Kinetics of quinine-deuterohemin binding

Area of Science:

• Biochemistry
• Physical Chemistry
• Pharmacology

Background:

• Quinine's antimalarial effect is linked to its interaction with free hemin in erythrocytes.
• Understanding this interaction is crucial for developing effective antimalarial drugs.
• Hemin dimerization in solution affects drug-heme interactions.

Purpose of the Study:

• To investigate the kinetics of quinine-deuterohemin complex formation.
• To analyze the influence of solvent composition and pH on binding kinetics.
• To elucidate the mechanism of quinine binding to hemin species.

Main Methods:

• Temperature jump relaxation spectroscopy was employed to study reaction kinetics.
• Ethyleneglycol-water mixtures were used as solvents to control hemin solubility and dimerization.
• Kinetic and equilibrium data were collected at varying solvent compositions and pH.

Main Results:

• Quinine binding to deuterohemin is a relatively slow process compared to hemin dimerization.
• A 1:1 complex formation mechanism was proposed for quinine and deuterohemin.
• Binding kinetics showed significant pH dependence, with rates decreasing as pH increased.

Conclusions:

• The study provides kinetic insights into quinine-hemin interactions relevant to antimalarial activity.
• Different hemin species (monomeric vs. dimeric) exhibit distinct reactivities.
• The findings contribute to understanding the molecular mechanisms of quinoline-based antimalarial drugs.