Interaction of ethidium bromide with heparin.

Area of Science:

• Biochemistry
• Chemical Kinetics
• Molecular Biophysics

Background:

• Ethidium bromide is a fluorescent intercalating agent used to stain nucleic acids.
• Heparin is a highly sulfated glycosaminoglycan anticoagulant.
• Understanding drug-biopolymer interactions is crucial for pharmacology.

Purpose of the Study:

• To investigate the binding of ethidium bromide to heparin using pulse radiolysis.
• To determine the effect of salt concentration and cation type on ethidium bromide-heparin complex dissociation.
• To elucidate the thermodynamic parameters of ethidium bromide-heparin interaction.

Main Methods:

• Pulse radiolysis was employed to generate hydrated electrons.
• The reaction of hydrated electrons was used to probe ethidium bromide binding to heparin.
• Complex dissociation was studied by varying salt concentrations and cation valency.
• Thermodynamic parameters were determined through temperature-dependent pulse-radiolysis experiments.

Main Results:

• Ethidium bromide forms complexes with heparin.
• Salt effectively dissociates ethidium bromide-heparin complexes.
• Divalent cations are more efficient than monovalent cations in dissociating the complexes.
• Thermodynamic parameters were found to be deltaH' = 11-6 kcal mole-1 and deltaS' = 42-6 cal deg-1 mole-1.

Conclusions:

• Pulse radiolysis is a viable method for studying ethidium bromide-heparin interactions.
• The binding is influenced by ionic strength and cation charge.
• The thermodynamic data provide insights into the nature of the ethidium bromide-heparin complex.