顺磁共振和傅里叶变换红外光谱法研究高温对荒漠苔藓质膜结构影响

运用顺磁共振波谱和原位傅立叶变换显微红外光谱研究了高温对荒漠植物刺叶墙藓不同叶龄水合组织质膜透性和膜蛋白二级结构的影响。自旋标记法研究质膜透性结果表明,处理前野生叶质膜透性普遍高于室内培养获得的原丝体和次生叶,处理后次生叶膜透性变化最大,比处理前增加4倍,其次为原丝体。质膜透性随叶龄增加,变化幅度逐渐降低。红外光谱的二阶求导、傅立叶自解卷积及拟合分峰等结果显示,各叶龄间蛋白质二级结构含量差异较大,表明各龄组织蛋白成分不完全相同;高温处理后次生叶和原丝体α螺旋含量分别比对照增加40%和16%;其它叶龄组织二级结构含量变化范围小,表明热胁迫下老龄组织蛋白质二级结构稳定。膜透性和膜蛋白二级结构分析证明,膜透性和蛋白质稳定性呈正相关,指示蛋白质组成和含量不同是造成各龄组织不同耐热性的主要原因之一。

典型盐地植物细胞脂质过氧化伤害与质膜超微结构变化的研究

典型盐地植物盐琐琐（Ｈａｌｏｃｎｅｍｕｍｓｔｒｏｂｉｌａｃｅｕｍ）、盐爪爪（Ｋａｌｉｄｉｕｍｆｏｒｉａｔｕｍ）和盐角草（Ｓａｌｉｃｏｒｎｉａｅｕｒｏｐａｅａ）在盐渍环境下细胞内脂质过氧化产物丙二醛（ＭＤＡ）增加，相应的超氧化物歧化酶（ＳＯＤ）也同样增加，且ＳＯＤ含量总保持比ＭＤＡ高１．２倍左右。质膜超微结构的特点是：内陷形成波浪状和在质膜下出现一些泡状结构，有的甚至在质膜下形成一泡状结构分布层。这些都是盐渍造成伤害的表现和标志，但由于细胞抗氧化机能的增强，结构修复的加快，使它们能抵抗高盐的胁迫，保持正常的生命活动。

“细胞由质膜包裹”一节的教学设计

在“细胞由质膜包裹”一节的教学中,以创设真实的情境出发,依托科学史实,引导学生小组合作,自主建构模型,培养学生的科学思维和科学探究能力,在实例分析和问题解决中,形成结构与功能观,增强社会责任感。

Effect of Lysophosphatidylcholine on ATP and ρ-Nitrophenyl Phosphate Hydrolysis by the Plasma Membrane H^+-ATPase from Soybean Hypocotyls

The stimulatory effect of lysophosphatidylcholine (lyso_PC) on ATP and ρ_nitrophenyl phosphate (PNPP) hydrolysis by the plasma membrane H +_ATPase from soybean (Glycine max (L.) Merr.) hypocotyls was studied. Results showed that lyso_PC stimulated the hydrolysis of ATP; ATP hydrolysis was enhanced dramatically when lyso_PC was within 0-0.03%, and increased slightly when lyso_PC was higher than 0.03%. At the concentration of 0.03%, lyso_PC stimulated ATP hydrolysis by 80.5%. Kinetics analysis showed that V max increased from 0.46 μmol P i·mg -1 protein·min -1 to 0.87 μmol P i·mg -1 protein·min -1 while K m increased from 0.88 mmol/L to 1.15 mmol/L under lyso_PC treatment. The optimum pH of ATP hydrolysis was shifted from 6.5 to 7.0 . Moreover, it was found lyso_PC enhanced the inhibition of ATP hydrolysis by hydroxylamine. In the presence of 200 mmol/L hydroxylamine, ATP hydrolysis was inhibited by 74.4%, while it was inhibited by 84.4% when treated with lyso_PC. However, PNPP hydrolysis and the inhibitory effect of vanadate were not affected by lyso_PC. The above results indicated that the kinase domain might be an action site or regulatory region of the C_terminal autoinhibitory domain in the plant plasma membrane H +_ATPase.

Involvement of gene expressions in apoptosis of vascularendothelial cells induced by rattlesnake venom

Formation of apoptotic bodies is a typical character ofaPoptotic cell death, but how the processes are controlledis not known. In this study, we compared two apoptosisinducing systems in vascular endothelial cells (VEC). Wefound that the formation of aPoptotic bodies during apop-tosis induced by rattlesnake venom, which is an unique andspecific aPoptosis inducer to vascular endotheliaI cells, wasmuch faster than that induced by deprivation of survivalfactors (aFGF and serum). When we blocked the synthesisof mRNAs in cells treated with rattlesnake venom by DRB(5, 6- dichloro- 1 -β- D- rib ofur anosylb enzimidazole ), an in-hibitor of transcription, the formation of aPoptotic bodieswas dramatically inhibited. We examined the expressionof Psa gene and found that its expression was much higherin apoptosis induced by rattlesnake venom than that inaPoptosis induced by deprivation of aFGF and serum. Ourresults suggest that gene expression is important and P53gene may play a major role in inducing the formation ofapoptotic bodies in VEC.

S-腺苷蛋氨酸通过降低Cav-1的表达保护KCl刺激引起的神经元损伤

目的探讨S-腺苷蛋氨酸(S-adenosylmethionine,SAM)对KCl刺激引起的原代培养的小鼠皮层神经元损伤是否有保护作用及机制。方法将原代培养1周的小鼠皮层神经元随机分为3组:正常(Control)组、KCl组、SAM-KCl组。用倒置显微镜观察各组细胞形态的变化,用q PCR、Western blot分别检测各组质膜微囊结构蛋白^(-1)(caveolin^(-1),Cav^(-1))mRNA及蛋白的表达变化。结果 0.05 mol·L^(-1)KCl作用于原代培养1周的小鼠皮层神经元12 h可使神经元产生明显的损伤,突起缩短变细,胞体变小,细胞聚团。0.02 mol·L^(-1)SAM预处理6 h可明显降低KCl引起的细胞损伤,q PCR、Western blot分析显示KCl可使原代培养1周的皮层神经元Cav^(-1) mRNA及蛋白表达增高(P<0.01),SAM可降低KCl引起的神经元Cav^(-1) mRNA及蛋白表达增高(P<0.05)。结论 SAM对KCl引起的神经元损伤有保护作用,该保护作用与其降低Cav^(-1)的表达有关。

Fabrication of GaAs/Si Heterostructures and Their Photoelectric Properties

Fabrication of GaAs/Si heterostructures and their photoelectric properties are investigated by Raman, photoluminescence and Hall-effect measurements. The crystallinity of GaAs epilayers grown on Si substrate is significantly affected by the substrate orientation and the growth method. The photoelectric properties of GaAs epilayers grown on Si (211) substrates deposited by using a two-step growth method are improved. These results indicate that GaAs epilayers grown on Si (100) and Si (211) substrates by using two-step growth method are promising for potential applications in high-speed and high-frequency photoelectric devices.

Structure and Oxygen Sensing Properties of TiO_2 Porous Semiconductor Thin Films

Semiconductor-type TiO2 oxygen sensing thin films were synthesized using tetrabutyl titanate （Ti （OBu）4） as precursor and diethanolamine （DEA） as complexing agent by the sol-get process. The porous and oxygen sensing TiO2 films were obtained by the addition of polyethylene glycol （PEG）. The micrographs of scanning electron microscope （SEM） show that the pores of the sample about 400-600 nm in size with PEG（2 000 g/mol） are larger than those about 300 nm in size with PEG（ 1 000 g/mol）, while the density of pores is lower. The results also indicate that increasing the content of PEG properly is beneficial to the formation of porous structure. With the increasing content of PEG from 0 g to 2.5 g, the oxygen sensitivity increases from 330 to more than 1 000 at 800 ℃, from 170 to more than 1 000 at 900℃, and the response time to O2 and H2 are about 1.5 s and less than 1s, respectively.

Effect of Hydrogen Reduction of Silver Ions on the Performance and Structure of New Solid Polymer Electrolyte PEI/Pebax2533/AgBF4 Composite Membranes

In this paper, the effect of hydrogen reduction of silver ions on the performance and structure of new solid polymer electrolyte polyetherimide （PEI）/Pebax2533 （Polynylonl2/tetramethylene oxide block copolymer, PA12-PTMO）/AgBF4 composite membranes is investigated. For PEI/Pebax2533/AgBF4 composite membranesprepared with dillerent AgBF4 concentration, the permeances of propylene and ethylene increase with the increase of AgBF4 concentration due to the carrier-facilitated transport, resulting in a high selectivity. But for propyl- ene/propane mixture, the mixed-gas selectivity is lower than its ideal selectivity. The hydrogen reduction strongly influences the membrane performance, which causes the decrease of propylene permeance and the increase of pro-pane permeance. With the increase of hydrogen reduction time, the membranes show a clearly color change from white to brown, yielding a great selectivity loss. The data of X-ray diffraction and FT-IR prove that silver ions are reduced to Ago after hydrogen reduction, and aggregated on the surface of PEI/Pebax2533/AgBF4 composite mem- branes.

Bandgap-tunable lateral and vertical heterostructures based on monolayer Mo1-xWxS2 alloys

The fabrication of heterostructures of two-dimensional semiconductors with specific bandgaps is an important approach to realizing the full potential of these materials in electronic and optoelectronic devices. Several groups have recently reported the direct growth of lateral and vertical heterostructures based on monolayers of typical semiconducting transition metal dichalcogenides （TMDCs） such as WSe2, MoSe2, WS2, and MoS2. Here, we demonstrate the single-step direct growth of lateral and vertical heterostructures based on bandgap-tunable Mo1-xWxS2 alloy monolayers by the sulfurization of patterned thin films of WO3 and MoO3. These patterned films are capable of generating a wide variety of concentration gradients by the diffusion of transition metals during the crystal growth phase. Under high temperatures, this leads to the formation of monolayer crystals of Mo1-xWxS2 alloys with various compositions and bandgaps, depending on the positions of the crystals on the substrates. Heterostructures of these alloys are obtained through stepwise changes in the ratio of W/Mo within a single domain during low-temperature growth. The stabilization of the monolayer Mo1-xWxS2 alloys, which often degrade even under gentle conditions, was accomplished by coating the alloys with other monolayers. The present findings demonstrate an efficient means of both studying and optimizing the optical and electrical properties of TMDC-based heterostructures to allow use of the materials in future device applications.

Microstructure and magnetic properties of CoFe_2O_4 thin films deposited on Si substrates with an Fe_3O_4 under-layer

The microstructure and magnetic properties of cobalt ferrite thin films deposited by the sputtering method on an Fe3o4 un- der-layer were investigated at different post-annealing temperatures. Results show that the Fe3o4 under-layer can accelerate the grain growth of cobalt ferrite films due to the phase transformation of the Fe3o4 under-layer at about 400℃-500℃. By intro- ducing the Fe3O4 under-layer, cobalt ferrite nanocrystalline thin films with high coercivity can be obtained at lower post-annealing temperatures.

Preparation of microtubular solid oxide fuel cells based on highly asymmetric structured electrolyte hollow fibers

A simple and cost-effective method has been developed for the fabrication of microtubular solid oxide fuel cells (MT-SOFCs). Highly asymmetric electrolyte hollow fibers composed of a thin dense skin layer and a thick porous substrate are first prepared by a modified phase inversion/sintering technique. The porous substrate is then formed into the anode by deposition of a Ni catalyst via an electroless plating method inside the pores while the thin dense skin layer serves directly as the electrolyte film of the fuel cells. A porous cathode layer is produced on the outer surface of the Ni-deposited hollow fibers by slurry coating and subsequent sintering to form a complete micro tubular fuel cell. The process has been employed to fabricate yttrium stabilized zirconia (YSZ) supported Ni-YSZ-YSZ-La0.6Sr0.4Co0.2Fe0.8O3-(LSCF) microtubular fuel cells. The maximum output of the resulting cells is 159.6 mW cm-2 at 800 °C when using H2 as the fuel feed and air as the oxidant.

Structural analysis of a nanoparticle containing a lipid bilayer used for detergent-free extraction of membrane proteins

In the past few years there has been a growth in the use of nanoparticles for stabilizing lipid membranes that contain embedded proteins. These bionanoparticles provide a solution to the challenging problem of membrane protein isolation by maintaining a lipid bilayer essential to protein integrity and activity. We have previously described the use of an amphipathic polymer （poly（styrene-co-maleic add）, SMA） to produce discoidal nanoparticles with a lipid bilayer core containing the embedded protein. However the structure of the nanoparticle itself has not yet been determined. This leaves a major gap in understanding how the SMA stabilizes the encapsulated bilayer and how the bilayer relates physically and structurally to an unencapsulated lipid bilayer. In this paper we address this issue by describing the structure of the SMA lipid particle （SMALP） using data from small angle neutron scattering （SANS）, electron microscopy （EM）, attenuated total reflection Fourier transform infrared spectroscopy （ATR-FTIR）, differential scanning calorimetry （DSC） and nuclear magnetic resonance spectroscopy （NMR）. We show that the particle is disc shaped containing a polymer ＂bracelet＂ encircling the lipid bilayer. The structure and orientation of the individual components within the bilayer and polymer are determined showing that styrene moieties within SMA intercalate between the lipid acyl chains. The dimensions of the encapsulated bilayer are also determined and match those measured for a natural membrane. Taken together, the description of the structure of the SMALP forms the foundation for future development and applications of SMALPs in membrane protein production and analysis.

Microstructure and magnetic properties of FeRh thin films with Pt doping

In this paper, the structure and magnetic properties of FeRh alloy thin films with a small amount of Pt doping fabricated onto a glass substrate by sputtering are investigated systematically. XRD results show that the diffraction pattern of as-deposited film exhibits only nonmagnetic y phase. After annealing, the disordered γphase transforms to an ordered α＇ phase. The temperature dependence of saturation magnetization of different annealing times and Pt contents are characterized. The phase transition temperature increases as the Pt component is increased, but the saturation magnetization reduces as the Pt component is in- creased. These results may be caused by the growth of the disordered γ phase.

Equilibrium Configurations of Lipid Bilayer Membranes and Carbon Nanostructures

The present article concerns the continuum modelling of the mechanical behaviour and equilibrium shapes of two types of nano-scale objects： fluid lipid bilayer membranes and carbon nanostructures. A unified continuum model is used to handle four different ease studies. Two of them consist in representing in analytic form cylindrical and axisymmetric equilibrium configurations of single-wall carbon nanotubes and fluid lipid bilayer membranes subjected to uniform hydrostatic pressure. The third one is concerned with determination of possible shapes of junctions between a single-wall carbon nanotube and a fiat graphene sheet or another single-wall carbon nanotube. The last one deals with the mechanical behaviour of closed fluid lipid bilayer membranes （vesicles） adhering onto a fiat homogeneous rigid substrate subjected to micro-injection and uniform hydrostatic pressure.