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Thermodynamic characterization of ethidium bromide binding to a unique site on a yeast tRNA Phe
Author(s) -
Sturgill Thomas W.
Publication year - 1978
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1978.360170713
Subject(s) - chemistry , ethidium bromide , dissociation constant , transfer rna , binding constant , binding site , molecule , crystallography , equilibrium constant , yeast , phenylalanine , stereochemistry , biochemistry , rna , organic chemistry , amino acid , dna , receptor , gene
A self‐consistent thermodynamic characterization of the binding of ethidium to yeast phenylalanine‐specific tRNA at 25°C, pH 7.0, in 11 n M MgCl 2 , 375 n M NaCl, and 25 m M sodium phosphate has been obtained. Two ethidium molecules bind per tRNA under these conditions. The stronger site has a dissociation constant equal to 1.9 ± 0.5 μ M and Δ H dis °′ = 12 ± 1 Kcal/mol, and the weaker sites has a dissociation constant equal to 24 ± 9 μ M and Δ H dis °′ = 8.9 ± 1.5 Kcal/mol. The average calorimetric Δ H dis °′ for the to sites 10.6 ± 0.4 kcal/mol. The thermodynamics of binding to the stranger sites are most probably the thermodynamics of interaction between A·U (6) and A·U (7), the unique site identified by Jones and Kearns. The binding is enthalpically driven and classical hydrophobic interactions do not appear to be important in the binding reaction.