TY - JOUR T1 - Optical rotation of the second harmonic radiation from retinal in bacteriorhodopsin monomers in Langmuir-Blodgett film: evidence for nonplanar retinal structure. JF - Biophysical journal Y1 - 1997 A1 - Volkov, V. V. A1 - Svirko, Y P A1 - Kamalov, Valey F. A1 - Song, Li A1 - El-Sayed, Mostafa A KW - Bacteriorhodopsins KW - Biophysical Phenomena KW - Biophysics KW - Circular Dichroism KW - Molecular Structure KW - Optics and Photonics KW - Retinaldehyde KW - Spectrophotometry AB - We observed optical rotation of the plane of polarization of the second harmonic (SH) radiation at 532 nm (in resonance with the retinal absorption) generated in reflection geometry in Langmuir-Blodgett film of bacteriorhodopsin (bR). The analysis of the experimental data showed that this effect arises from the nonvanishing contribution of the antisymmetrical part of the hyperpolarizability tensor. This requires that the dipole moment of the resonant electronic transition, the change of the dipole moment upon electronic excitation, and the long axis of the retinal not be coplanar. Such conditions are satisfied only if the retinal has a nonplanar geometry, a conclusion that could lend support to the heterogeneity model of the origin of the biphasic band shape of the linear CD spectrum of the retinal in bR. On the basis of our theoretical analysis, we were able to estimate the angle between the induced dipole moment and the plan that contains the long axis of the chromophore and the transition dipole moment of the retinal absorption. VL - 73 CP - 6 U1 - http://www.ncbi.nlm.nih.gov/pubmed/9414228?dopt=Abstract M3 - 10.1016/S0006-3495(97)78342-5 ER -