The function of protein in long-range biological electron transfer is a question of debate. We report some preliminary results in femtosecond spectroscopic study of photosynthetic bacterial light-harvesting antenna co...The function of protein in long-range biological electron transfer is a question of debate. We report some preliminary results in femtosecond spectroscopic study of photosynthetic bacterial light-harvesting antenna complex assembled onto TiO2 nanoparticle with an average size of 8 nm in diameter. Crystal structure shows that photosynthetic bacterial antenna complex LH2 has a ring-like structure composed by alpha- and beta-apoprotein helices. The alpha- and beta-transmembrance helices construct two concentric cylinders with pigments bacteriochlorophyll a (Bchl a) and carotenoid (Car) buried inside the protein. We attempt to insert TiO2 nanoparticle into the cavity of the inner cylindrical hollow of LH2 to investigate the nature of the electron transfer between the excited-state Bchl a and the TiO2 nanoparticle. A significant decrease in the ground state bleaching recovery time constant for Bchl a at 850 run (B850) in respect to that of the Bchl a in free LH2 has been observed. By using the relation of distance-dependent long-range electron transfer rate in protein, the distance between the donor B850 and the acceptor TiO2 nanoparticle has been estimated, which is about 0.6 nm. The proposed method of assembling proteins onto wide-gap semiconductor nanoparticle can be a promising way to determine the role of the protein playing in biological electron transfer processes.展开更多
This paper provides a detailed introduction to and analysis of the course of China's technological innovation in liquid hydrogen/liquid oxygen(LH2/LOX)rocket engines from a historical point of view.It starts with ...This paper provides a detailed introduction to and analysis of the course of China's technological innovation in liquid hydrogen/liquid oxygen(LH2/LOX)rocket engines from a historical point of view.It starts with the investigation of LH2/LOX rocket engines by relevant departments of the Chinese Academy of Sciences in the 1960s and their preliminary achievements.Then,the policy decision concerning LH2/LOX engine development,the project approval of the Long March-3(Chang Zheng-3,CZ-3)rocket,and the process of developing LH2/LOX engines are analyzed in detail,followed by an introduction to and summary of the development situation and technical innovation characteristics of China's LH2/LOX engines as they grew from 4 tons to 8 tons,and finally to 50 tons.Finally,the paper briefly analyzes the innovation experience connected with China's LH2/LOX engines.展开更多
Energy transfers in two kinds of peripheral light-harvesting complexes （LH2） of Rhodobacter sphaeroides （RS） 601 are studied by using femtosecond pump^probe spectroscopy with tunable laser wavelength at room tempe...Energy transfers in two kinds of peripheral light-harvesting complexes （LH2） of Rhodobacter sphaeroides （RS） 601 are studied by using femtosecond pump^probe spectroscopy with tunable laser wavelength at room temperature. These two complexes are native LH2 （RS601） and green carotenoid mutated LH2 （GM309）. The obtained results demonstrate that, compared with spheroidenes with ten conjugated double bonds in native RS601, carotenoid in GM309 containing neurosporenes with nine conjugated double bonds can lead to a reduction in energy transfer rate in the B800-to-B850 band and the disturbance in the energy relaxation processes within the excitonic B850 band.展开更多
Interactions between the light-harvesting subunits and the non-covalently bound photopigments attribute considerably to the spectral properties of photosynthetic bacteria light-harvesting complexes. In our previous st...Interactions between the light-harvesting subunits and the non-covalently bound photopigments attribute considerably to the spectral properties of photosynthetic bacteria light-harvesting complexes. In our previous studies, we have constructed a novel Rhodobacter sphaeroides expression system. In the present study, we focus on the spectral properties of LH2 when heterologously express LH2 with β-subunit- GFP fusion protein in Rb. sphaeroides. Near infra-red spectrum of LH2 remained nearly unchanged as measured by spectroscopy. Fluorescence spectrum suggested that the LH2 with β-subunit-GFP fusion protein complexes still possessed normal activity in energy transfer. However, photopigments contents were significantly decreased to a very low level in the LH2 with β-subunit-GFP fusion protein complexes compared to that of LH2. FT-IR spectra indicated that interactions between photopigments and LH2 α/β- subunits appeared not to be changed. It was concluded that the LH2 spectral properties exhibited very similar even when heterologously expressed LH2 b-subunit fusion protein in Rb. sphaeroides. Our present study may supply a new insight into better understand the interactions between light-harvesting subunits and photopigments and bacterial photosynthesis and promote the development of the novel Rb. sphaeroides expression system.展开更多
Ultrafast anisotropic decay is a prominent parameter revealing ultrafast energy and electron transfer; however, it is dimcult to be determined reliably owing to the requirement of a simultaneous availability of the pa...Ultrafast anisotropic decay is a prominent parameter revealing ultrafast energy and electron transfer; however, it is dimcult to be determined reliably owing to the requirement of a simultaneous availability of the parallel and perpendieular polarized decay kinetics. Nowadays, any measurement of anisotropic decay is a kind of approach to the exact simultaneity. Here we report a novel method for a synchronous ultrafast anisotropy decay measurement, which can well determine the anisotropy, even at a very early time, as the rising phase of the excitation laser pulse. The anisotropic decay of the B850 in bacteriM light harvesting antenna complex LH2 of rhodobacter sphaeroides in solution at room temperature with coherent excitation is detected by this method, which shows a polarization response time of 30 fs, and the energy transfer from the initial excitation to the bacteriochlorophylls in B850 ring takes about 7Ors. The anisotropic decay that is probed at the red side of the absorption spectrum, such as 880 nm, has an initial value of 0.4, corresponding to simulated emission, while the blue side with an anisotropy of 0.1 contributes to the ground-state bleaching. Our results show that the coherent excitation covering the whole ring might not be realized owing to the symmetry breaking of LH2： from C9 symmetry in membrane to C2 symmetry in solution.展开更多
In this work,we study environment-assisted excitation energy transfer(EET) through calculating energy transfer efficiency(ETE) in LH1-RC-type and LH2-type trimers,which can be used to mimic energy transfer behaviors i...In this work,we study environment-assisted excitation energy transfer(EET) through calculating energy transfer efficiency(ETE) in LH1-RC-type and LH2-type trimers,which can be used to mimic energy transfer behaviors in the basic unit cells of LH1-RC and LH2 light-harvesting complexes.Quantum state evolution of the trimers is described by a non-Hermitian quantum master equation.ETE in these trimer systems is investigated by the use of numerical solutions at finite temperatures for the non-Hermitian master equation.We theoretically reveal the temperature-assisted ETE enhancement.It is found that highly efficient EET with nearly unit efficiency may occur in the nearby regime of the critical point of quantum phase transition.展开更多
文摘The function of protein in long-range biological electron transfer is a question of debate. We report some preliminary results in femtosecond spectroscopic study of photosynthetic bacterial light-harvesting antenna complex assembled onto TiO2 nanoparticle with an average size of 8 nm in diameter. Crystal structure shows that photosynthetic bacterial antenna complex LH2 has a ring-like structure composed by alpha- and beta-apoprotein helices. The alpha- and beta-transmembrance helices construct two concentric cylinders with pigments bacteriochlorophyll a (Bchl a) and carotenoid (Car) buried inside the protein. We attempt to insert TiO2 nanoparticle into the cavity of the inner cylindrical hollow of LH2 to investigate the nature of the electron transfer between the excited-state Bchl a and the TiO2 nanoparticle. A significant decrease in the ground state bleaching recovery time constant for Bchl a at 850 run (B850) in respect to that of the Bchl a in free LH2 has been observed. By using the relation of distance-dependent long-range electron transfer rate in protein, the distance between the donor B850 and the acceptor TiO2 nanoparticle has been estimated, which is about 0.6 nm. The proposed method of assembling proteins onto wide-gap semiconductor nanoparticle can be a promising way to determine the role of the protein playing in biological electron transfer processes.
基金Projects funded by the National Social Science Fund (19BDJ064)
文摘This paper provides a detailed introduction to and analysis of the course of China's technological innovation in liquid hydrogen/liquid oxygen(LH2/LOX)rocket engines from a historical point of view.It starts with the investigation of LH2/LOX rocket engines by relevant departments of the Chinese Academy of Sciences in the 1960s and their preliminary achievements.Then,the policy decision concerning LH2/LOX engine development,the project approval of the Long March-3(Chang Zheng-3,CZ-3)rocket,and the process of developing LH2/LOX engines are analyzed in detail,followed by an introduction to and summary of the development situation and technical innovation characteristics of China's LH2/LOX engines as they grew from 4 tons to 8 tons,and finally to 50 tons.Finally,the paper briefly analyzes the innovation experience connected with China's LH2/LOX engines.
基金Project supported by the National Natural Science Foundation of China （Grant No 10274013）.
文摘Energy transfers in two kinds of peripheral light-harvesting complexes （LH2） of Rhodobacter sphaeroides （RS） 601 are studied by using femtosecond pump^probe spectroscopy with tunable laser wavelength at room temperature. These two complexes are native LH2 （RS601） and green carotenoid mutated LH2 （GM309）. The obtained results demonstrate that, compared with spheroidenes with ten conjugated double bonds in native RS601, carotenoid in GM309 containing neurosporenes with nine conjugated double bonds can lead to a reduction in energy transfer rate in the B800-to-B850 band and the disturbance in the energy relaxation processes within the excitonic B850 band.
文摘Interactions between the light-harvesting subunits and the non-covalently bound photopigments attribute considerably to the spectral properties of photosynthetic bacteria light-harvesting complexes. In our previous studies, we have constructed a novel Rhodobacter sphaeroides expression system. In the present study, we focus on the spectral properties of LH2 when heterologously express LH2 with β-subunit- GFP fusion protein in Rb. sphaeroides. Near infra-red spectrum of LH2 remained nearly unchanged as measured by spectroscopy. Fluorescence spectrum suggested that the LH2 with β-subunit-GFP fusion protein complexes still possessed normal activity in energy transfer. However, photopigments contents were significantly decreased to a very low level in the LH2 with β-subunit-GFP fusion protein complexes compared to that of LH2. FT-IR spectra indicated that interactions between photopigments and LH2 α/β- subunits appeared not to be changed. It was concluded that the LH2 spectral properties exhibited very similar even when heterologously expressed LH2 b-subunit fusion protein in Rb. sphaeroides. Our present study may supply a new insight into better understand the interactions between light-harvesting subunits and photopigments and bacterial photosynthesis and promote the development of the novel Rb. sphaeroides expression system.
基金Supported by the National Natural Science Foundation of China under Grant Nos 20925313,21227003,and 11004236the National Basic Research Program of China under Grant No 2009CB930700the Innovation Program of Chinese Academy of Sciences under Grant No KJCX2-YW-W25
文摘Ultrafast anisotropic decay is a prominent parameter revealing ultrafast energy and electron transfer; however, it is dimcult to be determined reliably owing to the requirement of a simultaneous availability of the parallel and perpendieular polarized decay kinetics. Nowadays, any measurement of anisotropic decay is a kind of approach to the exact simultaneity. Here we report a novel method for a synchronous ultrafast anisotropy decay measurement, which can well determine the anisotropy, even at a very early time, as the rising phase of the excitation laser pulse. The anisotropic decay of the B850 in bacteriM light harvesting antenna complex LH2 of rhodobacter sphaeroides in solution at room temperature with coherent excitation is detected by this method, which shows a polarization response time of 30 fs, and the energy transfer from the initial excitation to the bacteriochlorophylls in B850 ring takes about 7Ors. The anisotropic decay that is probed at the red side of the absorption spectrum, such as 880 nm, has an initial value of 0.4, corresponding to simulated emission, while the blue side with an anisotropy of 0.1 contributes to the ground-state bleaching. Our results show that the coherent excitation covering the whole ring might not be realized owing to the symmetry breaking of LH2： from C9 symmetry in membrane to C2 symmetry in solution.
基金supported by the National Fundamental Research Program (Grant No. 2007CB925204)the National Natural Science Foundation of China (Grant Nos. 11075050 and 10775048)+1 种基金the Program for Changjiang Scholars and Innovative Research Team in University (Grant No. IRT0964)the Hunan Provincial Natural Science Foundation (Grant No. 11JJ7001)
文摘In this work,we study environment-assisted excitation energy transfer(EET) through calculating energy transfer efficiency(ETE) in LH1-RC-type and LH2-type trimers,which can be used to mimic energy transfer behaviors in the basic unit cells of LH1-RC and LH2 light-harvesting complexes.Quantum state evolution of the trimers is described by a non-Hermitian quantum master equation.ETE in these trimer systems is investigated by the use of numerical solutions at finite temperatures for the non-Hermitian master equation.We theoretically reveal the temperature-assisted ETE enhancement.It is found that highly efficient EET with nearly unit efficiency may occur in the nearby regime of the critical point of quantum phase transition.
