Substrate-assisted laser-initiated ejection of proteins embedded in water films

Molecular dynamics simulations have been employed to investigate laser initiated liftoff of the protein enkephalin embedded in a H₂O film adsorbed onto a gold substrate. The laser energy is deposited solely into the gold substrate at different heating rates. For fast heating rates on the picosecond time scale, the results show that large clusters of the H₂O molecules are ejected from the film entraining the enkephalin molecule away from the metal surface. For heating on the nanosecond time scale, the H₂O overlayer evaporates in the form of individual molecules and small clusters that are unable to entrain the enkephalin molecule.