Bacteriorhodopsin of purple membrane reverses anisotropy outside the pH range of proton pumping based on logic gate realization

Description

Hamdy Mostafa and Abdo Elfiki probe a light-sensing protein that behaves like a tiny logic device, in a 2024 paper. The protein, bacteriorhodopsin, sits in the purple membrane of a microbe and pumps protons when light hits it, a trick that makes it attractive for bioelectronic parts. Between mildly acidic and mildly alkaline conditions its electrical response holds steady while it pumps.

The authors ask what happens outside that working range. In strong acid the membrane turns blue, in strong alkali reddish, and at both extremes the protein's directional electrical bias most likely flips sign. That reversal suggests the protein could act as a switch whose state depends on acidity, a primitive logic gate. Such behavior, long studied since the protein's discovery in 1971, may guide designs for sensors and optical devices built from biological molecules.

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Source: https://europepmc.org/articles/PMC11603030