IONIC STRENGTH

Abstract —The photosensitization of native DNA is observed as an induction of free radicals in the DNA moiety of proflavine-DNA complexes. The intensity of the electron paramagnetic resonance spectra (at 77 K) is a measure of the number of free radicals present in frozen solutions of DNA-proflavine complexes after irradiation with visible light (Λ > 320 nm). In the absence of O₂, the photosensitization is significant but very low; it increases slightly with increasing NaCl ionic strength; it appears to be due to intercalated dye molecules and the qualitative analysis of the spectra obtained shows that mainly thymidine is involved. The reaction measured after saturation with O₂ is the same as the reaction in air but is quantitatively higher; the free radicals observed are peroxides. This induction of free radicals appears to be due to the intercalated dye molecules, each molecule acting independently. The important observation is a very sharp and large (around a hundred-fold) increase in the photosensitizing efficiency of the bound dye molecules occurring in NaCl between μ, # 0–25 and μ= 0–5 and in MgCl₂ between μ# 0–01 and μ=0–1.     

CARBOXYLATED ZINC-PHTHALOCYANINE, INFLUENCE OF DIMERIZATION ON THE SPECTROSCOPIC PROPERTIES. AN ABSORPTION, EMISSION, AND THERMAL LENSING STUDY

Monomer and dimer absorption and emission spectra, and dimerization constants are reported for the diamide of the zinc-tetracarboxyphthalocyanine in pure dimethylformamide (DMF) and in H₂O/DMF mixtures at room temperature. The dimerization constant increases steadily with the water content. The monomer absorption Q-band is insensitive to the solvent composition, whereas dimer spectra show great variations with the water content. Stationary emission measurements show that fluorescence originates exclusively from the monomers. The fluorescence spectrum as well as its absolute fluorescence quantum yield, measured by steady-state thermal lensing, are also insensitive to the solvent composition. The thermal lensing method is discussed for the case of two absorbing species in equilibrium.     

THE EFFECTS OF HIGH-INTENSITY UV-RADIATION ON NUCLEIC ACIDS AND THEIR COMPONENTS—I. THYMINE

Abstract— The set of final products of thymine conversion induced by high-intensity UV irradiation (λ= 266nm, intensity 10²⁴-5 × 10²⁹ photons·s⁻¹·m⁻², pulse duration 10ns) of the dilute aqueous solution to the first approximation is similar to that formed with ionizing irradiation (γ-irradiation of aqueous solution or autoradiolysis of a solid 2-[¹⁴C]-thymine). The data obtained suggest that high-intensity UV-induced photochemical conversion of thymine involves photoionization and/or photodissociation. These processes pass through the higher excited state(s) populated as a result of the second photon absorption by excited (most probably in the T₁ triplet state) thymine molecules.     

SINGLET AND TRIPLET ENERGY TRANSFER IN α-DIKETONE DERIVATIVES OF URACIL and THYMINE

Irradiation of 1-(3,4-dioxopentyl)uracil (UPD) and 1-(3.4-dioxopentyl)thymine (TPD) in acetonitrile solution at 25°C, at the wavelength (280 nm) where only the pyrimidine absorbs the light, sensitizes both fluorescence and phosphorescence of the diketone chromophore in the sidechain. From comparison of the intensity in the corrected excitation spectra with the absorption spectra in acetonitrile solution, it was estimated that the yield of singlet energy transfer in UPD was 0.17 and in TPD was 0.44. It was also observed that the ratio of phosphorescence to fluorescence was greater in the sensitized emission than in that from direct excitation of the diketone chromophore. The yield of triplet energy transfer thus measured corresponds to minimum values for the yields of intersystem crossing from singlet excited state to triplet excited state of 0.075 in the uracil chromophore of UPD and of 0.14 in the thymine chromophore of TPD. These are in agreement with other recent values for these quantities. The value of this type of system as an intramolecular triplet counter is discussed.     

pH值对有机化合物富集与伏安溶出过程的影响

在碳糊电极上有机化合物的富集能够增加溶出伏安法的灵敏度和选择性。不同的有机化合物的碳糊电极上的富集机理不同,在电极上的伏安溶出条件也不同。使用碳糊电极时,对有机化合物的富集、溶出影响因素是多方面的,其中富集液和溶出液的ｐＨ值对它的影响十分重要文中通过碳糊电极对一些简单有机体例物如氯丙嗪（冬眠灵）、丁基羟基甲醚（ＢＨＡ）、Ｎ,Ｎ－二甲基苯胺（ＤＭＡ）、对苯二酚的富集与伏安溶出进程的研究,从理论和试验     

TIME RESOLVED STUDIES OF 1.27 μm LUMINESCENCE FROM SINGLET OXYGEN GENERATED IN HOMOGENEOUS and MICROHETEROGENEOUS FLUIDS

-The luminescence at 1.27 μm from the ³→→¹δ_g transition of the oxygen molecule has been detected from a variety of liquid systems. A Q-switched laser delivering pulses of 532 nm light was the excitation source, a germanium photodiode was the detector and substituted porphyrins were used as photosensitizers. Protio- and deutero- forms of several solvents were studied and the singlet oxygen lifetimes determined directly agreed well with published values. T_δ in D₂O was found to be 55 μs and, by extrapolation from a series of H₂O - D₂O mixtures, a value of 3.3 μs was obtained for T_δ in H₂O. The technique was shown to be useful in measuring T_δ values in several microheterogeneous systems such as surfactant micelles, vesicles and human serum albumin.     

高氯酸与硫酸溶液中铂电极上氧阳极析出动力学与机理

本文研究了不同浓度的HClO₄和H₂SO₄溶液中铂电极上氧阳极析出过程的动力学。稳态极化曲线上有三个区域:电位突跃前的低极化区,突跃区和突跃后的高极化区。前两个区域内对于α_w的反应级数均为1,在后一区域内对于α_w·α_ClO4^-或αw·α_HSO4^-的反应级数接近于1/2。文中对在各区域内的反应机理和产生电位突跃的原因进行了探讨。     

ABSORPTION AND FLUORESCENCE SPECTROSCOPIC STUDIES ON DIMERIZATION OF CHLOROALUMINUM (III) PHTHALOCYANINE TETRASULFONATE IN AQUEOUS ALCOHOLIC SOLUTIONS

Dimerization of chloroaluminum (III) phthalocyanine tetrasulfonates (AIPCS) has been observed in different aqueous alcoholic solvents at room temperature by absorption and fluorescence spectroscopic methods. Both absorption and fluorescence spectral bands of the dimer are red shifted by ca 550 cm^-1 from the monomer Q bands in the corresponding spectra, suggesting that the interaction energy between the two monomer subunits is very weak. The fluorescence lifetime of the dimer is longer ( ca 9.5 ns) than that of the monomer ( ca 7–8 ns). These spectral behaviors of AIPCS dimer contrast with those of transition-metallaloid phthalocyanine dimers, which usually have a nonfluorescent face-to-face stacking conformation. The dimer fluorescence is interpreted to be due to the fact that the lowest excited singlet state of the dimer is lower in energy than a charge-resonance state, based on the excitoncoupling theory applied to the face-to-face slipping conformation. The dimerization constant determined spectrometrically decreases with an increase of water content in the aqueous alcoholic solution. Propanol and ethanol have been observed to be more effective than methanol in promoting dimerization. These results indicate that a specific interaction of water with AIPCS plays an important role in the inhibition of dimerization of AIPCS.