Viruses in the family Reoviridae are non-enveloped particles comprising a segmented double-stranded RNA genome surrounded by a two-layered or multi-layered icosahedral protein capsid.These viruses are classified into ...Viruses in the family Reoviridae are non-enveloped particles comprising a segmented double-stranded RNA genome surrounded by a two-layered or multi-layered icosahedral protein capsid.These viruses are classified into two sub-families based on their particle structural organization.Recent studies have focused on high-resolution three-dimensional structures of reovirus particles by using cryo-electron microscopy (cryo-EM) to approach the resolutions seen in X-ray crystallographic structures.The results of cryo-EM image reconstructions allow tracing of most of the protein side chains,and thus permit integration of structural and functional information into a coherent mechanism for reovirus assembly and entry.展开更多
Novel preservation condition without ultra-low temperature is needed for the study of pathogen in marine fishes. Freeze-drying is such a method usually used for preservation of terrigenous bacteria. However, studies u...Novel preservation condition without ultra-low temperature is needed for the study of pathogen in marine fishes. Freeze-drying is such a method usually used for preservation of terrigenous bacteria. However, studies using freeze-drying method to preserving marine microorganisms remain very limited. In this study, we optimized the composition of protectants during the freeze-drying of Edwardsiella tarda, a fish pathogen that causes systemic infection in marine fishes. We found that the optimal composition of protectant mixture contained trehalose(8.0%), skim milk(12.0%), sodium citrate(2.0%), serum(12.0%) and PVP(2.0%). Orthogonal and interaction analyses demonstrated the interaction between serum and skim milk or sodium citrate. The highest survival rate of E. tarda was observed when the concentration of Na Cl was 10.0, 30.0 and between 5.0 and 10.0 g L^(-1) for preparing TSB medium, E. tarda suspension and protectant mixture, respectively. When E. tarda was frozen at-80℃ or-40℃ for 6 h, its survival rate was higher than that under other tested conditions. Under the optimized conditions, when the protectant mixture was used during freeze-drying process, the survival rate(79.63%–82.30%) of E. tarda was significantly higher than that obtained using single protectant. Scanning electron microscopy(SEM) image indicated that E. tarda was embedded in thick matrix with detectable aggregation. In sum, the protectant mixture may be used as a novel cryoprotective additive for E. tarda.展开更多
Objective: To evaluate penetration capacity of human sperm preserved in electrolyte-free (EF) solution at 4 ℃.Methods: The motility, acrosomal status penetration rate and fertility index of human sperm were assessed ...Objective: To evaluate penetration capacity of human sperm preserved in electrolyte-free (EF) solution at 4 ℃.Methods: The motility, acrosomal status penetration rate and fertility index of human sperm were assessed before and after cold-preservation in EF solution, respectively.Results: The motility of human sperm cold-preserved in EF solution for 1 week was significantly higher than that of human sperm cold-preserved in modified human tubal fluid (mHTF) (43.4%±7.9% vs 9.5%±2.5%, P<0.01 ).Although acrosomal status of human sperm cold-preserved in the EF solution before reinitiation was not different from those of the fresh sperm (capacitated sperm: 7.6%±1.8% vs 6.4±1.8%; acrosome-reacted sperm: 3.0%±1.7% vs 2.4±1.1%, P>0.05), the percentage of capacitated and acrosome-reacted sperm in the EF solution significantly increased after reinitiation (capacitated sperm: 16.0%±2.3% vs 7.6±1.8%, acrosome-reacted sperm: 9.4%±2.1% vs 3.0%±1.7%, P<0.01).The penetration rate and fertility index of cool-preserved human sperm in the EF solution were comparable with those of fresh sperm (48.1% vs 50.9%; 1.38±0.16 vs 1.29±0.13, respectively, P>0.05).Conclusion: Cold-preservation did not induce capacitation and acrosome reaction of human sperm in the EF solution, but human sperm cold-preserved in the EF solution for 1 week possesses as much penetration capacity as fresh sperm.展开更多
Cryogenic electron microscopy(cryo-EM)has extensively boosted structural biology research since the“resolution revolution”in the year of 2013 which was soon awarded the Nobel Prize in Chemistry in 2017.The advances ...Cryogenic electron microscopy(cryo-EM)has extensively boosted structural biology research since the“resolution revolution”in the year of 2013 which was soon awarded the Nobel Prize in Chemistry in 2017.The advances in camera techniques and software algorithms enabled cryoEM to routinely characterize the three-dimensional structures of biomolecules at near-atomic resolution.Biomolecules are basically sensitive to electron irradiation damage,which can be minimized at cryo-temperature.This principle has inspired material scientists to characterize electron beam-or air-sensitive materials by cryo-EM,such as the electrodes in the lithium-ion battery,metal-organic frameworks(MOFs),covalent-organic frameworks(COFs)and zeolites.In addition,the reaction systems can be fast-frozen at vitreous ice in cryoEM,which correspondingly preserves the materials at the close-to-native state.Herein,we summarized the development and applications of both the cryo-EM technique and other emerging cryo-techniques in materials science,and energy storage and conversion.Cryo-EM techniques,capable of the direct observation of sensitive materials and electrochemical reaction processes,will greatly renew our understanding of materials science and related mechanisms.展开更多
Recently, significant technical breakthroughs in both hardware equipment and software algorithms have enabled cryo-electron microscopy(cryo-EM) to become one of the most important techniques in biological structural a...Recently, significant technical breakthroughs in both hardware equipment and software algorithms have enabled cryo-electron microscopy(cryo-EM) to become one of the most important techniques in biological structural analysis. The technical aspects of cryo-EM define its unique advantages and the direction of development. As a rapidly emerging field, cryo-EM has benefitted from highly interdisciplinary research efforts. Here we review the current status of cryo-EM in the context of structural biology and discuss the technical challenges. It may eventually merge structural and cell biology at multiple scales.展开更多
Cryo-electron microscopy (cryo-EM) plays an important role in determining the structure of proteins, viruses, and even the whole cell. It can capture dynamic structural changes of large protein complexes, which other ...Cryo-electron microscopy (cryo-EM) plays an important role in determining the structure of proteins, viruses, and even the whole cell. It can capture dynamic structural changes of large protein complexes, which other methods such as X-ray crystallography and nuclear magnetic resonance analysis find difficult. The signal-to-noise ratio of cryo-EM images is low and the contrast is very weak, and therefore, the images are very noisy and require filtering. In this paper, a filtering method based on non-local means and Zernike moments is proposed. The method takes into account the rotational symmetry of some biological molecules to enhance the signal-to-noise ratio of cryo-EM images. The method may be useful in cryo-EM image processing such as the automatic selection of particles, orientation determination, and the building of initial models.展开更多
Infectious bursal disease virus(IBDV)causes a highly contagious immunosuppressive disease in chickens,resulting in significant economic losses.The very virulent IBDV strain(vvIBDV)causes high mortality and cannot adap...Infectious bursal disease virus(IBDV)causes a highly contagious immunosuppressive disease in chickens,resulting in significant economic losses.The very virulent IBDV strain(vvIBDV)causes high mortality and cannot adapt to cell culture.In contrast,attenuated strains of IBDV are nonpathogenic to chickens and can replicate in cell culture.Although the crystal structure of T=1 subviral particles(SVP)has been reported,the structures of intact IBDV virions with different virulences remain elusive.Here,we determined the cryo-electron microscopy(cryo-EM)structures of the vvIBDV Gx strain and its attenuated IBDV strain Gt at resolutions of 3.3 Å and 3.2 Å,respectively.Compared with the structure of T=1 SVP,IBDV contains several conserved structural elements unique to the T=13 virion.Notably,the Nterminus of VP2,which is disordered in the SVP,interacts with the S_(F) strand of VP2 from its neighboring trimer,completing theβ-sheet of the S domain.This interaction helps to form a contact network by tethering the adjacent VP2 trimers and contributes to the assembly and stability of the IBDV virion.Structural comparison of the Gx and Gt strains indicates that H253 and T284 in the VP2 P domain of Gt,in contrast to Gx,form a hydrogen bond with a positively charged surface.This suggests that the combined mutations Q253 H/A284 T and the associated structural electrostatic features of the attenuated Gt strain may contribute to adaptation to cell culture.Furthermore,a negatively charged groove in VP2,containing an integrin binding IDA motif that is critical for virus attachment,was speculated to play a functional role in the entry of IBDV.展开更多
Nano-sized LiFePO_4·Li_3V_2（PO_4）_3/C was synthesized via a sol-gel route combining with freeze-drying. X-ray diffraction results show that this composite mainly consists of olivine Li Fe PO4 and monoclinic Li3...Nano-sized LiFePO_4·Li_3V_2（PO_4）_3/C was synthesized via a sol-gel route combining with freeze-drying. X-ray diffraction results show that this composite mainly consists of olivine Li Fe PO4 and monoclinic Li3 V2（PO4）3 phases with small amounts of V-doped LiFePO_4 and Fe-doped Li_3V_2（PO_4）_3. The magnetic properties of LiFePO_4·Li_3V_2（PO_4）_3/C are significantly different from LiFePO_4/C. Trace quantities of ferromagnetic impurities and Fe_2P are verified in LiFePO_4/C and LiFePO_4·Li_3V_2（PO_4）_3/C by magnetic tests, respectively. LiFePO_4·Li_3 V_2（PO_4）_3/C possesses relatively better rate capacities and cyclic stabilities, especially at high charge-discharge rates.The initial discharge capacities are 136.4 and 130.0 mA h g^（-1）,and the capacity retentions are more than 98% after 100 cycles at 2C and 5C, respectively, remarkably better than those of LiFePO_4/C. The excellent electrochemical performances are ascribed to the mutual doping of V^（3＋）and Fe^（2＋）, complementary advantages of LiFePO_4 and Li_3V_2（PO_4）_3 phases, the residual high-ordered carbon and Fe_2P with outstanding electric conductivity in the nanocomposite.展开更多
基金supported by grants from the National Natural Science Foundation of China(31172434,31372565)
文摘Viruses in the family Reoviridae are non-enveloped particles comprising a segmented double-stranded RNA genome surrounded by a two-layered or multi-layered icosahedral protein capsid.These viruses are classified into two sub-families based on their particle structural organization.Recent studies have focused on high-resolution three-dimensional structures of reovirus particles by using cryo-electron microscopy (cryo-EM) to approach the resolutions seen in X-ray crystallographic structures.The results of cryo-EM image reconstructions allow tracing of most of the protein side chains,and thus permit integration of structural and functional information into a coherent mechanism for reovirus assembly and entry.
基金the National Natural Science Foundation of China (No. 31302206)Special Research Funds for Independent Innovation and Scientific & Technology Achievements Transformation of Shandong Province (No. 2014ZZCX06205)Agriculture Seed Improvement Project of Shandong Province
文摘Novel preservation condition without ultra-low temperature is needed for the study of pathogen in marine fishes. Freeze-drying is such a method usually used for preservation of terrigenous bacteria. However, studies using freeze-drying method to preserving marine microorganisms remain very limited. In this study, we optimized the composition of protectants during the freeze-drying of Edwardsiella tarda, a fish pathogen that causes systemic infection in marine fishes. We found that the optimal composition of protectant mixture contained trehalose(8.0%), skim milk(12.0%), sodium citrate(2.0%), serum(12.0%) and PVP(2.0%). Orthogonal and interaction analyses demonstrated the interaction between serum and skim milk or sodium citrate. The highest survival rate of E. tarda was observed when the concentration of Na Cl was 10.0, 30.0 and between 5.0 and 10.0 g L^(-1) for preparing TSB medium, E. tarda suspension and protectant mixture, respectively. When E. tarda was frozen at-80℃ or-40℃ for 6 h, its survival rate was higher than that under other tested conditions. Under the optimized conditions, when the protectant mixture was used during freeze-drying process, the survival rate(79.63%–82.30%) of E. tarda was significantly higher than that obtained using single protectant. Scanning electron microscopy(SEM) image indicated that E. tarda was embedded in thick matrix with detectable aggregation. In sum, the protectant mixture may be used as a novel cryoprotective additive for E. tarda.
文摘Objective: To evaluate penetration capacity of human sperm preserved in electrolyte-free (EF) solution at 4 ℃.Methods: The motility, acrosomal status penetration rate and fertility index of human sperm were assessed before and after cold-preservation in EF solution, respectively.Results: The motility of human sperm cold-preserved in EF solution for 1 week was significantly higher than that of human sperm cold-preserved in modified human tubal fluid (mHTF) (43.4%±7.9% vs 9.5%±2.5%, P<0.01 ).Although acrosomal status of human sperm cold-preserved in the EF solution before reinitiation was not different from those of the fresh sperm (capacitated sperm: 7.6%±1.8% vs 6.4±1.8%; acrosome-reacted sperm: 3.0%±1.7% vs 2.4±1.1%, P>0.05), the percentage of capacitated and acrosome-reacted sperm in the EF solution significantly increased after reinitiation (capacitated sperm: 16.0%±2.3% vs 7.6±1.8%, acrosome-reacted sperm: 9.4%±2.1% vs 3.0%±1.7%, P<0.01).The penetration rate and fertility index of cool-preserved human sperm in the EF solution were comparable with those of fresh sperm (48.1% vs 50.9%; 1.38±0.16 vs 1.29±0.13, respectively, P>0.05).Conclusion: Cold-preservation did not induce capacitation and acrosome reaction of human sperm in the EF solution, but human sperm cold-preserved in the EF solution for 1 week possesses as much penetration capacity as fresh sperm.
基金supported by the National Natural Science Foundation of China(52171219 and 91963113)。
文摘Cryogenic electron microscopy(cryo-EM)has extensively boosted structural biology research since the“resolution revolution”in the year of 2013 which was soon awarded the Nobel Prize in Chemistry in 2017.The advances in camera techniques and software algorithms enabled cryoEM to routinely characterize the three-dimensional structures of biomolecules at near-atomic resolution.Biomolecules are basically sensitive to electron irradiation damage,which can be minimized at cryo-temperature.This principle has inspired material scientists to characterize electron beam-or air-sensitive materials by cryo-EM,such as the electrodes in the lithium-ion battery,metal-organic frameworks(MOFs),covalent-organic frameworks(COFs)and zeolites.In addition,the reaction systems can be fast-frozen at vitreous ice in cryoEM,which correspondingly preserves the materials at the close-to-native state.Herein,we summarized the development and applications of both the cryo-EM technique and other emerging cryo-techniques in materials science,and energy storage and conversion.Cryo-EM techniques,capable of the direct observation of sensitive materials and electrochemical reaction processes,will greatly renew our understanding of materials science and related mechanisms.
文摘Recently, significant technical breakthroughs in both hardware equipment and software algorithms have enabled cryo-electron microscopy(cryo-EM) to become one of the most important techniques in biological structural analysis. The technical aspects of cryo-EM define its unique advantages and the direction of development. As a rapidly emerging field, cryo-EM has benefitted from highly interdisciplinary research efforts. Here we review the current status of cryo-EM in the context of structural biology and discuss the technical challenges. It may eventually merge structural and cell biology at multiple scales.
基金supported by the National Basic Research Program of China (2010CB912400)
文摘Cryo-electron microscopy (cryo-EM) plays an important role in determining the structure of proteins, viruses, and even the whole cell. It can capture dynamic structural changes of large protein complexes, which other methods such as X-ray crystallography and nuclear magnetic resonance analysis find difficult. The signal-to-noise ratio of cryo-EM images is low and the contrast is very weak, and therefore, the images are very noisy and require filtering. In this paper, a filtering method based on non-local means and Zernike moments is proposed. The method takes into account the rotational symmetry of some biological molecules to enhance the signal-to-noise ratio of cryo-EM images. The method may be useful in cryo-EM image processing such as the automatic selection of particles, orientation determination, and the building of initial models.
基金supported by the National Natural Science Foundation of China(U20A2061,31730023,31521002,32072852)the Chinese Ministry of Science and Technology(2017YFA0504700)+2 种基金the Chinese Academy of Sciences(CAS)(XDB37010100)the State Key Laboratory of Veterinary Biotechnology Foundation(SKLVBF201702)the National Laboratory of Biomacromolecules of China(2020KF12)。
文摘Infectious bursal disease virus(IBDV)causes a highly contagious immunosuppressive disease in chickens,resulting in significant economic losses.The very virulent IBDV strain(vvIBDV)causes high mortality and cannot adapt to cell culture.In contrast,attenuated strains of IBDV are nonpathogenic to chickens and can replicate in cell culture.Although the crystal structure of T=1 subviral particles(SVP)has been reported,the structures of intact IBDV virions with different virulences remain elusive.Here,we determined the cryo-electron microscopy(cryo-EM)structures of the vvIBDV Gx strain and its attenuated IBDV strain Gt at resolutions of 3.3 Å and 3.2 Å,respectively.Compared with the structure of T=1 SVP,IBDV contains several conserved structural elements unique to the T=13 virion.Notably,the Nterminus of VP2,which is disordered in the SVP,interacts with the S_(F) strand of VP2 from its neighboring trimer,completing theβ-sheet of the S domain.This interaction helps to form a contact network by tethering the adjacent VP2 trimers and contributes to the assembly and stability of the IBDV virion.Structural comparison of the Gx and Gt strains indicates that H253 and T284 in the VP2 P domain of Gt,in contrast to Gx,form a hydrogen bond with a positively charged surface.This suggests that the combined mutations Q253 H/A284 T and the associated structural electrostatic features of the attenuated Gt strain may contribute to adaptation to cell culture.Furthermore,a negatively charged groove in VP2,containing an integrin binding IDA motif that is critical for virus attachment,was speculated to play a functional role in the entry of IBDV.
基金supported by the National Natural Science Foundation of China (21673051)Guangdong Province Science & Technology Bureau (2014A010106029, 2014B010106005 and 2016A010104015)+3 种基金Guangzhou Science & Innovative Committee (201604030037)the Youth Foundation of Guangdong University of Technology (252151038)the link project of the National Natural Science Foundation of China and Guangdong Province (U1401246)the Science and Technology Program of Guangzhou City of China (201508030018)
文摘Nano-sized LiFePO_4·Li_3V_2（PO_4）_3/C was synthesized via a sol-gel route combining with freeze-drying. X-ray diffraction results show that this composite mainly consists of olivine Li Fe PO4 and monoclinic Li3 V2（PO4）3 phases with small amounts of V-doped LiFePO_4 and Fe-doped Li_3V_2（PO_4）_3. The magnetic properties of LiFePO_4·Li_3V_2（PO_4）_3/C are significantly different from LiFePO_4/C. Trace quantities of ferromagnetic impurities and Fe_2P are verified in LiFePO_4/C and LiFePO_4·Li_3V_2（PO_4）_3/C by magnetic tests, respectively. LiFePO_4·Li_3 V_2（PO_4）_3/C possesses relatively better rate capacities and cyclic stabilities, especially at high charge-discharge rates.The initial discharge capacities are 136.4 and 130.0 mA h g^（-1）,and the capacity retentions are more than 98% after 100 cycles at 2C and 5C, respectively, remarkably better than those of LiFePO_4/C. The excellent electrochemical performances are ascribed to the mutual doping of V^（3＋）and Fe^（2＋）, complementary advantages of LiFePO_4 and Li_3V_2（PO_4）_3 phases, the residual high-ordered carbon and Fe_2P with outstanding electric conductivity in the nanocomposite.
