Biohybrid & Bioinspired Antennas: Design and Characterization
Photosynthetic organisms such as bacteria, algae and plants use antenna systems to capture light energy and transfer the energy to reaction centers (RCs) where photochemistry occurs. Antenna complexes are diverse structures that are highly specialized and optimized to allow photosynthetic organisms to capture the maximum light energy available in their environment. However, they do so in what are often strikingly different types of complexes, with different structural architectures and even different types of pigments. One step toward understanding how these disparate antenna systems function in an efficient manner is provided by detailed structural information, as studied under Theme 1. A parallel approach is to investigate natural antenna systems on well-defined surfaces, and other constructs that form biohybrid antennas. The latter approach is the main emphasis of Theme 2 research.
New tools have been developed that for the first time offer the exciting prospect of building such a synthetic membrane assembly, component-by-component. This is illustrated using the LH1 and LH2 complexes from purple photosynthetic bacteria. (Fig. 1). By controlling the spatial juxtaposition of light-harvesting and RC complexes, the plan is to explore the function of these membrane proteins from the bottom up, and to develop a quantitative understanding of the influence of antenna size, antenna geometry and the position and number of RCs in the system on energy transfer and trapping.
Neutron Scattering and Diffraction. Neutron scattering and diffraction provide detailed information on the structure and dynamics of biomaterials and systems across time and length scales that range from pico- to nano-second resolution and from 1-10,000 Å spatial resolution, respectively. Applications range from the atomic-resolution analysis of individual hydrogen atoms in enzymes through the meso- and macro-scale analysis of complex biological structures, substrates, scaffolds, membranes or assemblies. Because neutron scattering and diffraction techniques have not previously been used extensively to study photosynthetic antenna complexes, this represents a new territory for exploration. Neutron scattering is a powerful tool for characterization and analysis of complex structure function and interfacial relationships between membrane, polymer and macromolecular systems at the interface of Biology and Materials Science.
Microscopy of Natural & Biohybrid Antenna: Scanning Probe and Hyperspectral Imaging Confocal Microscopy. Both structural and functional information on natural light-harvesting systems can be obtained using state-of-the-art scanning probe microscopic techniques. The methods include atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM). Variants of the latter technique will be utilized with native light-harvesting complexes on patterned surfaces for the study of biohybrid antenna complexes (Fig. 3).
Hyperspectral confocal fluorescence microscopy (HCM) is a newly developed technique (Fig. 4). The emission wavelengths and spatial organization of the various photosynthetic pigments are very close together and until this technological advance, it was impossible to visualize their locations independently within the living cell. Both techniques will be applied to arrays of biohybrid antenna complexes.
Solar Cells Derived from Natural Antenna complexes. An example of this approach is best illustrated in Figure 5, which utilizes chlorosomes from green photosynthetic bacteria and incorporates columnar titanium oxide surfaces.
Structural information gained through Theme 2 research will underpin functional studies and synthetic strategies. One of the strengths of the PARC team is that it includes experts in a remarkable collection of methods that give structural and functional information of different sorts and at different levels of organization. Therefore, it is an essential part of the research plan.
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