Nonlinear optical properties of bacteriorhodopsin: assignment of the third-order polarizability based on two-photon absorption spectroscopy

Robert R. Birge; M. B. Masthay; Jeffrey A. Stuart; Jack R. Tallent; Chian-Fan Zhang

doi:10.1117/12.44213

1 June 1991 Nonlinear optical properties of bacteriorhodopsin: assignment of the third-order polarizability based on two-photon absorption spectroscopy

Robert R. Birge, M. B. Masthay, Jeffrey A. Stuart, Jack R. Tallent, Chian-Fan Zhang

Author Affiliations +

Proceedings Volume 1432, Biomolecular Spectroscopy II; (1991) https://doi.org/10.1117/12.44213
Event: Optics, Electro-Optics, and Laser Applications in Science and Engineering, 1991, Los Angeles, CA, United States

Abstract

The third-order (pi) -electron polarizability, (gamma) (pi), of bacteriorhodopsin in the 0.0 - 1.2 eV optical region is assigned based on an analysis of the experimental two-photon properties of the low-lying singlet state manifold. The following selected values of (gamma) (pi) (units of 10-36 esu) are observed: (gamma) (0;0,0,0) equals 2482 +/- 327; (gamma) (-3(omega) ;(omega) ,(omega) ,(omega) ) equals 2976 +/- 385 ((omega) equals 0.25 eV), 5867 +/- 704 ((omega) = 0.5 eV), 14863 +/- 1614 ((omega) = 0.66 eV), 15817 +/- 2314 ((omega) equals 1.0 eV), 10755 +/- 1733 ((omega) equals 1.17 eV). The third-order polarizability of this protein which contains an all-trans retinyl protonated Schiff base chromophore with six double bonds, is comparable to that observed for much longer chain polyenes (for example, dodecapreno (beta) -carotene, a polyene with 19 double bonds, exhibits a third-order (pi) -electron polarizability at 0.66 eV of 17000 +/- 6000 X 10-36 esu. The authors attribute the enhanced third-order nonlinearity associated with the protein bound chromophore of bacteriorhodopsin to two mutually enhancing origins. First, the chromophore is protonated, and the resultant charge reorganization enhances the polarizability in a fashion that is similar to that known to occur for polaronic and bipolaronic chromophores. It is estimated that protonation generates a five-fold enhancement in (gamma) (pi). Second, the protein bound chromophore exhibits a large change in dipole moment upon excitation into the lowest-lying, strongly-allowed 1B*u+-like state ((Delta) (mu) = 13.5 D). The latter property is responsible for a Type III enhancement of the third-order polarizability, and yields at least a 20-fold increase in (gamma) (pi).

Citation Download Citation

Robert R. Birge, M. B. Masthay, Jeffrey A. Stuart, Jack R. Tallent, and Chian-Fan Zhang "Nonlinear optical properties of bacteriorhodopsin: assignment of the third-order polarizability based on two-photon absorption spectroscopy", Proc. SPIE 1432, Biomolecular Spectroscopy II, (1 June 1991); https://doi.org/10.1117/12.44213

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