First hyperpolarizability of bacteriorhodopsin, retinal and related molecules revisited

The previously reported β values of BR and retinal based chromophores were very high but subsequent measurements found them to be much less. We have found that the β values of these compounds do not vary so much with experimental conditions as with the method of analysis. Hyper-Rayleigh scattering measurements at 1543 and 1907 nm produce more realistic β values close to the intrinsic (static) hyperpolarizability, β0 which for BR is still very high (275 × 10−30 esu). The optical nonlinearity of BR arises entirely due to the protonated retinal Schiff Base (PRSB) which in its isolated form has the same intrinsic hyperpolarizability as that of the protein.

Graphical abstractThe first hyperpolarizabilities of bacteriorhodopsin, retinal and related chromophores have been revisited and found to be much less compared to what were reported earlier. Dispersion curves for BR and other chromophores.Download full-size image