NMR properties of Fenna-Matthews-Olson light harvesting complex: Photosynthesis and its biomedical applications

In this article we study the structural properties of the bacteriochlorophyll taken from the Fenna-Matthews-Olson (FMO) light harvesting complex found in the green sulphur bacteria. This study is motivated by a range of applications of photosynthetic complexes, including their increasing role in biomedicine, where our better understanding of their properties become critical. Specifically, in our current study we present the nulcear magnetic resonance (NMR) spectrum of the bacteriochlorophyll that is directly taken from the FMO complex, as well as the spectrum for this system for its optimized geometry. We use density functional theory to calculate the optimized geometry and the NMR spectra of the bacteriochlorophyll. From our calculations we found that the chemical shift values are slightly lower for the optimized geometry of the bacteriochlorophyll than the values obtained for the unoptimized bacteriochlorophyll. The differences observed between these two spectra are due to the fact that the unoptimized structure of the bacteriochlorophyll possess the influence of the protein environment of FMO complex.