Effect of amphotericin B on membranes: a spin probe study

Area of Science:

• Biochemistry
• Membrane Biophysics
• Pharmacology

Background:

• Amphotericin B is a polyene antibiotic used to treat fungal infections.
• Its mechanism of action in biological membranes is not fully understood.
• Pore models have been proposed to explain its membrane interactions.

Purpose of the Study:

• To investigate the effects of amphotericin B on model membranes using electron paramagnetic resonance (EPR) spectroscopy.
• To examine the interaction of amphotericin B with lipid probes within model membranes.
• To evaluate existing pore models for amphotericin B membrane interactions.

Main Methods:

• Utilized electron paramagnetic resonance (EPR) spectroscopy to analyze lipid probes in model membranes.
• Incorporated amphotericin B during membrane preparation and added it to the aqueous phase separately.
• Employed a spin probe that partitions between aqueous and membrane phases.

Main Results:

• Incorporating amphotericin B during membrane preparation induced spectral changes indicative of a new phase.
• No spectral effects were observed when amphotericin B was added to the aqueous phase post-membrane formation.
• An interaction between amphotericin B and the spin probe was detected in the aqueous phase, not within the membrane.
• Observed slow achievement of some equilibria involving amphotericin B.

Conclusions:

• The observed spectral changes do not fully support previously proposed pore models for amphotericin B.
• Amphotericin B's interaction with lipid probes occurs in the aqueous phase with aggregated antibiotic.
• The method of antibiotic incorporation significantly influences its effect on model membrane structure and probe interactions.