PROMISCUOUS LIGANDS AND ATTRACTIVE CAVITIES

A group of ~500 soluble proteins in the PDB (PDBselect) were analyzed for the presence and volume of internal cavities, and this figure shows the results for the largest cavity found in each. Note that most proteins only have small cavities (~40-50 cubic angstroms), but around 10% have internal cavities which could fit typical inhaled anesthetics (~150 cubic angstroms), as indicated by the red line. Note that this simple analysis does not include membrane proteins that generally have larger cavities, nor does it include open hydrophobic pockets on the proteins, which may also bind anesthetics, albeit more weakly.