THE TRIPLET AND RADICAL SPECIES OF HAEMATOPORPHYRIN AND SOME OF ITS DERIVATIVES

Abstract— Nanosecond laser flash photolysis and pulse radiolysis have been used to generate and characterise the triplet state, and semioxidised and semireduced radicals of haematoporphyrin, and three 0 -acyl compounds derived from it (the monoacetate, the diacetate and the disuccinate).
After 347 nm irradiation in water containing 2% Triton X-100, haematoporphyrin forms the triplet state (φ_T= 0.92) and photoionises monophotonically (φ_I= 0.03). For the O -acyl derivatives, φ_T approaches unity and photoionisation is reduced. In acetone the triplet yield of all four compounds are close to unity. The difference and corrected spectra for the triplet species are presented and decay rates ( k ₁˜10⁴s^-1) and oxygen quenching constants ( k _Q˜1.5times10⁹ M ^-1s^-1) for the triplet state have been measured. The difference and corrected spectra for the semi-reduced species in methanol and semi-oxidised species in aqueous Triton X-100 are presented.
The photophysical characteristics in fluid solution of haematoporphyrin and its 0 -acyl derivatives are rather similar to those previously recorded for other photosensitising porphyrins.     

TRIPLET EXCITED STATE OF FUROCOUMARINS: REACTION WITH NUCLEIC ACID BASES AND AMINO ACIDS

Abstract. The triplet-triplet absorption spectra of psoralen, xanthotoxin, angelicin and bergapten have been determined using the technique of pulse radiolysis and laser flash photolysis in benzene and water. The extinction coefficients of the triplet transitions have been measured and used to determine the singlet → triplet intersystem crossing quantum yields for 353 nm excitation. These yields vary considerably in passing from benzene to water as solvent. The highest yields were obtained for psoralen and angelicin in water, being 0.45 and 0.33, respectively. Reaction rate constants of the psoralen and angelicin triplets with various pyrimidine and purine nucleic acid bases and amino acids have been measured. The high reactivities support the suggestion that the photosensitising properties of furocou-marins are mediated by the corresponding furocoumarin triplet states. The similarly high S → T quantum yields, and triplet reactivities with pyrimidines of psoralen and angelicin, also support the suggestion that the observed differences in photosensitising properties of these two psoralens may be due to their differing geometries, which allow psoralen itself to intercalate DNA more easily than angelicin. The efficient reactions also found for psoralen and angelicin triplets with amino acids suggest that such triplets in vivo may also react with these components. Significant damage may thus be caused to protein as well as nucleic acid components of the cell.     

离子色谱法测定浴盐中的阴、阳离子

用离子色谱法测定浴盐中的Na^ 、K^ 、Mg^2 、Ca^2 、Cl^-、Br^-、SO4^2-时，分离阳离子的色谱柱为ICS-C25阳离子交换柱，淋洗液为2.0mmol/L均苯四甲酸溶液，流速为0.6mL/min；分离阴离子时的色谱柱为shim-pack IC-Al阴离子交换柱，淋洗液为2.5mmol/L邻苯二甲酸溶液－2.4mmol/L三羟基氨基甲烷溶液（体积比为1：1），流速为1.0mL/min。所测离子Na^ 、K^ 、Mg^2 、Ca^2 、Cl^-、Br^-、SO4^2-在较宽浓度范围内有良好的线性关系，回收率为94.7%-102.4%，检出限为0.001-0.02mg/L，相对标准偏差为1.03%-1.63%。     

ESR TRIPLET SPECTRA OF ACRIDINE DYES

Abstract— The triplet states of some acridine dyes (proflavine, acriflavine, acridine yellow, acridine orange, ethacridine (Rivanol), benzoflavine), dissolved in a dimethylformamide/water matrix were investigated at 90°K by ESR. Zero-field splitting parameters were calculated from the ESR spectra. The relationship between the zero-field splitting and the distribution of the spin-density of the electrons of the triplet state of the acridine derivatives is discussed.     

SOME FUROCOUMARINS AND ANALOGS: COMPARISON OF TRIPLET PROPERTIES IN SOLUTION WITH PHOTOBIOLOGICAL ACTIVITIES IN YEAST

Abstract— Some photophysical and photochemical properties of two furocoumarins, three furochro-menes and one difurobenzene have been studied in ethanol by laser flash spectroscopy. Such properties included the triplet absorption spectra. extinction coefficients, quantum yields of formation and reactivities with the nucleic acid bases thymine and uracil, and the amino acid tryptophan. The effects the same compounds have on survival of the yeast, Saccharomyces cerevisiae , after 365 nm photosensitization were also investigated. These effects on survival differed markedly for the different compounds. Possible correlations between the photophysical, photochemical and photobiological data are discussed.     

六同多钨酸阴离子的振动光谱

本文观测了六同多钨酸阴离子的红外和喇曼光谱, 并用MUBFF、UBFF和GVFF三种力场对W_6O_(19)~(2-)的振动作了简正坐标分析。得到了力常数、振动频率和振动势能分布。对振动频率作出归属, 讨论了力常数间的关系, 给出了用MUBFF的计算结果。     

THE ASSOCIATION OF THE 5-METHYLPHENAZINIUM CATION AND THE 5-METHYL-10-HYDRO-PHENAZINIUM RADICAL CATION WITH MICELLES*

Abstract— 5-Methylphenazinium (MP⁺) cation salts are known to stimulate photophosphorylation in photosynthetic systems. The mechanism is thought to involve the translocation of protons across the thylakoid membrane although few details are known concerning the mechanism and the identity of the proton carrier. As there is some indication that the semireduced species, the 5-methyl-10-hydro-phenazinium (MPH⁺) cation radical, may be the proton carrier, we have studied the interaction of MPH⁺ with micelles as a model system for aqueouslipid interactions in a membrane. In this study we have used the techniques of NMR and EPR. In the presence of sodium dodecyl sulfate (NaLS) micelles the EPR spectrum of MPH ⁺ is broadened indicating specific binding of MPH⁺ to the micelle. A binding constant of -10⁵M^-1 was obtained. The 220 MHz NMR spectrum of a micellar solution with added MPH! shows specific broadening of the alkyl protons. The use of model paramagnetic adducts has allowed us to infer from the NMR results that the MPH⁺ ion penetrates the hydrocarbon part of the micelle to a considerable extent. This would indicate to us that MPH⁺ can indeed function as a proton carrier as it should be able to penetrate deeply into the lipid layer of the membrane. From these results, we conclude that:

• 1 Both MP⁺ and MPH⁺ interact strongly with NaLS micelles. MPH⁺ interacts more weakly with neutral Triton X-100 micelles while in this case, no evidence of interaction is seen for MP⁺. No binding of either MP⁺ or MPH⁺ is observed with cationic micelles from CTAB.
• 2 MP⁺ is adsorbed to NaLS micelles in a very hydrophilic region, probably In the Stern layer. MPH⁺, however, is much less hydrophilic than MP⁺ and appears to reside in the Palisade layer a few angstroms below the head groups.

On the basis of these results, we make the following proposals:

• 1 MPH⁺ is sufficiently hydrophobic to be a candidate for the reduced MP⁺ species which actually carries the proton across the thylakoid membrane.
• 2 The site at which MP⁺ is reduced by X must be anionic in nature in order for MP⁺ to be bound strongly.

     

CHEMICAL REACTIONS OF SUPEROXIDE ANION RADICAL IN APROTIC SOLVENTS

Abstract— While superoxide anion radical does not normally react with olefins, it does react with activated double bonds. Thus O^-₂ oxidatively cleaves certain α,β-unsaturated ketones such as chalcones and tetracyclone and electron poor olefins such as 1,1-dicyano and 1,1-dinitro olefins. Similarly O^-₂ can react with substituted nitrobenzenes to yield the corresponding nitrophenols. EPR and oxygen labeling (KO³⁶₂) experiments confirm an electron transfer mechanism.     

ANION AND SOLVENT EFFECTS ON THE RATE OF REDUCTION OF TRIPLET EXCITED THIAZINE DYES BY FERROUS IONS

Abstract— The lifetimes of the triplet excited states of thionine and methylene blue were measured in aqueous and 50 v/v% aqueous acetonitrile solutions acidified with 0.01 N sulfuric or trifluoromethyl-sulfonic acid. The rate constants for reaction of the triplet excited dyes with ferrous ions were measured in the same solutions. The triplet lifetimes in the absence of added quenchers were insensitive to a change in acid from trifluoromethylsulfonic to sulfuric or to a change in solvent from water to 50v/v% aqueous acetonitrile (τ for triplet thionine ˜7.5 μs, τ for triplet methylene blue ˜4.5 μs). In contrast, the rate constant for reaction of the triplet dyes with ferrous ions increased by nearly a factor of 10 with a change in acid from trifluoromethylsulfonic to sulfuric. In solutions containing sulfate ions this reaction rate constant increased with increasing sulfate concentration and with a change in solvent from water to 50 v/v% aqueous acetonitrile. The results are discussed in terms of the possibility of association of the positively charged reactive ions with sulfate anions. Quenching of the triplet excited dyes by ferric ions or by ground state dye molecules was shown to be negligible at the concentration used for the ferrous ion quenching study.     

ABSORPTION CHANGES IN THE REACTION CENTER OF PHOTOSYNTHETIC BACTERIA AND n-ELECTRON CALCULATIONS ON BACTERIOCHLOROPHYLL, ITS MONO CATION AND ANION

Abstract— π-Electron calculations of the MO-SCF-CI type in the PPP approximations are carried out for the tetra pyrrole ring of the bacteriochlorophyll molecule, its mono cation and anion.
According to the calculations the formation of the positive ion will be accompanied by the disappearance of the longest wavelength absorption band of the neutral system and the appearance of a new band near 1200 nm. Absorption changes of the same kind are found in the reaction center of photosynthetic bacteria upon illumination, supporting the hypothesis that the primary reaction is an expulsion of an electron from the π-electron system of the reaction center bacteriochlorophyll.     

CRYSTAL AND MOLECULAR STRUCTURE OF N—ETHYLPHENOTHIAZINE RADICAL CATION HEXACHLOROANTIMONATE EPT^＋SbCl6^—

<正> C14H13Cl6NSSb, Mr =561.8, Monoclinic, C2/c1 8=15,32(1), b= 11.72(1), c= 11.10(1)A,β=99.31(3)°,V=1969(1)A3,Dc=1,902g.cm-3, Z=4,CuKα,λ=1.5418A,μ=200.95cm-1.Room temperature, final R=0.051 for 1197 unique reflections with I>, 3.0σ(I).Pronounced defornation of the Molecular structure has been observed when the neutral N-ethylphenothia-zine is transformed into its radical cation. The structural features of the radical cation are compared with those of N-methyl analogue.     

CRYSTAL AND MOLRCULAR STRUCTURE OF-N-METHYLPHENOTHIAZINE RADICAL CATION HEXACHLOHOANTIMONATK,MPT SbCl6-

<正> C13H11NSSbCl6,Mr = 547.8, Monoclinic,C2, a = 11.045(2), b 11.466(3), c = 8.606(2)A,β=121.4(2)°,V=930.2A3,Z = 2.MoKα,λ 0.711 A. Room temperature, final R=0.038 for 1389 unique reflections wit I> 3.00(I).Pronounced deformation of the molecular structure has been ob served when the neutral N-methylphenothiazine is transformed into its radi cal cation MPT+.     

EFFECT OF CHLORIDE ON CHLOROPHYLL PHOTOCHEMISTRY IN SOLUTION: ENHANCEMENT OF CATION RADICAL AND SEMIQUINONE YIELDS

Abstract—Illumination with red light at low temperatures of a degassed ethanol solution of chlorophyll and ferric chloride reversibly produces an EPR signal due to the chlorophyll cation radical (Chl+). The magnitude of this signal is about ten times larger than is obtained with chlorophyll alone. When benzoquinone is also present, an EPR signal due to Chl+ and the neutral semiquinone radical (QH.) is photoproduced. The semiquinone signal is about five times larger than in the absence of ferric chloride. Both of these systems show first order radical decay when the light is turned off, suggesting that radical complexes are being formed. These results indicate that iron is capable of serving as an electron transfer bridge between chlorophyll and quinone.     

QUENCHING OF A RETINAL TRIPLET STATE BY A NITROXYL RADICAL

Abstract— The long lived triplets from all-trans retinal and 11-cis retinal are quenched by a nitroxyl radical, 4-hydroxy-2,2,6,6-tetramethylpiperidinoyl, with essentially identical rate constants. The rates vary with solvent but do not correlate with solvent polarity. The results confirm implications of earlier work with oxygen quenching and are compatible with the view that isomerization occurs in non-relaxed triplets or that the triplet (or triplets) observed spectroscopically decay by way of a single triplet state which has a small electronic energy gap to ground state isomers.     

KINETICS OF TRIPLET OXIDATION OF METALLO-PORPHYRIN COMPOUNDS TO THEIR CORRESPONDING RADICAL CATIONS

Abstract— The kinetics of photooxidation of triplets of metalloporphyrin compounds to their corresponding radical cations was investigated. Zn-tetraphenyl porphyrin (ZnTPP) and Mg-tetraphenylpor-phyrin (MgTPP) triplets were oxidized by europium salt with rate constants of 4.8 × 10⁵M^-1s^-1 and 2.1 × 10⁶M^-1s^-1, respectively. The high rate constant of oxidation of MgTPP triplet might be related to the ground state oxidation potential, being 0.54 V (SCE) for the Mg complex and 0.71 (SCE) for the Zn complex.
The rate constant of oxidation of ZnTPP excited singlet is in the order of diffusion control, i.e. ˜ 10¹⁰M ^-1 s^-1. Excitation of ferric, cupric, cobaltic, and vanadyl tetraphenylporphyrin did not result in a long-lived triplet state that would allow oxidation studies using flash photolysis.     

FOURIER TRANSFORM INFRARED SPECTROELECTROCHEMISTRY OF THE BACTERIOCHLOROPHYLL a ANION RADICAL

Abstract— Fourier transform infrared (FTIR) difference spectroscopy of the electrochemically generated anion radical of bacteriochlorophyll a was used to follow the molecular changes upon one-electron reduction. An IR spectroelectrochemical cell was constructed, allowing in situ electrolysis in connection with spectroscopic investigations from 200 to 10 000 nm. FTIR difference spectra of the BChl a anion formation in THF d₈ at U =+0.9 V (as determined by ferrocene calibration) were obtained. After complete formation of the radical, the reverse process was followed. Comparison of visible and IR spectra of the reduction and re-oxidation processes indicates that more than 90% of the BChl a anion could be formed with 90% of it being reversible. The main IR absorbance changes are observed for the conjugated and even for the non-conjugated C=O groups of BChl a . These results demonstrate the use of the combination of FTIR spectroscopy and electrochemistry for the characterization of radicals of the isolated pigments and of their in vivo bonding to the protein environment.     

ACTION SPECTRA AND CHROMOPHORES FOR LETHAL PHOTOSENSITIZATION OF Candida albicans BY DNA MONOADDUCTS FORMED BY 8-METHOXYPSORALEN AND MONOFUNCTIONAL FUROCOUMARINS

The red-shift of furocoumarin action spectra, compared with their absorption spectra, has been investigated. An action spectrum for 8-methoxypsoralen (8-MOP) monoadduct formation in the yeast Candida albicans has been determined. The yeast cells were initially exposed to sublethal doses of monochromatic UVA at different wavelengths. Monoadduct formation was monitored by growth inhibition induced, after washing out any unbound 8-MOP, by re-irradiation with a constant second (non-lethal) dose of 330 nm radiation. A comparison between this action spectrum and the absorption spectrum of the dark complex of 8-MOP and DNA was made. In addition, the action spectra of monoadduct formation of five monofunctional compounds including a coumarin derivative have been determined. These action spectra were compared with their respective DNA dark complex absorption spectra. In general, the peaks of the furocoumarin DNA dark complexes show a red-shift when compared with the free furocoumarin molecule and the action spectra show peaks which correspond with the peaks of the dark complexes. Such data indicate that the DNA dark complex is the chromophore for growth inhibition in yeast rather than the free furocoumarin. The similarity of the 8-MOP monoadduct formation action spectrum and 8-MOP action spectra suggests that spectral dependence for the photobiological effects (including the red-shift) is dependent on monoadduct formation rather than, as previously suggested by several authors, crosslink formation. The action spectrum for the coumarin derivative 4-methyl N-ethylpyrrolo (3,2-g) coumarin (PCNEt) correlated well with the free molecule absorption spectrum rather than DNA dark complex indicating that the free molecule is the chromophore.(ABSTRACT TRUNCATED AT 250 WORDS)     

自由基照相体系的ESR波谱研究

本文用自旋捕获剂t-BuNO(2-甲基2-亚硝基丙烷)与ESR技术结合的方法研究了CBr₄-φ₂NH、CBr₄-LCV及CBr₄-LMG体系的光化学过程。从ESR谱的超精细结构及其随组分浓度的变化,证实了上述体系中除有Br^·外,还分别形成了 自由基。由这些体系在避光条件下的UV谱,证明溶液中存在(HX…CBr₄)型的部分电荷转移络合物。因此,上述自由基照相体系的光引发反应既包括CBr₄的光解,又包括(HX…CBr₄)^*的光解。