SINGLET OXYGEN GENERATING EFFICIENCY OF α-TERTHIENYL and SOME OF ITS SYNTHETIC ANALOGUES*

The singlet oxygen generating efficiency of several thiophenic compounds, including oc-terthienyl (αT) and some of its synthetic analogues, has been determined using laser flash photolysis techniques. The method, which is based on the time-resolved bleaching of 1,3-diphenylisobenzofuran, led to relatively high efficiencies for all the substrates examined; for example the values were 0.86, 0.69 and 0.63 for αT, DBrαT and TNP, respectively in chloroform-d at 293K. Our results also indicate that high intersystem crossing efficiencies must be a common characteristic in these compounds. The variations in singlet oxygen yields were found to be modest in comparison with changes in the biological activity of these compounds, therefore suggesting that other factors are also quite important in determining the latter.     

PHOTOSENSITIZED INHIBITION OF PHOTOSYNTHETIC 14CO2 FIXATION BY α-TERTHIENYL AND ULTRAVIOLET-A*

Abstract: A variety of naturally occurring photosensitizers of plant origin were tested for their ability to cause ultraviolet-A (UVA)-dependent inhibition of photosynthetic ¹⁴CO₂ fixation in leaf disks of Pisum sativum L. At 0.1 mM concentrations and 60 min UVA irradiation, α-terthienyl was strongly inhibitory, harmine and sanguinarine inhibited to a lesser degree, and curcumin, 8-methoxypsoralen and nordihydroguaiaretic acid had no effect under the conditions tested. Alpha-terthienyl + UVA treatments that fully inhibited ¹⁴CO₂ fixation had no effect on fresh weight, chlorophyll or protein content of the tissue. Chloroplast malate dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase were inhibited 45% and 29%, respectively, by α-terthienyl + UVA treatment. Electron transport from H₂O to the reducing side of photosystem I was inhibited to a similar extent, suggesting interference with the reductive activation of chloroplast enzymes. Alpha-terthienyl + UVA-treated tissue exhibited a seven-fold increase in leakage of labeled photosynthate into the external medium. Treated leaf disks showed no ability to recover ¹⁴CO₂ fixing ability over a 24 h period. These results indicate photosensitized damage at the level of the thylakoid membranes resulting in partial loss of electron transport capability and more general damage to chloroplast and cell membranes.     

TWO DIFFERENT TYPES OF PHOTOCHEMISTRY IN PHYCOERYTHROCYANIN α-SUBUNIT*

The photochemical activities of phycoerythrocyanin α-subunits from Mastigocladus laminosus separated by isoelectric focusing were tested by irradiating at 500, 550, 577 and 600 nm. Two types of photoreversible photochromic responses have been characterized by absorption and absorption difference spectroscopy. Type I is the well-known absorption shift from 571 to 506 nm. Type II is a new response characterized by a line-broadening of the 570 nm absorption.     

PHOTOCHEMISTRY OF DI(9-ANTHRYL)- AND BENZYL-SUBSTITUTED SILANES AND RELATED COMPOUNDS1

Abstract

By irradiation, both di(9-anthryl)dimethylsilane and germane afforded a new type of [4 + 2] intramolecular addition product that underwent quantitative cycloreversion by thermolysis. The photoproduct from the former was converted to a novel naphthotriptycene derivative. A phosphorus analogue, di(9-anthryl)phenylphosphine, however did not undergo the reaction. Photochemical reactions of benzyltrimethylsilane and acyloxymetyl(benzyl)dimethylsilanes (RC(O)OCH₂SiMe₂CH₂Ph: R = CH₃ and R = t - Bu) are also reported for the first time. The mechanisms of these new photochemical reactions are discussed.     

PHOTOSENSITIZED INHIBITION OF PHOTOSYNTHETIC 14 CO2 FIXATION BY α-TERTHIENYL and ULTRAVIOLET-A*

Abstract –A variety of naturally occurring photosensitizers of plant origin were tested for their ability to cause ultraviolet-A (UVA)-dependent inhibition of photosynthetic ¹⁴CO₂ fixation in leaf disks of Pisum sativum L. At 0.1 mM concentrations and 60 min UVA irradiation, α-terthienyl was strongly inhibitory, harmine and sanguinarine inhibited to a lesser degree, and curcumin, 8-methoxypsoralen and nordihydroguaiaretic acid had no effect under the conditions tested. Alpha-terthienyl + UVA treatments that fully inhibited ¹⁴CO₂ fixation had no effect on fresh weight, chlorophyll or protein content of the tissue. Chloroplast malate dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase were inhibited 45% and 29%, respectively, by α-terthienyl + UVA treatment. Electron transport from H₂O to the reducing side of photosystem I was inhibited to a similar extent, suggesting interference with the reductive activation of chloroplast enzymes. Alpha-terthienyl + UVA-treated tissue exhibited a seven-fold increase in leakage of labeled photosynthate into the external medium. Treated leaf disks showed no ability to recover ¹⁴CO₂ fixing ability over a 24 h period. These results indicate photosensitized damage at the level of the thylakoid membranes resulting in partial loss of electron transport capability and more general damage to chloroplast and cell membranes.     

SOME REACTIONS OF CHOLESTERYL N-PHENYL-PHOSPHORAMIDIC CHLORIDE AND RELATED COMPOUNDS

Abstract

Cholesteryl N-phenylphosphoramidic chloride has been converted to the corresponding phosphoramidic hydrazide and azide. The former compound was characterised by the preparation of a number of hydrazones, while the latter has been reacted with norbornene, dimethylsulphoxide, and triphenylphosphine. However, the azide did not react with decane, o-anisole, or butylamine. 17-Oxoandrost-5-ene-3β-yl N-phenylphosphoramidic chloride was prepared and was converted to the hydrazide, but a pure sample of the azide could not be isolated. Cholesteryl N-phenyl phosphoramidic triphenylphosphinimine has been reacted with eight carbonyl compounds and the structures of the products investigated. Cholesteryl N-cyclohexylphosphoramidic chloride was converted to the azide and the triphenylphosphinimine; the latter was reacted with acetone and p-nitrobenzaldehyde.

Cholesteryl phosphorodichloridate has been condensed with phenol, p-nitrophenol, and p-methoxyphenol to give the corresponding O-arylphosphorochloridates. The O-phenyl and O-p-methoxyphenyl phosphorochloridates have been converted to the corresponding azides, but the azide from the p-nitrophenyl derivative could not be isolated. The reactions of cholesteryl phosphorodichloridate with diethylamine, hydrazine, and sodium azide have also been examined; and cholesteryl phosphorodichloridothioate has been condensed with aniline and benzylamine.     

氨基硫脲及其相关化合物的化学

本文综述了氨基硫脲及其相关化合的合成、波谱和化学性质以及在药物、工业、农业等方面的应用。     

MONOALKYL α-OXOAMIDES: PHOTOCHEMISTRY IN HOMOGENEOUS and IN MICROHETEROGENEOUS MEDIA*

An investigation of the photoreactivity of the amphiphilic α-oxoamide, N-(12-dodecanoic acid)benzoylformamide, (1), in aqueous (pH 10) solution and its inclusion complexes with β-cyclodextrin (β-CD) and carboxymethylamylose (CMA). In all three media photolysis of 1 yields predominantly the fragmentation products from hydrolysis, mandelamide and the corresponding aldehyde. The most reasonable mechanism for the reaction is an intramolecular quenching of a ketone-localized excited state by electron transfer from the amide nitrogen followed by proton transfer and a second electron transfer (zwitterion-1 → diradical ? zwitterion-2) to yield ultimately the mandelamide-imine precursor which hydrolyzes to the observed products. The quantum yields for 1 decomposition and mandelamide appearance in aqueous solution (pH 10) are 0.21 and 0.16, respectively. Compound 1 forms a 1:1 and 1:2 complex with β-CD and shows enhanced quantum efficiencies for reaction, especially the 1:2 complex. 1 also forms a complex with CMA which shows a similar binding constant to other similar chain length amphiphiles in other studies. Here again reactivity is enhanced for the photoreaction of 1 upon complexation, indicating that neither the electron transfer quenching of the excited states nor reaction of subsequent intermediates is prohibited in the complexes. Mechanistic implications of these results are discussed.     

QUALITATIVE STUDIES OF THE LOW TEMPERATURE PHOTOCHEMISTRY OF RHODOPSIN AND RELATED PIGMENTS

Abstract— Rhodopsin, the isomeric pigments formed from 9- cis - and 9, 13- dicis -retinal, and the synthetic pigments formed from 9- cis - and 11- cis -14-methylretinal were irradiated with 490 nm light at -196C. Absorption spectral changes indicate that a distinguishable bathorhodopsin type intermediate may be formed for each pigment. The bathorhodopsin intermediates of the 9- cis pigments have band maxima hypsochromically shifted by4–5 nm compared to their corresponding rhodopsins. The bathorhodopsin type intermediate formed upon irradiation of 9, 13- dicis -rhodopsin has an absorption that maximizes 6 nm shorter than that of rhodopsin. Band maxima of the bathorhodopsin intermediates of the 14-methylrhodopsins are bathochromatically shifted ca. 8 nm compared to their corresponding rhodopsins.     

ON THE PHOTOSENSITIZING PROPERTIES OF N-FORMYLKYNURENINE AND RELATED COMPOUNDS

Abstract— The photochemical and photosensitizing properties of N -formylkynurenine (FK) and related compounds have been investigated using the laser flash photolysis technique by exciting water solutions with 265 nm or 353 nm radiation. The FK molecules in their first excited singlet state readily react with water leading probably to OH formation. FK triplet state reacts with many biological compounds including vitamins, amino acids and nucleic acid bases. The semi-reduced FK thus formed can, in turn, reduce substrates such as cytochrome c or O₂.     

THE MASS SPECTRAL FRAGMENTATION OF SULFENAMIDES AND RELATED COMPOUNDS

Abstract

Plausible mechanistic interpretations of the major ions formed in the mass spectrometric fragmentation of a number of sulfenamides and related derivatives are presented. High resolution mass spectrometry was used to determine the composition of most of the ions investigated.     

PHYTOCHROME MODELS,PART 9. CONFORMATION SELECTIVITY OF THE PHOTOCYCLIZATION OF THE BILIVERDIN IX γ and IX δ DIMETHYL ESTERS*

Abstract— The photocyclization of the biliverdin IX γ and IX δ dimethyl esters to phorcabilin and neobiliverdin IX δ dimethyl ester, respectively, markedly depends on the irradiation wavelength within the first electronic absorption band. The quantum yields of reaction are highest on irradiation at575–600 nm. As judged from fluorescence excitation studies, absorption by the stretched conformations of the biliverdins is relatively important at these wavelengths. At longer wavelengths, where the reaction efficiency sharply declines, absorption by the coiled form predominates. Based on these findings and on supporting evidence from the solvent and temperature influence on the reaction, the photocyclization is proposed to occur selectively from a stretched conformation (an example of the principle of nonequilibration of excited rotamers), competing with E-Z isomerization of the centralC–10 double bond. A kinetic hydrogen isotope effect on the photochemical reaction rate of N,N,N-trideuteriated biliverdin IX δ dimethyl ester indicates that the primary photoproduct in the cyclization reaction is labile and reacts via two competing processes: reopening to the starting material and a solvent-mediated proton shift. The latter process leads to the phorcabilin and neobiliverdin IX δ esters. The results suggest, as a general rule, that the stretching of coiled biliverdins is confined to thermal and photochemical transformations within the B/C partial structure, while the Z-syn geometry of the A/B and C/D moieties is retained.     

Absolute Konfiguration der enantiomeren α-CyclogeraniumsäUren, α-Cyclogeraniale, α-Jonone, γ-Jonone, α-und ϵ-Carotine

By chemical correlation with manool and ambrein the absolute configurations of the enantiomeric α-cyclogeranic acids, α-cyclogeranials, α-ionones and α- and ?-carotenes have been elucidated.     

EFFECTS OF SOME PHENYLETHYNYLSILICON COMPOUNDS ON HEAT-CURABLE SILICONE RUBBER Ⅲ 1, 1, 3, 3-TETRAMETHYL-1, 3-DIPHENYLETHYNYL-DISILOXANE*

We have shown that some phenylethynylsilicon compounds are good cure crosslinkersof heat-curable silicone rubber(HCSR). In this paper the effects of 1, 1, 3, 3-tetramethyl-1, 3-diphenylethynyldisiloxane (TMDPDS) as a crosslinker on HCSR were studied. Thevulcanizates with fine mechanical properties could be obtained with suitable amounts ofTMDPDS. Sol fractions, and crosslinking density of vulcanizates and vulcanizationretardation effect of TMDPDS on hydrosilation curing silicone rubber were also discussed.     

高Tc超导体及相关化合物探索研究新进展

所有已知的层状铜氧化合物超导体结构均可按连接单元、分隔单元和三种不同的铜氧平面进行分类，由这几种基本的结构单元也可组合设计出新的结构类型，通过进一步的实验研究可以获得新结构类型的层状铜氧化合物超导体。以这一思想为出发点，本文从材料设计的角度总结了近五年来在新结构层状铜氧化合物超导体探索中的新进展。     

ON THE PHOTOCHEMISTRY OF THE DINUCLEOTIDE TpC*

Abstract— In an aqueous buffered solution of TpC monochromatic ultraviolet light lowers the absorption peak to approximately half its value, characterized by a photostationary state. The quantum yield for this photochemical decomposition is independent of the wavelength between 2400 and 3000 Å.At pH 7 the quantum yield amounts to 0.006, at pH 2 to 0.002, respectively. At neutral pH about 85 per cent of the photochemical transformation produced are reversible in the dark, at pH 2 only 40 per cent. Three photoproducts, being non-reversible in the dark, were isolated electrophoretically and characterized by their absorption spectra. These three compounds have an absorption peak around 2680 Å, one compound has a second absorption maximum at 3120 Å (pH 7).     

PHOTOCHEMISTRY OF THE PHOTOTOXIC POLYACETYLENE PHENYLHEPTATRIYNE*

Abstract— Investigation of the photochemistry of the phototoxic polyacetylene phenylheptatriyne, PHT, was undertaken to obtain further information on competing photo-oxidative type II and non-oxidative processes observed in vivo. Laser excitation (308 or 337 nm) led to the formation of a strong triplet signal with a lifetime of 28 μs in MeOH. The triplet was efficiently quenched by the triplet quencher 1,3-octadiene (k_q - 1.6 × 10⁹M^-1s^-1). Quenching by O₂ occurred with a rate constant (1.7 × 10⁹M^-1s^-1) comparable to the rate of electron transfer to methylviologen (1.4 × 10⁹M^-1 s^-1). The formation of singlet oxygen established earlier (type II reaction) in the former case and the semioxidized PHT radical in the latter case are consistent with the competing phototoxic processes observed in vivo.