Chromatic acclimation （CA） provides many cyanobacteria with the ability to tailor the properties of their light-harvesting antennae to the spectral distribution of ambient light. CA was originally discovered as a re...Chromatic acclimation （CA） provides many cyanobacteria with the ability to tailor the properties of their light-harvesting antennae to the spectral distribution of ambient light. CA was originally discovered as a result of its dramatic cellular phenotype in red and green light. However, discoveries over the past decade have revealed that many pairs of light colors, ranging from blue to infrared, can trigger CA responses. The capacity to undergo CA is widespread geographically, occurs in most habitats around the world, and is found within all major cyanobacterial groups. In addition, many other cellular activities have been found to be under CA control, resulting in distinct physiological and morphological states for cells under different light-color conditions. Several types of CA appear to be the result of convergent evolution, where different strategies are used to achieve the final goal of optimizing light-harvesting antenna composition to maximize photon capture. The regulation of CA has been found to occur primarily at the level of RNA abundance. The CA-regulatory pathways uncovered thus far are two-component systems that use phytochrome-class photoreceptors with sensor-kinase domains to control response regulators that function as transcription factors. However, there is also at least one CA- regulatory pathway that operates at the post-transcriptional level. It is becoming increasingly clear that large numbers of cyanobacterial species have the capacity to acclimate to a wide variety of light colors through the use of a range of different CA processes.展开更多
: During the non-frost season, the condensation of dew makes Nostoc flagelliforme Born. et Flah., a highly drought-tolerant terrestrial cyanobacterium, frequently undergo rehydration-dehydration. Rehydration begins in...: During the non-frost season, the condensation of dew makes Nostoc flagelliforme Born. et Flah., a highly drought-tolerant terrestrial cyanobacterium, frequently undergo rehydration-dehydration. Rehydration begins in the dark at night. After rewetting in the dark, photochemical activity and the structure of photosystem (PS) II were not recovered at all; the structure of PSI, energy transfer in phycobilisomes, and energy transfer from phycobilisomes to PSI were recovered within 5 min, as in the light. The recovery of energy transfer from phycobilisomes to PSII was light dependent and energy transfer from phycobilisomes to PSII was only partially recovered in the dark. These results suggest that the two-trigger control (water and light) of photo synthetic recovery may make N. flagelliforme avoid unnecessary energy consumption and, at the same time, the partial recovery of energy transfer from phycobilisomes to PSII in the dark could help N. flagelliforme accumulate more photosynthetic products during the transient period of rehydration-dehydration.展开更多
The excitation energy transfer processes in nionomeric phycoerythrocyanins ( PEC)have been studied in detail using steady-state and time-resolved fluorescence spectra techniques as well as the deconvolution fech nique...The excitation energy transfer processes in nionomeric phycoerythrocyanins ( PEC)have been studied in detail using steady-state and time-resolved fluorescence spectra techniques as well as the deconvolution fech nique of spectra.The results indicate that the energy transfer processes should take place between α84 PVB md β8 or β155-PCB chromophores,the time constants of energy transfer are 34.7 and 130 ps individually;the component with lifetime of 1.57 ns originates from the fluorescence lifetime of the terminal emitter of β84 and /or β155 PCB chre-mophores; and the component with lifetime of 515 ps might be assigned to the energy transfer between two PCB chro mophores of β subunit.展开更多
The excitation energy transfer processes in trimeric PEC have been studied by using steady state and time resolved fluorescence spectra techniques in detail. The results indicate that the energy transfer processes sho...The excitation energy transfer processes in trimeric PEC have been studied by using steady state and time resolved fluorescence spectra techniques in detail. The results indicate that the energy transfer processes should take place between α 84 PVB and β 84 or β 155 PCB chromophores with the time constants 34.7 ps and 175-200 ps individually; in contrast with monomeric PEC, from time resolved fluorescence anisotropic spectrum technique, the decay constant of 45 ps which was assigned to the energy transfer time among three β 84 PCB chromophores was observed and the energy levels of β 84 and/or β 155 PCB chromophores were confirmed to turn over in trimeric PEC.展开更多
The phycobilisomes, composed of chromophoric biliproteins and colorless accessory linker proteins, serve as light-harvesting antennae in blue-green and red algae. Studies have been thoroughly made in many species of b...The phycobilisomes, composed of chromophoric biliproteins and colorless accessory linker proteins, serve as light-harvesting antennae in blue-green and red algae. Studies have been thoroughly made in many species of blue-green algae and some species of red algae. However, the composition of the accessory undenatured proteins of phycobilisomes has展开更多
Glycine betaine(GB) is a biologically important small molecule protecting cells,proteins and enzymes in vivo and in vitro under environmental stresses.Recently,it was found that GB could also relax the structure and i...Glycine betaine(GB) is a biologically important small molecule protecting cells,proteins and enzymes in vivo and in vitro under environmental stresses.Recently,it was found that GB could also relax the structure and inactivate the function of phycobiliproteins and phycobilisome(PBS),a kind of supramolecular complexes,in cyanobacterial cells.The molecular mechanisms for the opposite phenomena are quite ambiguous.Taking PBS and a trimeric or monomeric C-phycocyanin(C-PC) as models,the molecular mechanism for the interaction of GB with supra-molecular complexes or nuclear proteins was investigated.The energetic decoupling of PBS components induced by GB suggests that the PBS core-membrane linking polypeptide was the most sensitive site while the rod-core linker was the next.Biochemistry analysis proves that PBS structure was loosened but not dissociated into the components.On the basis of the results and structure knowledge,it was proposed that GB screened the electrostatic attraction of the opposite charges on a linker and a protein leading to a much looser structure.It was observed that GB induced a spectral blue shift for trimeric C-PC but a red shift for a monomeric C-PC(a nuclear protein),which were ascribed to GB's screening of the electrostatic attraction of a linker to a protein and strengthening of the hydrophobic interaction between C-PC monomers.The trimers and monomers' forming of the same products under high concentration of GB was ascribed to a compromise of the opposite interaction forces.展开更多
Excitation energy transfer processes and mechanism in C-PC hexamer have been studied in detail by picosecond time-resolved fluorescencs isotropic and anisotropic spectroscopy methods. The experimental results show tha...Excitation energy transfer processes and mechanism in C-PC hexamer have been studied in detail by picosecond time-resolved fluorescencs isotropic and anisotropic spectroscopy methods. The experimental results show that there are two types of principal channels, with large probability or amplitude, for linking two trimers viam?m and s?s energy transfer pathways, the energy-transfer time constants of them are about 20 and 10 ps, respectively. Indeed, there exists the evidence for energy-transfer channels of s?f steps in the same monomer and threef?f steps in the same trimer of the C-PC hexamer unit, with small probability or amplitude, and the time constants of them might be ca. 50 and 45 ps separately. Also, the present results show that the hexamer possesses an optimal structure for energy-transfer and for the first time confirm that the dominant energy-transfer processes except those between 1 m?2f, 2m?3f and 3m?1f and so on, in isolated C-PC hexamer, could be described by F?rster dipole-dipole resonance mechanism.展开更多
文摘Chromatic acclimation （CA） provides many cyanobacteria with the ability to tailor the properties of their light-harvesting antennae to the spectral distribution of ambient light. CA was originally discovered as a result of its dramatic cellular phenotype in red and green light. However, discoveries over the past decade have revealed that many pairs of light colors, ranging from blue to infrared, can trigger CA responses. The capacity to undergo CA is widespread geographically, occurs in most habitats around the world, and is found within all major cyanobacterial groups. In addition, many other cellular activities have been found to be under CA control, resulting in distinct physiological and morphological states for cells under different light-color conditions. Several types of CA appear to be the result of convergent evolution, where different strategies are used to achieve the final goal of optimizing light-harvesting antenna composition to maximize photon capture. The regulation of CA has been found to occur primarily at the level of RNA abundance. The CA-regulatory pathways uncovered thus far are two-component systems that use phytochrome-class photoreceptors with sensor-kinase domains to control response regulators that function as transcription factors. However, there is also at least one CA- regulatory pathway that operates at the post-transcriptional level. It is becoming increasingly clear that large numbers of cyanobacterial species have the capacity to acclimate to a wide variety of light colors through the use of a range of different CA processes.
文摘: During the non-frost season, the condensation of dew makes Nostoc flagelliforme Born. et Flah., a highly drought-tolerant terrestrial cyanobacterium, frequently undergo rehydration-dehydration. Rehydration begins in the dark at night. After rewetting in the dark, photochemical activity and the structure of photosystem (PS) II were not recovered at all; the structure of PSI, energy transfer in phycobilisomes, and energy transfer from phycobilisomes to PSI were recovered within 5 min, as in the light. The recovery of energy transfer from phycobilisomes to PSII was light dependent and energy transfer from phycobilisomes to PSII was only partially recovered in the dark. These results suggest that the two-trigger control (water and light) of photo synthetic recovery may make N. flagelliforme avoid unnecessary energy consumption and, at the same time, the partial recovery of energy transfer from phycobilisomes to PSII in the dark could help N. flagelliforme accumulate more photosynthetic products during the transient period of rehydration-dehydration.
基金Project supported hy the National Natural Science Foundation of China
文摘The excitation energy transfer processes in nionomeric phycoerythrocyanins ( PEC)have been studied in detail using steady-state and time-resolved fluorescence spectra techniques as well as the deconvolution fech nique of spectra.The results indicate that the energy transfer processes should take place between α84 PVB md β8 or β155-PCB chromophores,the time constants of energy transfer are 34.7 and 130 ps individually;the component with lifetime of 1.57 ns originates from the fluorescence lifetime of the terminal emitter of β84 and /or β155 PCB chre-mophores; and the component with lifetime of 515 ps might be assigned to the energy transfer between two PCB chro mophores of β subunit.
文摘The excitation energy transfer processes in trimeric PEC have been studied by using steady state and time resolved fluorescence spectra techniques in detail. The results indicate that the energy transfer processes should take place between α 84 PVB and β 84 or β 155 PCB chromophores with the time constants 34.7 ps and 175-200 ps individually; in contrast with monomeric PEC, from time resolved fluorescence anisotropic spectrum technique, the decay constant of 45 ps which was assigned to the energy transfer time among three β 84 PCB chromophores was observed and the energy levels of β 84 and/or β 155 PCB chromophores were confirmed to turn over in trimeric PEC.
基金This investigation was supported by the Smithsonian Institution, USA, through the Office of Fellowships and Grants, and in part by the National Natural Science Foundation of China
文摘The phycobilisomes, composed of chromophoric biliproteins and colorless accessory linker proteins, serve as light-harvesting antennae in blue-green and red algae. Studies have been thoroughly made in many species of blue-green algae and some species of red algae. However, the composition of the accessory undenatured proteins of phycobilisomes has
基金Supported by the National Natural Science Foundation of China (Grant No. 20872144)
文摘Glycine betaine(GB) is a biologically important small molecule protecting cells,proteins and enzymes in vivo and in vitro under environmental stresses.Recently,it was found that GB could also relax the structure and inactivate the function of phycobiliproteins and phycobilisome(PBS),a kind of supramolecular complexes,in cyanobacterial cells.The molecular mechanisms for the opposite phenomena are quite ambiguous.Taking PBS and a trimeric or monomeric C-phycocyanin(C-PC) as models,the molecular mechanism for the interaction of GB with supra-molecular complexes or nuclear proteins was investigated.The energetic decoupling of PBS components induced by GB suggests that the PBS core-membrane linking polypeptide was the most sensitive site while the rod-core linker was the next.Biochemistry analysis proves that PBS structure was loosened but not dissociated into the components.On the basis of the results and structure knowledge,it was proposed that GB screened the electrostatic attraction of the opposite charges on a linker and a protein leading to a much looser structure.It was observed that GB induced a spectral blue shift for trimeric C-PC but a red shift for a monomeric C-PC(a nuclear protein),which were ascribed to GB's screening of the electrostatic attraction of a linker to a protein and strengthening of the hydrophobic interaction between C-PC monomers.The trimers and monomers' forming of the same products under high concentration of GB was ascribed to a compromise of the opposite interaction forces.
文摘Excitation energy transfer processes and mechanism in C-PC hexamer have been studied in detail by picosecond time-resolved fluorescencs isotropic and anisotropic spectroscopy methods. The experimental results show that there are two types of principal channels, with large probability or amplitude, for linking two trimers viam?m and s?s energy transfer pathways, the energy-transfer time constants of them are about 20 and 10 ps, respectively. Indeed, there exists the evidence for energy-transfer channels of s?f steps in the same monomer and threef?f steps in the same trimer of the C-PC hexamer unit, with small probability or amplitude, and the time constants of them might be ca. 50 and 45 ps separately. Also, the present results show that the hexamer possesses an optimal structure for energy-transfer and for the first time confirm that the dominant energy-transfer processes except those between 1 m?2f, 2m?3f and 3m?1f and so on, in isolated C-PC hexamer, could be described by F?rster dipole-dipole resonance mechanism.
