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Inhaled anesthetic gas molecules travel through the lungs and blood to the brain. Barely soluble in water/blood, anesthetics are highly soluble in a particular lipid-like environment akin to olive oil. It turns out the brain is loaded with such stuff, both in lipid membranes and tiny water-free ("hydrophobic") lipid-like pockets within certain brain proteins. To make a long story short, Nicholas Franks and William Lieb at Imperial College in London showed in a series of articles in the 1980's that anesthetics act primarily in these tiny hydrophobic pockets in several types of brain proteins. The anesthetic binding is extremely weak and the pockets are only 1 /50 of each protein's volume, so it's unclear why such seemingly minimal interactions should have significant effects. Franks and Lieb suggested the mere presence of one anesthetic molecule per pocket per protein prevents the protein from changing shape to do its job. However subsequent evidence showed that certain other gas molecules could occupy the same pockets and not cause anesthesia (and in fact cause excitation or convulsions). Anesthetic molecules just "being there" can't account for anesthesia. Some natural process critical to consciousness and perturbed by anesthetics must be happening in the pockets. What could that be?
Anesthetic gases dissolve in hydrophobic pockets by extremely weak quantum mechanical forces known as London dispersion forces. The weak binding accounts for easy reversibility - as the anesthetic gas flow is turned off, concentrations drop in the breathing circuit and blood, anesthetic molecules are gently sucked out of the pockets and the patient wakes up. Weak but influential quantum London forces also occur in the hydrophobic pockets in the absence of anesthetics and govern normal protein movement and shape. A logical conclusion is that anesthetics perturb normally occurring quantum effects in hydrophobic pockets of brain proteins.