SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS–XVI. ISPERSE BLUE 35

The photochemistry (Type I and II) of the phototoxic textile dye Disperse Blue (DB-35) and its purified components has been studied using electron spin resonance in conjunction with spin trapping technique and the direct detection of singlet oxygen (1O2) luminescence. The main components of DB-35 (which is synthesized by the successive nitration, reduction and methylation of 1,8-dihydroxy-anthraquinone) were separated by HPLC and identified by mass spectrometry and 2-D NMR as 4,5-diamino-1,8-dihydroxyanthraquinone (4,5-DDHAQ; 62% of total dye) and 2,7-diamino-1,8-dihydroxyanthraquinone (2,7-DDHAQ; 31% of total dye). Minor components included 2,5-diamino-1,8-dihydroxyanthraquinone (2,5-DDHAQ) and a monomethylated derivative of either 4,5-DDHAQ or 2,7-DDHAQ. Irradiation (624 nm) of 4,5-DDHAQ and 2,7-DDHAQ in dimethylsulfoxide resulted in the generation of superoxide which was trapped by 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). Visible light irradiation of the components in ethanol generated 1O2 with the yields decreasing in the following order: 4,5-DDHAQ greater than 2,5-DDHAQ greater than 2,7-DDHAQ. These findings indicate that upon irradiation by visible light DB-35 can generate active oxygen species which may be responsible for the photocontact dermatitis caused by this dye.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS–III. SPIN TRAPPING OF PHOTOLYSIS PRODUCTS FROM SULFANILAMIDE ANALOGS

The photodecomposition of sulfanilamide (4-aminobenzenesulfonamide), sulfacetamide. sulfathiazole. sulfadiazine, carbutamide and tolbutamide has been studied using the spin traps 2-methyl-2-nitrosopropanc and 5,5-dimethyl-l-pyrroline-l-oxide. The following radicals were trapped during the photolysis of sulfanilamide in aqueous solution: H' and HNC₆H₄SO₂NH, (α-fission). SO₂NH₂ and C₆H₄NH₂ (δ fission). H₂NC₆H₄SO₂ and NH₂ (δ-fission). Although the C.,H₄SO₂NH₂ and the SO; radicals were also detected these were not formed directly by homolytic bond fission. Homolytic bond fission was also observed during the irradiation of sulfacetamide (α.δ), sulfadiazine (α). carbutamide (α,δ) and tolbutamide (δ). All of the analogs, with the exception of tolbutamide, generated the SO; radical. Sulfacetamide, sulfadiazine and carbutamide generated the C₆H₄SO_2;NHR radical by some process that did not involve homolytic bond fission. The free radicals generated by these agents may play an important role in their phototoxic and photoallergic effects.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS–VIII. A SPIN-TRAPPING STUDY OF LIGHT INDUCED FREE RADICALS FROM CHLORPROMAZINE and PROMAZINE

Abstract— The clinically important phenothiazine drugs, particularly chlorpromazine, often elicit phototoxic and photoallergic reactions. We have used the spin traps 2-methyl-2-nitrosopropane (MNP) and 5,5-dimethyl-pyrroline-N-oxide (DMPO) to define the radical photolysis pathways of chlorpromazine and promazine. In the absence of oxygen the dechlorination product of chlorpromazine is trapped by MNP. The reactivity of the dechlorination product is similar to that of the phenyl radical as shown by its ability to extract hydrogen atoms from donors. Our results suggest that the dechlorination product is sufficiently reactive to account for the observation that chlorpromazine is more phototoxic than its parent promazine. In the presence of oxygen both chlorpromazine and promazine form a superoxide-dismutase-insensitive oxygen-centered intermediate which, when trapped by DMPO, rapidly decays to DMPO-OOH and subsequently to DMPO-OH. In addition, chlorpromazine readily undergoes photoelectron ejection only when it is excited into the second excited singlet state (Δ < 280 nra). This previously unknown wavelength dependence of photoionization should be considered in establishing the mechanism of chlorpromazine photosensitization.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS. XVIII. INDOMETHACIN

Abstract— The photochemistry, photophysics, and photosensitization (Type I and II) of indomethacin (IN) (N-[p-chlorobenzoyl]-5-methoxy-2-methylindole-3-acetic acid) has been studied in a variety of solvents using NMR, high performance liquid chromatography-mass spectroscopy, transient spectroscopy, electron paramagnetic resonance in conjunction with the spin trapping technique, and the direct detection of singlet molecular oxygen (^l O₂) luminescence. Photodecomposition of IN (λ_ex > 330 nm) in degassed or air-saturated benzene proceeds rapidly to yield a major (2; N-[p-chlorobenzoyl]-5-methoxy-2-methyl-3-methylene-indoline) and a minor (3; N-[p-chlorobenzoyl]-5-methoxy-2, 3-dimethyl-indole) decarboxylated product and a minor indoline (5; 1-en-5-methoxy-2-methyl-3-methylene-in-doline), which is formed by loss of the p-chlorobenzoyl moiety. In air-saturated solvents two minor oxidized products 4 (N-[p-chlorobenzoyl]-5-methoxy-2-methylindol-3-aldehyde) and 6 (5-methoxy-2-methyl-indole-3-aldehyde) are also formed. When photolysis was carried out in ¹⁸O₂-saturated benzene, the oxidized products 4 and 6 contained ¹⁸O, indicating that oxidation was mediated by dissolved oxygen in the solvent. In more polar solvents such as acetonitrile or ethanol, photodecomposition is extremely slow and inefficient. Phosphorescence of IN at 77 K shows strong solvent dependence and its emission is greatly reduced as polarity of solvent is increased. Flash excitation of IN in degassed ethanol or acetonitrile produces no transients. A weak transient is observed at 375 nm in degassed benzene, which is not quenched by oxygen. Irradiation of IN (λ_ex > 325 nm) in N₂-gassed C₆H₆ in the presence of 5, 5-dimethyl-1-pyrroline-N-oxide (DMPO) results in the trapping of two carbon-centered radicals by DMPO. One adduct was identified as DMPO/^.COC₆H₄-p-CI, while the other was probably derived from a radical formed during IN decarboxylation. In air-saturated benzene, (hydro) peroxyl and alkoxyl radical adducts of DMPO are observed. A very weak luminescence signal from ¹O₂ at 1268 nm is observed initially upon irradiation (λ_ex= 325 nm) of IN in air-saturated benzene or chloroform. The intensity of this ¹O₂ signal increases as irradiation is continued suggesting that the enhancement in ¹O₂ yield is due to photoproduct(s). Accordingly, when 2 and 3 were tested directly, 2 was found to be a much better sensitizer of ¹O₂ than IN. In air-saturated ethanol or acetonitrile no IN ¹O₂ luminescence is detected even on continuous irradiation. The inability of IN to cause phototoxicity may be related to its photo stability in polar solvents, coupled with the low yield of active oxygen species (¹O₂, O₂^?_-) upon UV irradiation.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS. XVII. BENZANTHRONE

The photochemistry of benzanthrone (7H-benz[de]-anthracene-7-one) has been studied using electron paramagnetic resonance (EPR) in conjunction with the spin trapping technique and the direct detection of singlet molecular oxygen luminescence. Irradiation (lambda ex = 394 nm) of benzanthrone (BA) in aerated ethanol, dimethylsulfoxide or benzene resulted in the generation of superoxide (O2-.) which was trapped by 5,5-dimethyl-1-pyrroline-N-oxide. The ethoxy radical was also detected in ethanol. Photolysis of BA in deaerated basic ethanol led to the formation of BA anion radical, BA-., which was detected directly by ESR. This radical anion decayed back to BA with a unimolecular rate constant of 1.5 x 10(-3) s-1. The 1O2 quantum yields (lambda ex greater than 345 nm) for BA in ethanol, 90% ethanol and basic ethanol (0.1N NaOH) were 0.89, 0.88 and 0.28 respectively relative to Rose Bengal. The lower yield of 1O2 in basic ethanol may be attributable to the reaction of oxygen with BA-. (which is generated in higher yield at alkaline pH) to give O2-.. These findings suggest that on exposure to light BA can generate active oxygen species which may be responsible for the photocontact dermatitis caused by BA in industrial workers exposed to this chemical.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS–XII. SPIN TRAPPING STUDY OF THE FREE RADICALS GENERATED DURING THE PHOTOLYSIS OF PHOTO ALLERGENS BITHIONOL and FENTICHLOR

Free radicals were trapped and observed by ESR when photoallergens bithionol and fentichlor were irradiated in the presence of spin traps N- t -butyl-α-phenylnitrone (PBN) and 5,5-dimethyl-pyrroline-N-oxide (DMPO). In the absence of air, both PBN and DMPO trapped a carbon-centered radical. The carbon-centered radical, which was capable of abstracting a hydrogen atom from cysteine, glutathione, ethanol and formate, was identified as an aryl radical derived from the homolytic cleavage of the carbon-chlorine bond. In the presence of air, both carbon-centered radicals and hydroxyl radicals were trapped by DMPO. Under similar conditions, the yield of the hydroxyl radicals was greater from bithionol than from fentichlor. The presence of the hydroxyl radical was confirmed by kinetic experiments employing hydroxyl radical scavengers (ethanol, formate). Superoxide and H₂O₂ were not involved. Experiments with oxygen-¹⁷O indicated that the hydroxyl radicals came exclusively from dissolved oxygen. The precursor of the hydroxyl radical is postulated to be a peroxy intermediate (ArOO*) derived from the reaction of an aryl radical (Ar*) with molecular oxygen. Both bithionol and fentichlor photoionized only when excited in the UVC (<270 nm) region. Free radicals have long been postulated in the photodechlorination of bithionol and fentichlor and the present study provides supporting evidence for such a mechanism. Aryl and hydroxyl radicals are reactive chemical species which may trigger a series of events that culminate in photoallergy.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS—XL PHOTOLYSIS OF CHLORPROMAZINE METABOLITES: A SPIN-TRAPPING STUDY

Abstract. The photochemistry of chlorpromazine (CPZ) and its metabolites, 7-hydroxychlorpromazine (7OHCPZ), desmethylchlorpromazine (DCPZ), didesmethylchlorpromazine (DDCPZ) and chlorpromazine sulfoxide (CPZSO) was studied by the spin trapping technique with 2-methyl-2-nitrosopropane and 5,5-dimethyl-l-pyrroline- N -oxide. 7-Hydroxychlorpromazine generated hydroxyl radicals when excited at 330 nm under either anaerobic or aerobic conditions. 7-Hydroxychlorpromazine, DCPZ and DDCPZ all underwent dechlorination upon photoexcitation which was enhanced in the absence of air. Chlorpromazine sulfoxide did not undergo photodechlorination but instead generated a high yield of the hydroxyl radical. A comparison among CPZ and its derivatives shows that the yield of the photodechlorinated product is directly related to the degree of phototoxicity. This suggests photodechlorination is an important factor in the phototoxicity of CPZ and its metabolites.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS—IX. A SPIN TRAPPING STUDY OF THE PHOTOLYSIS OF AMIODARONE AND DESETHYLAMIODARONE

The photolysis of amiodarone (AM) and its major metabolite mono-N-desethylamiodarone (DEA), has been studied by absorption spectroscopy, electron spin resonance spectroscopy (spin trapping) and oxygraph measurements. Changes in the absorption spectrum of both AM and DEA upon UV irradiation indicate that both drugs undergo deiodination. Spin trapping experiments with 2-methyl-2-nitrosopropane (MNP), α-phenyl-N- tert -butyl-nitrone (PBN) and 5.5-dimethyl-1-pyrroline-N-oxide (DMPO) suggest the formation of an aryl radical from AM during UV irradiation. Amiodarone also undergoes photoionization. Under aerobic conditions the photoelectron is scavenged by oxygen to give superoxide, which is trapped by DMPO. Oxygraph measurements further confirmed the consumption of oxygen and the generation of superoxide during the irradiation of aqueous solutions of AM. Deiodination, photoionization and superoxide formation were all observed at wavelengths as low as 335 nm, suggesting that some or all of these processes may be involved in AM-induced photosensitivity. The aryl radical derived from AM during UV irradiation abstracted a hydrogen atom from suitable donors (ethanol, glutathione, cysteine, linoleic acid). Reaction of the dienyl radical derived from linoleic acid would yield the corresponding peroxy radical thereby initiating lipid peroxidation. This would explain the deposition of lipofuscin, a pigment formed from the products of lipid peroxidation, in the skin of patients receiving AM.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS—XL PHOTOLYSIS OF CHLORPROMAZINE METABOLITES: A SPIN-TRAPPING STUDY

Abstract. The photochemistry of chlorpromazine (CPZ) and its metabolites, 7-hydroxychlorpromazine (7OHCPZ), desmethylchlorpromazine (DCPZ), didesmethylchlorpromazine (DDCPZ) and chlorpromazine sulfoxide (CPZSO) was studied by the spin trapping technique with 2-methyl-2-nitrosopropane and 5,5-dimethyl-l-pyrroline-N-oxide. 7-Hydroxychlorpromazine generated hydroxyl radicals when excited at 330 nm under either anaerobic or aerobic conditions. 7-Hydroxychlorpromazine, DCPZ and DDCPZ all underwent dechlorination upon photoexcitation which was enhanced in the absence of air. Chlorpromazine sulfoxide did not undergo photodechlorination but instead generated a high yield of the hydroxyl radical. A comparison among CPZ and its derivatives shows that the yield of the photodechlorinated product is directly related to the degree of phototoxicity. This suggests photodechlorination is an important factor in the phototoxicity of CPZ and its metabolites.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS—IV. THE PHOTOLYSIS OF BENOXAPROFEN, AN ANTI-INFLAMMATORY DRUG WITH PHOTOTOXIC PROPERTIES

Abstract— Benoxaprofen [2-(4-chlorophenyl)-α-methyl-5-benzoxazole acetic acid] is an anti-inflammatory drug that causes acute phototoxicity in many patients. Photolysis studies in organic solvents (ethanol, benzene, dimethylsulfoxide) showed that benoxaprofen underwent both Type I and Type II reactions. Irradiation of an anerobic solution of benoxaprofen in ethanol resulted in hydrogen abstraction from the solvent to yield hydroxyethyl and ethoxyl radicals. In the presence of oxygen, superoxide, singlet oxygen and hydroxyethyl radicals were detected. Photolysis of benoxaprofen in air-saturated benzene or dimethylsulfoxide gave superoxide. However, under anerobic conditions the drug yielded a carbon-centered radical in benzene that could not be identified. These findings suggest that both oxygen-dependent and oxygen-independent processes may be important in the phototoxic reactions of benoxaprofen.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS—X. A SPIN-TRAPPING AND DIRECT ELECTRON SPIN RESONANCE STUDY OF THE PHOTOCHEMICAL PATHWAYS OF DAUNOMYCIN AND ADRIAMYCIN

Abstract— Irradiation of daunomycin (or adriamycin) and the spin trap 5,5-dimethyl-l-pyrroline-1-oxide (DMPO) at 490 nm in the presence or in the absence of air generated the hydroxyl radical adduct (DMPO-OH). The observed DMPO-OH signal was not affected by the addition of hydroxyl radical scavengers (ethanol, formate), suggesting that direct trapping of the hydroxyl radical was not involved. The DMPO-OH signal was insensitive to superoxide dismutase and catalase, which ruled out the possibility of superoxide or H₂O₂ involvement. These findings demonstrate that daunomycin (or adriamycin) does not generate hydroxyl radicals or superoxide radical anions when subjected to 490-nm excitation. However, when daunomycin (or adriamycin) was irradiated at 310 nm DMPO adducts derived from two carbon-centered radicals, superoxide and the hydroxyl radical were detected. The superoxide adduct of DMPO was abolished by the addition of SOD, providing unequivocal evidence for the generation of the superoxide anion radical. The daunomycin semiquinone radical, observed upon 310-nm irradiation of daunomycin in the absence of DMPO, appears to be the precursor of the superoxide radical anion. One of the carbon-centered radicals trapped by DMPO exhibited a unique set of hyperfine parameters and was identified as an acyl radical. This suggests that the known photochemical deacylation of daunomycin occurs via a homolytic cleavage mechanism. The free radicals generated photolytically from adriamycin and daunomycin may be involved in the etiology of the skin ulceration and inflammation caused by these drugs. A knowledge of the dependence of these photogenerated radicals on the wavelength of excitation may be important in the development of adriamycin and daunomycin for photodynamic therapy.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS—I. SPIN TRAPPING OF PHOTOLYSIS PRODUCTS FROM SULFANILAMIDE, 4-AMINOBENZOIC ACID AND RELATED COMPOUNDS

The photodecomposition of sulfanilamide, 4-aminobenzoic acid and other related analogs has been studied with the aid of the spin trap 2-methyl-2-nitrosopropane. UV photolysis of an aqueous solution of sulfanilamide yielded the following radicals C˙₆H₄SO₂NH₂, C₆H₅SO_2˙, S˙O₂NH₂ and SO^-_#˙ (or SO^-_2dot;). Under the same conditions 4-aminobenzoic acid gave C˙₆H₄COOH. In addition both sulfanilamide and 4-aminobenzoic acid, but not 4-dimethylaminobenzoic acid, generated e^-_aq or hydrogen atoms during UV irradiation. The C₆H₄SO₂NH₂ radical was also produced by photolysis of 4-iodobenzenesul-fonamide and 4-nitrobenzenesulfonamide. The C₆H₄COOH radical was generated by photolysis of 4-nitrobenzoic acid and 4-iodobenzoic acid. Finally the C₆H₄NO₂ radical was formed during the irradiation of 4-nitroaniline, 1,4-dinitrobenzene and 4-iodonitrobenzene. The free radicals generated by sulfanilamide and 4-aminobenzoic acid may play an important role in the phototoxic and photoallergic responses elicited by these drugs in certain individuals.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS-XIV. THE SPIN TRAPPING OF FREE RADICALS FORMED DURING THE PHOTOLYSIS OF HALOGENATED SALICYLANILIDE ANTIBACTERIAL AGENTS

Several antibacterial halogenated salicylanilides, including 3,3',4',5-tetrachlorosalicylanilide (TCSA) and 3,4',5-tribromosalicylanilide (TBSA) are known to cause photoallergy. We have carried out photochemical and spin trapping studies to determine whether free radicals may be involved in the photoallergic response. Irradiation (lambda greater than 300 nm) of TCSA in buffered (pH 7.4) 50% ethanol resulted in the rapid loss of the 3-chloro atom, followed by the much slower release of 5- and then the 4'-chloro atoms to give 3'-chlorosalicylanilide as a stable photoproduct. Under the same conditions TBSA successively lost the 3-, 5- and 4'-bromine atoms to give salicylanilide. When TCSA or TBSA were irradiated (lambda = 356 nm) in buffered (pH 7.4) 50% ethanol containing 2-methyl-2-nitrosopropane (MNP) only solvent-derived free radicals were detected. However, irradiation (lambda = 356 nm) of TCSA and MNP in 0.1 N NaOH generated an ESR spectrum consisting of a broad triplet (aN = 15.6 G). This spectrum was attributed to the adduct formed by the reaction of MNP with the aryl radical generated by the loss of a chlorine atom from the sterically hindered 3-(or 4'-)-position. Under the same conditions TBSA initially generated a broad triplet (aN = 15.5 G) similar to that observed for TCSA. However, upon further irradiation a 21-line spectrum (aN = 14.4 G, a2H = 2.0 G and a2H = 0.9 G) appeared.(ABSTRACT TRUNCATED AT 250 WORDS)     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS—VI. IDENTIFICATION OF THE FREE RADICALS GENERATED DURING THE PHOTOLYSIS OF MUSK AMBRETTE, MUSK XYLENE AND MUSK KETONE

Musk ambrette (4-tert-butyl-3-methoxy-2,5-dinitrotoluene), a common component of perfumes, soaps, and some food flavorings, can cause cutaneous photosensitization reactions including photoallergy. These may be mediated through free radicals formed during photolysis. When musk ambrette was photolyzed under nitrogen in basic methanol, two distinct nitro anion radicals were identified by electron spin resonance. One radical was centered on a nitro group in the plane of the aromatic ring, while the other was centered on a nitro group twisted out of the plane of the ring due to steric hindrance by bulky substituents on either side of the group: the two radicals appeared to interconvert and maintain an equilibrium concentration ratio. Two closely related compounds which are also used in perfumes, but have not been reported to cause photosensitizing reactions, also produced free radicals during photolysis. Musk xylene (2,4,6-trinitro-1,3-dimethyl-5-tert-butylbenzene) generated two nitro anion radicals, both of which were centered on twisted nitro groups, while musk ketone (3,5-dinitro-2,6-dimethyl-4-tert-butylacetophenone) produced only one nitro anion radical, which is also twisted. Athough these nitro anion radicals are probably the first step in the photolysis of these nitroarornatic molecules, it seems likely that in vivo they will undergo further reduction to produce more reactive species including the corresponding nitroso and hydroxylamine derivatives. In addition, autoxidation of the nitro anion radical intermediate forms superoxide.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS—II. SPIN TRAPPING OF PHOTOLYSIS PRODUCTS FROM SULFANILAMIDE AND 4-AMINOBENZOIC ACID USING 5,5-DIMETHYL-1-PYRROLINE-1-OXIDE

Abstract— The photodecomposition of sulfanilamide, 4-aminobenzoic acid and related analogs in aqueous solution has been studied with the aid of spin traps 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) and CH₃NO₂ as well as by direct electron spin resonance techniques. The NH₂ radical was trapped by DMPO during the photolysis of aqueous solutions of sulfanilamide with a Xe arc lamp. Studies with [¹⁵N¹]-sulfanilamide indicated that the NH₂ radical was generated by homolytic fission of the sulfur-nitrogen bond. Under the same conditions DMPO trapped the H and SO⁻₃ radicals during photolysis of sulfanic acid. Direct photolysis of sulfanilamide, sulfanilic acid and Na₂SO₃ in the absence of any spin trap yielded the SO⁻³ radical. Photolysis of 4-aminobenzoic acid at pH 7 gave the H radical which was trapped by DMPO. At low pH values OH and C₆H₄COOH radicals were generated during the photolysis of 4-aminobenzoic acid. No e⁻_aq were trapped by CH₃NO₂ when acid (pH 4) and neutral aqueous solutions of sulfanilamide or 4-aminobenzoic acid were photoirradiated. The mechanism of formation of known photoproducts from the free radicals generated by sulfanilamide and 4-aminobenzoic acid during irradiation are discussed. The free radicals generated by these agents may play an important role in their phototoxic and photoallergic effects.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS-XIII. pH DEPENDENCE OF THE PHOTOCHEMISTRY OF PHOTO ALLERGENS BITHIONOL AND FENTICHLOR: AN ELECTRON spIN RESONANCE STUDY OF THE FREE RADICAL PHOTOPRODUCTS

Abstract The photoallergens bithionol (BT) and fentichlor (FT) generated free radical photoproducts upon UV photolysis which were observable by direct electron spin resonance (ESR). Both the yield and the type of free radical photoproducts were affected by pH, and to some extent, concentration of oxygen and concentrations of the photosensitizers. At pH 8.5, bithionol (0.9 mM) generated a semiquinone type free radical (BI) via a mechanism which probably involves substitution of the 4-chlorine by hydroxyl to form the corresponding hydroquinone followed by oxidation. The photolysis of 4-chlorophenol, 4-chlorocatechol and 2,2'-methylene-bis(4-chlorophenol) also generated the corresponding semiquinone radicals, suggesting that this mechanism is shared by other 4-chlorophenols. At pH 8.5, only photoproduct BI was observed during the irradiation of BT; FT related photoproducts were not observed at this pH. However, at higher pH values (pH 10.7 or pH 12), FT photoproducts were also observed in addition to BI upon prolonged irradiation. Moreover, the yield of BI increased drastically at higher pH. Oxygen did not play any role at pH 10.7, although it enhanced the yield of BI at pH 8.5. At pH 8.5, irradiated fentichlor generated, in roughly equal amounts, a semiquinone radical (Fla) and an unidentified species which contained two inequivalent protons (FII). At higher pH values (pH 10.7 and pH 12), at least four species were observed. All of the species are believed to be semiquinone radicals and two have been unambiguously identified. The yield of FI increased by a factor of 50 as the pH was increased from 8.5 to 12. Oxygen played only a minor role at pH 10.7 and above. However, at pH 8.5, it also enhanced the yield of FI.     

神府大柳塔烟煤及其热处理产物碱氧氧化的研究

对神府大柳塔烟煤及其３００、４００、５５０、７００℃干馏产物，在７５ｇＫＯＨ／３０ｇ试样（ａｄ．）水溶液、氧初压为５．５ＭＰａ或６．０ＭＰａ和２５０℃的条件下氧化２ｈ，其氧化产物水溶酸的产率及其组成随干馏温度的升高而变化，在干馏温度为４００℃时水溶酸的产率达到最大（５４．９６％对ｄａｆ．试样），并采用气相色谱法进行定性、定量分析。     

ORGANIC PHOTOCHEMISTRY—XV. APPLICATIONS OF PHOTOCYCLOADDITION REACTIONS IN NATURAL PRODUCT SYNTHESES*,†

Abstract— Photocycloaddition reactions which have been employed as one of the steps in the total/ synthesis of natural products are reviewed. The utility of the cycloadducts in these syntheses is also discussed.     

STUDIES ON HETEROLOGOUS EXPRESSION OF Rhizobium meliloti nifA GENE AND OXYGEN SENSITIVITY OF ITS PRODUCT

When the R. meliloti (Rm) nifA'-lacZ fusion-carrying plasmids were introduced intothe strains of Agrobacterium tumefaciens, R. trifolii and R. astragalus, β-galactosidaseactivity was demonstrated. However, activity was not induced by microaerobiosis. Further-more, R. meliloti nifA'-lacZ fusion was also not expressed in the nodule bacteroids ofR. trifolii and R. astragalus. We speculate that some factor(s) important for the inductionof Rm nifA presumed to be the fixLJ regulatory system would not be operative in thesebacteria. Experiments using R. meliloti nifH'-lacZ/ K. Pneumoniae nifH'-lacZ fusion and theconstitutive Rm nifA system to test the nifA-dependent expression of nifH'-lacZ underaerobic and microaerobic conditions in E. coli were performed. The inhibition of the RmnifA activation of nifH'-lacZ expression in the bacteria grown in the aerobic conditionwas shown. Assays on the Rm nifA-m RNA produced by the constitutive Rm nifA in E.coli under aerobic and microaerobic conditions with the cloned ni     

THE BEHAVIOR OF DYE-MUCOPOLYSACCHARIDE COMPLEXES—I. SPECTROSCOPIC STUDIES OF THE SYSTEM CHONDROITIN SULFATE A-ACRIDINE ORANGE

Abstract —Absorption, fluorescence, and circular dichroism (CD) spectra have been obtained for a mucopolysaccharide—cationic dye complex. The dye acridine orange exhibits a blue shift in its absorption maximum and a red shift in its fluorescence maximum when mixed with chondroitin sulfate A in aqueous solution. The spectral shifts of the dye appear to be reversed by addition of salt, divalent cations being more effective than monovalent cations. The complex exhibits induced optical activity in the visible absorption spectrum of acridine orange. The biphasic nature of the CD curve is compatible with interpretations involving chromophore coupling.