Heterotricyclodecane XIX. Umlagerungen von 4,8-disubstituierten 2,6-Dioxa- und 2-Oxa-6-aza-adamantanen zu 4,10-disubstituierten 2,7-Dioxa- und 2-Oxa-7-aza-isotwistanen sowie -twistanen

Rearrangements of 4,8-disubstituted 2,6-dioxa- and 2-oxa-6-aza-adamantanes to 4,10-disubstituted 2,7-dioxa- and 2-oxa-7-aza-isotwistanes as well as -twistanes. Substitutions and rearrangements involving neighboring group participation starting from 4,8-diiodo-2,6-dioxa- and 4,8-diiodo-2-oxa-6-aza-adamantanes ( 5 and 6, 12 and 48 , resp.) were studied, yielding 4,8-disubstituted 2,6-dioxa- and 2-oxa-6-aza-adamantanes ( 7, 9, 39, 42 and 13, 15, 50, 52 , resp.), 4,10-disubstituted 2,7-dioxa- and 2-oxa-7-aza-isotwistanes ( 8, 10, 41, 43 and 14, 16, 51, 53 , resp.) and corresponding-twistanes ( 11 and 17 , resp.).     

伊敏褐煤中微量元素的地球化学特征及其无机-有机亲和性分析

采用脱矿物质、提取腐殖酸等方法结合ICP-MS对伊敏15_上、16_下煤中的32种微量元素的含量及其赋存特征进行了分析。与地壳克拉克值及中国侏罗-白垩纪煤和世界褐煤中微量元素含量相比,伊敏褐煤中微量元素没有明显富集。脱矿物质处理后,Ni明显富集,As略比原煤高,其他微量元素都低于原煤。原煤提取腐殖酸和脱矿物煤提取腐殖酸中Ni、Mo、Cd、Sn、W明显富集,这表明Ni、Mo、Cd、Sn、W和腐殖酸形成了稳定的有机态化合物。原煤提取腐殖酸残煤和脱矿物煤提取腐殖酸残煤中V、Ni、As富集,表明V、Ni、As与煤的大分子结构形成了稳定的有机态化合物。根据微量元素和灰分的相关性系数,把微量元素分为以下几类:无机富集元素Cr、U;亲无机元素Cu、Cd、In、Sn、Ga、Y、Zr、Hf、Bi、Th;偏无机元素Be、Sc、Rb、Sr、Nb、Cs、Ta、Pb;偏有机元素V、As、Tl、Ba、Se;亲有机元素Li、Co、W;有机富集元素Ni、Zn、Mo、Sb。     

Sixteen capillary electrophoresis applications for viral vaccine analysis

A broad range of CE applications from our organization is reviewed to give a flavor of the use of CE within the field of vaccine analyses. Applicability of CE for viral vaccine characterization, and release and stability testing of seasonal influenza virosomal vaccines, universal subunit influenza vaccines, Sabin inactivated polio vaccines (sIPV), and adenovirus vector vaccines were demonstrated. Diverse CZE, CE-SDS, CGE, and cIEF methods were developed, validated, and applied for virus, protein, posttranslational modifications, DNA, and excipient concentration determinations, as well as for the integrity and composition verifications, and identity testing (e.g., CZE for intact virus particles, CE-SDS application for hemagglutinin quantification and influenza strain identification, chloride or bromide determination in process samples). Results were supported by other methods such as RP-HPLC, dynamic light scattering (DLS), and zeta potential measurements. Overall, 16 CE methods are presented that were developed and applied, comprising six adenovirus methods, five viral protein methods, and methods for antibodies determination of glycans, host cell-DNA, excipient chloride, and process impurity bromide. These methods were applied to support in-process control, release, stability, process- and product characterization and development, and critical reagent testing. Thirteen methods were validated. Intact virus particles were analyzed at concentrations as low as 0.8 pmol/L. Overall, CE took viral vaccine testing beyond what was previously possible, improved process and product understanding, and, in total, safety, efficacy, and quality.     

Determination of carbohydrates and sweeteners in foods and biologically active additives by high-performance liquid chromatography

A method for the determination of large amounts of carbohydrates (glucose, lactose, maltose, mannose, sucrose, and fructose) and sweeteners (xylitol and sorbitol) by reversed-phase liquid chromatography with refractive index detection without derivatization has been developed. The limits of determination for glucose, fructose, and sucrose in liquid samples were 0.1 g/L, and for xylite, lactose, maltose, mannose, and sorbite, 1 g/L. In solid samples the limits of determination for glucose, fructose, and sucrose were 0.1%, and for xylite, lactose, maltose, mannose, and sorbite, 0.6%. The method is applicable to the analysis of samples of wine, juice, honey, cookies, dairy products, and biologically active additives. The developed method for the determination of carbohydrates and sweeteners in foods and biologically active additives was certified in the Mendeleev Institute for Metrology (St. Petersburg).     

Simultaneous separation and determination of hydrocarbons and organochlorine compounds by using a two-step microcolumn.

The simultaneous separation and determination of a mixture of hydrocarbons and organochlorine compounds was successfully carried out by using sorption chromatography on a two-step microcolumn of silica and aluminium oxide for their fractionation, and a dual detector system. In addition to the separation and identification of hydrocarbons and heterocompounds containing nitrogen, oxygen and sulphur atoms, separation and identification of chlorinated hydrocarbons (dichlorobenzenes, p-chlorotoluene, hexachlorobutadiene, 1,2,4-trichlorobenzene and 2-chloronaphthalene), pesticides (chlorpicrin, aldrin, lindane, alpha- and beta-benzene hexachloride (BHC), endrin, dieldrin, endosulphan, methoxychlor) and herbicides (propanil, dichlobenil, trifluralin, difolatan) were achieved in mixtures containing polychlorinated biphenyl, strobane and chlordane.     

Structures of new cucurbitane-type triterpenes and glycosides, karavilagenins and karavilosides, from the dried fruit of Momordica charantia L. in Sri Lanka

Three new cucurbitane-type triterpene called karavilagenins A, B, and C and five new cucurbitane-type triterpene glycosides called karavilosides I, II, III, IV, and V were isolated from the dried fruit of Sri Lanka Momordica charantia L. (Cucurbitaceae) together with two known cucurbitane-type triterpenes, 19(R)-methoxy-5beta,19-epoxycucurbita-6,23-dien-3beta,25-diol and 5,19-epoxycucurbita-6,23-diene-3,25-diol, and nine known cucurbitane-type triterpene glycosides, goyaglycosides-b, -c, and -d, and momordicosides F1, F2, G, I, K, and L. The structures of karavilagenins and karavilosides were elucidated on the basis of chemical and physicochemical evidence.     

Reaction of sulfolenes and their derivatives with some sulfur-containing nucleophiles

Reaction of 2-sulfolene, 4-hydroxy-2-sulfolene, 4-bromo- and 3-chloro-2-sulfolenes, 3-chloro-4-hydroxysulfolane, and 3,4-dibromo(dichloro)sulfolanes with sodium methane-, hexane-, allene-, benzene-, and p-toluenesulfinates and magnesium gave 3-methyl-, 3-hexyl-, 3-allyl-, 3-phenyl-, and 3-(p-tolylsulfonyl)sulfolanes, 3-methyl-, 3-phenyl-, and 3-(p-tolylsulfonyl)-4-hydroxysulfolanes, and 3-phenyl- and 4-phenylsulfonyl-2-sulfolenes.     

含希夫碱侧基聚酯及其锌配合物的合成和性能

经多步反应合成2种新型含希夫碱侧基聚酯(P5,P6),进一步与醋酸锌反应得到2种聚酯锌配合物(P5-Zn,P6-Zn)。 采用元素分析、FT-IR、UV-Vis、¹H NMR、GPC、TG、DSC和荧光光谱等技术手段对其结构和性能进行表征。 P5和P6均溶于四氢呋喃(THF)、氯仿(CHCl₃)、N,N-二甲基甲酰胺(DMF)、N,N-二甲基乙酰胺(DMAc)、二甲基亚砜(DMSO)、N-甲基吡咯烷酮法(NMP)等有机溶剂,P5-Zn和P6-Zn部分溶于THF及CHCl₃,溶于DMF、DMAc、DMSO、NMP等有机溶剂。 P5和P6的重均相对分子质量M_w及相对分子质量分布指数PDI分别为4164、6148 g/mol和1.42、1.43。 P5、P6、P5-Zn和P6-Zn的5%失重温度分别为339、348、367和358℃。 P5、P6、P5-Zn和P6-Zn的玻璃化转变温度T_g分别为88.8、123.3、39.8和63.8 ℃。 P5和P6的DMF溶液(5×10^-5 mol/L)在418和416 nm处发射弱紫色荧光,P5-Zn和P6-Zn的DMF溶液(5×10^-5 mol/L)在505和506 nm处发射强绿色荧光,固体P5-Zn和P6-Zn在527和532 nm处发射强绿色荧光。     

中国科学院检验检测机构资质认定概况

中国科学院检验检测机构的使命与定位是为国家科技战略发展提供技术支撑和高水平服务,为中国科学院系统各单位的科研和工程及社会需求提供高科技含量的检验检测服务,满足社会的高新技术、新兴产业检验检测的需求,为高新技术、新兴产业的产品质量检验检测提供有效的技术保障.中国科学院系统现有检验检测机构67个,分布在21个省、市、地区,...     

Recent developments in capillary and microchip electroseparations of peptides (2017–mid 2019)

The review presents a comprehensive survey of recent developments and applications of high performance capillary and microchip electroseparation methods (zone electrophoresis, isotachophoresis, isoelectric focusing, affinity electrophoresis, electrokinetic chromatography, and electrochromatography) for analysis, micropreparation, and physicochemical and biochemical characterization of peptides since 2017 up to about the middle of 2019. Progress in the study of electromigration properties of peptides and in the methodology of their analysis (sample preseparation, preconcentration and derivatization, adsorption suppression, EOF control, and detection) are described. Advances in CE and CEC methods are demonstrated and their applications in the following areas are presented: qualitative and quantitative analysis, determination in complex (bio)matrices, monitoring of chemical and enzymatical reactions and physical changes, amino acid, sequence and chiral analysis, and peptide mapping of proteins. In addition, micropreparative separations and determinations of important physicochemical characteristics of peptides by CE and CEC methods are reported.     

Organic heterocyclic-based colorimetric and fluorimetric chemosensors for the detection of different analytes: a review (from 2015 to 2022)

Heterocyclic organic compounds, also called heterocycles, are any major class of organic compounds having at least one atom other than carbon in the ring. Due to their excellent electronic and structural features, these compounds exhibit a wide range of biological and nonbiological applications. Among these, indole, benzimidazole, benzothiazole, and benzoxazole are versatile organic heterocyclic compounds widely used in different fields. They show a wide range of applications in polymer, coordination chemistry, pharmacy, dyes, food packages, medicine, and industries. These compounds contain heteroatoms like S-, N-, and O-, through which they interact with metal ions, anions, and neutral species, giving measurable analytical signals that can be used as fluorimetric and colorimetric chemosensors for detecting different analytes in biological, agricultural and environmental samples. This review summarizes indole, benzimidazole, benzothiazole, and benzoxazole-based fluorimetric and colorimetric chemosensors for detecting metal ions, anions, and neutral species. Furthermore, the recognition mechanisms have been discussed in detail, which could help researchers to design efficient, highly selective, and sensitive chemosensors to recognize and determine heavy metal cations.     

Simultaneous determination of caffeine, 8-chlorotheophylline, and chlorphenoxamine hydrochloride in ternary mixtures by ratio-spectra zero-crossing first-derivative spectrophotometric and chemometric methods

A ratio-spectra zero-crossing first-derivative spectrophotometric method and 2 chemometric methods have been used for the simultaneous determination of ternary mixtures of caffeine (A), 8-chlorotheophylline (B), and chlorphenoxamine hydrochloride (C) in bulk powder and dosage forms. In the ratio-spectra zero-crossing first-derivative spectrophotometric technique (1DD), calibration curves were linear in the range of 4-20 microg/mL for A, B, and C (r = 0.9992, 0.9994, and 0.9976, respectively). The measurements were carried out at 212, 209.2, and 231.4 nm for A, B, and C, respectively. The detection limits for A, B, and C were calculated to be 0.24, 0.34, and 0.13 microg/mL, and the percentage recoveries were 99.1 +/- 0.89, 100.1 +/- 0.95, and 100.1 +/- 1.0, respectively. Two chemometric methods, namely, the partial least-squares (PLS) model and the principal component regression (PCR) model, were also used for the simultaneous determination of the 3 drugs in the ternary mixture. A training set consisting of 15 mixtures containing different ratios of A, B, and C was used. The concentration used for the construction of the PLS and PCR models varied between 4 and 25 microg/mL for each drug. These models were used after their validation for the prediction of the concentrations of A, B, and C in mixtures. The detection limits for A, B, and C were calculated to be 0.13, 0.15, and 0.14 microg/mL, respectively, and the percent recoveries were found to be 99.8 micro 0.96, 99.9 micro 0.94, and 99.9 micro 1.18, respectively, for both methods. The 3 proposed procedures are rapid, simple, sensitive, and accurate. No preliminary separation steps or resolution equations are required; thus, they can be applied to the simultaneous determination of the 3 drugs in commercial tablets and suppositories or in quality-control laboratories.     

Mononuclear,polynuclear, and cluster complexes of molybdenum and their reactions as models of biochemical systems and processes

Data on the composition, structure, and properties (electronic and geometric structure, optical properties, thermodynamic functions) of mononuclear, polynuclear, and cluster complexes of bi-, tri-, tetra-, penta-, and hexavalent molybdenum are summarized and correlated. The thermodynamics, kinetics, and mechanisms of the ligand exchange, protonation deprotonation, redox reactions, and formation decomposition of cluster cores of molybdenum complexes in aqueous solutions are characterized.     

Progress of Indeno-type Organic Diradicaloids

Organic diradicaloids have unusual open-shell nature and properties and are promising materials for organic electronics, spintronics, energy storage and nonlinear optics. In this review, we focus on indeno-type organic diradicaloids and summarize their molecular design and synthesis, as well as topological structures, open-shell characters and diradical properties. The molecular systems are classified into indenofluorenes and diindenoacenes, indeno-based molecules with one-dimensional, two-dimensional and unique topological structures, and heterocyclic indeno-based molecules. By constructing these various topological π-skeletons with tunable conjugation modes and variation of atomic composition, their key open-shell parameters, such as diradical characters and singlet-triplet energy gaps, along with the optical, electronic and magnetic properties, as well as stabilities are efficiently modulated. More attention may be paid to accurate computational analysis, rational design and synthesis, and novel functions of indeno-type diradicaloids, which will promote the development of radical chemistry and materials.     

Complexation-induced unfolding of heterocyclic ureas. Simple foldamers equilibrate with multiply hydrogen-bonded sheetlike structures.

The synthesis and conformational studies of heterocyclic ureas (amides) 1-7 and their concentration-dependent unfolding to form multiply hydrogen-bonded complexes are described. Ureas 1 and 7 were prepared by reacting 2-aminopyridine and aminonaphthyridine 25, respectively, with triphosgene and 4-(dimethylamino)pyridine (DMAP). Amine 25, in turn, was synthesized by a Knorr condensation of 2,6-diaminopyridine and 4,6-nonanedione. Heterocyclic ureas 3, 4, and 16 were prepared by treating their corresponding amino precursors with butylisocyanate, whereas bisureido naphthyridines 6 and 17 were prepared by heating 2,7-diamino-1,8-naphthyridine (13) with butylisocyanate and 3,4,5-tridodecyloxyphenyl isocyanate, respectively. The hydrogen-bonding modules 2 and 5 were synthesized by reacting 13 and 2-amino-1,8-naphthyridine with valeric anhydride. X-ray crystallographic analyses were performed on ureas 1, 3, 16, and 17, indicating that these ureas are intramolecularly hydrogen-bonded in the solid state. Moreover, detailed 1H NMR solution studies of 1, 3, 4, 6, and 7 indicate that similar folded structures form in chloroform. In addition, naphthyridinylureas 3 and 7 unfold and dimerize by forming four hydrogen bonds at high concentrations, and ureas 1 and 4 unfold in the presence of their hydrogen-bonding complements, amides 2 and 5, to form complexes with three and four hydrogen bonds, respectively. Likewise, the mixing of 6 and 7 results in a mutual unfolding and formation of a robust, sheetlike, sextuply hydrogen-bonded complex. The hydrogen-bonding modules described are useful building blocks for self-assembly, and the unfolding process represents a very primitive mimicry of the helix-to-sheet transition shown by peptides and potentially shown by the hypothetical naphthyridinylurea 8.     

A review on elastic graphene aerogels: Design,preparation, and applications

Graphene aerogels with unique properties, such as ultralow density, super-elasticity, high specific surface area, and excellent thermal stability, have undergone great progress in the past decades. Especially, super-elastic graphene aerogels provide a highly attention-catching platform for developing advanced energy devices, pressure sensors, contaminates adsorbents, and electromagnetic wave shielding and absorption materials, and so forth. In this review, we begin with the introduction and discussion of various fabrication techniques and compare their advantages and disadvantages, focusing on the template-free assembly process and template-assisted assembly process. Then, we summarize the factors influencing the compressibility and elasticity of graphene aerogels, including intrinsic properties of building blocks, constituent materials, and structure design, and their wide applications. At the end, we discuss the current challenges and future prospects of this field.     

Recent advances in thin-layer chromatography of pesticides

Advances in the applications of thin-layer chromatography (TLC) and high-performance thin-layer chromatography (HPTLC) for the separation, detection, and qualitative and quantitative determination of pesticides, other agrochemicals, and related compounds are reviewed for the period 1998-2000. Analyses are covered for a variety of samples, such as food, biological, and environmental, and for residues of pesticides of various types, including insecticides, herbicides, and fungicides, belonging to different chemical classes. References on formulation analysis, hydrophobicity studies, and the use of TLC and thin-layer radiochromatography (TLRC) for studies of pesticide metabolism, degradation, uptake, and related studies are also included.     

Density,viscosity, and surface tension of binary liquid systems: Ethanoic acid,propanoic acid,and butanoic acid with nitrobenzene

Density, viscosity, and surface tension of three binary liquid systems: ethanoic acid+nitrobenzene, propanoic acid+nitrobenzene, and butanoic acid+nitrobenzene have been determined at 25, 35, and 45°C, over the whole composition range. The excess molar volumes, viscosities, Gibbs energies for the activation of flow, and surface tension were evaluated and fitted to a Redlich-Kister type of equation. The Grunberg-Nissan parameter d was also calculated. Binary viscosity data were fitted to the models of McAllister, Heric, Krishnan, and Laddha, Auslander, and Teja and Rice. Surface tension data were fitted to the models of Zihao and Jufu, Rice, and Teja, and an empirical two-constant model.     

1H and 13C NMR assignments for two lignans from the heartwood of Streblus asper

In our ongoing investigation of the bioactive constituents from plants, two new lignans, magnolignan A-2-O-beta-D-glucopyranoside and strebluslignanol were isolated from heartwood of Streblus asper, along with three known lignans, magnolignan A, magnolol, and magnaldehyde D. 1D and 2D NMR experiments, including COSY, HMQC, and HMBC, and other spectroscopic methods, including UV, IR, and MS were used for the determination of the structures and NMR assignments. Primary bioassays showed that magnolignan A-2-O-beta-D-glucopyranoside and strebluslignanol have medium cytotoxic activity against HEp-2 and HepG2 cells, with IC(50) of 13.3 microM, 46.4 microM and 10.1 microM, 21.7 microM, respectively.     

Polymer-surfactant and protein-surfactant interactions

The phase behavior and some physicochemical properties of homopolymers (HP) and hydrophobically modified (HMP) polymers, as well as of polyelectrolytes (PE) and proteins (PR), in the presence of aqueous surfactants, or their mixtures, are discussed. Mixing the above components gives rise to the formation of organized phases, whose properties are controlled by polymer and/or surfactant content, temperature, pH, and ionic strength. Depending on the nature, concentration, and net charge of both solutes, molecular solutions, polymer-surfactant complexes, adsorption onto micelles and vesicles, gels, liquid crystalline phases, and precipitates are observed. Such rich polymorphic behavior is the result of a complex balance between electrostatic, excluded volume, van der Waals, and other contributions to overall system stability. It is also modulated by the molecular details and architecture of both the polymer and the surfactant. Different experimental methods allow investigation of the above systems and getting information on the nature of polymer-surfactant interactions (PSI). Surface adsorption and thermodynamic methods, together with investigation of the phase diagrams, give information on the forces controlling PSI and on the existence of different phases. Conductivity, QELS and viscosity allow estimating the size and shape of polymer-surfactant (protein-surfactant) complexes. Optical microscopy, cryo-TEM, AFM, NMR, fluorescence, and relaxation methods give more information on the above systems. Use of the above mixtures in controlling gelation, surface covering, preparing dielectric layers, and drug release is suggested.