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Author(s): Yuangang Xu [1]; Qian Wang [1]; Cheng Shen [1]; Qiuhan Lin [1]; Pengcheng Wang (corresponding author) [1]; Ming Lu (corresponding author) [1] Singly or doubly bonded polynitrogen compounds can [...]

The synthesis and characterization of mononuclear [[(L)(CI)[Ru.sup.II](tppz)].sup.} and dinuclear [(L)(I)[[Ru.sup.II]([mu]-tppz)[Ru.sup.II](CI)(L)].sup.2} complexes is presented. These display four and five successive reduction processes, respectively, involving both tppz- and dpk-based unoccupied [[PI].sup.*] orbitals.

The paper describes a method for determining homologous classes of compounds in a multicomponent complex chromatogram obtained under programming elution conditions. The method is based on the computation of the autocovariance function of the experimental chromatogram (EACVF). The EACVF plot, if properly interpreted, can be regarded as a 'class chromatogram' i.e., a virtual chromatogram formed by peaks whose positions and heights allow identification and quantification of the different homologous series, even if they are embedded in a random complex chromatogram. Theoretical models were developed to describe complex chromatograms displaying random retention pattern, ordered sequences or a combination of them. On the basis of theoretical autocovariance function, the properties of the chromatogram can be experimentally evaluated, under well-defined conditions: in particular, the two components of the chromatogram, ordered and random, can be identified. Moreover, the total number of single components (SCs) and the separated number of the SCs belonging to the random and ordered components can be determined, when the two components display the same concentration. If the mixture contains several homologous series with common frequency and different phase values, the number and identity of the different homologous series as well as the number of SCs belonging to each of them can be evaluated. Moreover, the power of the EACVF method can be magnified by applying it to the single ion monitoring (SIM) signals to selectively detect specific compound classes in order to identify the different homologous series. By this way, a full 'decoding' of the complex multicomponent chromatogram is achieved. The method was validated on synthetic mixtures containing known amount of SCs belonging to homologous series of hydrocarbon, alcohols, ketones, and aromatic compounds in addition to other not structurally related SCs. The method was applied to both the total ion monitoring (TIC) and the SIM signals, to describe step by step the essence of the procedure. Moreover, the systematic use of both SIM and TIC can simplify the decoding procedure of complex chromatograms by singling out only specific compound classes or by confirming the identification of the different homologous series. The method was further applied to a sample containing unknown number of compounds and homologous series (a petroleum benzin, bp 140-160[degrees]C): the results obtained were meaningful in terms of both the identified number of components and identified homologous series.

Abstract -- A GC-MS procedure was developed to determine sophocarpine (SC), matrine (MT), and sophoridine (SRI) in KUHUANG injection. The chromatographic separation was performed on an HP-5MS column (30 m [...]

Several recent conceptual advances, which take advantage of the design criteria and practical techniques of molecular-level control in organic chemistry, allow preparation of well-defined polymers and nanostructured materials. Two trends are clear: the realization that synthesis of complex macromolecules poses major challenges and opportunities and the expectation that such materials will exhibit distinctive properties and functions. Polymer synthesis methods now being developed will yield well-defined synthetic macromolecules that are capable of mimicking many of the features of proteins (for example, three-dimensional folded structure) and other natural materials. These macromolecules have far-reaching potential for the study of molecular-level behavior at interfaces, in thin films, and in solution, while also enabling the development of encapsulation, drug-delivery, and nanoscale-patterning technologies., By varying the three-dimensional (3D) structure and position of functional groups, synthetic organic chemists have developed the ability to accurately control, and in some cases predict, the physical properties of [...]

Computational techniques that build models to correctly assign chemical compounds to various classes of interest have many applications in pharmaceutical research and are used extensively at various phases during the drug development process. These techniques are used to solve a number of classification problems such as predicting whether or not a chemical compound has the desired biological activity, is toxic or nontoxic, and filtering out drug-like compounds from large compound libraries. This paper presents a substructure-based classification algorithm that decouples the substructure discovery process from the classification model construction and uses frequent subgraph discovery algorithms to find all topological and geometric substructures present in the data set. The advantage of this approach is that during classification model construction, all relevant substructures are available allowing the classifier to intelligently select the most discriminating ones. The computational scalability is ensured by the use of highly efficient frequent subgraph discovery algorithms coupled with aggressive feature selection. Experimental evaluation on eight different classification problems shows that our approach is computationally scalable and, on average, outperforms existing schemes by 7 percent to 35 percent. Index Terms--Classification, chemical compounds, virtual screening, graphs, SVM.

Positive and negative ions generated by laser-based ionization methods from three gold:thiolate cluster compounds are mass analyzed by time-of-flight mass spectrometry. The three compounds have similar inorganic core masses (~29 kDa, ~145 Au atoms) but different n-alkanethiolate ligands associated with each cluster compound (Au:SR, R = butane, hexane, dodecane). Irradiation of neat films (laser desorption/ionization) and films generated by dilution of the cluster compounds in an organic acid matrix (matrix-assisted laser desorption/ ionization) with a nitrogen laser (337 nm) produced distinct ion abundances that are relevant to different structural aspects of the cluster compound. Laser desorption/ionization of neat Au:SR compound films produces ions consistent with the inorganic core mass (i.e., devoid of original hydrocarbon content). Matrix-assisted laser desorption/ionization produces either ions with m/z values consistent with the core mass of the cluster compounds or ions with m/z values consistent with the approximate molecular weight of the cluster compounds, depending on ionization conditions. The ion abundances, and ionization conditions under which they are detected, provide insight into desorption/ionization processes for these unique cluster compounds as well as other analytes typically studied by matrix-assisted laser desorption/ ionization.

A device that releases chemical compounds in small volumes and at multiple, well defined locations would be a powerful tool for clinical therapeutics and biological research. Many biomedical devices such as neurotransmitter-based prostheses or drug delivery devices require precise release of chemical compounds. Additionally, the ability to control chemical gradients will have applications in basic research such as studies of cell microenvironments, stem cell niches, metaplasia, or chemotaxis. We present such a device with repeatable delivery of chemical compounds at multiple locations on a chip surface. Using electroosmosis to drive flow through microfluidic channels, we pulse minute quantities of a bradykinin solution through four 5-[micro]m apertures onto PC12 cells and show stimulation of individual cells using a [Ca.sup.2+]-sensitive fluorescent dye. We also present basic computational results with experimental verification of both fluid ejection and fluid withdrawal by imaging pH changes by using a fluorescent dye. This 'artificial synapse chip' is a prototype neural interface that introduces a new paradigm for neural stimulation, with eventual application in treating macular degeneration and other neurological disorders.

1. INTRODUCTION Studies of the related subjects of strain, structure, stability and reactivity represent one of the major areas of chemistry. The other is concerned with synthesis, or the preparation [...]

The dynamics of the double helix affects the Frenkel excitons that correspond to the low-energy absorption band of DNA. It is deduced that although structural fluctuations reduce both the mixing between different monomer transitions and the spatial extent of the eigenstates, excitations still remain delocalized over several bases.

An efficient algorithm for the comparison of two chemical structures of compounds is presented, where the chemical structure is treated as a graph consisting of atoms as nodes and covalent bonds as edges. When the procedure was applied to 9383 compounds in the KEGG/LIGAND database, the largest clusters of similar compounds were found to be related to carbohydrates, and the clusters corresponded well to the categorization of pathways as represented by the KEGG pathway map numbers.

Investigating the hot-seeding melt growth of large (Sm-Eu)123 single domains is discussed in air with Nd123 seeds is presented. It is concluded that the RE-Ba chemical substitution can be effectively suppressed by employing a two-step crystallization: a fast cooling followed by a long time slow cooling.

Byline: A. Hollnagel (1), L. W. Kroh (1) Keywords: Key wordsaNon-enzymatic browning; Dicarbonyls; Sugar fragments Abstract: aGlyoxal, methylglyoxal and diacetyl were identified as reaction products from non-enzymatic browning of D-glucose (Glc), D-fructose (Fru), maltose and maltulose. The [alpha]-dicarbonyl compounds were quantified throughout the reaction. Monosaccharides formed more dicarbonyl fragments than disaccharides and Glc formed more than Fru. It is suggested that Fru tends to yield cyclic products rather than fragmentation products under the reaction conditions used. Furthermore, a mechanism for the fragmentation of disaccharides is proposed. Author Affiliation: (1) Institut fur Lebensmittelchemie, Technische Universitat Berlin, Gustav-Meyer-Allee 25, D-13355 Berlin, Germany e-mail: kroh1530@mailszrz.zrz.tu-berlin.de, DE Article note: Received: 27 November 1997 / Revised version: 9 January 1998

A conservation principle that holds for various sizes of compound, ranging form diatomic molecules to clusters and bulk crystals is reported. The entire range bond order conservation (ER-BOC) provides an effective way to correlate bulk properties of crystals with those of the corresponding molecules and small clusters.

Current methods to combine soft materials are limited and can restrict the manufacturing process. But now, researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), [...]

The discovery of a compound that interrupts the production of a specific protein could open up a fresh path to drug discovery. Cells rely on complex molecular machines called ribosomes [...]

A new study by an international team of researchers led by the University of Minnesota, St. Paul, highlights how manipulating 2D materials could make modern day devices faster, smaller, and [...]

A laboratory experiment that emphasizes the interpretation of both infrared (IR) and nuclear magnetic resonance (NMR) spectra in the elucidation of the structure of an unknown compound was developed. The method helps students determine (super 1)H- and (super 13)C-NMR spectra from the structures of compounds and to interpret the same.

The concept of using phase homologies to achieve 'design' in solid-state chemistry based on a single series is discussed. The additional conceptual links between the existence of homologies and their implications for synthetic design in solid-state chemistry is presented.

The results of time-dependent density functional theory (TDDFT) calculations of resonance Raman intensities are combined with experimental deep-ultraviolet resonance Raman measurements at a single wavelength, 244 nm, in order to test the possibility to distinguish several very similar compounds. There is an agreement with the Raman spectra of pyrene and its substituted analogues in terms of frequencies and intensities

The guanidinate compounds are paramagnetic with two unpaired electrons at room temperature and appear diamagnetic at 2K, but Ru-Ru distance remain constant between 27 and 296 K. It indicates that electron configuration remains invariant, and the decrease in magnetic susceptibility as the room temperature decreases is may be due to zero-field splitting.

The Bergman cyclization reaction of (Z)-3-hexene-1,5- diynes (enediynes) to 1,4-didehydrobenzene birradicals and the Myers-Saito cyclinzation reaction of heptatrien-6-ynes to alpha.3-didehydrotoluene biradicals are investigated. The efficiency and selectivity of the cycloaromatization reaction could be enhanced by the introduction of 1.1 to 10 equiv of dimethylphenylsilyl chloride to the reaction mixture to capture the resulting zwitterion.

A regioselective quinazoline-directed ortholithiation on an adjacent quinoline moiety is used as key step for a short, efficient and practical synthesis of the human DNA topoisomerase I poison luotonin A and luotonins Band E. The reaction of dilithiated interimediate 6 with DMF directly furnished luotonin B (1b) in 81 percent yield and luotonin B (1b) on methylation with p-TSA/methanol gave luotonin E (1c) in 82 percent yield.

The synthesis of a ring FR182877 involving the enyne RCM is studied. Systematic comparisons of enyme versus diene RCM for the formation of cyclopentene derivatives show that the latter metathesis precedes much more easily even for the ringsize.

The synthesis of two cluster compounds, one containing six secondary dialkylammonium ion centers and the other possessing six benzo-m-phenylene [25] crown-8 (BMP25C8) macrocycles both appended to hexakis (thiophenyl) benzene cores is studied. The clustering of recognition sites together in one molecule is detrimental to their individual abilities to bind monovalent ligands.

A novel terpeniod-related compound, stolonilactone (1) isolated from the Okinawan soft coral Clavularia koellikeri is investigated. A possible biogenesis of 1 through the [4+2]-cycloaddition of a trisnorsesquiterpeniod-type diene and a cembranolide-type dinenophile is proposed.

The NMR studies of the inclusion complexes formed between beta-CD and different types of alpha-phenyl-N-tert-butylnitrone (PBN) derivatives are presented. The NMR technique allows the characterization of the inclusion process in terms of stoichiometry, association constant and geometry of the complexes.

The analytic dependence of the dynamical electrostatic potential derived (D-RESP) charges on the coordinates of the system, on the position of the atoms and on the electronic density, is illustrated. The interaction potentials helps in improving the computational efficiency of the electrostatic coupling between the quantum mechanics (QM) and the molecular mechanics (MM) subsystems and also defines the QM/MM analogue of the exclusion schemes.

Thermodynamics is employed to understand the coupled diffusion of solution components caused by differences in the molecular size. The thermodynamic model of coupled diffusion, though limited in scope to ideal or nearly-ideal nonelectrolyte solutions, can be used to more complicated systems by including terms for hydration, association, activity coefficients, ionic migration in diffusion-induced electric fields and polydisperity.

The atomistic molecular dynamics computer simulations are performed on the columnar state of the discogen hexakis(pentyloxy)triphenylene (HAT5) based on the parameters of the empirical model potential taken from the AMBER and OPLS force fields. The results obtained from the simulations indicate that the description of the columnar phase of HAT5 at ZT = 375 K and ambient pressure is fairly close to that provided by the experimental data.

The FTIR spectroscopy and temperature-programmed desorption (TPD) are employed to study the interaction of NH3 and NO2 with heterogeneous bundles of carbon single-walled nanotubes (SWNTs). The interaction between the small molecules and SWNT are discussed.

The mechanism of the hydrogen desorbing reaction from LiH and LiNH2 to Li2NH and H2, based on the experimental results, is discussed. The existence of LiH near the surface of LiNH2 is highlighted, as it is very important for the progress of the reaction at temperatures lower than 200 degrees C.

The influence of hydrostatic pressure, up to 1.2 GPa, on the spin transition behavior in [Fe(phen)2(NCS)2] polymorph II and [CrI2(depe)2] is investigated. As both are mononuclear spin crossover (SCO) systems, they show similar (abrupt) spin transition properties at atmospheric pressure despite the differences in the chemical coordination sphere.