Proteoliposomes as energy transferring nanomaterials: enhancing the spectral range of light-harvesting proteins using lipid-linked chromophores

Abstract

Self-assembled proteoliposomes allow highly efficient energy transfer from the spectrally-complementary chromophore Texas Red to the plant light-harvesting protein LHCII, increasing the effective absorption range of this bio-hybrid system.

Understanding the photophysics and structural organization of photosynthetic proteins using model lipid membranes assembled from natural plant thylakoids

“…The fluorescence intensity of hybrid membranes was compared to the fluorescence intensity of control samples containing a known amount of photosynthetic proteins, whilst taking into account changes in the level of quenching and keeping consistent acquisition parameters. A control sample of "LHCII proteoliposomes" was prepared from a defined quantity of purified LHCII and natural thylakoid lipids, as previously described 41 . The density of proteins in hybrid membranes was then calculated in terms of "LHCII equivalents" in a three stage calculation process.…”

“…77,78 The excellent amenability of hybrid membranes to FLIM and AFM allowed us to explain their resulting structure and photophysical properties by imaging the self-assembly of lipids and photosynthetic proteins onto the solid surface in real time. In future, it may be possible to take advantage of the self-assembly mechanism to introduce additional lipophilic components, in order to enhance the photosynthetic activity to generate idealized designs of membranes (e.g., broadening the spectral range with additional pigments 41 ). We found that the hydrophobic edge of the lipid corral and the admixture of DOPC liposomes promoted the formation of flat and contiguous membranes, even with the challenging starting material of extracted thylakoids (possibly due to an energy minimization considerations 56,79 ).…”

“…18 LHCII proteoliposomes were prepared by combining specified quantifies of lipids, detergent and purified LHCII protein in an aquesous buffer and then inducing the self-assembly of membranes by removing the detergent using Biobeads, as described previously. 41 Lipid vesicles, required for hybrid membranes formations, were formed from high purity 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) lipids following standard probe sonication procedures, with Texas Red lipids (Texas Red 1,2-dihexadecanoyl-snglycero-3-phosphoethanolamine) included only when tracking lipids was required.…”

“…The photophysical properties of LH proteins have also been studied utilizing nanoscale array patterns of proteins on solid surfaces [33][34][35] and LH proteins incorporated into model membranes (proteoliposomes). 21,[36][37][38][39][40][41] These model systems offer several advantages as platform to study the inherent physicochemical properties of the proteins, such as providing precise control over protein arrangement, known membrane composition and the incorporation of specific lipids to help maintain protein stability. 38,42 However, many of these models require extensive biochemical purification, chemical alteration of the protein or the support surface, and/or removal of the native lipids, any of which may affect the stability and photophysical state of LH and PS proteins.…”

Membrane Protein Modified Electrodes in Bioelectrocatalysis

“…Another limitation of biophotoelectrodes is that photosynthetic proteins only use a limited range of the solar spectrum which reduces solar conversion efficiency. The absorption spectral range can be enhanced by attaching complementary chromophores to light-harvesting complex proteins [188]. It also can be improved by integrating biological light-harvesting antenna complexes or organic dyes/synthetic compounds to the RCs [189,190].…”