Abstract
Photosynthesis is a key process for converting light energy into chemical energy and providing food for lives on Earth. Understanding the mechanism for the energy transfers could provide insights into regulating energy transfers in photosynthesis and designing artificial photosynthesis systems. Many efforts have been devoted to exploring the mechanism of temperature variations affecting the excitonic properties of LH2. In this study, we performed all-atom molecular dynamics (MD) simulations and quantum mechanics calculations for LH2 complex from purple bacteria along with its membrane environment under three typical temperatures: 270, 300, and 330 K. The structural analysis from validated MD simulations showed that the higher temperature impaired interactions at N-terminus of both α and β polypeptide helices and led to the dissociation of this hetero polypeptide dimer. Rhodopin-β-D-glucosides (RG1) moved centripetally with α polypeptide helices when temperature increased and enlarged their distances with bacteriochlorophylls molecules that have the absorption peak at 850 nm (B850), which resulted in reducing the coupling strengths between RG1 and B850 molecules. The present study reported a cascading mechanism for temperature regulating the energy transfers in LH2 of purple bacteria.
Highlights
Photosynthesis is one of the most important bio-activities on the planet that converts light energy into chemical energy and stores in carbohydrate molecules by plants, algae, and photosynthetic bacteria
The molecular model of light-harvesting complex 2 (LH2) in molecular dynamics (MD) simulations reproduced the structural stabilities and essential intermolecular hydrogen bond interactions observed in the experimental data
Variations of the absorption spectrums for LH2 under different temperatures obtained from quantum mechanics (QM) calculations reproduced those experimentally measured ones, whose changes were attributed to the increased heterogeneity of the exactions for the pigment molecules
Summary
Photosynthesis is one of the most important bio-activities on the planet that converts light energy into chemical energy and stores in carbohydrate molecules by plants, algae, and photosynthetic bacteria. Many studies employed photosynthetic bacteria, such as purple bacteria, as the model for energy transfer apparatus in photosynthesis due to the simplicity and symmetry of their light harvesting systems as well as the similarity of their energy transfers to those in plants and algae (Cogdell et al, 2006; Shrestha and Jakubikova, 2015; Sisto et al, 2017; Cupellini et al, 2018). On the basis of the established energy transfer pathway, many efforts have been devoted to understand the mechanisms for regulating the energy transfers in LH2, which could provide vital information for designing artificial photosynthesis systems (Mirkovic et al, 2017)
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