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FLUORESCENCE QUENCHING IN PHENYLALANINE AND MODEL COMPOUNDS *
Author(s) -
TOUR J.,
KUNTZ E.,
ELBAYOUMI M. ASHRAF
Publication year - 1972
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.1751-1097.1972.tb06310.x
Subject(s) - chemistry , phenylalanine , quenching (fluorescence) , fluorescence , photochemistry , intramolecular force , intersystem crossing , substituent , stereochemistry , amino acid , singlet state , excited state , biochemistry , physics , quantum mechanics , nuclear physics
— The effects of the carboxylic and amino groups in their neutral and charged forms on the absorption and emission properties of phenylalanine are analyzed with the help of model compounds containing either substituent. Fluorescence yields of phenylalanine and model compounds were measured as a function of pH. Fluorescence quenching occurs in going from COO ‐ to COOH and from NH 3 + to NH 2 . Lowering the ionization potential of the phenyl group by substitution increases the quenching effect. This provides more evidence that an intramolecular charge‐transfer mechanism may be responsible for intersystem‐crossing rate enhancement and fluorescence quenching in phenylalanine and model compounds.