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Comparative microcalorimetric and dilatometric analysis of the interactions of quinacrine, chloroquine, and ethidium bromide with DNA
Author(s) -
Delben Franco,
Quadrifoglio Franco,
Giancotti Vincenzo,
Crescenzi Vittorio
Publication year - 1982
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.360210208
Subject(s) - ethidium bromide , chemistry , dna , intercalation (chemistry) , chloroquine , ionic bonding , ionic strength , molecule , biophysics , chromatography , aqueous solution , biochemistry , organic chemistry , ion , malaria , immunology , biology
The enthalpies of binding of chloroquine and quinacrine to DNA at different molar ratios of drug to DNA and at different ionic strengths have been measured. The limiting values obtained with quinacrine fall in the range found for typical intercalating agents (e.g., ethidium, proflavin, adriamycin), whereas the value obtained with chloroquine is always zero, independent of the ratio of drug to DNA and ionic strength. The dilatometric measurements performed on the same systems and on the ethidium–DNA system show that when ethidium and quinacrine bind to DNA at low drug/DNA ratios, a volume decrease of about 16 mL/mol of bound drug occurs. No change in volume is observed when the two drugs bind to DNA through external, electrostatic forces. The volume change can be attributed to the loss of structured water around hydrophobic moieties of the drug molecules, following intercalation. In contrast, chloroquine binding to DNA at low drug/DNA ratios is characterized by a volume change distinctly smaller than that shown by quinacrine. The low Δ V B and Δ H B values shown by chloroquine are discussed in terms of the mechanism of interaction with DNA.