β-Glucans are biomacromolecules that present biological properties of medical and pharmacological interest, The chemical modification of the primary structure of these carbohydrate biopolymers is a way to enhance or ...β-Glucans are biomacromolecules that present biological properties of medical and pharmacological interest, The chemical modification of the primary structure of these carbohydrate biopolymers is a way to enhance or achieve new biological properties. Acetylated derivatives of （1→6）-β-D-glucan （lasiodiplodan） with different degrees of substitution （0.48, 0.66, 1.03 and 1.26） were obtained and characterized by infra-red and NMR （nuclear magnetic resonance） spectroscopy, thermal analysis, X-ray diffraction and antioxidant capacity. Acetylation was confirmed by FT-IR, and βC NMR spectroscopy. Thermal analysis indicated that unmodified lasiodiplodan and the O-acetylated β-glucan derivative of degree of substitution 0.48 presented three stages of mass-loss, whereas acetylated derivatives of DS （degree of substitution） of 0.66, 1.03 and 1.26 presented four stages of mass-loss. X-ray diffractograms demonstrated that both native and acetylated lasiodiplodan presented crystalline regions in an amorphous polymeric matrix. Scanning electron microscopy revealed that O-acetylation promoted morphologic changes in the biopolymer according to the DS. Acetylation also contributed to improve antioxidant capacity.展开更多
Localisation microscopy overcomes the diffraction limit by measuring the position of individual molecules to obtain optical images with a lateral resolution better than 30 nm. Single molecule localisation microscopy w...Localisation microscopy overcomes the diffraction limit by measuring the position of individual molecules to obtain optical images with a lateral resolution better than 30 nm. Single molecule localisation microscopy was originally demonstrated only in two dimensions but has recently been extended to three dimensions. Here we develop a new approach to three-dimensional （3D） localisation microscopy by engineering of the point-spread function （PSF） of a fluorescence microscope. By introducing a linear phase gradient between the two halves of the objective pupil plane the PSF is split into two lateral lobes whose relative position depends on defocus. Calculations suggested that the phase gradient resulting from the very small tolerances in parallelism of conventional slides made from float glass would be sufficient to generate a two-lobed PSF. We demonstrate that insertion of a suitably chosen microscope slide that occupies half the objective aperture combined with a novel fast fitting algorithm for 3D localisation estimation allows nanoscopic imaging with detail resolution well below 100 nm in all three dimensions （standard deviations of 20, 16, and 42 nm in x, y, and z directions, respectively）. The utility of the approach is shown by imaging the complex 3D distribution of microtubules in cardiac muscle cells that were stained with conventional near infrared fluorochromes. The straightforward optical setup, minimal hardware requirements and large axial localisation range make this approach suitable for many nanoscopic imaging applications.展开更多
Ryanodine receptors are ion channels that allow for the release of Ca2+ from the endoplasmic or sarcoplasmic reticulum.They are expressed in many different cell types but are best known for their predominance in skele...Ryanodine receptors are ion channels that allow for the release of Ca2+ from the endoplasmic or sarcoplasmic reticulum.They are expressed in many different cell types but are best known for their predominance in skeletal and cardiac myocytes,where they are directly involved in excitation-contraction coupling.With molecular weights exceeding 2 MDa,Ryanodine Receptors are the largest ion channels known to date and present major challenges for structural biology.Since their discovery in the 1980s,significant progress has been made in understanding their behaviour through multiple structural methods.Cryo-electron microscopy reconstructions of intact channels depict a mushroom-shaped structure with a large cytoplasmic region that pre-sents many binding sites for regulatory molecules.This region undergoes significant motions during opening and closing of the channel,demonstrating that the Ryanodine Receptor is a bona fide allosteric protein.High-resolution structures through X-ray crystallography and NMR currently cover～11% of the entire protein.The combination of high-and low-resolution methods allows us to build pseudo-atomic models.Here we present an overview of the electron microscopy,NMR,and crystallographic analyses of this membrane protein giant.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
As a member of the 2 D family of materials, h-BN is an intrinsic insulator and could be employed as a dielectric or insulating inter-layer in ultra-thin devices. Monolayer h-BN can be synthesized on Rh(111) surfaces u...As a member of the 2 D family of materials, h-BN is an intrinsic insulator and could be employed as a dielectric or insulating inter-layer in ultra-thin devices. Monolayer h-BN can be synthesized on Rh(111) surfaces using borazine as a precursor. Using in-situ variable-temperature scanning tunneling microscopy(STM), we directly observed the formation of h-BN in real-time. By analyzing the deposition under variable substrate temperatures and the filling rate of the h-BN overlayer vacant hollows during growth, we studied the growth kinetics of how the borazine molecules construct the h-BN overlayer grown on the Rh surface.展开更多
Silicon （Si） has been supplied to plants via application of calcium silicate to soil; however, high doses of calcium silicate are required because of its low solubility. Nanoparticles can reduce Si doses and be appl...Silicon （Si） has been supplied to plants via application of calcium silicate to soil; however, high doses of calcium silicate are required because of its low solubility. Nanoparticles can reduce Si doses and be applied to seeding furrows. This study investigated the effects of liquid Si sources, i.e., highly soluble silicate （115.2 g L^-1 Si and 60.5 g L^-1 Na20） and nanosilica （〈 200 nm）, on Si uptake by rice plants, plant lignification, plant C：N：P stoichiometry, plant physiology, and grain yield using an Oxisol under greanhouse condistions. The treatments included the application of nanosilica and soluble silicate to seeding furrows at Si doses of 0, 605, 1210, and 2 420 g ha^-1. Plant uptake and treatment effects were evaluated by measuring C and lignin contents, Si, N, and P accumulation, physiological characteristics, and grain yield of rice. The deposition of silica bodies and amorphous silica in the flag leaves was analyzed using scanning electron microscopy. Application of liquid Si increased Si accumulation in rice by 47.3% in relation to the control （0 g ha^-1 Si）, regardless of the Si sources used. Nanosilica application increased leaf lignin content by 112.7% when compared to that in the control. Silicon moderately affected the net C assimilation （increased by 1.83%） and transpiration rates （increased by 48.3%）; however, Si influenced neither plant growth nor grain yield of rice. These results are explained by the lack of biotic or abiotic stress in rice plants during the experiment. To the best of our knowledge, in Brazilian agriculture, this is the first report on the use of nanosilica as a Si fertilizer and its effect on plant nutrition. This study provides evidence that rice plants absorb and accumulate nanoparticles; however, further studies are required to investigate the use of nanoparticles in other plant species.展开更多
Nanoparticles in solution offer unique electrical, mechanical and thermal properties due to their physical presence and interac- tion with the state of dispersion. This work is aimed to study the effects of hydroxyapa...Nanoparticles in solution offer unique electrical, mechanical and thermal properties due to their physical presence and interac- tion with the state of dispersion. This work is aimed to study the effects of hydroxyapatite （HA） nanoparticles on the behavior of devitrification and recrystallization of glycerol （60% w/w） and PEG-600 （50% w/w） solutions during warming. HA nano- particles of different sizes （20, 40, 60 nm） and concentrations （0.1%, 0.5%, w/w） were incorporated into solutions, and were studied by calorimetric analysis coupled with cryomicroscopy. The presence of HA nanoparticles has little effect on the devit- rification end temperatures, but affects the devitrification onset temperatures of glycerol and PEG-600 solutions. The investi- gation with the cryomicroscope observed that the ice morphologies of glycerol and PEG-600 solutions are dendritic and spher- ic respectively. The ice fraction of glycerol solution containing 0.1% HA with the size of 60 nm decreased to 2/5 of that of the solution without nanoparticles at -45℃. The ice fractions of PEG-600 solutions increased signifcantly between -64℃ and -54℃, and the ice fraction of PEG-600 solution without nanoparticles increased by 92% within the temperature range. The findings have significant implications for biomaterial cryopreservation, cryosurgery, and food manufacturing. The complexity of ice crystal growth kinetics in nanoparticle-containing solutions awaits further study.展开更多
文摘β-Glucans are biomacromolecules that present biological properties of medical and pharmacological interest, The chemical modification of the primary structure of these carbohydrate biopolymers is a way to enhance or achieve new biological properties. Acetylated derivatives of （1→6）-β-D-glucan （lasiodiplodan） with different degrees of substitution （0.48, 0.66, 1.03 and 1.26） were obtained and characterized by infra-red and NMR （nuclear magnetic resonance） spectroscopy, thermal analysis, X-ray diffraction and antioxidant capacity. Acetylation was confirmed by FT-IR, and βC NMR spectroscopy. Thermal analysis indicated that unmodified lasiodiplodan and the O-acetylated β-glucan derivative of degree of substitution 0.48 presented three stages of mass-loss, whereas acetylated derivatives of DS （degree of substitution） of 0.66, 1.03 and 1.26 presented four stages of mass-loss. X-ray diffractograms demonstrated that both native and acetylated lasiodiplodan presented crystalline regions in an amorphous polymeric matrix. Scanning electron microscopy revealed that O-acetylation promoted morphologic changes in the biopolymer according to the DS. Acetylation also contributed to improve antioxidant capacity.
文摘Localisation microscopy overcomes the diffraction limit by measuring the position of individual molecules to obtain optical images with a lateral resolution better than 30 nm. Single molecule localisation microscopy was originally demonstrated only in two dimensions but has recently been extended to three dimensions. Here we develop a new approach to three-dimensional （3D） localisation microscopy by engineering of the point-spread function （PSF） of a fluorescence microscope. By introducing a linear phase gradient between the two halves of the objective pupil plane the PSF is split into two lateral lobes whose relative position depends on defocus. Calculations suggested that the phase gradient resulting from the very small tolerances in parallelism of conventional slides made from float glass would be sufficient to generate a two-lobed PSF. We demonstrate that insertion of a suitably chosen microscope slide that occupies half the objective aperture combined with a novel fast fitting algorithm for 3D localisation estimation allows nanoscopic imaging with detail resolution well below 100 nm in all three dimensions （standard deviations of 20, 16, and 42 nm in x, y, and z directions, respectively）. The utility of the approach is shown by imaging the complex 3D distribution of microtubules in cardiac muscle cells that were stained with conventional near infrared fluorochromes. The straightforward optical setup, minimal hardware requirements and large axial localisation range make this approach suitable for many nanoscopic imaging applications.
基金funded by the CIHR(operating grant 84350)the Heart and Stroke Foundation of Canadaa CIHR new investigator and a Michael Smith Foundation for Health Research Scholar
文摘Ryanodine receptors are ion channels that allow for the release of Ca2+ from the endoplasmic or sarcoplasmic reticulum.They are expressed in many different cell types but are best known for their predominance in skeletal and cardiac myocytes,where they are directly involved in excitation-contraction coupling.With molecular weights exceeding 2 MDa,Ryanodine Receptors are the largest ion channels known to date and present major challenges for structural biology.Since their discovery in the 1980s,significant progress has been made in understanding their behaviour through multiple structural methods.Cryo-electron microscopy reconstructions of intact channels depict a mushroom-shaped structure with a large cytoplasmic region that pre-sents many binding sites for regulatory molecules.This region undergoes significant motions during opening and closing of the channel,demonstrating that the Ryanodine Receptor is a bona fide allosteric protein.High-resolution structures through X-ray crystallography and NMR currently cover～11% of the entire protein.The combination of high-and low-resolution methods allows us to build pseudo-atomic models.Here we present an overview of the electron microscopy,NMR,and crystallographic analyses of this membrane protein giant.
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 Natural Science Foundation of China(Grant Nos.51402026,11774154,and 11790311)the Program for High-Level Entrepreneurial and Innovative Talents Introduction,Jiangsu Province,the Basic Research Program of Jiangsu Province(Grant No.BK20130236)the National Key Research and Development Plan(Grant No.2016YFE0125200)
文摘As a member of the 2 D family of materials, h-BN is an intrinsic insulator and could be employed as a dielectric or insulating inter-layer in ultra-thin devices. Monolayer h-BN can be synthesized on Rh(111) surfaces using borazine as a precursor. Using in-situ variable-temperature scanning tunneling microscopy(STM), we directly observed the formation of h-BN in real-time. By analyzing the deposition under variable substrate temperatures and the filling rate of the h-BN overlayer vacant hollows during growth, we studied the growth kinetics of how the borazine molecules construct the h-BN overlayer grown on the Rh surface.
基金supported by the Coordination for the Improvement of Higher Education Personnel Project of Brazil (No. 129126)the National Academic Cooperation Program (PROCAD) of Brazil (Notice 71/2013)
文摘Silicon （Si） has been supplied to plants via application of calcium silicate to soil; however, high doses of calcium silicate are required because of its low solubility. Nanoparticles can reduce Si doses and be applied to seeding furrows. This study investigated the effects of liquid Si sources, i.e., highly soluble silicate （115.2 g L^-1 Si and 60.5 g L^-1 Na20） and nanosilica （〈 200 nm）, on Si uptake by rice plants, plant lignification, plant C：N：P stoichiometry, plant physiology, and grain yield using an Oxisol under greanhouse condistions. The treatments included the application of nanosilica and soluble silicate to seeding furrows at Si doses of 0, 605, 1210, and 2 420 g ha^-1. Plant uptake and treatment effects were evaluated by measuring C and lignin contents, Si, N, and P accumulation, physiological characteristics, and grain yield of rice. The deposition of silica bodies and amorphous silica in the flag leaves was analyzed using scanning electron microscopy. Application of liquid Si increased Si accumulation in rice by 47.3% in relation to the control （0 g ha^-1 Si）, regardless of the Si sources used. Nanosilica application increased leaf lignin content by 112.7% when compared to that in the control. Silicon moderately affected the net C assimilation （increased by 1.83%） and transpiration rates （increased by 48.3%）; however, Si influenced neither plant growth nor grain yield of rice. These results are explained by the lack of biotic or abiotic stress in rice plants during the experiment. To the best of our knowledge, in Brazilian agriculture, this is the first report on the use of nanosilica as a Si fertilizer and its effect on plant nutrition. This study provides evidence that rice plants absorb and accumulate nanoparticles; however, further studies are required to investigate the use of nanoparticles in other plant species.
基金supported by the National Natural Science Foundation of China(Grant No.51076108)the Doctoral Program(Grant No.20103120110005)the Shanghai Dongfang Scholars Program
文摘Nanoparticles in solution offer unique electrical, mechanical and thermal properties due to their physical presence and interac- tion with the state of dispersion. This work is aimed to study the effects of hydroxyapatite （HA） nanoparticles on the behavior of devitrification and recrystallization of glycerol （60% w/w） and PEG-600 （50% w/w） solutions during warming. HA nano- particles of different sizes （20, 40, 60 nm） and concentrations （0.1%, 0.5%, w/w） were incorporated into solutions, and were studied by calorimetric analysis coupled with cryomicroscopy. The presence of HA nanoparticles has little effect on the devit- rification end temperatures, but affects the devitrification onset temperatures of glycerol and PEG-600 solutions. The investi- gation with the cryomicroscope observed that the ice morphologies of glycerol and PEG-600 solutions are dendritic and spher- ic respectively. The ice fraction of glycerol solution containing 0.1% HA with the size of 60 nm decreased to 2/5 of that of the solution without nanoparticles at -45℃. The ice fractions of PEG-600 solutions increased signifcantly between -64℃ and -54℃, and the ice fraction of PEG-600 solution without nanoparticles increased by 92% within the temperature range. The findings have significant implications for biomaterial cryopreservation, cryosurgery, and food manufacturing. The complexity of ice crystal growth kinetics in nanoparticle-containing solutions awaits further study.
