  To study the correlation between internal protein dynamics and protein
functionality of bacteriorhodopsin, we have performed time-resolved
quasielastic neutron scattering (QENS) experiments combined with in situ laser
activation of protein function. A set of purple membrane samples with different
lamellar lattice constants and, hence, different hydration levels has been
examined at different time delays between the laser and neutron pulses. While
the water content affected the lineshapes of QENS spectra, the laser-induced
response remained constant within the accuracy of the method.
