The grant for 1 million supercomputing hours, known as an INCITE grant, was awarded by the DOE's Office of Science and is one of just three such awards granted. The project focuses on the electronic structure of carotenoids, a natural compound found in plants and eyes that is important in mitigating free radical cell damage to cells exposed to strong light. Read more about the NERSC INCITE project in the Berkeley Lab View

Carotenoids are nature’s chemical of choice for protection against chemical damage to cells and tissues by radical species such as singlet oxygen. Damage is a particularly acute problem in cells exposed to strong light, and cartotenoids are prevalent in leaves and also in our eyes for this reason. In photosynthesis, the most important function of carotenoids is the quenching of triplet chlorophyll molecules, which would otherwise generate singlet oxygen, damaging or even killing the plant. Specific carotenoids also play a role in regulating the efficiency of photosynthesis.

Despite their importance, the mechanism by which carotenoids achieve photoprotection is not well understood, in large measure because the relevant excited states cannot be studied directly by optical spectroscopy. Electronic structure calculations are necessary to understand the way in which carotenoids function, yet their electronic structure is complex, and calculations without uncontrolled approximations appeared beyond the current state-of-the art in quantum chemistry. The development of Quantum Monte Carlo (QMC) methods by Phillip Lester and others (in particular the diffusion QMC method) allows electronic structure calculations for carotenoids free of the usual approximations and limitations of standard methods.

The QMC method requires enormous computing power (for a typical carotenoid about 80,000 NERSC hours per state), but it is capable of experimental accuracy. The planned calculations will be the larges rigorous ab initio calculations performed to date on molecular systems. We will also calculate chlorophyll excited states and thus explore the carotenoids-chlorophyll interactions that lie at the heart of their function. Fleming expects theresults to provide a benchmark for accurate calculations of the electronic structure of biomolecules.