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Photoisomerization acceleration in retinal protonated Schiff-base models
Adalgisa Sinicropi1, Annapaola Migani, Luca De Vico
1Dipartimento di Chimica, Università di Siena, via Aldo Moro, I-53100 Siena, Italy.
Summary
Structural factors can accelerate the cis-trans isomerization of the 11-cis retinal chromophore. These factors, including chain shortening and twisting, enhance excited-state decay in rhodopsin models.
Area of Science:
- Computational chemistry
- Photochemistry
- Molecular biophysics
Background:
- Rhodopsin's visual pigment function relies on the 11-cis retinal chromophore's photoisomerization.
- Understanding the excited-state decay mechanisms is crucial for visual pigment function.
Purpose of the Study:
- To investigate computational models of the 11-cis retinal chromophore.
- To identify structural and environmental factors influencing excited-state decay and cis-trans isomerization.
Main Methods:
- CASSCF/6-31G* computational methods were employed.
- Photoisomerization pathways of model chromophores were analyzed.
- Protonated Schiff-base models were utilized to simulate environmental factors.
Main Results:
- Certain structural modifications and intramolecular interactions accelerate excited-state decay.
- Reducing conjugated chain length, twisting the chain, and ring locking were identified as key factors.
- These factors increase the excited-state surface slope and enhance mode coupling.
Conclusions:
- Structural and environmental factors can significantly influence the speed of cis-trans isomerization in the retinal chromophore.
- The principles observed in computational models may explain protein catalysis in rhodopsin.
- This research provides insights into the molecular mechanisms of vision.