Ultrafast energy transfer between self-assembled fluorophore and photosynthetic light-harvesting complex 2 (LH2) in lipid bilayer

Abstract

Photosynthetic light-harvesting (LH) systems consist of photosynthetic pigments, which are non-covalently self-assembled with protein scaffolds in many phototrophs and attain highly efficient excitation energy transfer via ultrafast dynamics. In this study, we constructed a biohybrid LH system composed of an LH complex (LH2) from Rhodoblastus acidophilus strain 10050 and a hydrophobic fluorophore ATTO647N (ATTO) as an extrinsic antenna in the lipid bilayer. Through the addition of ATTOs into a solution of LH2-reconstituted lipid vesicles, ATTOs were incorporated into the hydrophobic interior of the lipid bilayer to configure the non-covalently self-assembled biohybrid LH. Steady-state fluorescence spectroscopy clearly showed efficient energy transfer from ATTO to B850 bacteriochlorophylls in LH2. Femtosecond transient absorption spectroscopy revealed that the energy transfer took place in the time range of 3–13 ps, comparable to that of the covalently linked LH2-ATTO that we previously reported. In addition, the biohybrid LH system exhibited a much higher antenna effect than the LH2-ATTO system because of the higher loading level of ATTO in the membrane. These findings suggest that the facile self-assembled biohybrid LH system is a promising system for constructing LH for solar-energy conversion.

Functional Coupling of Biohybrid Photosynthetic Antennae and Reaction Center Complexes: Quantitative Comparison with Native Antennae

“…As reported in our previous study, the rate and yield of energy transfer from the AT647N to B800/B850 are faster and considerably higher (τ av = 6.0 ps, 78% yield) than those from A647 to B800/B850 (τ av = 10 ps, 44% yield) when the biohybrid LH2s are reconstituted into a lipid bilayer. 21 The hydrophobic dye AT647N was incorporated in the hydrophobic interior of the lipid bilayer, 48,49 in which AT647N was located near the acceptor B800/B850, which resulted in the fast and efficient energy transfer. 21 Meanwhile, the hydrophilic dye, A647, was placed in the hydrophilic area apart from the B800/B850.…”

Enhancing the spectral range of plant and bacterial Light-Harvesting pigment-protein complexes with various synthetic chromophores incorporated into lipid vesicles

“…The bulk lipid used for preparing samples for plant LHCII was soy asolectin lipid extract, whereas, the bulk lipid was DOPG for bacterial LH2. These lipids were chosen because they were previously established to provide a stable membrane environment for these specific protein complexes [33][34][35]. Aliquots of ~0.5 mg dry lipid mixture (as prepared above) were solubilised with an aqueous buffer of 0.5% α-DDM, 20 mM HEPES (pH 7.5) at room temperature for 12-16 hr with agitation to generate a mixed micellar lipid-DDM solution to a detergent-to-lipid molar ratio of ~9:1.…”