In this study,circular dichroism(CD)and molecular dynamics(MD)simulation were used to investigate the thermal unfolding pathway of staphylococcal enterotoxin B(SEB)at temperatures of 298–371 and 298–500 K,and the re...In this study,circular dichroism(CD)and molecular dynamics(MD)simulation were used to investigate the thermal unfolding pathway of staphylococcal enterotoxin B(SEB)at temperatures of 298–371 and 298–500 K,and the relationship between the experimental and simulation results were explored.Our computational findings on the secondary structure of SEB showed that at room temperature,the CD spectroscopic results were highly consistent with the MD results.Moreover,under heating conditions,the changing trends of helix,sheet and random coil obtained by CD spectral fitting were highly consistent with those obtained by MD.In order to gain a deeper understanding of the thermal stability mechanism of SEB,the MD trajectories were analyzed in terms of root mean square deviation(RMSD),secondary structure assignment(SSA),radius of gyration(R_(g)),free energy surfaces(FES),solvent-accessible surface area(SASA),hydrogen bonds and salt bridges.The results showed that at low heating temperature,domain Ⅰ without loops(omitting the mobile loop region)mainly relied on hydrophobic interaction to maintain its thermal stability,whereas the thermal stability of domain Ⅱ was mainly controlled by salt bridges and hydrogen bonds.Under high heating temperature conditions,the hydrophobic interactions in domain Ⅰ without loops were destroyed and the secondary structure was almost completely lost,while domain Ⅱ could still rely on salt bridges as molecular staples to barely maintain the stability of the secondary structure.These results help us to understand the thermodynamic and kinetic mechanisms that maintain the thermal stability of SEB at the molecular level,and provide a direction for establishing safer and more effective food sterilization processes.展开更多
The interconnection of polarization and phase in electromagnetic scattering process has attracted both fundamental and practical interest.Here we propose the principle and experimental demonstration of a scatteringcon...The interconnection of polarization and phase in electromagnetic scattering process has attracted both fundamental and practical interest.Here we propose the principle and experimental demonstration of a scatteringcontrol mechanism based on the simultaneous control of polarization and phase via a continuously shaped planar metasurface.Under circularly polarized illumination,the scattering is redirected to off-specular direction,leading to significant reduction of the scattering cross section.Theoretical investigation shows that the underlying physical mechanism is the spin-dependent phase modulation in the anisotropic scattering process.Our approach would provide valuable guidance for the full control of electromagnetic wave for diverse applications.展开更多
Based on the starch hydrolysis reaction accelerated by microwave irradiation with α-amylase, the circular dichroism （CD） and secondary structure changes of α-amylase under the condition of microwave irradiation an...Based on the starch hydrolysis reaction accelerated by microwave irradiation with α-amylase, the circular dichroism （CD） and secondary structure changes of α-amylase under the condition of microwave irradiation and water bath were studied by circular dichroism spectra. The results showed that, both the peak heights （at 2=193 nm） of the CD spectra of the samples treated by microwave irradiation and water bath reduced. The reduced rate by microwave irradiation ranged from 140% to 220%, while the reduced rate by water bath ranged from 60% to 140%. The peak of the sample treated by microwave irradiation for 60 min disappeared at λ=193 nm, while the sample showed a wake peak by water bath. The peak position by microwave irradiation emerged a blue shift in the range of 5-8 nm at λ=204 nm and λ=220 nm, while it emerged in the range of 3-5 nm by water bath. With time going on, the microwave irradiation and water bath have prompted the secondary structure of α-helix, β-sheet, β-turn and the mutual transformations of random coil, but the trends were different.展开更多
In human cells, the heterogeneous nuclear ribonucleoproteins (hnRNP) are represented by a group of polypeptides, with various molecular properties, comprizing the most abundant constituents of the cell nucleus. Autoan...In human cells, the heterogeneous nuclear ribonucleoproteins (hnRNP) are represented by a group of polypeptides, with various molecular properties, comprizing the most abundant constituents of the cell nucleus. Autoantibodies to hnRNPs have been reported in patients suffering from different rheumatic dieseases since 1980s. Experimental evidence indicates that hnRNP complexes undergo substantial structural changes during mRNA formation and export. However, how this contributes to disease development still has to be elucidated. Here some preliminary physicochemical features of RNA-protein folding and stability patterns of newly characterized hnRNP A3 with further functional implications in development of systemic human autoimmune states are reported.展开更多
Interactions between Cd 2+ ions and salmon sperm DNA were investigated via UV Vis, Circular Dichroism(CD) and FT Raman spectroscopies. The experimental results show that Cd 2+ ions can coordinate with the phosphate gr...Interactions between Cd 2+ ions and salmon sperm DNA were investigated via UV Vis, Circular Dichroism(CD) and FT Raman spectroscopies. The experimental results show that Cd 2+ ions can coordinate with the phosphate groups of DNA and thus induce conformation changes of the DNA from B to A type.展开更多
大豆蛋白加入小麦粉中改善面制品营养品质的同时也会对面团的面筋蛋白组成和结构产生影响。醇溶蛋白是小麦面筋的主要组分,赋予面团黏性和延伸性。为探究大豆蛋白对面团中醇溶蛋白的影响,将大豆分离蛋白(soy protein isolate,SPI)、大...大豆蛋白加入小麦粉中改善面制品营养品质的同时也会对面团的面筋蛋白组成和结构产生影响。醇溶蛋白是小麦面筋的主要组分,赋予面团黏性和延伸性。为探究大豆蛋白对面团中醇溶蛋白的影响,将大豆分离蛋白(soy protein isolate,SPI)、大豆浓缩蛋白(soy protein concentrate,SPC)、质构化大豆蛋白(texturized soy protein,TSP)分别以不同比例添加到小麦粉中制成面团,分离醇溶蛋白,通过内源荧光光谱、紫外光谱扫描及酸性聚丙烯酰胺电泳等方法对面团中醇溶蛋白的结构和组成进行评价。结果表明,与小麦粉面团相比,添加8%(质量分数,下同)的SPI、SPC、TSP后,面团中醇溶蛋白相对含量分别下降了9.65%、9.85%、5.97%;添加8%的SPI后,面团α-醇溶蛋白比例增加0.79%,β-,γ-醇溶蛋白比例无显著性变化,ω-醇溶蛋白比例下降2.27%;添加8%的SPC后,面团α-醇溶蛋白比例下降1.42%,β-醇溶蛋白比例下降1.59%,γ-醇溶蛋白无显著性变化,ω-醇溶蛋白比例增加3.25%;添加8%的TSP后,面团α-醇溶蛋白比例下降1.47%,β-,γ-醇溶蛋白比例无显著性变化,ω-醇溶蛋白比例增加1.12%。添加SPI和TSP均能使面团中醇溶蛋白肽链伸展,α-螺旋含量降低;添加SPI使面团中醇溶蛋白β-转角含量降低;添加SPC对面团中醇溶蛋白结构无显著影响。综上,添加大豆蛋白使面团中醇溶蛋白相对含量下降,肽链结构伸展,蛋白组分发生变化,从而改变醇溶蛋白黏附在麦谷蛋白骨架的状态,增大面团拉断力,缩短面团拉伸距离。该研究建立了一种探究面团中醇溶蛋白组成和结构的方法体系,为植物源蛋白在面制品中的应用提供理论基础和新思路。展开更多
文摘In this study,circular dichroism(CD)and molecular dynamics(MD)simulation were used to investigate the thermal unfolding pathway of staphylococcal enterotoxin B(SEB)at temperatures of 298–371 and 298–500 K,and the relationship between the experimental and simulation results were explored.Our computational findings on the secondary structure of SEB showed that at room temperature,the CD spectroscopic results were highly consistent with the MD results.Moreover,under heating conditions,the changing trends of helix,sheet and random coil obtained by CD spectral fitting were highly consistent with those obtained by MD.In order to gain a deeper understanding of the thermal stability mechanism of SEB,the MD trajectories were analyzed in terms of root mean square deviation(RMSD),secondary structure assignment(SSA),radius of gyration(R_(g)),free energy surfaces(FES),solvent-accessible surface area(SASA),hydrogen bonds and salt bridges.The results showed that at low heating temperature,domain Ⅰ without loops(omitting the mobile loop region)mainly relied on hydrophobic interaction to maintain its thermal stability,whereas the thermal stability of domain Ⅱ was mainly controlled by salt bridges and hydrogen bonds.Under high heating temperature conditions,the hydrophobic interactions in domain Ⅰ without loops were destroyed and the secondary structure was almost completely lost,while domain Ⅱ could still rely on salt bridges as molecular staples to barely maintain the stability of the secondary structure.These results help us to understand the thermodynamic and kinetic mechanisms that maintain the thermal stability of SEB at the molecular level,and provide a direction for establishing safer and more effective food sterilization processes.
基金the China Triumph International Engineering Co. Ltd.(CTIEC),Shanghai,China,which offers generous financial support for this work
文摘The interconnection of polarization and phase in electromagnetic scattering process has attracted both fundamental and practical interest.Here we propose the principle and experimental demonstration of a scatteringcontrol mechanism based on the simultaneous control of polarization and phase via a continuously shaped planar metasurface.Under circularly polarized illumination,the scattering is redirected to off-specular direction,leading to significant reduction of the scattering cross section.Theoretical investigation shows that the underlying physical mechanism is the spin-dependent phase modulation in the anisotropic scattering process.Our approach would provide valuable guidance for the full control of electromagnetic wave for diverse applications.
基金Project(08A080) supported by the Scientific Research Fund of Hunan Provincial Education Department,China
文摘Based on the starch hydrolysis reaction accelerated by microwave irradiation with α-amylase, the circular dichroism （CD） and secondary structure changes of α-amylase under the condition of microwave irradiation and water bath were studied by circular dichroism spectra. The results showed that, both the peak heights （at 2=193 nm） of the CD spectra of the samples treated by microwave irradiation and water bath reduced. The reduced rate by microwave irradiation ranged from 140% to 220%, while the reduced rate by water bath ranged from 60% to 140%. The peak of the sample treated by microwave irradiation for 60 min disappeared at λ=193 nm, while the sample showed a wake peak by water bath. The peak position by microwave irradiation emerged a blue shift in the range of 5-8 nm at λ=204 nm and λ=220 nm, while it emerged in the range of 3-5 nm by water bath. With time going on, the microwave irradiation and water bath have prompted the secondary structure of α-helix, β-sheet, β-turn and the mutual transformations of random coil, but the trends were different.
文摘In human cells, the heterogeneous nuclear ribonucleoproteins (hnRNP) are represented by a group of polypeptides, with various molecular properties, comprizing the most abundant constituents of the cell nucleus. Autoantibodies to hnRNPs have been reported in patients suffering from different rheumatic dieseases since 1980s. Experimental evidence indicates that hnRNP complexes undergo substantial structural changes during mRNA formation and export. However, how this contributes to disease development still has to be elucidated. Here some preliminary physicochemical features of RNA-protein folding and stability patterns of newly characterized hnRNP A3 with further functional implications in development of systemic human autoimmune states are reported.
文摘Interactions between Cd 2+ ions and salmon sperm DNA were investigated via UV Vis, Circular Dichroism(CD) and FT Raman spectroscopies. The experimental results show that Cd 2+ ions can coordinate with the phosphate groups of DNA and thus induce conformation changes of the DNA from B to A type.
文摘大豆蛋白加入小麦粉中改善面制品营养品质的同时也会对面团的面筋蛋白组成和结构产生影响。醇溶蛋白是小麦面筋的主要组分,赋予面团黏性和延伸性。为探究大豆蛋白对面团中醇溶蛋白的影响,将大豆分离蛋白(soy protein isolate,SPI)、大豆浓缩蛋白(soy protein concentrate,SPC)、质构化大豆蛋白(texturized soy protein,TSP)分别以不同比例添加到小麦粉中制成面团,分离醇溶蛋白,通过内源荧光光谱、紫外光谱扫描及酸性聚丙烯酰胺电泳等方法对面团中醇溶蛋白的结构和组成进行评价。结果表明,与小麦粉面团相比,添加8%(质量分数,下同)的SPI、SPC、TSP后,面团中醇溶蛋白相对含量分别下降了9.65%、9.85%、5.97%;添加8%的SPI后,面团α-醇溶蛋白比例增加0.79%,β-,γ-醇溶蛋白比例无显著性变化,ω-醇溶蛋白比例下降2.27%;添加8%的SPC后,面团α-醇溶蛋白比例下降1.42%,β-醇溶蛋白比例下降1.59%,γ-醇溶蛋白无显著性变化,ω-醇溶蛋白比例增加3.25%;添加8%的TSP后,面团α-醇溶蛋白比例下降1.47%,β-,γ-醇溶蛋白比例无显著性变化,ω-醇溶蛋白比例增加1.12%。添加SPI和TSP均能使面团中醇溶蛋白肽链伸展,α-螺旋含量降低;添加SPI使面团中醇溶蛋白β-转角含量降低;添加SPC对面团中醇溶蛋白结构无显著影响。综上,添加大豆蛋白使面团中醇溶蛋白相对含量下降,肽链结构伸展,蛋白组分发生变化,从而改变醇溶蛋白黏附在麦谷蛋白骨架的状态,增大面团拉断力,缩短面团拉伸距离。该研究建立了一种探究面团中醇溶蛋白组成和结构的方法体系,为植物源蛋白在面制品中的应用提供理论基础和新思路。
