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GEOMETRIC REQUIREMENTS FOR THE INTRAMOLECULAR QUENCHING OF INDOLE FLUORESCENCE BY AMIDE AND CARBOXYLIC ACID GROUPS IN RIGID MOLECULES WITH THE [2,2,1]BICYCLOHEPTENYL SKELETON
Author(s) -
Royer Jacques,
BeugelmansVerrier Michèle,
Biellmann JeanFrançois
Publication year - 1981
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1981.tb09061.x
Subject(s) - intramolecular force , indole test , amide , fluorescence , carboxylic acid , chemistry , skeleton (computer programming) , molecule , quenching (fluorescence) , stereochemistry , polymer chemistry , biology , organic chemistry , physics , anatomy , quantum mechanics
— The geometric requirements for intramolecular fluorescence quenching of indole by carboxylic acid and amide functions have been determined in rigid norbornyl ([2.2,1]bicycloheptenyl) skeleton: trans and cis 3‐(3′‐indolyl) norbornene 2‐dimethylcarboxamides or carboxylic acids. The reference compound was the 3‐(3′‐indolyl) N‐dimethylpropionamide or ‐propanoic acid. The quenching occurs mainly in protic solvents. In the cis compounds, the quantum yields are strongly decreased when compared to the trans and open chain compounds. As determined by the pH dependence of fluorescence of the acids, it is in the acid form—COOH that the fluorescence is quenched; in the ionized species ‐CO − 2 , only small quenching is observed. The K s of Stern‐Volmer equations are very small for the cis bicyclic acid and amide, the indole nucleus being shielded on one side only. The results support the hypothesis that small rearrangement of the peptide bond in protein conformation changes may be detected by fluorescence.