Giiti Tomita

EFFECTS OF INDOLE AND TRYPTOPHAN ON FURAN OXIDATION BY SINGLET OXYGEN IN MICELLAR SOLUTIONS

Abstract— The 1,3‐diphenylisobenzofuran oxidation by singlet oxygen was investigated in aqueous dode‐cyltrimethylammonium chloride micellar solutions using pyrene as photosensitizer. It was found that indole and tryptophan markedly enhanced the furan oxidation in micellar solutions. This enhancement effect strongly depended on the ethanol content in micellar solutions; enhancement effect below about 0.3 mol fraction of ethanol and inhibition effect above this mole fraction. In the former ethanol range, a quenching of pyrene fluorescence by indole or tryptophan and a difference spectrum of furan between micellar solutions in the presence and absence of indole or tryptophan appeared strongly, but they were weakened in the latter ethanol range. The interactions between indole or tryptophan and pyrene and/or furan might be responsible for the enhancement effect observed. Discussion was made in connection with the micelle structure.

Molecular Complexes of acridine orange and nucleosides

SummaryThe addition of various nucleosides to the aqueous AO solution brings about the red shift of the absorption band of AO monomer and the enhancement of the AO fluorescence emission. These phenomena are attributable to the formation of a kind of molecular complex between AO monomer and nucleoside.The absorption and fluorescence characteristics and their thermal behaviours enable us to determine the association constant and the binding energy. The binding energy of AO with purines is larger than that with pyrimidines, and the association constant between AO and the deoxyribonucleoside is larger than that between AO and the ribonucleoside. For the molecular complexes dealt with, the face-to-face arrangement of AO and nucleoside, linking of AO with sugar by hydrogen bridge, may be more preferential than the side-by-side arrangement with the direct linkage between AO and nucleic acid base by hydrogen bonding. The Van der Waals-London interactions may be one of the essential factors for the binding in these molecular complexes.The association constant and the binding energy for AO-DNA and -RNA systems were also determined. The magnitude of these quantities seems to reflect the difference in the structure of these nucleic acids. The rather open structure of RNA compared with DNA is in favour of affinity with AO and gives the larger association constant than that for AO-DNA. The binding energy is somewhat larger for AO-DNA complex than for AO-RNA complex, probably due to the structural difference of the base arrangement; the stacked base pairs for DNA and the stacked bases for RNA.

Production and Reaction of Singlet Oxygen in Aqueous Micellar Solutions Using Pyrene as Photosensitizer

Abstract The reaction of singlet oxygen with 1,3-diphenylisobenzofuran was investigated in aqueous micellar solutions of sodium dodecyl sulfate and dodecyl trimethylammonium chloride using pyrene as photosensitizer. Singlet oxygen, produced by the photosensitization of pyrene bound to micelles, oxidized efficiently 1,3-diphenylisobenzofuran bound to micelles. The quantum yield for singlet oxygen production and the rate constant for furan oxidation were determined by the kinetic analysis for the oxidation reaction of furan. Quenching of singlet oxygen by sodium azide competed with the furan oxidation, and its rate constant was also determined. Results obtained were compared with those in methanolic solutions. The quantum yield for singlet oxygen production and the rate constant for furan oxidation were much higher in micellar solutions than those in methanolic solutions. Empty micelles wxas found to act as a considerably strong scavenger for singlet oxygen. The penetration probability of singlet oxygen from aqueous phase into the interior of micelles which bound furan was also estimated

Effect of polyethylene glycol on heat inactivation of the hill reaction

Abstract Protection of the Hill reaction from heat inactivation by polyethylene glycol was found in spinach chloroplasts. The protective action of the polymer is discussed in relation to chloroplast membrane structure.

Dimer and polymers in solutions of chlorophyll a

SummaryChlorophyll a in n-hexane solution exhibits the main red absorption band at 662 nm, an absorption shoulder at 680 nm and the far red absorption band at 745 nm. These are attributable to the absorptions in monomer, dimer and high polymers (or microcrystals), respectively. The thermal behaviours of absorption spectra give us some useful informations about the dissociation processes of high polymers into monomers, the molecular arrangement in high polymers and the conformation change by heat.

The photoconversion of Chenopodium chlorophyll protein.

Abstract— Changes in the UV absorption spectrum with the photoconversion of Chenopodium chlorophyll protein, CP668 ⇆ CP743, and with the pH change of the CP668 and CP743 solutions, were measured. The change in the absorption spectrum of the apoprotein caused by the pH change was reversible, whereas that caused by the photoconversion was irreversible. The apoprotein may undergo a proton dissociation or association of the phenolic group in tyrosine residues upon pH change. A photooxidation in CP668 (loss of electron) caused by irradiation of CP668 solution may induce a change in the ionization state of some amino acid residues. The isoelectric points of CP668 and CP743 were determined to be 9.3 and 7.2, respectively.

FLUORESCENCE AND PHOTOOXIDATION OF 1—ANILINONAPHTHALENE—8—SULFONIC ACID IN REVERSED MICELLAR SOLUTIONS AND THE EFFECT OF CCl4

Abstract— The 1‐anilinonaphthalene‐8‐sulfonic acid solubilized in dodecylammonium propionate reversed micellar cyclohexanic solutions, emitted a strong fluorescence, and was photooxidized under aerobic conditions. Carbon tetrachloride (CCl4) highly quenched the fluorescence and remarkably enhanced the oxidation reaction. The fluorescence quenching obeyed the Stern‐Volmer relation, and the photooxidation was caused by the singlet oxygen generated by the photosensitization of the dye. From the kinetic analysis, it was known that the intersystem crossing rate from the dye excited singlet to triplet was enhanced by CCl4. Carbon tetrachloride did not quench the triplet state. The ratio of quantum yields for the oxidation in the presence and absence of CCl4 was independent of the oxygen concentration in the reaction mixture. The fluorescence quenching constant and the intersystem crossing rate were obtained at various solubilized water contents.

Singlet Oxygen Production Photosensitized by Fluorescein in Reversed Micellar Solutions

Abstract The quantum yield of singlet oxygen production was investigated in dodecylammonium propionate reversed micellar solutions containing 1,3-diphenylisobenzofuran and fluo-rescein as photosensitizer. The quantum yield was highly enhanced by the binding of fluorescein to reversed micelles, and increased with decreasing the solubilized water content in reversed micelles. Results obtained was discussed with the optical properties of fluorescein (absorption, fluorescence and phosphorescence) in reversed micellar solutions.

Quenching of Singlet Oxygen by Sodium Azide in Reversed Micellar Systems

Abstract The oxidation reaction of singlet oxygen with 1,3-diphenylisobenzofuran was investigated in cyclohexanic reversed micellar solutions of dodecylammonium propionate, using pyrene as photosensitizer. The furan oxidation was effectively inhibited by azide ion-bound reversed micelles. Empty reversed micelles also inhibited the furan oxidation to some extent. The inhibition of the furan oxidation was due to the quenching of singlet oxygen by azide ion-bound and empty reversed micelles. Such singlet oxygen quenching was dependent on the concentration of water added. Results obtained were discussed in connection with the polarity in the interior of reversed micelles, micellar size, the state of water solubilized in reversed micelles and the lifetime of singlet oxygen. The heavy atom effect on the quenching of singlet oxygen was also studied using heavy water.

Fluorescein-photosensitized Furan Oxidation in Methanolic and Reversed Micellar Solutions, Part II Kinetic Analysis

Abstract The 1,3-diphenylisobenzofuran oxidation was investigated in methanolic and dodecyl-ammonium propionate reversed micellar solutions using fluorescein sodium as photosensitizer. The furan oxidation was caused by the singlet oxygen mechanism (Type II). Aniline enhanced remarkably the furan oxidation in methanolic solutions, but inhibited highly this oxidation in the reversed micellar solutions. This enhancement of the furan oxidation was considered to be brought about by the occurrence of a radical mechanism (Type I) besides Type II mechanism. No Type I reaction occurred in the micellar solutions. The rate constants concerning with both reaction processes were evaluated by kinetic analysis, employing various aryl-and alkyl-amines. The reaction mechanism of Type I and the quenching mechanism of singlet oxygen by amines were discussed from the relationship between the rate constants, and the ionization potential of amines and the solvent polarity.