Research Projects - Quantum Biology
Many important biological processes taking place in cells are driven and controlled by events that involve electronic degrees of freedom and, therefore, require a quantum mechanical description. An important example are enzymatically catalyzed, cellular biochemical reactions. Here, bond breaking and bond formation events are intimately tied to changes in the electronic degrees of freedom. Key events during photosynthesis in plants and energy metabolism in eucaryotes also warrant a quantum mechanical description - from the absorption of light in the form of photons by the photosynthetic apparatus to electron transfer processes sustaining the electrochemical membrane potential. Because of the importance of sensing light to both plants (for regulating vital functions) and animals (for vision), the interaction between light and biological photoreceptors is widespread in nature, and also requires a quantum mechanical description. A prime example is the protein rhodopsin which is present in the retina of the human eye and plays a key role in vision. Our computational tool are combined quantum mechanical/molecular (QM/MM) simulations, that allow to combine an electronic level description of the active region with a classical model of the environment provided by the remainder of the biomolecular system and solvent. This allows us to study the electronic level processes underlying these systems in their natural cellular environment.
In light-harvesting complexes, carotenoids act as light-absorbers in the blue-green region of the spectrum. Absorption of a photon is followed by rapid singlet excitation energy transfer to bacteriochlorophyll (BChl). In addition to their light-harvesting role, carotenoids photoprotect antenna complexes, i.e., they prevent the formation of photo-oxidizing singlet oxygen by quenching BChl triplet states through triplet excitation transfer. Light-harvesting and photoprotection by carotenoids is studied in Theoretical Biophysics Group in two proteins, the Light-Harvesting Complex II of Purple Bacteria, and the Peridinin-Chlorophyll-Protein of Dinoflagellates.
Papers
Atomic level structural and functional model of a bacterial photosynthetic membrane vesicle. Melih K. Sener, John D. Olsen, C. Neil Hunter, and Klaus Schulten. Proceedings of the National Academy of Sciences, USA, 104:15723-15728, 2007.
Comparison of the light harvesting networks of plant and cyanobacterial photosystem I. Melih K. Sener, Craig Jolley, Adam Ben-Shem, Petra Fromme, Nathan Nelson, Roberta Croce, and Klaus Schulten. Biophysical Journal, 89:1630-1642, 2005.
When light falls in LOV: A quantum mechanical/molecular mechanical study of photoexcitation in Phot-LOV1 of Chlamydomonas reinhardtii. Markus Dittrich, Peter L. Freddolino, and Klaus Schulten. Journal of Physical Chemistry B, 109:13006-13013, 2005.
ATP hydrolysis in the bTP and bDP catalytic sites of F1-ATPase. Markus Dittrich, Shigehiko Hayashi, and Klaus Schulten. Biophysical Journal, 87:2954-2967, 2004.
Role of hydrogen-bond network in energy storage of bacteriorhodopsin's light-driven proton pump revealed by ab initio normal mode analysis. Shigehiko Hayashi, Emad Tajkhorshid, Hideki Kandori, and Klaus Schulten. Journal of the American Chemical Society, 126:10516-10517, 2004.
Molecular dynamics simulation of bacteriorhodopsin's photoisomerization using ab initio forces for the excited chromophore. Shigehiko Hayashi, Emad Tajkhorshid, and Klaus Schulten. Biophysical Journal, 85:1440-1449, 2003.
A general random matrix approach to account for the effect of static disorder on the spectral properties of light harvesting systems. Melih Sener and Klaus Schulten. Physical Review E, 65:031916, 2002. (12 pages).
Structural determinants of spectral tuning in retinal proteins - bacteriorhodopsin vs sensory rhodopsin II. Shigehiko Hayashi, Emad Tajkhorshid, Eva Pebay-Peyroula, Antoine Royant, Ehud M. Landau, Javier Navarro, and Klaus Schulten. Journal of Physical Chemistry B, 105:10124-10131, 2001.
Kinetics of excitation migration and trapping in the photosynthetic unit of purple bacteria. Thorsten Ritz, Sanghyun Park, and Klaus Schulten. Journal of Physical Chemistry B, 105:8259-8267, 2001.
A model for photoreceptor-based magnetoreception in birds. Thorsten Ritz, Salih Adem, and Klaus Schulten. Biophysical Journal, 78:707-718, 2000.