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Selected AbstractsPrediction of Tyrosinase Inhibition Activity Using Atom-Based Bilinear IndicesCHEMMEDCHEM, Issue 4 2007Yovani Marrero-Ponce Prof. Abstract A set of novel atom-based molecular fingerprints is proposed based on a bilinear map similar to that defined in linear algebra. These molecular descriptors (MDs) are proposed as a new means of molecular parametrization easily calculated from 2D molecular information. The nonstochastic and stochastic molecular indices match molecular structure provided by molecular topology by using the kth nonstochastic and stochastic graph-theoretical electronic-density matrices, Mk and Sk, respectively. Thus, the kth nonstochastic and stochastic bilinear indices are calculated using Mk and Sk as matrix operators of bilinear transformations. Chemical information is coded by using different pair combinations of atomic weightings (mass, polarizability, vdW volume, and electronegativity). The results of QSAR studies of tyrosinase inhibitors using the new MDs and linear discriminant analysis (LDA) demonstrate the ability of the bilinear indices in testing biological properties. A database of 246 structurally diverse tyrosinase inhibitors was assembled. An inactive set of 412 drugs with other clinical uses was used; both active and inactive sets were processed by hierarchical and partitional cluster analyses to design training and predicting sets. Twelve LDA-based QSAR models were obtained, the first six using the nonstochastic total and local bilinear indices and the last six with the stochastic MDs. The discriminant models were applied; globally good classifications of 99.58 and 89.96,% were observed for the best nonstochastic and stochastic bilinear indices models in the training set along with high Matthews correlation coefficients (C) of 0.99 and 0.79, respectively, in the learning set. External prediction sets used to validate the models obtained were correctly classified, with accuracies of 100 and 87.78,%, respectively, yielding C values of 1.00 and 0.73. This subset contains 180 active and inactive compounds not considered to fit the models. A simulated virtual screen demonstrated this approach in searching tyrosinase inhibitors from compounds never considered in either training or predicting series. These fitted models permitted the selection of new cycloartane compounds isolated from herbal plants as new tyrosinase inhibitors. A good correspondence between theoretical and experimental inhibitory effects on tyrosinase was observed; compound CA6 (IC50=1.32,,M) showed higher activity than the reference compounds kojic acid (IC50=16.67,,M) and L -mimosine (IC50=3.68,,M). [source] Predator Inspection Behaviour in a Characin Fish: an Interaction between Chemical and Visual Information?ETHOLOGY, Issue 9 2003Grant E. Brown Recent evidence suggests that predator inspection behaviour by Ostariophysan prey fishes is regulated by both the chemical and visual cues of potential predators. In laboratory trials, we assessed the relative importance of chemical and visual information during inspection visits by varying both ambient light (visual cues) and predator odour (chemical cues) in a 2 × 2 experimental design. Shoals of glowlight tetras (Hemigrammus erythrozonus) were exposed to a live convict cichlid (Archocentrus nigrofasciatus) predator under low (3 lux) or high (50 lux) light levels and in the presence of the odour of a cichild fed tetras (with an alarm cue) or swordtails (Xiphophorus helleri, with an alarm cue not recognized by tetras). Tetras exhibited threat-sensitive inspection behaviour (increased latency to inspect, reduced frequency of inspection, smaller inspecting group sizes and increased minimum approach distance) towards a predator paired with a tetra-fed diet cue, regardless of light levels. Similar threat-sensitive inspection patterns were observed towards cichlids paired with a swordtail-fed diet cue only under high light conditions. Our data suggest that chemical cues in the form of prey alarm cues in the diet of the predator, are the primary source of information regarding local predation risk during inspection behaviour, and that visual cues are used when chemical information is unavailable or ambiguous. [source] The importance of cerebrospinal fluid on neural cell proliferation in developing chick cerebral cortexEUROPEAN JOURNAL OF NEUROLOGY, Issue 3 2006F. Mashayekhi Cerebrospinal fluid (CSF) is mainly produced by the choroid plexuses within the ventricles of the brain. The CSF circulates in a regular manner after the ventricular system and the choroids plexuses have developed, and the foramina in the fourth ventricle have opened to enable it to carry chemical information. CSF flows through the ventricular system passing over all regions of germinal activity. In this study, chick embryos were used to show the importance of CSF on neural cell proliferation in the developing cerebral cortex. The chick embryos were cannulated in situ with a fine capillary tube to drain CSF out of the ventricular system. At the same time, BrdU was administered to the embryos. After surgery the embryos were incubated for another 3 days. Quantitative measurements showed that the thicknesses of the germinal epithelium and cerebral cortex in CSF-drained embryos were less than those in the control group at the same age. The number of cells produced in the germinal epithelium of CSF-drained embryos was decreased when compared with the normal group. This study provides confirmatory evidence that CSF is important for neural cell proliferation and therefore normal development of the cerebral cortex. It is proposed that CSF is vital in controlling development of the cerebral cortex. [source] Prediction of missing enzyme genes in a bacterial metabolic networkFEBS JOURNAL, Issue 9 2007Reconstruction of the lysine-degradation pathway of Pseudomonas aeruginosa The metabolic network is an important biological network which consists of enzymes and chemical compounds. However, a large number of metabolic pathways remains unknown, and most organism-specific metabolic pathways contain many missing enzymes. We present a novel method to identify the genes coding for missing enzymes using available genomic and chemical information from bacterial genomes. The proposed method consists of two steps: (a) estimation of the functional association between the genes with respect to chromosomal proximity and evolutionary association, using supervised network inference; and (b) selection of gene candidates for missing enzymes based on the original candidate score and the chemical reaction information encoded in the EC number. We applied the proposed methods to infer the metabolic network for the bacteria Pseudomonas aeruginosa from two genomic datasets: gene position and phylogenetic profiles. Next, we predicted several missing enzyme genes to reconstruct the lysine-degradation pathway in P. aeruginosa using EC number information. As a result, we identified PA0266 as a putative 5-aminovalerate aminotransferase (EC 2.6.1.48) and PA0265 as a putative glutarate semialdehyde dehydrogenase (EC 1.2.1.20). To verify our prediction, we conducted biochemical assays and examined the activity of the products of the predicted genes, PA0265 and PA0266, in a coupled reaction. We observed that the predicted gene products catalyzed the expected reactions; no activity was seen when both gene products were omitted from the reaction. [source] Linking biological and artificial olfaction: biomimetic quartz crystal microbalance odor sensorsIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 3 2009Bartosz Wyszynski Non-member Abstract Biological olfaction is a powerful system enabling acquisition and processing of various chemical information from environment. Vast significance of the sense of smell is reflected in attempts to create instrumental techniques mimicking the biological system,artificial/machine olfaction. Following the biological systems, the artificial olfaction relies on arrays of gas sensors with broad specificities to odorants. Arguably, among available gas-sensing technologies, the most suitable choices for artificial olfaction are acoustic wave sensors, including quartz crystal microbalance (QCM) gas/odor sensors. The short review herein presents basic information on organization and principles of biological and artificial olfaction systems as well as several methods for fabrication of biomimetic or bioinspired (QCM) sensors for artificial olfaction. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Label-free biochemical characterization of stem cells using vibrational spectroscopyJOURNAL OF BIOPHOTONICS, Issue 11 2009James W. Chan Abstract Raman and infrared (IR) spectroscopy are two complementary vibrational spectroscopic techniques that have experienced a tremendous growth in their use in biological and biomedical research. This is, in large part, due to their unique capability of providing label-free intrinsic chemical information of living biological samples at tissue, cellular, or sub-cellular resolutions. This article reviews recent developments in applying these techniques for the characterization of stem cells. A discussion of the potential for these methods to address some of the major challenges in stem cell research is presented, as well as the technological and scientific advancements that are needed to progress the knowledge in the field. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Model-based biological Raman spectral imagingJOURNAL OF CELLULAR BIOCHEMISTRY, Issue S39 2002Karen E. Shafer-Peltier Abstract Raman spectral imaging is a powerful tool for determining chemical information in a biological specimen. The challenge is to condense the large amount of spectral information into an easily visualized form with high information content. Researchers have applied a range of techniques, from peak-height ratios to sophisticated models, to produce interpretable Raman images. The purpose of this article is to review some of the more common imaging approaches, in particular principal components analysis, multivariate curve resolution, and Euclidean distance, as well as to present a new technique, morphological modeling. How to best extract meaningful chemical information using each imaging approach will be discussed and examples of images produced with each will be shown. J. Cell. Biochem. Suppl. 39: 125,137, 2002. © 2002 Wiley-Liss, Inc. [source] A physiochemical theory on the applicability of soft mathematical models,experimentally interpretedJOURNAL OF CHEMOMETRICS, Issue 7-8 2010L. Munck Abstract An extension of chemometric theory was experimentally explored to explain the physiochemical basis of the very high efficiency of soft modelling of data from nature. Soft modelling in self-organisation was interpreted by studying the unique chemical patterns of mutants in an isogenic barley model on endosperm development. Extremely reproducible, differential Near Infrared (NIR) spectral patterns specifically overviewed the effect on cell composition of each mutant cause. Extended Canonical Variates Analysis (ECVA) classified spectra in wild type, starch and protein mutants. The spectra were interpreted by chemometric data analysis and by pattern inspection to morphological, genetic, molecular and chemical information. Deterministic chemical reactions were defined in the glucan pathway. A drastic mutation in a gene controlling the starch/ß-glucan composition changed water activity that introduced a diffusive, stochastic effect on the catalysis of all active enzymes. ,Decision making' in self-organisation is autonomous and performed by the soft modelling of the chemical deterministic and stochastic reactions in the endosperm cell as a whole. Uncertainty in the analysis of endosperm emergence was experimentally delimited as the ,indeterminacy' in local molecular path modelling ,bottom up' and the ,irreducibility' of the phenomenological NIR spectra ,top down'. The experiment confirmed Ilya Prigogine's interpretation of self-organisation by his dynamic computer model programmed with a self-modeled non-local extension of quantum mechanics (QM). The significance of self- organisation explained by Prigogine here interpreted as physiochemical soft modelling introduces a paradigm shift in macroscopic science that forwards a major argument for soft mathematical modelling and chemometrics to obtain full scientific legitimacy. Copyright © 2010 John Wiley & Sons, Ltd. [source] Empirical preprocessing methods and their impact on NIR calibrations: a simulation studyJOURNAL OF CHEMOMETRICS, Issue 2 2005S. N. Thennadil Abstract The extraction of chemical information from dense particulate suspensions, such as industrial slurries and biological suspensions, using near-infrared (NIR) spectroscopic measurements is complicated by sample-to-sample path length variations due to light scattering. Empirical preprocessing techniques such as multiplicative scatter correction (MSC), extended MSC and derivatives have been applied to remove these effects and in some cases have shown promise. While the performance of these techniques and other related approaches is known to depend on the nature and extent of the variations and on the measurement configuration, detailed investigations into the efficacy of these approaches under various conditions have not been previously undertaken. The main obstacle to carrying out such investigations has been the lack of, and the difficulty in obtaining, an accurate and comprehensive experimental data set. In this work, simulations that generate ,actual' measurements were carried out to obtain ,experimental' spectroscopic data on particulate systems. This was achieved by solving the exact transport equation for light propagation. A model system comprising four chemical components with one consisting of spherical submicron particles was considered. Total diffuse transmittance and reflectance data generated through simulations for moderate particle concentrations were used as the basis for examining the effect of particle size variations and measurement configurations on the efficacy of a number of preprocessing techniques in enhancing the performance of partial least squares (PLS) models for predicting the concentration of one of the non-scattering chemical species. Additionally, a form of extended multiplicative signal correction based on considerations arising from fundamental light scattering theory is proposed and found to perform better than the other techniques for the cases considered in the study. Copyright © 2005 John Wiley & Sons, Ltd. [source] DETECTION OF OLIVE OIL ADULTERATION WITH RAPESEED AND SUNFLOWER OILS USING MOS ELECTRONIC NOSE AND SMPE-MSJOURNAL OF FOOD QUALITY, Issue 1 2010SYLWIA MILDNER-SZKUDLARZ ABSTRACT The study analyzed the effectiveness of two types of electronic nose systems to detect adulteration of extra virgin olive oil (EVOO) with rapeseed and sunflower oils. Tested methods included volatile analysis with the electronic nose based on MOS sensors (HS-E nose) and by direct coupling of SPME to MS (SPME-MS). Volatile compounds were analyzed also by SPME-GC/MS. Samples of EVOO were mixed with different proportions, ranging from 5 to 50% (v/v), of seed oils and fingerprints of volatile profiles of all samples were generated. In order to obtain as much chemical information as possible and to find a volatile marker to detect adulterations of EVOO with seed oils, principal component analysis (PCA) and partial least squares (PLS) analyses were applied to the data. The application of PCA and PLS analyses to the data from two electronic noses and SMPE-GC/MS were sufficient to differentiate the adulterated samples from pure EVOO. Excellent results were obtained in the prediction of the percentage of adulteration by PLS analysis. SPME-GC-MS analysis with subsequent PCA yielded good results; however, it was time-consuming. The two electronic noses, with subsequent PCA treatment of data, offering the advantages of rapidity and reliability, enabled detection of olive oil adulteration with different contents of seed oils. PRACTICAL APPLICATIONS Virgin olive oil is highly appreciated by consumers due to its nutritional benefits. Thus, its adulteration with low-grade olive oils or cheaper vegetable oils could potentially be very profitable for sellers or raw material suppliers and may yield large economic profits. In this way, authentication of virgin olive oils has become an interesting subject from both commercial and health perspectives. It has been proved that the two proposed types of electronic nose systems facilitate reliable detection of rapeseed and sunflower oils in extra virgin olive oil. Both MOS and MS electronic noses are faster than the conventional SMPE-GC/MS analysis. These well-correlated methodologies, offering the advantages of rapidity and reliability, opened up a new way of detecting adulteration of virgin olive oils. [source] PTR-TOF-MS and data-mining methods for rapid characterisation of agro-industrial samples: influence of milk storage conditions on the volatile compounds profile of Trentingrana cheese,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2010Alessandra Fabris Abstract Proton transfer reaction-mass spectrometry (PTR-MS), a direct injection mass spectrometric technique based on an efficient implementation of chemical ionisation, allows for fast and high-sensitivity monitoring of volatile organic compounds (VOCs). The first implementations of PTR-MS, based on quadrupole mass analyzers (PTR-Quad-MS), provided only the nominal mass of the ions measured and thus little chemical information. To partially overcome these limitations and improve the analytical capability of this technique, the coupling of proton transfer reaction ionisation with a time-of-flight mass analyser has been recently realised and commercialised (PTR-TOF-MS). Here we discuss the very first application of this new instrument to agro-industrial problems and dairy science in particular. As a case study, we show here that the rapid PTR-TOF-MS fingerprinting coupled with data-mining methods can quickly verify whether the storage condition of the milk affects the final quality of cheese and we provide relevant examples of better compound identification in comparison with the previous PTR-MS implementations. In particular, ,Trentingrana' cheese produced by four different procedures for milk storage are compared both in the case of winter and summer production. It is indeed possible to set classification models with low prediction errors and to identify the chemical formula of the ion peaks used for classification, providing evidence of the role that this novel spectrometric technique can play for fundamental and applied agro-industrial themes. Copyright © 2010 John Wiley & Sons, Ltd. [source] On the mechanism of resorption zoning in metamorphic garnetJOURNAL OF METAMORPHIC GEOLOGY, Issue 8 2003S. L. Hwang Abstract An analytical electron microscope study of almandine garnet from a metamorphosed Al,Fe-rich rock revealed detailed composition profiles and defect microstructures of resorption zoning along fluid-infiltrated veins and even into the garnet/ilmenite (inclusion) interface. This indicates a limited volume diffusion for the cations in substitution (mainly Ca and Fe) and an interface-controlled partition for the extension of a composition-invariant margin. A corrugated interface between the Ca-rich margin/zone and the almandine garnet core is characterized by dislocation arrays and recovery texture further suggesting a resorption process facilitated by diffusion-induced recrystallization, diffusion-induced dislocation migration and diffusion,induced grain boundary migration. Integrated microstructural and chemical studies are essential for understanding the underlying mechanisms of processes such as garnet zoning and its modification. Without this understanding, it will not be possible to reliably use garnet compositions for thermobarometry and other applications that rely on garnet chemical information. [source] Multivariate chemometric approach to thermal solid-state FT-IR monitoring of pharmaceutical drug compoundJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2008Wei Jian Tan Abstract The study of thermal-related solid-state reaction monitored by spectroscopic method needs the use of advanced multivariate chemometric approach. It is because visual inspection of spectral data on particular functional groups or spectral bands is difficult to reveal the complete physical and chemical information. The spectral contributions from various species involved in the solid-state changes are generally highly overlapping and the spectral differences between reactant and product are usually quite minute. In this article, we demonstrate the use of multivariate chemometric approach to resolve the in situ thermal-dependent Fourier-transform infrared (FT-IR) mixture spectra of lisinopril dihydrate when it was heated from 24 to 170°C. The collected FT-IR mixture spectra were first subjected to singular value decomposition (SVD) to obtain the right singular vectors. The right singular vectors were rotated into a set of pure component spectral estimates based on entropy minimization and spectral dissimilarity objective functions. The resulting pure component spectral estimates were then further refined using alternating least squares (ALS). In current study, four pure component spectra, that is, lisinopril dihydrate, monohydrate, anhydrate, and diketopiperazine (DKP) were all resolved and the relative thermal-dependent contributions of each component were also obtained. These relative contributions revealed the critical temperature for each transformation and degradation. This novel approach provides better interpretation of the pathway of dehydration and intramolecular cyclization of lisinopril dihydrate in the solid state. In addition, it can be used to complement the information obtained from differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97: 3379,3387, 2008 [source] Migration of mercury from dental amalgam through human teethJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2008Hugh H. Harris Exposure to mercury from dental amalgams, with possible negative health effects, has generally been considered to occur via either erosion or evaporation directly from the surface of fillings, followed by ingestion. The aim of this study was to determine the relative importance of the direct migration of mercury through the tooth as an alternative exposure pathway. X-ray fluorescence imaging has been used to determine quantitatively the spatial distribution of Hg, Ca, Zn and Cu in sections of human teeth that had been filled with amalgam for more than 20 years. X-ray absorption near-edge spectroscopy (XANES) was also employed to gain chemical information on the mercury present in the teeth. Hg (up to ,10,mg,g,1) and Zn (>100,mg,g,1) were detected in the teeth several millimetres from the location of the amalgams. At high resolution, Hg showed higher concentrations in dentinal tubules while Zn was generally evenly distributed. XANES showed that the chemical form of Hg that had migrated into the tooth had been altered from that present in the amalgam. The differing spatial distributions of Hg and Zn suggest distinct transport mechanisms for the two metals, presumably chemical for Zn and initially physical for Hg. Subsequent oxidation of Hg may lead to a loss of mobility or the development of a secondary transport mechanism. Most importantly the detection of Hg in areas of the tooth that once contained an active bloodstream and in calculus indicates that both exposure pathways should be considered as significant. [source] Quantitative X-Ray Spectrum Imaging of Lead Lanthanum Zirconate Titanate PLZT Thin-FilmsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2008Chad M. Parish The high permittivity of Pb(Zr,Ti)O3 and (Pb,La)(Zr,Ti)O3,PZT and PLZT, respectively,thin films and the flexibility of chemical solution deposition (CSD) make solution-derived P(L)ZT thin films extremely attractive for integrated capacitor applications. However, Pb-loss or cation segregation during processing results in degraded properties of the final film. Here, we have extended the use of multivariate statistical analysis (MSA) of energy-dispersive spectroscopy (EDS) spectrum images (SIs) in scanning transmission electron microscopy (STEM) to allow the two-dimensional (2D) quantitative analysis of cation segregation and depletion in P(L)ZT thin films. Quantified STEM-EDS SIs allow high-resolution (< ,10 nm) quantification of these cation distributions. Surface Pb depletion is found after crystallization and is replenished by a unique post-crystallization PbO overcoat+anneal processes. Zr/Ti and La segregation are found to develop in a decidedly nonplanar fashion during crystallization, especially in PLZT 12/70/30 material, highlighting the need for 2D analysis. Quantitative 2D chemical information is essential for improved processing of homogeneous P(L)ZT films with optimal electrical properties. [source] Natural intramolecular isotope measurements in physiology: elements of the case for an effort toward high-precision position-specific isotope analysis,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2001J. T. Brenna Chemical information available in organisms can be categorized into three major domains, macromolecular, small molecules, and isotope ratios. Information about physiological state is commonly obtained by qualitative and quantitative analysis in the macromolecular and small molecule domains. Genomics and proteomics are emerging approaches to analysis of macromolecules, and both areas yield definitive information on present physiological state. There is relatively little record of past physiological states of the individual available in these domains. Natural isotopic variability, particularly on an intramolecular level, is likely to retain more physiological history. Because of ubiquitous isotopic fractionation, every stereochemically unique position in every molecule has an isotope ratio that reflects the processes of synthesis and degradation. This fact highlights a vast amount of organismal chemical information that is essentially unstudied. Isotope measurements can be classified according to the chemical complexity of the analyte into bulk, compound-specific, and position-specific or intramolecular levels. Recent advances in analysis of isotope ratios are transforming natural science, and particularly answering questions about ecosystems using bulk methods; however, they have had relatively little impact on physiology. This may be because the vast complexities of physiological questions demand very selective information available in position-specific isotope analysis (PSIA). The relatively few high-precision PSIA studies, based on isotope ratio mass spectrometry (IRMS), have revealed intramolecular isotope ratio differences in pivotal physiological compounds including amino acids, glucose, glycerol, acetate, fatty acids, and purines. The majority of these analyses have been accomplished by laborious offline methods; however, recent advances in instrumentation presage rapid PSIA that will be necessary to attack real physiological problems. Gas-phase pyrolysis has been shown to be an effective method to determine 13C/12C at high precision for molecular fragments, and technologies to extend C-based PSIA to N and other organic elements are emerging. Two related efforts are warranted, (a) development of rapid, convenient, and sensitive methods for high-precision PSIA, a necessary precursor to (b) a concerted investigation into the relationship of metabolic state to intramolecular isotope ratio. Inherent in this latter goal is the need to identify long-lived molecules in long-lived cells that retain a record of early isotopic conditions, as has been shown for post-mortem human neuronal DNA. Using known metabolic precursor-product relationships between intramolecular positions, future studies of physiological isotope fractionation should reveal the relationship of diet and environment to observed isotope ratio. This science of isotope physiology, or simply isotopics, should add an important tool for elucidation of early factors that effect later health, probably the most difficult class of biomedical issues. Copyright © 2001 John Wiley & Sons, Ltd. [source] Apical and basal neurones isolated from the mouse vomeronasal organ differ for voltage-dependent currentsTHE JOURNAL OF PHYSIOLOGY, Issue 2 2003Francesca Fieni The mammalian vomeronasal organ (VNO) contains specialized neurones that transduce the chemical information related to pheromones into discharge of action potentials to the brain. Molecular and biochemical studies have shown that specific components of the pheromonal transduction systems are segregated into two distinct subsets of vomeronasal neurones: apical neurones and basal neurones. However, it is still unknown whether these neuronal subsets also differ in other functional characteristics, such as their membrane properties. We addressed this issue by studying the electrophysiological properties of vomeronasal neurones isolated from mouse VNO. We used the patch-clamp technique to examine both the passive membrane properties and the voltage-gated Na+, K+ and Ca2+ currents. Apical neurones were distinguished from basal ones by the length of their dendrites and by their distinct immunoreactivity for the putative pheromone receptor V2R2. The analysis of passive properties revealed that there were no significant differences between the two neuronal subsets. Also, apical neurones were similar to basal neurones in their biophysical and pharmacological properties of voltage-gated Na+ and K+ currents. However, we found that the density of Na+ currents was about 2-3 times greater in apical neurones than in basal neurones. Consistently, in situ hybridization analysis revealed a higher expression of the Na+ channel subtype III in apical neurones than in basal ones. In contrast, basal neurones were endowed with Ca2+ currents (T-type) of greater magnitude than apical neurones. Our findings indicate that apical and basal neurones in the VNO exhibit distinct electrical properties. This might have a profound effect on the sensory processes occurring in the VNO during pheromone detection. [source] Fashioning and Demarcation of the Danish Chemical Community in the 19th CenturyCENTAURUS, Issue 3 2007Anita Kildebęk Nielsen The development of Danish chemistry in the 19th century was a complex process involving the establishment of boundaries for chemistry, creation of professional identities, and institutional constructions. Many of these factors can be analysed through detailed studies of the media carrying chemical information. This paper explores the development process by studying three Danish chemical periodicals published in the vernacular. By analysing their contents, editorial lines, and intended audiences, these three periodicals give specific information on the social evolution of chemistry and the process of demarcation of chemistry from non-chemistry. The analysis is linked to the early history of the Danish Chemical Society in order to address the question of what it meant to be a chemist in second half of the 19th-century Denmark. Taken together, examination of specific aspects of the society and the three periodicals provide new perspectives on the relationships between the three most important groups of chemical practitioners: academics, engineers, and pharmacists. [source] Structural Diversity in the Self-Assembly of Pseudopeptidic MacrocyclesCHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2010Ignacio Alfonso Dr. Abstract The self-assembling abilities of several pseudopeptidic macrocycles have been thoroughly studied both in the solid (SEM, TEM, FTIR) and in solution (NMR, UV, CD, FTIR) states. Detailed microscopy revealed large differences in the morphology of the self-assembling micro/nanostructures depending on the macrocyclic chemical structures. Self-assembly was triggered by the presence of additional methylene groups or by changing from para to meta geometry of the aromatic phenylene backbone moiety. More interestingly, the nature of the side chain also plays a fundamental role in some of the obtained nanostructures, thus producing structures from long fibers to hollow spheres. These nanostructures were obtained in different solvents and on different surfaces, thus implying that the chemical information for the self-assembly is contained in the molecular structure. Dilution NMR studies (chemical shift and self-diffusion rates) suggest the formation of incipient aggregates in solution by a combination of hydrogen-bonding and ,,, interactions, thus implicating amide and aryl groups, respectively. Electronic spectroscopy further supports the ,,, interactions because the compounds that lead to fibers show large hypochromic shifts in the UV spectra. Moreover, the fiber-forming macrocycles also showed a more intense CD signature. The hydrogen-bonding interactions within the nanostructures were also characterized by attenuated total-reflectance FTIR spectroscopy, which allowed us to monitor the complete transition from the solution to the dried nanostructure. Overall, we concluded that the self-assembly of this family of pseudopeptidic macrocycles is dictated by a synergic action of hydrogen-bonding and ,,, interactions. The feasibility and geometrical disposition of these interactions finally render a hierarchical organization, which has been rationalized with a proposal of a model. The understanding of the process at the molecular level has allowed us to prepare hybrid soft materials. [source] | |||||||||||||||||||