Orientational and Magnetic Ordering of Buckyballs in TDAE-C60

Spin ordering in the low-temperature magnetic phase is directly linked to the orientational ordering of C(60) molecules in organically doped fullerene derivatives. Electron spin resonance and alternating current susceptometry measurements on tetrakis(dimethylamino)ethylene-C(60) (TDAE-C(60)) (Curie temperature T(c) = 16 kelvin) show a direct coupling between spin and merohedral degrees of freedom. This coupling was experimentally demonstrated by showing that ordering the spins in the magnetic phase imprints a merohedral order on the solid or, conversely, that merohedrally ordering the C(60) molecules influences the spin order at low temperature. The merohedral disorder gives rise to a distribution of pi-lectron exchange interactions between spins on neighboring C(60) molecules, suggesting a microscopic origin for the observed spinglass behavior of the magnetic state.     

Atomic Force Microscope Studies of Fullerene Films: Highly Stable C60 fcc (311) Free Surfaces

Atomic force microscopy and x-ray diffractometry were used to study 1500 A-thick films of pure C(60) grown by sublimation in ultrahigh vacuum onto a CaF(2) (111) substrate. Topographs of the films did not reveal the expected close-packed structures, but they showed instead large regions that correspond to a face-centered cubic (311) surface and distortions of this surface. The open (311) structure may have a relatively low free energy because the low packing density contributes to a high entropy of the exposed surface.     

Compressibility of M3C60 Fullerene Superconductors: Relation Between Tc and Lattice Parameter

X-ray diffraction and diamond anvil techniques were used to measure the isothermal compressibility of K(3)C(60) and Rb(3)C(60), the superconducting, binary alkali-metal intercalation compounds of solid buckminsterfullerene. These results, combined with the pressure dependence of the superconducting onset temperature T(c) measured by other groups, establish a universal first-order relation between T(c) and the lattice parameter a over a broad range, between 13.9 and 14.5 angstroms. A small secondorder intercalate-specific effect was observed that appears to rule out the participation of intercalate-fullerene optic modes in the pairing interaction.     

C60H2: Synthesis of the Simplest C60 Hydrocarbon Derivative

The reaction of C(60) with BH(3): tetrahydrofuran in toluene followed by hydrolysis yielded C(60)H(2). This product was separated by high-performance liquid chromatography and characterized as the addition product of H(2) to a 6,6-ring fusion (1alb isomer). The (1)H nuclear magnetic resonance (NMR) spectrum of the product remained a sharp singlet between -80 degrees and +100 degrees C, which suggests a static structure on the NMR time scale. Hydrolysis of the proposed borane addition product with acetic acid-d(1) or D(2)O yielded C(60)HD, and its (3)J(HD) coupling constant is consistent with vicinal addition. The observation of a single C(60)H(2) isomer is in complete agreement with earlier calculations that indicated that at most 2 of the 23 possible isomers of C(60) would be observable at equilibrium at room temperature. These results suggest that organoborane chemistry may be applied to further functionalization of fullerenes.     

Ordered Overlayers of C60 on GaAs(110) Studied with Scanning Tunneling Microscopy

Studies of C(60) overlayer growth on GaAs(110) with scanning tunneling microscopy show large first monolayer islands that are locally well ordered, structurally stable, and commensurate with the GaAs surface owing to molecule-substrate interactions. Within the distorted close-packed structure, two distinct adsorption sites were identified, one of them being elevated because of stress in the C(60) monolayer.     

Orientational Disorder of C60 in Li2CsC60

The x-ray diffraction of the nonsuperconducting ternary fulleride Li(2)CsC(60) reveals at room temperature a face-centered-cubic (Fm3m) disordered structure that persists to a temperature of 13 Kelvin. The crystal structure is best modeled as containing quasispherical [radius of 3.556(4) angstroms] C(60)(3-) ions, in sharp contrast to their orientational state in superconducting face-centered-cubic K(3)C(60) (merohedral disorder) and primitive cubic Na(2)CsC(60) (orientational order). The orientational disorder of the carbon atoms on the C(60)(3-) sphere was analyzed with symmetry-adapted spherical-harmonic functions. Excess atomic density is evident in the <111> directions, indicating strong bonding Li(+)-C interactions, not encountered before in any of the superconducting alkali fullerides. The intercalate-carbon interactions and the orientational state of the fullerenes have evidently affected the superconducting pair-binding mechanism in this material.     

High-temperature superconductivity in lattice-expanded C60

C60 single crystals have been intercalated with CHCl3 and CHBr3 in order to expand the lattice. High densities of electrons and holes have been induced by gate doping in a field-effect transistor geometry. At low temperatures, the material turns superconducting with a maximum transition temperature of 117 K in hole-doped C60/CHBr3. The increasing spacing between the C60 molecules follows the general trend of alkali metal-doped C60 and suggests routes to even higher transition temperatures.     

C60分子中原子坐标的计算

运用Ｃ６０分子的Ｉｎ对称性及矢量运算方法，引入调节参数λ计算了正二十面体被截取顶角后的具有Ｃ６０分子结构的原子坐标，当输入的调节参数λ＝０．３３７，Ｃ６０分子的半径Ｒｃ＝３．５５Ａ时，计算得到的长短键分别为１．４４９６Ａ和１．４０Ａ，与测量值相符，并计算了在Ｃ６０面心立方晶体为１．４４９６Ａ和１．４０Ａ，与实验测量值相符，并计算了在Ｃ６０面心立方晶体中，Ｃ６０的二次轴与晶轴取向一致时的各碳原子坐标     

Salt transport organelle in Artemia salenis (brine shrimp)

The branchiae of Artemia adapted to triple-strength sea water (105 per mil salinity) were studied with the electron microscope. The epithelial lining of the metepipodite segment possesses organelles composed of stacks of disc-shaped mitochondria interlaced with flattened extensions of a canalicular system that in turn communicates with the plasma-bound surface of the cells. The distance between the canalicular and mitochondrial membranes is small and quite constant. The marked similarity to "mitochondrial pumps" in the anal papillae of tosquito larvae suggests that the organelle is concerned with salt transport.     

小麦热激蛋白60(HSP60)基因的克隆与原核表达

[目的]构建小麦热激蛋白60基因的原核表达载体,并在E.coli中进行高效表达。[方法]根据GenBank中收录的小麦热激蛋白60基因序列设计合成1对引物P1/P2,利用RT-PCR方法从小麦RNA中扩增小麦HSP60基因,应用基因重组技术构建pGEX-4T-1-HSP60表达载体,将构建好的小麦HSP60基因原核表达载体pGEX-4T-1-HSP60转化至大肠杆菌表达菌株E.coli-BL21感受态细胞。[结果]对重组质粒进行酶切分析及序列测定鉴定正确后,与GenBank中收录的小麦HSP60基因序列比对分析,同源性达100%。在IPTG诱导下获得了目的蛋白,所表达的GST-HSP60融合蛋白分子量约为90 KD。蛋白质电泳（SDS-PAGE）结果表明,表达的蛋白条带与预期的大小一致。[结论]成功构建了pGEX-4T-1-HSP60的原核表达载体,在E.coli-BL21中高效表达了HSP60蛋白,为进一步研究该蛋白的功能及其作用机制奠定了基础。     

Packing C60 in boron nitride nanotubes

We have created insulated C60 nanowire by packing C60 molecules into the interior of insulating boron nitride nanotubes (BNNTs). For small-diameter BNNTs, the wire consists of a linear chain of C60 molecules.With increasing BNNT inner diameter, unusual C60 stacking configurations are obtained (including helical, hollow core, and incommensurate) that are unknown for bulk or thin-film forms of C60.C60 in BNNTs thus presents a model system for studying the properties of dimensionally constrained "silo" crystal structures. For the linear-chain case, we have fused the C60 molecules to form a single-walled carbon nanotube inside the insulating BNNT.     

(RbxK1-x)3C60 Superconductors: Formation of a Continuous Series of Solid Solutions

By means of an approach that employs alkali-metal alloys, bulk single-phase (RbxK1-x)(3)C(6O) superconductors have been prepared for all x between 0 and 1. For x = 1 it is shown that the maximum superconducting fraction, which approaches 100% in sintered pellets, occurs at a Rb to C(60) ratio of 3:1. More importantly, single-phase superconductors are formed at all intermediate values of x, and it is shown that the transition temperature (T(c)) increases linearly with x in this series of materials. The formation of a continuous range of solid solutions demonstrates that the rubidium- and potassium-doped C(60) superconducting phases must be isostructural, and furthermore, suggests that the linear increase in T(c) with x results from a chemical pressure effect.     

盐逆境胁迫下施钾对降低小麦盐害的生理效应研究

在盐逆境下施用钾肥可以增加小麦灌浆期旗叶的叶绿素含量,延长叶片的功能期,提高植株叶片的K+及K+/Na+,增强叶片的保水能力,提高旗叶光合速率和籽粒产量。在本试验条件下,以施用K2O 90kg/hm2处理效果最佳,在此基础上再增加施钾量则效果下降。     

小麦热激蛋白60(HSP60)基因的克隆与原核表达(摘要)(英文)

[目的]构建小麦热激蛋白60(HSP60)基因的原核表达载体,并在E.coli中进行高效表达。[方法]根据GenBank中收录的小麦HSP60基因序列设计合成1对引物P1/P2,利用RT-PCR方法从小麦RNA中扩增小麦HSP60基因,应用基因重组技术构建pGEX-4T-1-HSP60表达载体,将构建好的小麦HSP60基因原核表达载体pGEX-4T-1-HSP60转化至大肠杆菌表达菌株E.coliBL21感受态细胞。[结果]对重组质粒进行酶切分析及序列测定鉴定正确后,与GenBank中收录的小麦HSP60基因序列比对分析,同源性达100%。在IPTG诱导下获得了目的蛋白,所表达的GST-HSP60融合蛋白分子量约为90kD。蛋白质电泳(SDS-PAGE)结果表明,表达的蛋白条带与预期大小一致。[结论]成功构建了pGEX-4T-1-HSP60的原核表达载体,在E.coliBL21中高效表达了HSP60蛋白,为进一步研究该蛋白的功能及其作用机制奠定了基础。     

Taming superacids: stabilization of the fullerene cations HC60+ and C60.+

A new superacid, H(CB11H6X6) (where X = chlorine or bromine), whose conjugate base is the exceptionally inert CB11H6X6- carborane anion, separates Bronsted acidity from oxidizing capacity and anion nucleophilicity in a manner not previously achieved. Reaction of this superacid with C60 gives HC60+ as a stable ion in solution and in the solid state. In a separate experiment, an oxidant was developed such that the long-sought C60.+ ion can be synthesized in solution. The preparation of these two fullerene carbocations is a notable departure from the prevalent chemistry of C60, which is dominated by the formation of anions or the addition of nucleophiles. The H(CB11H6X6) superacid overcomes the major limitations of presently known superacids and has potentially wide application.