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  Calculating Absorption Shifts for Retinal Proteins:  Computational Challenges

Wanko, M., Hoffmann, M., Strodel, P., Koslowski, A., Thiel, W., Neese, F., et al. (2005). Calculating Absorption Shifts for Retinal Proteins:  Computational Challenges. The Journal of Physical Chemistry B, 109(8), 3606-3615. doi:10.1021/jp0463060.

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Wanko, M.1, Author
Hoffmann, M.1, Author
Strodel, P.1, 2, Author
Koslowski, A.3, Author              
Thiel, W.3, Author              
Neese, F.4, Author              
Frauenheim, T.1, Author
Elstner, M.1, 2, Author
Affiliations:
1Department of Theoretical Physics, University of Paderborn, D-33098 Paderborn, Germany, ou_persistent22              
2Department of Molecular Biophysics, German Cancer Research Center, D-60120 Heidelberg, Germany, ou_persistent22              
3Research Department Thiel, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445590              
4Research Department Wieghardt, Max Planck Institute for Bioinorganic Chemistry, Max Planck Society, ou_3023881              

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 Abstract: Rhodopsins can modulate the optical properties of their chromophores over a wide range of wavelengths. The mechanism for this spectral tuning is based on the response of the retinal chromophore to external stress and the interaction with the charged, polar, and polarizable amino acids of the protein environment and is connected to its large change in dipole moment upon excitation, its large electronic polarizability, and its structural flexibility. In this work, we investigate the accuracy of computational approaches for modeling changes in absorption energies with respect to changes in geometry and applied external electric fields. We illustrate the high sensitivity of absorption energies on the ground-state structure of retinal, which varies significantly with the computational method used for geometry optimization. The response to external fields, in particular to point charges which model the protein environment in combined quantum mechanical/molecular mechanical (QM/MM) applications, is a crucial feature, which is not properly represented by previously used methods, such as time-dependent density functional theory (TDDFT), complete active space self-consistent field (CASSCF), and Hartree-Fock (HF) or semiempirical configuration interaction singles (CIS). This is discussed in detail for bacteriorhodopsin (bR), a protein which blue-shifts retinal gas-phase excitation energy by about 0.5 eV. As a result of this study, we propose a procedure which combines structure optimization or molecular dynamics simulation using DFT methods with a semiempirical or ab initio multireference configuration interaction treatment of the excitation energies. Using a conventional QM/MM point charge representation of the protein environment, we obtain an absorption energy for bR of 2.34 eV. This result is already close to the experimental value of 2.18 eV, even without considering the effects of protein polarization, differential dispersion, and conformational sampling.

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Language(s): eng - English
 Dates: 2004-08-162005-01-282005-03-01
 Publication Status: Published in print
 Pages: 10
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1021/jp0463060
 Degree: -

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Title: The Journal of Physical Chemistry B
  Abbreviation : J. Phys. Chem. B
Source Genre: Journal
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Publ. Info: Washington, D.C. : American Chemical Society
Pages: - Volume / Issue: 109 (8) Sequence Number: - Start / End Page: 3606 - 3615 Identifier: ISSN: 1520-6106
CoNE: https://pure.mpg.de/cone/journals/resource/1000000000293370_1