Tunneling through life.

Imagine being completely drained by the formation of holes all over your body. That is what a cell should feel when encountering the drug Amphotericin B. It is an antifungal agent typically used against athletes foot and systematically against life-threatening fungal diseases. Athletes foot is the kind of fungal infection one can get when walking barefoot in moisty places as saunas, bathhouses, swimming pool, etc. It is also called ringworm of the foot because of the holes appearing.

The compound is a natural product derived from a microorganism: Streptomyces nodosus. These are bacteria that often produce spores and have an "earthy" odor. Secondary metabolism in Streptomyces bacteria is responsible for a large range of antifungals, antibacterials, antiparasites, immunosuppressant and even herbicide or piscicide drugs. All involved in a survival instinct mechanism.

 

This fascinating molecule contains an hydrophobic part made up of double bonds in a long carbon chain. The other part formed by the different hydroxyl groups is hydrophilic.

The fungal membrane cell is built of a lipidic bilayer. Several amphotericin molecules cluster together such that the alkene chains are to the exterior and interact favourably with the hydrophobic center of the cell membrane.

The tunnel resulting from this cluster is lined with the hydroxyl groups and so it is hydrophilic, allowing the polar (aqueous) contents of the cell to drain away.

This drug drills literally in the cell and because of forces as coalescence, electrostatic interactions and gradient concentration, every constituent is sucked out of it.