Infrared intensities: A new tool in chemistry.

The interpretation of the infrared intensities in terms of atomic polar tensors and of electrooptical parameters allows to derive rich information on the charge distribution in the molecules. Using the results of several studies of this kind, it is now possible to derive information on intramolecular and intermolecular interactions even from “poor” data such as absolute intensities of whole regions in the spectrum or even from relative intensities.     

A facile single-step approach to achieve in situ expanded g-C3N4 for improved photodegradation performance

Improved graphitic carbon nitride (g-C₃N₄) was synthesized through a unique one-step cost-effective technique involving a dynamic gas bubbling phenomenon using ammonium chloride (NH₄Cl) as a bubbling agent. An extensive investigation was carried out to optimize the weight ratio of NH₄Cl and melamine during the thermal pyrolysis process. Here, we report an improved form of g-C₃N₄ namely “expanded g-C₃N₄” with increased interlayer distance and remarkable volume expansion. The surface area of this improved version has notably increased leading to higher photocatalytic efficiency as compared with its counterpart, an synthesized without adding NH₄Cl. Synthesized photocatalyst materials were further used to study the Rhodamine B photodegradation under visible light. It was observed that the expanded g-C₃N₄ showed a 2.4 times higher photodegradation rate than its counterpart and degraded 94% of the dye in just 30 min.     

Parallel processing on minicomputers: A powerful tool for quantum chemistry

It is shown that performance of quantum chemistry program systems on minicomputers may be enhanced by a factor between 2.5 and 2.8 utilizing microprogramming techniques and a computer architecture allowing four processor activities to operate in parallel, i.e., memory access, basic arithmetic operations, and two high-speed 64-bit floating-point arithmetic units.     

The use of a short-end injection procedure to achieve improved performance in capillary electrophoresis

Summary Minimum capillary lengths on commercial instruments are fixed and cannot be decreased further. To effectively reduce the capillary length used for separation the sample can be injected from the end of the capillary nearest the detector. This procedure is known as a short-end injection and can reduces analysis times by at least two-thirds compared to conventional injections. The time reduction benefits are shown in rapid separations of basic drugs, drug-related impurities and chiral compounds. Short-end injections, in combination with both increased electrolyte strength and reduced voltage are an effective approach to reducing the detrimental impact of high sample solution ionic strength. They can also lead to improved resolution by increasing stacking effects and reducing peak tailing. Peak area and migration time precision obtained are shown to be equivalent to those obtained for conventional injection procedures. It is concluded that short-end injections should be considered for routine operation as they are a useful means of reducing analysis time, increasing sensitivity, decreasing buffer depletion effects. They also allow use of higher electrolyte strengths which can improve resolution and reduce peak tailing, and can overcome significant problems which occur when analysing samples containing high salt contents.     

A new tool to assess ceramide bioactivity: 6-bromo-7-hydroxycoumarinyl-caged ceramide

The bioactivity of natural, long-chain ceramides has until now been studied after its delivery to cells in organic solvent mixtures containing dodecane. We have synthesized ceramides conjugated to a (6-bromo-7-hydroxycoumarin-4-yl)methyl group. The photocaged ceramide is efficiently released with 350 nm light in aqueous solution at neutral pH, thus providing a promising new tool to study ceramide's properties.     

A new high frequency dynamic mechanical analysis system: An approach to direct high frequency testing of tire tread rubber

Dynamic Mechanical Analysis (DMA) systems are measurement devices for obtaining master curves and complex modules of viscoelastic materials, such as rubbers. The conventional DMAs measurement systems in market have several limitations, which restrict their ability for operating at high frequencies. Thus, Williams, Landel and Ferry (WLF) relation is used to produce master curves and predict the material properties at high frequencies. In conventional DMAs, experiments are done in a range of temperatures, and then a master curve is made for a chosen reference temperature by shifting the measurements data to high frequencies. Therefore, the obtained results, which are not based on direct measurements, can be inaccurate. In order to overcome this problem a new simple shear high-frequency DMA (HFDMA) system is designed and built to directly measure the dynamic mechanical properties of viscoelastic material at high frequencies and the strain levels sufficient for tire manufacturers. The new HFDMA can be used to test any viscoelastic materials which have glass transmission temperature (Tg) lower than room temperature (about 23 °C) such as the Styrene-butadiene rubber (SBR). The SBR is the base material for tire tread. The designing process of this new HFDMA is presented in this paper. The rubber specimen shape is chosen by taking into account the shear elastic wave effect, bending, buckling effect and heat generation in the specimen. The repeatability test is accomplished to ensure that the results obtained from the new HFDMA are repeatable and the repeatability uncertainty is about 0.04%. The new HFDMA is validated by comparing to the direct test results of conventional DMA at 100 Hz. The direct high frequency (5 kHz) complex shear modulus and damping factor are compared with the master curve of the conventional DMA developed by the use of WLF relation for SBR. This comparison revealed that the complex shear modulus and damping factor of the SBR obtained from the HFDMA at 5 kHz and 0.05% strain amplitude are about 7% and 6.5% higher than those obtained from the conventional DMA, respectively.     

A new approach to processing electronic diffuse reflectance spectra

The fundamental absorption band edge in the diffuse reflectance spectra can be represented as the superposition of bands described by the Fermi-Dirac distribution to determine the coordination state of element-containing structures formed on the surface of a matrix. The suggested procedure is compared with the other spectrum processing methods (the determination of the position of the absorption band edge and transformation in the Gurevich-Kubelka-Munk or (αhν) ^m coordinates). It was shown that the use of the Fermi-Dirac distribution allows not only experimental data to be correctly described but also separation of complex spectra to be performed with isolating the contribution of surface structures containing atom-modifiers in various coordination states. Original Russian Text ? E.A. Sosnov, A.A. Malkov, A.A. Malygin, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 4, pp. 746–752.     

Synchrotron fourier transform infrared microspectroscopy: A new tool to monitor the fate of organic contaminants in plants

FTIR microspectroscopy, with synchrotron radiation as a source, was used for the first time to study changes in plant structure induced by organic contaminants. Sunflower (Helianthus annuus L.) plants were grown hydroponically in the presence of benzotriazole. Changes in the plant structure due to uptake, incorporation, and/or transformation of benzotriazole were observed. False color intensity maps of benzotriazole treated secondary root sections showed changes in plant structure, as well as the presence of aromatic CH peaks due to incorporation of benzotriazole within the plant. The presence of the characteristic benzotriazole CH out-of-plane bending mode suggests that the contaminant aromatic ring remains intact upon the uptake by the plant. Simultaneously, the changes in the lignin structure suggest that the plant suffered damage by the uptake of the benzotriazole. Spectral variations between the untreated and benzotriazole treated sunflowers were uncovered using principal components analysis (PCA). PCA also revealed clustering according to the different benzotriazole treatments.     

GlycoMiner: a new software tool to elucidate glycopeptide composition

New computer software, GlycoMiner, has been developed to automatically identify tandem (MS/MS) spectra obtained in liquid chromatography/mass spectrometry (LC/MS) runs which correspond to N-glycopeptides. The program complements conventional proteomics analysis, and can be used in a high-throughput environment. The program interprets the spectra and determines the structure of the corresponding glycopeptides. GlycoMiner runs under Windows, can process spectra obtained on various instruments, and can be downloaded from our website (w3.chemres.hu/ms/glycominer). The algorithm works similarly to a human expert; evaluates the low mass oxonium ions; deduces oligosaccharide losses from the protonated molecule; and identifies the mass of the peptide residue. The program has been tested on tryptic digests of two glycopeptides: AGP (which has five different N-glycosylation sites) and transferrin (with two N-glycosylation sites). Results have been evaluated both manually and by GlycoMiner. Out of 3132 MS/MS spectra 338 were found to correspond to glycopeptides; identification by GlycoMiner showed a 0.1% false positive and 0.1% false negative rate. From these it was possible to identify 196 glycan structures manually; GlycoMiner correctly identified all of these, with no false positives. The rest were low quality spectra, not suitable for structure assignment.     

Immunosorbents: A new tool for pesticide sample handling in environmental analysis

 Immunoaffinity techniques have been widely used for the determination of different analytes in the medical field. However the use of antibodies immobilized in an appropriate support material to preconcentrate pesticides from environmental samples is only recent. The production of antibodies, election of supports, antibody immobilization procedures, elution of analytes from immunosorbents and the more recent applications in the field of pesticide analysis are reviewed. The present review concludes that immunosorbents have great potential and discusses the present limitations and expected future trends. Received: 29 July 1996 / Accepted: 14 August 1996     

A new tool in peptide engineering: a photoswitchable stilbene-type beta-hairpin mimetic

Peptide secondary structure mimetics are important tools in medicinal chemistry, as they provide analogues of endogenous peptides with new physicochemical and pharmacological properties. The development, synthesis, photochemical investigation, and conformational analysis of a stilbene-type beta-hairpin mimetic capable of light-triggered conformational changes have been achieved. In addition to standard spectroscopic techniques (nuclear Overhauser effects, amide temperature coefficients, circular dichroism spectroscopy), the applicability of self-diffusion measurements (longitudinal eddy current delay pulsed-field gradient spin echo (LED-PGSE) NMR technique) in conformational studies of oligopeptides is demonstrated. The title compound shows photoisomerization of the stilbene chromophore, resulting in a change in solution conformation between an unfolded structure and a folded beta-hairpin.     

Charged particle induced X-ray analysis: A new tool in forensic science

The application of the charged particle X-ray excitation technique (CPXE) to the problem of determination of residues from gun firing is described. Preliminary results indicate that certain elements, including S, Ba, Fe, and Pb can be detected in statistically significant larger amounts on firing hands than on nonfiring hands with 90 to 98% confidence limits. Results for other elements including K, Ca, Sb, Cr, Mn, Ni, Cu, are also discussed. The simplicity on the technique, together with the number of elements detected, offers advantages over other techniques for firearm discharge residue detection.     

Copolymerization: A new tool to selectively induce poly(butylene naphthalate) crystal form

Poly(butylene/diethylene naphthalate) copolymers (PBN‐PDEN) were synthesized in bulk according to the polycondensation procedure and examined by NMR, GPC, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and XRD. At room temperature they appeared as semicrystalline materials; the copolymerization caused a lowering in the T_g value, a decrement of T_m and of the crystallization rate. Pure α or β′ form was obtained at low and high DEN unit content, respectively; crystalline form transition never occurred in the solid state, analogously to PBN. After cooling from the melt, the pure α form was always evidenced in PBN‐PDEN10 and PBN‐PDEN20, whereas the pure β′ crystal phase develops in the copolymer containing 40 mol % DEN units, independently on the cooling rate. In the case of PBN‐PDEN30 a pure α or β′ form was obtained at low and high cooling rate, respectively. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1356–1367, 2009     

Imaging reflection IR spectroscopy as a tool to achieve higher integration for high-throughput experimentation in catalysis research

FTIR spectroscopy in reflection mode combined with a focal plane array (FPA) detector was employed for high-throughput screening of activity of catalysts in n-pentane hydroisomerization. The reactor system was evaluated using reference catalysts Pt-MOR and gamma-alumina of known catalytic activity. By using the reflection setup, a higher degree of parallelization was possible, as compared to previous reports, in which transmission cells had been used. The 49-channel parallel reactor in combination with the FPA-IR optical setup was able to provide reliable information about the activity of different catalysts with relative data error of less than +/-20%.     

Single electron densities: a new tool to analyze molecular wavefunctions

A new partitioning scheme for the electron density of a many-electron wavefunction into single electron densities is proposed. These densities are based on the most probable arrangement of the electrons in an atom or molecule. Therefore, they contain information about the electron-electron interaction and, most notably, the Fermi hole due to the antisymmetry of the many-electron wavefunction. The single electron densities overlap and can be combined to electron pair distributions close to the qualitative electron pairs that represent, for instance, the basis of the valence shell electron pair repulsion model. Single electron analyses are presented for the water, ethane, and ethene molecules. The effect of electron correlation on the single electron and pair densities is investigated for the water molecule.     

A new tool for the rational design of methylbiotin hosts

To study the binding mode of biotin related compounds with artificial hosts, we have developed a new tool to be used as a guide to test their behaviour prior to their synthesis. In that way, we have considered a set of 23 complexes comprising biotin and urea derivatives with synthetic hosts to develop a Partial Least Squares Cross-Validated (PLS-CV) model. The data, for such a model, are the binding constants (K_b) of each complex and the interaction energies (−E_min) calculated by molecular mechanics with AMBER and OPLS force fields. The predictive power of the model has been verified.