Absorption spectra of the purple nonsulfur bacteria light-harvesting complex: a DFT study of the B800 part

• Main Authors: Begunovich, L. V, Kovaleva, E. A, Korshunov, M. M, Shabanov, V. F
• Format: Journal Article
• Language: English
• Published: 03-11-2023
• Subjects: Physics - Atomic and Molecular Clusters; Physics - Biological Physics; Physics - Chemical Physics; Physics - Quantum Physics
• DOI: 10.48550/arxiv.2311.02024

Journal of Photochemistry & Photobiology, A: Chemistry 450, 115454
(2024) We've studied the B800 part of Rhodoblastus acidophilus light-harvesting
complex (LH2) by several quantum chemical techniques based on the density
functional theory (DFT) and determined the specific method and a minimal
reliable model suitable for further studies of the LH2. In addition to
bacteriochlorophyll a molecules, the minimal model includes two $\alpha$ and
one $\beta$ chain amino acids. Within the model, we are able to reproduce the
contribution of the B800 ring of nine bacteriochlorophyll a molecules to the
near infrared $Q_y$ absorption band. We also discuss the use of hybrid DFT
calculations for precise energy and optical estimations and DFT-based tight
binding (DFTB) method for the large-scale calculations. Crucial importance of
Hartree-Fock exchange interaction for the correct description of B800 peak
position was shown.