Aromatic cross-links in insect cuticle: detection by solid-state 13C and 15N NMR

Cross-polarization magic-angle-spinning nuclear magnetic resonance spectroscopy has been used to determine insect cuticle composition and cross-link structure during sclerotization or tanning. Unsclerotized cuticle from newly ecdysed pupae of the tobacco hornworm, Manduca sexta L., had a high protein content with lesser amounts of lipid and chitin. Concentrations of chitin, protein, and catechol increased substantially as dehydration and sclerotization progressed. Analysis of intact cuticle specifically labeled with carbon-13 and nitrogen-15 revealed direct covalent linkages between ring nitrogens of protein histidyl residues and ring carbons derived from the catecholamine dopamine. This carbon-nitrogen adduct was present in chitin isolated from cuticle by alkaline extraction and is probably bound covalently to chitin. These data support the hypothesis that the stiffening of insect cuticle during sclerotization results primarily from the deposition of protein and chitin polymers and their crosslinking by quinonoid derivatives of catecholamines.     

含偶氮类光学活性侧基淀粉的合成及表征

以硫酸铈铵盐和过硫酸钾-亚硫酸氢钠为引发剂,十二烷基苯磺酸钠为乳化剂,引发可溶性淀粉与3种偶氮苯衍生物的乙烯基单体接枝共聚.通过TGA、DSC、SEM等手段对接枝共聚物结构的表征,证明发生了接枝共聚反应.     

Detection of hydroxyl ions in bone mineral by solid-state NMR spectroscopy

Previous measurements of the hydroxyl (OH-) ion content of the calcium phosphate crystals of bone mineral have indicated a substantial depletion or near-absence of OH-, despite its presumed status as a constituent of the hydroxyapatite lattice. Analytical methods for determining bone crystal OH- content have depended on procedures or assumptions that may have biased the results, such as chemical pretreatment to eliminate interference from the organic matrix. We demonstrate a two-dimensional solid-state nuclear magnetic resonance (NMR) spectroscopy technique that detects the proton spectrum of bone crystals while suppressing the interfering matrix signals, eliminating the need for specimen pretreatment other than cryogenic grinding. Results on fresh-frozen and ground whole bone of several mammalian species show that the bone crystal OH- is readily detectable; a rough estimate yields an OH- content of human cortical bone of about 20% of the amount expected in stoichiometric hydroxyapatite. This finding sheds light on the biochemical processes underlying normal and abnormal bone mineral metabolism.     

Intercalation complex of proflavine with DNA: structure and dynamics by solid-state NMR

The structure of the complex formed between the intercalating agent proflavine and fibrous native DNA was studied by one- and two-dimensional high-resolution solid-state nuclear magnetic resonance (NMR). Carbon-13-labeled proflavine was used to show that the drug is stacked with the aromatic ring plane perpendicular to the fiber axis and that it is essentially immobile. Natural abundance carbon-13 NMR of the DNA itself shows that proflavine binding does not change the puckering of the deoxyribose ring. However, phosphorus-31 NMR spectra show profound changes in the orientation of the phosphodiester grouping on proflavine binding, with some of the phosphodiesters tilting almost parallel to the helix axis, and a second set almost perpendicular. The first group to the phosphodiesters probably spans the intercalation sites, whereas the tilting of the second set likely compensates for the unwinding of the DNA by the intercalator.     

Mechanisms of proton conduction and gating in influenza M2 proton channels from solid-state NMR

The M2 protein of influenza viruses forms an acid-activated tetrameric proton channel. We used solid-state nuclear magnetic resonance spectroscopy to determine the structure and functional dynamics of the pH-sensing and proton-selective histidine-37 in M2 bound to a cholesterol-containing virus-envelope-mimetic membrane so as to better understand the proton conduction mechanism. In the high-pH closed state, the four histidines form an edge-face π-stacked structure, preventing the formation of a hydrogen-bonded water chain to conduct protons. In the low-pH conducting state, the imidazoliums hydrogen-bond extensively with water and undergo microsecond ring reorientations with an energy barrier greater than 59 kilojoules per mole. This barrier is consistent with the temperature dependence of proton conductivity, suggesting that histidine-37 dynamically shuttles protons into the virion. We propose a proton conduction mechanism in which ring-flip-assisted imidazole deprotonation is the rate-limiting step.     

异维A酸衍生物合成与结构表征

在考察了不同的反应条件后，建立了以二环己基碳酰亚胺(DCC)为脱水剂、合成具有药物活性的异维A酸酯和异维A酰胺的合成方法。在温和条件下(0℃至室温)以4-二甲氨基吡啶(DMAP)为催化剂，将在通常情况下极易异构化的异维A酸3能顺利地转化为它们的衍生物．收率为42．3％～82．4％。合成了10种尚未见文献报道的异维A酸酯和异维A酰胺，并考察了它们的分离纯化条件，以^1H，^13C NMR和MS对它们的结构进行了表征。     

烟叶果胶糖醛酸结构的固态核磁共振波谱表征

烟叶果胶不同糖醛酸结构的含量分布,对其生理功能和产品品质有着重要影响。为表征烟叶果胶糖醛酸结构,采用固态¹³C交叉极化/魔角旋转核磁共振波谱技术(¹³C CP/MAS NMR),以二甲基硅橡胶管为内标物质,建立烤烟烟叶中果胶含量的定量分析方法。选择NMR图谱中果胶C-6区域的波谱峰,应用PeakFit软件进行去卷积分峰处理,实现烟草样品果胶不同糖醛酸结构,即果胶酸(-COOH)、甲酯化果胶(-COOCH₃)、果胶酸钙盐(-COO^-)等定性和含量分布的分析表征。应用固态核磁共振波谱分析表征了不同部位9种烟叶样品中的果胶含量及其糖醛酸结构。结果表明,烟叶果胶含量随着烟叶部位上升而逐渐增高。样品烟叶中甲酯化果胶的含量分布均小于50%,属低甲酯化果胶。对比中部烟叶,上部叶的甲酯化果胶含量偏高,下部叶偏低,而上部叶的果胶酸钙盐含量较低,下部叶较高。结果为烟草果胶大分子结构与性能的关系研究,提供准确、简便的技术方法。     

Quantitation of hepatic glycogenolysis and gluconeogenesis in fasting humans with 13C NMR

The rate of net hepatic glycogenolysis was assessed in humans by serially measuring hepatic glycogen concentration at 3- to 12-hour intervals during a 68-hour fast with 13C nuclear magnetic resonance spectroscopy. The net rate of gluconeogenesis was calculated by subtracting the rate of net hepatic glycogenolysis from the rate of glucose production in the whole body measured with tritiated glucose. Gluconeogenesis accounted for 64 +/- 5% (mean +/- standard error of the mean) of total glucose production during the first 22 hours of fasting. In the subsequent 14-hour and 18-hour periods of the fast, gluconeogenesis accounted for 82 +/- 5% and 96 +/- 1% of total glucose production, respectively. These data show that gluconeogenesis accounts for a substantial fraction of total glucose production even during the first 22 hours of a fast in humans.     

一株海洋弧菌噬菌体--NP13的生物学特性研究

１９９６年夏季,从大连星海湾海滨浴场采集的海水样品中,以河流弧菌Ⅱ（Ｖｉｂｒｉｏ ｆｌｕｖｉａｌｉｓ－Ⅱ）为批示菌,从中分离出一株噬菌体－ＮＰ１３。对ＮＰ１３的形态进行了电子显微镜观察分析。并对其生物学特性进行了初步的研究。结果表明：ＮＰ１３在５０℃、３０ｍｉｎ和６０℃、３０ｍｉｎ下的存活率各约为９５％和４５％,并在ｐＨ５～１１之间均具有很高的稳定性。     

Synthesis and characterization of anisometric cobalt nanoclusters

Sonication of aqueous Co(2+) and hydrazine resulted in the formation of anisometric (disk-shaped) cobalt nanoclusters that averaged about 100 nanometers in width and 15 nanometers in thickness. Electron diffraction from single particles revealed that they were oriented (001) crystals that conformed to a trigonal or hexagonal unit cell four times the size of the cell adopted by bulk alpha-cobalt. Lorentz microscopy indicated that these were single-magnetic domain particles, with the axis of magnetization located in the (101) plane, offset at some appreciable angle from the (001) axis.     

Atomic-level characterization of the structural dynamics of proteins

Molecular dynamics (MD) simulations are widely used to study protein motions at an atomic level of detail, but they have been limited to time scales shorter than those of many biologically critical conformational changes. We examined two fundamental processes in protein dynamics--protein folding and conformational change within the folded state--by means of extremely long all-atom MD simulations conducted on a special-purpose machine. Equilibrium simulations of a WW protein domain captured multiple folding and unfolding events that consistently follow a well-defined folding pathway; separate simulations of the protein's constituent substructures shed light on possible determinants of this pathway. A 1-millisecond simulation of the folded protein BPTI reveals a small number of structurally distinct conformational states whose reversible interconversion is slower than local relaxations within those states by a factor of more than 1000.     

客家黄酒多糖的分离纯化及结构表征

以客家黄酒为原料提取制备的客家黄酒多糖,经离子交换层析分离得到中性和酸性两个级分,中性多糖经凝胶柱纯化得到G1组分,利用GC-MS和HPLC-ELSD测定中性多糖G1组分.结果表明,中性多糖级分G1以葡萄糖为主要组分,还含有甘露糖、半乳糖,少量的核糖、阿拉伯糖、木糖、异麦芽糖、麦芽三糖、异麦芽三糖等.对G1的结构进行表征,结果表明,客家黄酒多糖G1含有α型和β型糖苷、吡喃糖环构型,是一种含有甘露糖、不含糖醛酸的、由17种糖组成的杂多糖.     

环丙氨嗪人工抗原的合成与鉴定

本研究拟通过抗原合成、多克隆抗体制备等途径建立快速的环丙氨嗪酶联免疫检测方法.主要采用戊二醛桥连法,偶联半抗原环丙氨嗪和载体牛血清白蛋白(BSA)或卵清白蛋白(OVA),制备酶联检测的免疫抗原和包被抗原.经紫外光谱和气相-傅里叶-红外光谱鉴定,在紫外265 nm波长处得到环丙氨嗪-BSA吸收峰;在红外3 350～3 300 cm-1、1 660～1 500 cm-1和1 695～1 665 cm-1波长处分别得到环丙氨嗪-BSA和环丙氨嗪-OVA特征性偶联吸收峰,证实本试验人工合成的2对抗原均偶联成功.免疫抗原和包被抗原的偶联比分别达到25.9 ∶ 1、23.1 ∶ 1,为进一步制备抗血清和酶联检测方法的建立奠定了工作基础.     

棉属AD远缘杂种的合成及性状鉴定

[目的]棉属A、D组棉种是研究物种形成过程中生殖隔离机制和基因组互作的良好材料,本研究旨在获得AD远缘杂种并从形态学初步鉴定杂种的真实性,探讨A、D组棉种间生殖隔离的先后顺序,并进一步探究亲本基因组在杂种中的互作模式。[方法]选用A组亚洲棉、草棉为母本,D组雷蒙德氏和瑟伯氏棉为父本进行远缘杂交,获得杂种并进行统计分析和形态性状鉴定。[结果]结果表明四个组合中只有亚雷、草雷和亚瑟获得杂种并长成植株,亚雷和草雷组合的杂种植株长势旺盛并能开花,且杂种大部分性状间于双亲之间;亚瑟组合收到种子并能成苗,但植株生长受阻不现蕾;草瑟组合没有收到饱满种子。[结论]草瑟组合属于合子前生殖隔离;草雷、亚雷、亚瑟生殖隔离是由合子前和合子后生殖隔离共同起作用。且草雷、亚雷杂种基因组互作亲和,而亚瑟杂种基因组互作不亲和。D组雷蒙德氏棉能同时和A1、A2组杂交成功并获得杂种后代,进一步验证了雷蒙德氏棉被视为四倍体棉种祖先的直接证据。     

蒸汽爆破/氧化钙联合预处理对水稻秸秆厌氧干发酵影响研究

为了提高水稻秸秆在厌氧干发酵中的利用效率,采用蒸汽爆破、氧化钙以及蒸汽爆破/氧化钙联合预处理(以下简称"联合处理")水稻秸秆,考察不同处理方式对水稻秸秆的理化性质和厌氧干发酵的影响。结果表明:从扫描电子显微镜照片观察到,联合处理组与其他处理方式相比对水稻秸秆结构破坏最彻底。木质素含量测试结果显示,经过联合处理水稻秸秆中木质素含量从17.2%下降到12.2%,去除率可达29.1%。纤维素酶水解实验中,联合处理组的葡萄糖产量与木糖产量分别为877.56 mg·L~(-1)和400.85 mg·L~(-1),比CK组提高了85.43%和1 283.39%。在厌氧干发酵实验中,联合处理组产甲烷延滞期最短(5 d),比CK组缩短了约6 d,第30 d累积产甲烷量占总产甲烷量(60 d)的86.4%,而CK组仅占55.7%,原料产甲烷率提升最明显(0.24 L·g-1VS),比CK组提高了20.0%。动力学模型拟合结果表明,与蒸汽爆破处理、氧化钙处理相比,联合处理组对厌氧干发酵的促进作用最显著。     

Synthesis and characterization of helical multi-shell gold nanowires

Suspended gold nanowires were made in an ultra-high vacuum. The finest of them was 0.6 nanometer in diameter and 6 nanometers in length. By high-resolution electron microscopy, they were shown to have a multi-shell structure composed of coaxial tubes. Each tube consists of helical atom rows coiled round the wire axis. The difference between the numbers of atom rows in outer and inner shells is seven, resulting in magic shell-closing numbers.     

Synthesis and characterization of castor oil-based polymeric surfactants

Dehydrated castor oil was epoxidized using phosphoric acid as a catalyst and acetic acid peroxide as an oxidant to produce epoxidized castor oil (ECO). Ring-opening polymerization with stannic chloride was used to produce polymerized ECO (PECO), and sodium hydroxide used to give hydrolyzed PECO (HPECO). The HPECO was characterized by Fourier transform infrared, ¹H and ¹³C nuclear magnetic resonance spectroscopies, gel permeation chromatography, and differential scanning calorimetry. The weight-average molecular weight of soluble PECO and HPECO were 5026 and 2274 g·mol^-1, respectively. PECO and HPECO exhibited glass transition. Through neutralizing the carboxylic acid of HPECO with different counterions, castor oil-based polymeric surfactants (HPECO-M, where M= Na⁺, K⁺ or triethanolamine ion) exhibited high efficiency to reduce the surface tension of water. The critical micelle concentration (CMC) values of HPECO-M ranged from 0.042 to 0.098 g·L^-1 and the minimum equilibrium surface tensions at CMC (g_cmc) of HPECO-M ranged from 25.6 to 30.0 mN·m^-1. The water-hexadecane interfacial energy was calculated from measured surface tension using harmonic and geometric mean methods. Measured values of water-hexadecane interfacial tension agreed well with those calculated using the harmonic and geometric mean methods.     

Synthesis of buried oxide and silicide layers with ion beams

Ion implantation, because it is inherently a strongly nonequilibrium process, can add a new dimension to materials studies. A large variety of chemical elements may be readily introduced into a target substrate by ion bombardment at concentrations considerably greater than the normal solid solubilities. In addition, the interaction of the accelerated ions with the target produces lattice defects. Both effects have been studied extensively in experiments directed at understanding the mechanisms of formation of buried oxide and silicide layers in silicon with high-dose ion implantation. These layers have properties that are difficult to attain with conventional techniques.     

苦皮藤素Ⅴ人工抗原的合成与鉴定

采用琥珀酸酐法合成了苦皮藤素 的衍生物苦皮藤素 -半琥珀酸酯(CA-SG),在此基础上,分别采用混合酸酐法和碳化二亚胺法合成了苦皮藤素 的人工抗原(CA-BSA,CA-BSA2),采用紫外分光光度计法、SDS-PAGE及PAGE电泳法对合成的人工抗原进行了定性鉴定,结果均表明人工抗原合成成功。根据半抗原、人工抗原及其载体在240nm处的紫外吸光值,计算出2种人工抗原中半抗原与载体的分子结合比率分别为11.6和10.7。     

Synthesis and characterization of the nitrides of platinum and iridium

Transition metal nitrides are of great technological and fundamental importance because of their strength and durability and because of their useful optical, electronic, and magnetic properties. We have evaluated a recently synthesized platinum nitride (PtN) that was shown to have a large bulk modulus, and we propose a structure that is isostructural with pyrite and has the stoichiometry PtN2. We have also synthesized a recoverable nitride of iridium under nearly the same conditions of pressure and temperature as PtN2. Although it has the same stoichiometry, it exhibits much lower structural symmetry. Preliminary results suggest that the bulk modulus of this material is also very large.