[Quenching of chlorophyll and pheophytin fluorescence with fucoxanthin]. / Tushenie fluorestsentsii khlorofilla i feofitina fukoksantinom.

Quenching of chlorophyll a and pheophytin a fluorescence with fucoxanthin in acetone and n-hexanole at room temperature was investigated. The relationship between fluorescence yield and concentration of the quencher is subject to Stern--Folmer relation. The velocity constants were calculated and the efficiency of fluorescence quenching was determined. The energetic estimation has shown that the fluorescence quenching mechanism when the excited chlorophyll a molecule collides with fucoxanthin molecule may involve electron transfer from chlorophyll to fucoxanthin. In case of pheophytin a transfer of the electron from fucoxanthin to pheophytin is likely to take place.

[The photoelectrochemical effect in solid films of flucoxanthine].

A negative photopotential was shown to appear upon illumination on a fucoxanthin solid film-covered platinum electrode, immersed into an electrolyte solution. The effects of electrolyte pH and the reducing and oxidyzing agents on the photopotential value and its kinetic behaviour upon illumination and in the dark were studied. The data obtained are indicative of the ability of fucoxanthin to perform photochemical reactions at the level of electron transfers, which accounts for its photosensitizing activity.

[Photochemical properties of fucoxanthine]. / O fotokhimicheskikh svoistvakh fukoksantina

The ability of fucoxantine for photooxidation by oxygen in a number of organic solvents and for photoreduction by oxorbic acid and phenylhydrazine in pyridine is demonstrated. The reactions are irreversible under common conditions. At the same time fucoxanthine possesses a pronounced ability for photosensitization of red-ox reaction between methyl red and ascorbic acid or phenylhydrazine, which suggests a formation of reversible very labile intermediate pigment compounds at initial steps of photoreaction.