Dark and photoinduced interactions between riboflavin and indole auxins

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Title:Dark and photoinduced interactions between riboflavin and indole auxins
Creators:
Miskoski, Sandra
García, Norman A.
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 56, 9, pp. 1838-1849

Abstract

Interactions between riboflavin (RF) and indole auxins in the darkness and under conditions of irradiation with visible light were carried out. Dark complexation takes place in buffered (pH 7) aqueous solution. The association constants determined by static fluorescence quenching range from 70 to 150 mol<sup>-1</sup> dm<sup>3</sup>. The complexation is significant at relatively high indole auxin concentrations (above 10<sup>-3</sup> mol dm<sup>-3</sup>). It is governed by an additive effect of charge transfer, known for flavine-indole systems, and of the hydrophobic bond formation. The latter appears in the case of auxins as the driving force of the interaction. No quenching of singlet-excited RF was detected up to indole auxin concentrations of 5 . 10<sup>-3</sup> mol dm<sup>-3</sup>. Under irradiation with visible light a complex mechanism of competitive reactions is operative: both RF and especially the auxins are decomposed by a combination of type I and II photooxidations at indole auxins concentration of 10<sup>-4</sup> mol dm<sup>-3</sup>. The rate constants of the order of 10<sup>9</sup> mol<sup>-1</sup> dm<sup>3</sup> s<sup>-1</sup> were estimated for the quenching of triplet excited RF by the indoles. For comparative purposes Rose Bengal sensitized photooxidation of a series of indolecarboxylic acids of indole-3-acetic, -propionic and –butyric acid was examined. The rate constants of the photooxidative process, mediated by singelt molecular oxygen, were of the order of 10<sup>7</sup> mol<sup>-1</sup> dm<sup>3</sup> s<sup>-1</sup> for the auxins. As a result of the interaction, RF is protected against photobleaching and the auxins decompose via a different mechanism, depending on the relative flavin-auxin concentrations.

Title:Dark and photoinduced interactions between riboflavin and indole auxins
Creators:
Miskoski, Sandra
García, Norman A.
Divisions:Life and Chemical Sciences > Institute of Organic Chemistry and Biochemistry > Collection of Czechoslovak Chemical Communications
Journal or Publication Title:Collection of Czechoslovak Chemical Communications
Volume:56
Number:9
Page Range:pp. 1838-1849
ISSN:0010-0765
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc19911838UNSPECIFIED
ID Code:5109
Item Type:Article
Deposited On:22 Feb 2010 11:30
Last Modified:22 Feb 2010 10:31

Citation

Miskoski, Sandra; García, Norman A. (1991) Dark and photoinduced interactions between riboflavin and indole auxins. Collection of Czechoslovak Chemical Communications, 56 (9). pp. 1838-1849. ISSN 0010-0765

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