Benchmarking calculations of excitonic couplings between bacteriochlorophylls

Abstract

Excitonic couplings between (bacterio)chlorophyll molecules are necessary for simulating energy transport in photosynthetic complexes. Many techniques for calculating the couplings are in use, from the simple (but inaccurate) point-dipole approximation to fully quantum-chemical methods. We compared several approximations to determine their range of applicability, noting that the propagation of experimental uncertainties poses a fundamental limit on the achievable accuracy. In particular, the uncertainty in crystallographic coordinates yields an uncertainty of about 20% in the calculated couplings. Because quantum-chemical corrections are smaller than 20% in most biologically relevant cases, their considerable computational cost is rarely justified. We therefore recommend the electrostatic TrEsp method across the entire range of molecular separations and orientations because its cost is minimal and it generally agrees with quantum-chemical calculations to better than the geometric uncertainty. We also caution against computationally optimizing a crystal structure before calculating couplings, as it can lead to large, uncontrollable errors. Understanding the unavoidable uncertainties can guard against striving for unrealistic precision; at the same time, detailed benchmarks can allow important qualitative questions--which do not depend on the precise values of the simulation parameters--to be addressed with greater confidence about the conclusions.

References in corpus (4)

• Atomistic study of the long-lived quantum coherences in the Fenna-Matthews-Olson complex
• Calculations of the Exciton Coupling Elements Between the DNA Bases Using the Transition Density Cube Method
• Theoretical characterization of excitation energy transfer in chlorosome light-harvesting antennae from green sulfur bacteria
• Ab-Initio Calculation of Molecular Aggregation Effects: a Coumarin-343 Case Study

Cited by in corpus (4)

• Delocalized excitons in natural light harvesting complexes
• Distinguishing the roles of energy funnelling and delocalization in photosynthetic light harvesting
• Geometry, supertransfer, and optimality in the light harvesting of purple bacteria
• The minimal model of light harvesting complex with dipole-quadrupole interaction derived from ab initio calculation