A comprehensive profile of brain enzymes that hydrolyze the endocannabinoid 2-arachidonoylglycerol

Endogenous ligands for cannabinoid receptors (“endocannabinoids”) include the lipid transmitters anandamide and 2-arachidonoylglycerol (2-AG). Endocannabinoids modulate a diverse set of physiological processes and are tightly regulated by enzymatic biosynthesis and degradation. Termination of anandamide signaling by fatty acid amide hydrolase (FAAH) is well characterized, but less is known about the inactivation of 2-AG, which can be hydrolyzed by multiple enzymes in vitro, including FAAH and monoacylglycerol lipase (MAGL). Here, we have taken a functional proteomic approach to comprehensively map 2-AG hydrolases in the mouse brain. Our data reveal that 85% of brain 2-AG hydrolase activity can be ascribed to MAGL, and that the remaining 15% is mostly catalyzed by two uncharacterized enzymes, ABHD6 and ABHD12. Interestingly, MAGL, ABHD6, and ABHD12 display distinct subcellular distributions, suggesting that they may control different pools of 2-AG in the nervous system.     

Determination of sodium hydroxide in boiler water by a linear titration plot method

A simplified linear titration plot has been developed specifically for determining the sodium hydroxide content of boiler water. A known quantity of strong acid is added, in excess, to the alkaline sample which is then titrated with standard alkali. Functions are constructed from the titration data (pH, volume added) and known constants. These functions are linearly related, so that plotting one against the other gives a straight line of slope V_Y and intercept V_X, where V_X and V_Y are the volumes of titrant required to neutralize the “strong” (including for this purpose acetic and other carboxylic acids) and “weak” (ammonium ion and silicic acid) components. These are sufficient to enable the original sodium hydroxide concentration to be calculated. The constants required for the functions are the autoprotolysis constant of water and the association constant of ammonium ion. The functions can be calculated very easily with a programmable calculator.     

Ionization Constants of Aqueous Glycolic Acid at Temperatures up to 250 <Superscript>∘</Superscript>C Using Hydrothermal pH Indicators and UV-Visible Spectroscopy

Chemical equilibrium constants for the ionization of aqueous glycolic acid (hydroxyacetic acid, HOCH₂COOH) have been measured at temperatures 25–250 ^∘C and pressure p = 4.5 MPa, using UV-visible spectroscopy with a high-pressure flow cell and thermally-stable colorimetric pH indicators. These are the first experimental values for the ionization constant of glycolic acid above 100 ^∘C that have been reported. The results have been combined with recently determined values for the standard partial molar volumes of HOCH₂COOH(aq) and HOCH₂COO⁻(aq) under hydrothermal conditions to develop an “equation of state” that describes the temperature- and pressure-dependence of the equilibrium constant and standard partial molar properties of ionization from 25 to 325 ^∘C.     

Comparison of depth resolution from a microscopically modulated Rh/C film after sputter profiling by SIMS and SNMS

Sputter depth profiles of an Rh/C microscopically modulated thin film (double layer thickness 7 nm) were obtained by low energy SIMS and SNMS. The depth resolution was obtained using the linear superposition of error functions at the interfaces. In optimal cases the depth resolution was shown to be of the order of 1–2 nm for both techniques.     

On the correlation of implantation defects and implanted species

Using high-sensitive deep level transient spectroscopy (DLTS), we have determined ion-related defects in monocrystalline silicon in the asimplanted state. In comparison with secondary ion mass spectrometry (SIMS) data and neutron depth profiling (NDP) results it is demonstrated that the defect profiles and the chemical distributions have nearly identical shape. From these experimental facts it can be concluded that this electrical spectroscopy can be applied for the detection of very low concentrations (down to 10¹⁰ cm^–3) of implanted ion species.     

An experimental study on the “sequential order” rules in generalized two-dimensional correlation spectroscopy

Following our theoretical analysis on the “sequential order” rules in generalized two-dimensional (2D) correlation spectroscopy (H. Huang, Anal. Chem. 79 (2007) 8281–8292), an experimental study was conducted to test the “sequential order” rules using the FT-NIR data of poly(3-hydroxybutyrate) (PHB)/poly(l-lactic acid) (PLA) blends under uniaxial elongation and parallel polarization. The local sequential order concept proposed for the generalized two-dimensional (2D) correlation spectroscopy is now more clearly stated; “the intensity change at ν1 occurs predominantly before ν2” means that the starting time of the intensity change at ν1 is prior to that at ν2. It is this local sequential order which reflects the real and intuitive sequential order between two events in generalized situations. It has been found that the integrated/overall sequential order results obtained from the 2D correlation analysis may be contradictory to the intuitive local sequential order. In addition, different integrated/overall sequential orders could be obtained by selection of different sampling intervals from a certain set of experimental data, or choosing different number of the contours for the same sampling interval. These new experimental findings are a perfect reinforcement to our previous theoretical study and have further demonstrated the uncertainty of applying the “sequential order” rules in generalized 2D correlation spectroscopy.     

Investigation of high concentration effects of Sb and P in silicon by combination of SIMS and TEM

Summary The combination of SIMS, electrical resistance measurements and TEM was used for investigation of high concentration effects of Sb and P in silicon. For antimony implantation and annealing combined with and without preannealing were studied. The distributions and the precipitated fraction were determined by SIMS. TEM investigations showed that by preannealing at a temperature of 1150°C no dislocations but only precipitates are formed. Thus the precipitation kinetics for an isothermal case (1000°C) could be studied. The size distributions of precipitates were determined by image processing of plan view TEM micrographs. The kinetics of the precipitation process was simulated for the distribution function by a computer model and compared with experiments. A good agreement between experiment and simulation was obtained.For phosphorus, specimens implanted with medium and high doses were investigated. With medium doses small extrinsic dislocation loops (size 20–40 nm) were observed near the amorphous/cristalline boundary. The dislocation loops are formed by agglomeration of interstitial silicon atoms which are supersatured in the long range of the implantation profile.The coupled diffusion of high doses of P and low doses of Sb and B was studied. In the SIMS distributions enrichments of boron were observed. TEM measurements showed that they were correlating to a severe band of defects.SiP precipitates and large perfect dislocation half loops [mean radius (195±112) nm] were observed after annealing at 900°C for 120 min of implants with a dose of 5×10¹⁶ cm^–2 P. Because precipitation is occurring, simulation of phosphorus diffusion is at present not possible.

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Untersuchung von Hochkonzentrationseffekten von Sb und P in Silicium durch Kombination von SIMS und TEM

     

Application of SIMS in semiconductor research

Summary Nowadays SIMS is a well-established analytical technique in semiconductor research. Materials research and process development are the main fields of application in silicon technology, whereas for III–V compound semiconductors much attention has been paid to assessment of multilayer structures grown by advanced growth methods. Recent applications of SIMS in these fields are the subject of the present paper. Emphasis will be placed upon optimizing the SIMS results with respect to accuracy and depth resolution.

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Anwendungen von SIMS in der Halbleiterforschung

     

Carboxylic acid–pyridine supramolecular heterocatemer in a co-crystal

Robustness of carboxylic acid–pyridine supramolecular heterosynthon was examined in three 1:2 binary co-crystals of 4,4′-bipyridine with monocarboxylic acids, (4,4′-bipyridine)·(dl-hydroxyphenylacetic acid)₂, 1; (4,4′-bipyridine)_0.5·(4-bromonaphthalene-1-carboxylic acid), 2 and (4,4′-bipyridine)_0.5·(4-methylbenzoic acid), 3. All the three co-crystals form “two-component supermolecules” (consisting of one molecule of 4,4′-bipyridine and two molecules of the relevant carboxylic acid) stabilized through carboxylic acid–pyridine heterosynthons. Co-crystals 1 and 2 exhibits the expected carboxylic acid–pyridine dimer (heterodimer I) whereas co-crystal 3 forms a novel carboxylic acid–pyridine catemer (heterocatemer II).     

Original close-packed structure and magnetic properties of the Pb4Mn9O20 manganite

The crystal structure of the Pb₄Mn₉O₂₀ compound (previously known as “Pb_0.43MnO_2.18”) was solved from powder X-ray diffraction, electron diffraction, and high resolution electron microscopy data (S.G. Pnma, a=13.8888(2) Å, b=11.2665(2) Å, c=9.9867(1) Å, R_I=0.016, R_P=0.047). The structure is based on a 6H (cch)₂ close packing of pure oxygen “h”-type (O₁₆) layers alternating with mixed “c”-type (Pb₄O₁₂) layers. The Mn atoms occupy octahedral interstices formed by the oxygen atoms of the close-packed layers. The MnO₆ octahedra share edges within the layers, whereas the octahedra in neighboring layers are linked through corner sharing. The relationship with the closely related Pb₃Mn₇O₁₅ structure is discussed. Magnetization measurements reveal a peculiar magnetic behavior with a phase transition at 52 K, a small net magnetization below the transition temperature, and a tendency towards spin freezing.     

Reduction of cytochrome c at a lipid bilayer modified electrode

The reduction of horse heart cytochrome c has been investigated at a platinum electrode modified with a lipid bilayer membrane (BLM) which immobilized vinyl ferrocene as an electron mediator. The current—voltage curves show that the direct electrochemistry of cytochrome c at the metal electrode occurs quite efficiently. An adsorption equilibrium constant for cytochrome at the BLM surface, as well as an electron transfer rate constant between the protein and the modified electrode have been estimated from these results. The values of both parameters are much higher than those reported with other types of electrode modifications, indicating that a lipid bilayer-modified platinum electrode system using vinyl ferrocene as a mediator provides substantial improvements in electrochemical activity of cytochrome c at metal electrodes. The potential for modifying and utilizing this new class of “biomembrane-like” electrode surface for metalloprotein electrochemistry is briefly discussed.     

High mass accuracy and high mass resolving power FT-ICR secondary ion mass spectrometry for biological tissue imaging

Biological tissue imaging by secondary ion mass spectrometry has seen rapid development with the commercial availability of polyatomic primary ion sources. Endogenous lipids and other small bio-molecules can now be routinely mapped on the sub-micrometer scale. Such experiments are typically performed on time-of-flight mass spectrometers for high sensitivity and high repetition rate imaging. However, such mass analyzers lack the mass resolving power to ensure separation of isobaric ions and the mass accuracy for elemental formula assignment based on exact mass measurement. We have recently reported a secondary ion mass spectrometer with the combination of a C₆₀ primary ion gun with a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) for high mass resolving power, high mass measurement accuracy, and tandem mass spectrometry capabilities. In this work, high specificity and high sensitivity secondary ion FT-ICR MS was applied to chemical imaging of biological tissue. An entire rat brain tissue was measured with 150 μm spatial resolution (75 μm primary ion spot size) with mass resolving power (m/Δm _50%) of 67,500 (at m/z 750) and root-mean-square measurement accuracy less than two parts-per-million for intact phospholipids, small molecules and fragments. For the first time, ultra-high mass resolving power SIMS has been demonstrated, with m/Δm _50%?>?3,000,000. Higher spatial resolution capabilities of the platform were tested at a spatial resolution of 20 μm. The results represent order of magnitude improvements in mass resolving power and mass measurement accuracy for SIMS imaging and the promise of the platform for ultra-high mass resolving power and high spatial resolution imaging.

The design of molecular sensing interfaces with lipid-bilayer assemblies

We describe the current status of techniques for preparing planar lipid bilayers, the fusion of sensory elements and the design of bilayer interfaces for analytical applications. Advances in bilayer fabrication have allowed preparation of lipid bilayers with membrane resistance of >1 GΩ (“gigaseal”) in flow, microfluidic and array formats, which have enabled single-channel and multi-channel recording. Not only biological but also engineered channels have been adopted as sensory elements for lipid-bilayer-based biosensors. Synthetic and inorganic channels are also emerging for designing membranes for lipid-bilayer sensors. We discuss the potential of lipid bilayers containing biological, engineered or synthetic channels for the design of biosensors, including drug-screening biosensors.     

On the ionic conductivity and phase transitions in the Li2SO4---Li2WO4 system and their relation to ion transport mechanism

Secco et al. have performed several measurements of ionic conductivity, which they have considered as “convincing evidence” that the “paddle-wheel” mechanism does not contribute significantly to ion conductivity in Li₂SO₄-based compositions. However, a comparison of their results in the high-conductivity range with those of other investigators suggests that their data are artifacts. The cause of this is that the resistance of their sulfate-rich samples is about 0.1 ohm at high temperatures. Thus, their results are reliable only for “normal,” i.e., low, conductivities. It is briefly summarized why the “paddle-wheel” mechanism for ion transport is superior to a percolation-type mechanism for a few high-conducting phases.     

Development of capabilities for imaging mass spectrometry under ambient conditions with desorption electrospray ionization (DESI)

Aspects of the development of mass spectrometry over the past three decades are briefly reviewed and growth points in the subject are identified. Molecular imaging by mass spectrometry is one such growth area. The development of a capability for 2D chemical imaging of surfaces is described, based on the combination of a desorption electrospray ionization (DESI) ion source with an automated surface stage capable of x, y translational motion. The lateral resolution of this new system is found to be less than 200 microns, using a test ink pattern. Chemical imaging of surfaces is demonstrated using model examples of organic and biological systems: (i) imaging of a 2D pattern written in different colored inks on photographic paper and (ii) imaging of thin coronal sections of rat brain tissue fixed onto a glass microscope slide. In both cases, full mass spectra are recorded as a function of x,y-position on the surface. In the chemical imaging example, the distributions of the two different inks on the paper surface were mapped by tracking the abundance of the intact organic cation which characterizes each particular ink dye. In the tissue imaging example, distributions of specific lipids in coronal sections of rat brain tissue were followed from the abundance distributions in 2D space of the deprotonated lipid molecules recorded in the negative ion mass spectra. These latter distributions reveal distinct anatomical features of the rat brain. The results of these studies demonstrate the feasibility of performing surface imaging studies using DESI and show that at this stage of its development it has a lateral spatial resolution of a few hundred microns.     

Computer analysis of amino acid chromatograms and other linear elution spectra

A computer-aided method of evaluation of amino acid column chromatograms is proposed and compared with the usual synchronous peak-integration method. Spectra and their backgrounds are digitized separately by a curve digitizer; this allows a better estimate of the background time courses. A computer program then fits a set of superimposed Gaussian distributions to each corrected spectrum, thus circumventing the problems arising from incompletely separated peaks. Samples of known composition, run intermittently through the analyzer between the unknown spectra, allow a determination of the time dependence of the ratios of “peak areas over amounts of amino acids”; hence, the amounts of amino acids can automatically be corrected for aging effects of the analyzing system. A modified version of the computer program allows resolution of any spectrum to a sum of Gaussians, with least squares fitting of their amplitudes, widths and locations.     

Characterisation of Radioactive Particles by SIMS

 Secondary ion mass spectrometry (SIMS) was optimised for characterisation of uranium- and plutonium-containing particles in soils, swipes and forensic samples. This was done by analysing in-house produced spherical UO₂-particles. Screening techniques as α-autoradiography together with SIMS analysis were employed to detect UO₂-particles in a soil sample from Chernobyl. The use of SIMS was exploited for the identification of uranium- and plutonium-containing particles and for the determination of their isotopic composition. The particles collected on swipe samples were transferred to a special adhesive support for the analysis by SIMS. Particles containing highly enriched uranium with diameters up to 10 μm were also detected in a forensic sample. For the measurements of the isotopic ratios a mass resolution of 1000 was used. At this resolution flat-top peaks were obtained which greatly improve the accuracy of the measurement. The isotopic composition of the particles was measured with a typical accuracy and precision of 0.5%. Statistically meaningful results can be obtained, for instance, from a specimen containing as few as 10¹⁰ atoms/μm³ of uranium in particles of UO₂ weighing a few picograms.     

A thermodynamic interpretation of the behavior of higher fatty alcohols and acids upon the chromatographic paper

An idea was presented of treating the chromatographed substance as a “solute,” and the chromatographic system, composed of the stationary and the mobile phase as a “solvent.” Moreover the concept of “local equilibrium” was introduced, allowing to regard a given chromatographic spot as a “binary solution.” Thus a possibility arose to apply the classical thermodynamic approach, normally used for binary solutions, and namely: μ_i = μ_i + RT ln x_iƒ_i, where μ_i—chemical potential of the “i”-th compound in the solution, μ_i—chemical potential of the pure “i”-th compound, x_i-molar fraction of the “i”-th compound, ƒ_i—its activity coefficient, in a modified form, suitable for the chromatographic purpose.     

Die reaktion von 4-(α-hydroxyalkyliden)-Δ-5-isoxazolonen mit bifunktionellen stickstoffbasen

The 4-(α-hydroxyalkylidene)-Δ²-5-isoxazolones2 exist in the β-ketoenol form (“vinyloge car☐ylic acids”),2a,c react with guanidine and amidines to give only the enolates4, whereas they react both with hydrazines and 1,2-diamines to form the enamines6 and9 (“vinyloge amids”). The 4-(α-ethoxyalkylidene)-Δ²-5-isoxazolones 7 (“vinyloge esters”) condense with guanidine, benzamidine, and urea to affort the enamines8. Attempted ring-opening by bases failed whilst catalytic hydrogenation of the enamines6 and8 yielded the pyrazoles10,11 and diazepines12. The structures of the compounds have been elucidated by NMR and IR-spectra.     

Quantitative evaluation of hyperconjugation in the cyclopropylcarbinyl cation and in cyclopropylborane

An orbital deletion procedure (ODP) at HF/6-311G** have been used to evaluate the hyperconjugation effects in the cyclopropylcarbinyl cation (1) and in cyclopropylborane (2), as well as the conjugation effects in the allyl cation (3) and in vinylborane (4). The hyperconjugation (or conjugation) energies have been quantified by ODP in which the critical “vacant” carbocation (or boron) p orbital is “deactivated”. Comparisons between the bisected conformations of 1 with 3, and 2 with 4 demonstrate that cyclopropane can be just as effective as a π-electron donor as a C=C double bond.