A spectroscopic approach to the solvation of anesthetics in jets: propofol(H2O)n, n = 4-6.

Propofol is a widely used nonvolatile anesthetic that exerts its action by docking to GABAA receptors. The docking process is a competition between solvation of the anesthetic by the extracellular medium and the stabilization inside the active site, and therefore a deep knowledge of the process requires of a good understanding of the solvation process. In this work we create propofol-water complexes containing up to six water molecules using supersonic expansions. We determine their structure by means of a number of mass-resolved laser-based excitation spectroscopic techniques, namely two-color REMPI, UV/UV, and IR/UV double resonance techniques, combined with computational chemistry. The results clearly show that water tends to self-aggregate, interacting with the hydrophilic side of propofol. Furthermore, a transition from planar to three-dimensional structures is observed in propofol(H2O)6. Comparison with structural data from similar systems such as phenol-water and pure water clusters follows.