In photosynthesis, absorbed light energy transfers through a network of antenna proteins with nea... more In photosynthesis, absorbed light energy transfers through a network of antenna proteins with near-unity quantum efficiency to reach the reaction center, which initiates the downstream biochemical reactions. While the energy transfer dynamics within individual antenna proteins have been extensively studied over the past decades, the dynamics between the proteins are poorly understood due to the heterogeneous organization of the network. Previously reported timescales averaged over such heterogeneity, obscuring individual interprotein energy transfer steps. Here, we isolated and interrogated interprotein energy transfer by embedding two variants of the primary antenna protein from purple bacteria, light-harvesting complex 2 (LH2), together into a near-native membrane disc, known as a nanodisc. We integrated ultrafast transient absorption spectroscopy, quantum dynamics simulations, and cryogenic electron microscopy to determine interprotein energy transfer timescales. By varying the d...
Photosynthesis is generally assumed to be initiated by a single photon1–3 from the Sun, which, as... more Photosynthesis is generally assumed to be initiated by a single photon1–3 from the Sun, which, as a weak light source, delivers at most a few tens of photons per nanometre squared per second within a chlorophyll absorption band1. Yet much experimental and theoretical work over the past 40 years has explored the events during photosynthesis subsequent to absorption of light from intense, ultrashort laser pulses2–15. Here, we use single photons to excite under ambient conditions the light-harvesting 2 (LH2) complex of the purple bacterium Rhodobacter sphaeroides, comprising B800 and B850 rings that contain 9 and 18 bacteriochlorophyll molecules, respectively. Excitation of the B800 ring leads to electronic energy transfer to the B850 ring in approximately 0.7 ps, followed by rapid B850-to-B850 energy transfer on an approximately 100-fs timescale and light emission at 850–875 nm (refs. 16–19). Using a heralded single-photon source20,21 along with coincidence counting, we establish time...
Using a unique approach to solar energy conversion, photosynthetic organisms have developed a lig... more Using a unique approach to solar energy conversion, photosynthetic organisms have developed a light-harvesting process with near unity quantum efficiency. Light-harvesting proteins transfer energy from the sun to reach a central location, the reaction center, where charge separation occurs and energy is converted to chemical energy. Moreover, these proteins are able to carry out this efficient transfer in cellular membranes despite the complex environment found in these membranes. Particularly, light-harvesting in photosynthetic purple bacteria uses a diverse set of tools from species to species to efficiently transfer energy through this protein network. Induced by their habitats, external environmental pressures on the fitness of purple bacteria have caused species to evolve different mechanisms in order to deal with thesel pressures. Although these complexes have been studied for some time, there is still very little known about particular species. Additionally, most previous wor...
Photosynthetic purple bacteria convert solar energy to chemical energy with near unity quantum ef... more Photosynthetic purple bacteria convert solar energy to chemical energy with near unity quantum efficiency. The light-harvesting process begins with absorption of solar energy by an antenna protein called Light-Harvesting Complex 2 (LH2). Energy is subsequently transferred within LH2 and then through a network of additional light-harvesting proteins to a central location, termed the reaction center, where charge separation occurs. The energy transfer dynamics of LH2 are highly sensitive to intermolecular distances and relative organizations. As a result, minor structural perturbations can cause significant changes in these dynamics. Previous experiments have primarily been performed in two ways. One uses non-native samples where LH2 is solubilized in detergent, which can alter protein structure. The other uses complex membranes that contain multiple proteins within a large lipid area, which make it difficult to identify and distinguish perturbations caused by protein-protein interact...
In photosynthesis, absorbed light energy transfers through a network of antenna proteins with nea... more In photosynthesis, absorbed light energy transfers through a network of antenna proteins with near-unity quantum efficiency to reach the reaction center, which initiates the downstream biochemical reactions. While the energy transfer dynamics within individual antenna proteins have been extensively studied over the past decades, the dynamics between the proteins are poorly understood due to the heterogeneous organization of the network. Previously reported timescales averaged over such heterogeneity, obscuring individual interprotein energy transfer steps. Here, we isolated and interrogated interprotein energy transfer by embedding two variants of the primary antenna protein from purple bacteria, light-harvesting complex 2 (LH2), together into a near-native membrane disc, known as a nanodisc. We integrated ultrafast transient absorption spectroscopy, quantum dynamics simulations, and cryogenic electron microscopy to determine interprotein energy transfer timescales. By varying the d...
Photosynthesis is generally assumed to be initiated by a single photon1–3 from the Sun, which, as... more Photosynthesis is generally assumed to be initiated by a single photon1–3 from the Sun, which, as a weak light source, delivers at most a few tens of photons per nanometre squared per second within a chlorophyll absorption band1. Yet much experimental and theoretical work over the past 40 years has explored the events during photosynthesis subsequent to absorption of light from intense, ultrashort laser pulses2–15. Here, we use single photons to excite under ambient conditions the light-harvesting 2 (LH2) complex of the purple bacterium Rhodobacter sphaeroides, comprising B800 and B850 rings that contain 9 and 18 bacteriochlorophyll molecules, respectively. Excitation of the B800 ring leads to electronic energy transfer to the B850 ring in approximately 0.7 ps, followed by rapid B850-to-B850 energy transfer on an approximately 100-fs timescale and light emission at 850–875 nm (refs. 16–19). Using a heralded single-photon source20,21 along with coincidence counting, we establish time...
Using a unique approach to solar energy conversion, photosynthetic organisms have developed a lig... more Using a unique approach to solar energy conversion, photosynthetic organisms have developed a light-harvesting process with near unity quantum efficiency. Light-harvesting proteins transfer energy from the sun to reach a central location, the reaction center, where charge separation occurs and energy is converted to chemical energy. Moreover, these proteins are able to carry out this efficient transfer in cellular membranes despite the complex environment found in these membranes. Particularly, light-harvesting in photosynthetic purple bacteria uses a diverse set of tools from species to species to efficiently transfer energy through this protein network. Induced by their habitats, external environmental pressures on the fitness of purple bacteria have caused species to evolve different mechanisms in order to deal with thesel pressures. Although these complexes have been studied for some time, there is still very little known about particular species. Additionally, most previous wor...
Photosynthetic purple bacteria convert solar energy to chemical energy with near unity quantum ef... more Photosynthetic purple bacteria convert solar energy to chemical energy with near unity quantum efficiency. The light-harvesting process begins with absorption of solar energy by an antenna protein called Light-Harvesting Complex 2 (LH2). Energy is subsequently transferred within LH2 and then through a network of additional light-harvesting proteins to a central location, termed the reaction center, where charge separation occurs. The energy transfer dynamics of LH2 are highly sensitive to intermolecular distances and relative organizations. As a result, minor structural perturbations can cause significant changes in these dynamics. Previous experiments have primarily been performed in two ways. One uses non-native samples where LH2 is solubilized in detergent, which can alter protein structure. The other uses complex membranes that contain multiple proteins within a large lipid area, which make it difficult to identify and distinguish perturbations caused by protein-protein interact...
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Papers by Ashley Tong