Resolving the dynamic structure of chlorosomes in green sulfur bacteria by MAS NMR

Dsouza, L.A. (2026)

Doctoral Thesis

Understanding how nature captures and transfers solar energy is essential both for elucidating biological photosynthesis and for guiding the design of artificial light-harvesting systems. Chlorosomes from green sulfur bacteria represent the most extensive and efficient antenna assemblies known, allowing these organisms to survive in environments characterized by extremely low light intensity and the absence of oxygen. Although their functional performance is well recognized, the detailed molecular arrangement and dynamic behavior that govern their efficiency remain incompletely resolved. This thesis explores the structural organization and conformational dynamics of chlorosome antenna complexes from the green sulfur bacterium Chlorobaculum tepidum. Magic angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) spectroscopy serves as the principal investigative tool, enabling atomistic-level characterization of pigment packing and motion in systems that are not amenable to solution NMR or crystallographic methods. A range of advanced methodologies, including dynamic spectral editing (DYSE), homonuclear and heteronuclear recoupling experiments, and rotational echo double resonance (REDOR), is applied to differentiate rigid and mobile domains to quantify site-specific motions of bacteriochlorophyll assemblies and librational motion. Comparative analyses of wild-type Chlorobaculum tepidum and mutant strains bchQ and bchR demonstrate how modifications in pigment side-chain methylation affect supramolecular architecture and dynamic properties. Integration with cryo-electron microscopy and optical spectroscopy establishes correlations between molecular flexibility, structural organization, and light-harvesting function. The findings indicate that chlorosomes exhibit a balance between structural order and dynamic adaptability, a combination that is crucial for highly efficient excitonic energy transfer.

• Chlorosomes
• Green sulfur bacteria
• Solid-state NMR spectroscopy
• Magic angle spinning (MAS)
• Bacteriochlorophyll aggregation
• Light-harvesting dynamics

• All authors: Dsouza, L.A.
• Supervisor: Groot, H.J.M. de
• Co-supervisor: Sevink, G.J.A.
• Committee: Ubbink, M.; Jeuken, L.J.C.; Jansen, T.L.C.; Baldus, M.H.; Pandit, A.
• Qualification: Doctor (dr.)
• Awarding Institution: Leiden Institute of Chemistry (LIC), Faculty of Science, Leiden University
• Date: 2026-02-24