Optical and electrical studies on dansyllysine-valinomycin in thin lipid membranes

Area of Science:

• Biophysical Chemistry
• Membrane Biophysics
• Ion Transport

Background:

• Valinomycin is a potassium ionophore crucial for membrane transport studies.
• Fluorescent analogues aid in visualizing and quantifying ionophore behavior within membranes.

Purpose of the Study:

• To synthesize and characterize dansyllysine-valinomycin, a fluorescent analogue of valinomycin.
• To determine the concentration and conductance contribution of this analogue within black lipid membranes.
• To compare its properties with unmodified valinomycin.

Main Methods:

• Synthesis of dansyllysine-valinomycin.
• Incorporation into diphytanoyllecithin black lipid membranes.
• Fluorometric measurement of internal concentration.
• Electrical relaxation experiments analyzed via a carrier model.
• Conductance measurements.

Main Results:

• Concentration measurements by fluorescence and electrical methods agreed within an order of magnitude.
• A conductance increment of approximately 3 x 10(-17) omega-1 per carrier molecule was determined.
• This conductance was ~400 times lower than unmodified valinomycin in different membrane compositions.
• The reduction is attributed primarily to altered membrane properties.

Conclusions:

• Dansyllysine-valinomycin serves as a viable fluorescent probe for ionophore studies in lipid membranes.
• Membrane composition significantly impacts ionophore conductance.
• The study provides quantitative data on modified ionophore behavior in artificial membranes.