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INTERACTION BETWEEN PROFLAVINE AND GUANOSINE 5‘‐PHOSPHATE: IMPORTANCE OF PHOTOEXCITATION
Author(s) -
Badea M. G.,
Georghiou S.
Publication year - 1976
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.1751-1097.1976.tb06848.x
Subject(s) - proflavine , chemistry , acridine , phenanthridine , guanosine , nucleotide , photochemistry , phosphate , guanine , stereochemistry , dna , biochemistry , organic chemistry , gene
— The stoichiometry of the complex formed between the mutagenic drug proflavine and the nucleotide guanosine 5'‐phosphate has been demonstrated to be 1:1. Its association constant at room temperature is found to increase from 310 M ‐1 when proflavine is in its ground electronic state, to 1550 M ‐1 , when proflavine is in its first excited singlet state. Thus, light absorbed by the drug alters its reactivity which, in turn, results in an appreciable increase in its ability to bind to the nucleotide. The enthalpy and the entropy of the ground state proflavine‐guanosine 5'‐phosphate complex formation are ‐12.6 kJ/mol (‐3 kcal/mol) and ‐6.7 J/mol/deg (‐1.6 cal/mol/deg), respectively. The implications of these findings concerning the proflavine‐DNA interaction as well as the possible importance of electronic excitaton in acridine mutagenesis are discussed. An appraisal of the methodology for analyzing fluorescence quenching data is also given.