Home About us Contact
|
Home About us Contact | ||
|
|
||
Molecular Properties (molecular + property)
Selected AbstractsEffect of Nonthermal Treatment on the Molecular Properties of Mushroom PolyphenoloxidaseJOURNAL OF FOOD SCIENCE, Issue 5 2003N.K. Sun ABSTRACT To elucidate the mechanism of inactivation of mushroom polyphenoloxidase (PPO) by nonthermal treatment, PPO solutions were irradiated up to 10 kGy or pressurized at 600 MPa and 800 MPa, respectively. PPO activities were significantly affected by , irradiation, and treatment at 5 kGy decreased the activity by 93%. Treatment of PPO at 600 MPa decreased the activity slightly, yet 10 and 20 min treatments at 800 MPa decreased the activities by 28% and 43%, respectively. Circular dichroism study showed that nonthermal treatment altered the ellipticity values in the range of 210 and 225 nm, resulting in decrease of the ordered structure. Fluorescence spectroscopy indicated that nonthermal treatment quenched the emission intensity. [source] A Pragmatic Recipe for the Treatment of Hindered Rotations in the Vibrational Averaging of Molecular PropertiesCHEMPHYSCHEM, Issue 1 2008Brendan C. Mort Dr. Abstract A computational protocol for the treatment of hindered rotations in the vibrational averaging of molecular properties is described. As examples, the specific rotations of (R) -methyloxirane, (1S) -methylnorbornanone, and (S) -epichlorohydrin and the spin-spin coupling constant for are investigated. For each of the four molecules, the relaxed and unrelaxed potential energy surfaces along the rotational coordinate of interest are used to solve the nuclear Schrödinger equation using a pseudospectral method. Analysis of the results demonstrate that the vibrational averaging for low-frequency modes that represent hindered rotations can lead to unphysical behavior at high temperatures while simply neglecting the rotational contributions is also not desirable. The method described in this work connects the (an)harmonic oscillator behavior at low temperatures with the free rotor-like behavior at high temperatures. [source] Cerebellar granule cells show age-dependent migratory differences in vitroDEVELOPMENTAL NEUROBIOLOGY, Issue 2 2005Krisztián Tárnok Abstract Developmental differences between cerebellar granule cells during their migratory period were revealed using dissociated granule cell cultures isolated from 4, 7, or 10 days old (P4, P7, P10) mice. Under all culture conditions, the great majority of cultivated cell populations consisted of those granule cells that had not reach their final destination in the internal granule cell layer (IGL) by the age of isolation. In vitro morphological development and the expression of migratory markers (TAG-1, astrotactin, or EphB2) showed similar characteristics between the cultures. The migration of 1008 granule cells isolated from P4, P7, and P10 cerebella and cultivated under identical conditions were analyzed using statistical methods. In vitro time-lapse videomicroscopy revealed that P4 cells possessed the fastest migratory speed while P10 granule cells retained their migratory activity for the longest time in culture. Cultures obtained from younger postnatal ages showed more random migratory trajectories than P10 cultures. Our observations indicate that despite similar morphological and molecular properties, migratory differences exist in granule cell cultures isolated from different postnatal ages. Therefore, the age of investigation can substantially influence experimental results on the regulation of cell migration. © 2005 Wiley Periodicals, Inc. J Neurobiol, 2005 [source] Studies on structural and functional divergence among seven WhiB proteins of Mycobacterium tuberculosis H37RvFEBS JOURNAL, Issue 1 2009Md. Suhail Alam The whiB -like genes (1-7) of Mycobacterium tuberculosis are involved in cell division, nutrient starvation, pathogenesis, antibiotic resistance and stress sensing. Although the biochemical properties of WhiB1, WhiB3 and WhiB4 are known, there is no information about the other proteins. Here, we elucidate in detail the biochemical and biophysical properties of WhiB2, WhiB5, WhiB6 and WhiB7 of M. tuberculosis and present a comprehensive comparative study on the molecular properties of all WhiB proteins. UV,Vis spectroscopy has suggested the presence of a redox-sensitive [2Fe,2S] cluster in each of the WhiB proteins, which remains stably bound to the proteins in the presence of 8 m urea. The [2Fe,2S] cluster of each protein was oxidation labile but the rate of cluster loss decreased under reducing environments. The [2Fe,2S] cluster of each WhiB protein responded differently to the oxidative effect of air and oxidized glutathione. In all cases, disassembly of the [2Fe,2S] cluster was coupled with the oxidation of cysteine-thiols and the formation of two intramolecular disulfide bonds. Both CD and fluorescence spectroscopy revealed that WhiB proteins are structurally divergent members of the same family. Similar to WhiB1, WhiB3 and WhiB4, apo WhiB5, WhiB6 and WhiB7 also reduced the disulfide of insulin, a model substrate. However, the reduction efficiency varied significantly. Surprisingly, WhiB2 did not reduce the insulin disulfide, even though its basic properties were similar to those of others. The structural and functional divergence among WhiB proteins indicated that each WhiB protein is a distinguished member of the same family and together they may represent a novel redox system for M. tuberculosis. [source] Apoptosis-inhibiting activities of BIR family proteins in Xenopus egg extractsFEBS JOURNAL, Issue 9 2005Yuichi Tsuchiya In many animal species including Xenopus, ovulated eggs possess an intrinsic apoptotic execution system. This program is inhibited for a limited time by some maternal apoptosis inhibitors, although their molecular properties remain uncharacterized. Baculovirus IAP repeat (BIR) family proteins contain evolutionarily conserved BIR domains and play important roles in apoptosis suppression, and are therefore good candidates as maternal apoptosis inhibitors. We identified four maternal BIR family proteins in Xenopus eggs and, using the biochemical advantages of egg extracts, examined their physiological functions. These molecules included two survivin-related proteins, xEIAP/XLX, and a possible ortholog of XIAP named xXIAP. The addition of recombinant xXIAP greatly delayed apoptotic execution, whereas the immunodepletion of endogenous xXIAP significantly accelerated the onset of apoptosis. In contrast, xEIAP/XLX was a poor apoptosis inhibitor, and neither of the survivin orthologs showed anti-apoptotic activity in our assay. Both xEIAP/XLX and xXIAP were degraded by activated caspases, and also by a novel proteolytic system that required the presence of C-terminal RING finger domain but was insensitive to proteasome inhibition. Our data suggest that the regulation of endogenous xXIAP concentration is important for the survival of Xenopus eggs. [source] The oxidation process of Antarctic fish hemoglobinsFEBS JOURNAL, Issue 9 2004Luigi Vitagliano Analysis of the molecular properties of proteins extracted from organisms living under extreme conditions often highlights peculiar features. We investigated by UV-visible spectroscopy and X-ray crystallography the oxidation process, promoted by air or ferricyanide, of five hemoglobins extracted from Antarctic fishes (Notothenioidei). Spectroscopic analysis revealed that these hemoglobins share a common oxidation pathway, which shows striking differences from the oxidation processes of hemoglobins from other vertebrates. Indeed, simple exposure of these hemoglobins to air leads to the formation of a significant amount of the low-spin hexacoordinated form, denoted hemichrome. This hemichrome form, which is detected under a variety of experimental conditions, can be reversibly transformed to either carbomonoxy or deoxygenated forms with reducing agents. Interestingly, the spectra of the fully oxidized species, obtained by treating the protein with ferricyanide, show the simultaneous presence of peaks corresponding to different hexacoordinated states, the aquomet and the hemichrome. In order to assign the heme region state of the , and , chains, the air-oxidized and ferricyanide-oxidized forms of Trematomus bernacchii hemoglobin were crystallized. Crystallographic analysis revealed that these forms correspond to an ,(aquomet)-,(bishistidyl-hemichrome) state. This demonstrates that the , and , chains of Antarctic fish hemoglobins follow very different oxidation pathways. As found for Trematomus newnesi hemoglobin in a partial hemichrome state [Riccio, A., Vitagliano, L., di Prisco, G., Zagari, A. & Mazzarella, L. (2002) Proc. Natl Acad. Sci. USA99, 9801,9806], the quaternary structures of these ,(aquomet)-,(bishistidyl-hemichrome) forms are intermediate between the physiological R and T hemoglobin states. Together, these structures provide information on the general features of this intermediate state. [source] Comparative gene expression profiling of olfactory ensheathing glia and Schwann cells indicates distinct tissue repair characteristics of olfactory ensheathing gliaGLIA, Issue 12 2008Elske H.P. Franssen Abstract Olfactory ensheathing glia (OEG) are a specialized type of glia that support the growth of primary olfactory axons from the neuroepithelium in the nasal cavity to the brain. Transplantation of OEG in the injured spinal cord promotes sprouting of injured axons and results in reduced cavity formation, enhanced axonal and tissue sparing, remyelination, and angiogenesis. Gene expression analysis may help to identify the molecular mechanisms underlying the ability of OEG to recreate an environment that supports regeneration in the central nervous system. Here, we compared the transcriptome of cultured OEG (cOEG) with the transcriptomes of cultured Schwann cells (cSCs) and of OEG directly obtained from their natural environment (nOEG), the olfactory nerve layer of adult rats. Functional data mining by Gene Ontology (GO)-analysis revealed a number of overrepresented GO-classes associated with tissue repair. These classes include "response to wounding," "blood vessel development," "cell adhesion," and GO-classes related to the extracellular matrix and were overrepresented in the set of differentially expressed genes between both comparisons. The current screening approach combined with GO-analysis has identified distinct molecular properties of OEG that may underlie their efficacy and interaction with host tissue after implantation in the injured spinal cord. These observations can form the basis for studies on the function of novel target molecules for therapeutic intervention after neurotrauma. © 2008 Wiley-Liss, Inc. [source] From learning to forgetting: Behavioral, circuitry, and molecular properties define the different functional states of the recognition memory traceHIPPOCAMPUS, Issue 5 2010Rocío Romero-Granados Abstract Neuropsychological analyses of amnesic patients, as well as lesion experiments, indicate that the temporal lobe is essential for the encoding, storage, and expression of object recognition memory (ORM). However, temporal lobe structures directly involved in the consolidation and reconsolidation of these memories are not yet well-defined. We report here that systemic administration of a protein synthesis inhibitor before or up to 4 h after training or reactivation sessions impairs consolidation and reconsolidation of ORM, without affecting short-term memory. We have also observed that ORM reconsolidation is sensitive to protein synthesis inhibition, independently of the ORM trace age. Using bdnf and egr-1 gene expression analysis, we defined temporal lobe areas related to consolidation and reconsolidation of ORM. Training and reactivation 21 days after ORM acquisition sessions provoked changes in bdnf mRNA in somatosensory, perirhinal, and hippocampal cortices. Reactivation 2 days after the training session elicited changes in bdnf and egr-1 mRNA in entorhinal and prefrontal cortices, while reactivation 9 days post-training provoked an increase in egr-1 transcription in somatosensory and entorhinal cortices. The differences in activated circuits and in the capacity to recall the memory trace after 9 or 21 days post-training suggest that memory trace suffers functional changes in this period of time. All these results indicate that the functional state of the recognition memory trace, from acquisition to forgetting, can be specifically defined by behavioral, circuitry, and molecular properties. © 2009 Wiley-Liss, Inc. [source] Mismatch repair expression in testicular cancer predicts recurrence and survivalINTERNATIONAL JOURNAL OF CANCER, Issue 8 2008Alfredo Velasco Abstract We investigated mismatch repair (MMR) gene expression in testicular cancer as a molecular marker for clinical outcome (recurrence, response to chemotherapy and death) using protein expression and specific genetic alterations associated with the presence or absence of MMR activity. One hundred sixty-two cases of paraffin-embedded testis cancer specimens were subjected to immunohistochemical analysis using monoclonal antibody for MLH1 and MSH2 MMR proteins and genetic analysis using specific polymorphic markers. The degree of MMR immunoreactivity and genetic instability in the form of loss of heterozygosity (LOH) and/or microsatellite instability (MSI) were determined by comparing matched normal and tumor tissue. The degree of immunohistochemical staining for MMR expression was associated with a shorter time to tumor recurrence, resistance to chemotherapy and death. Furthermore, clinical relapse and cancer specific death was also associated with tumors exhibiting a high degree of MSI, p = 0.01 and 0.04, respectively. In contrast, LOH was not associated with recurrence, resistance to chemotherapy or death. Therefore, MMR expression defines testis cancers with distinct molecular properties and clinical behavior, such that tumors with decreased MMR immunostaining and/or increased frequency of MSI have a shorter time to recurrence and death despite chemotherapy. © 2007 Wiley-Liss, Inc. [source] Fell-Muir Lecture: Cartilage 2010 , The Known UnknownsINTERNATIONAL JOURNAL OF EXPERIMENTAL PATHOLOGY, Issue 3 2010Timothy E. Hardingham Summary Over the past 40 years there have been giant steps forward in our understanding of cellular and molecular biology that have given us the framework by which to understand tissue organization and tissue function on a range of scales. However, although the progress has been great, the more we have discovered, the more we are aware of what we don't yet know. In this article, I would like to flag up some issues of cartilage biology, function and pathology where we still have significant ignorance. As scientists we all provide contributions to add to the greater understanding of science and progress is on a broad front, but gaps are left where particular difficulty is encountered and in life sciences it is no different. Progress is fast where new knowledge and techniques pave the way, but where study is complex and relevant techniques poorly developed the gaps are left behind. In cartilage research and matrix biology, the gaps can particularly be seen at interfaces between disciplines and where technology development has lagged behind and in the particular challenges of understanding how molecular properties can explain tissue macro properties. [source] Theoretical study of NMR chemical shift induced by H/D isotope effectINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 15 2010Kimikazu Sugimori Abstract The isotope effect induced by deuterium substituted species is observed in molecular properties, such as geometry, kinetics, and electronic state, of the molecules through nuclear-electron interaction. Theoretical considerations and experimental alignments have been studied by ab initio molecular orbital, density functional theory, and other empirical strategies. The Born-Oppenheimer approximation with nuclear vibrational wavefunction can treat isotope effect because nuclear mass effect account for the average distance of vibrational motion. In this study, we introduce Morse anharmonic oscillator model to calculate average internuclear distance of diatomic molecules having X-H bonding and X-D bonding. Morse parameters are determined by fitting to potential energy surface of molecular orbital and/or density functional calculations, and then the average distance are obtained as the expectation value of the analytical Morse vibrational wavefunction. Nuclear magnetic resonance shielding constants of the H/D isotopomer are calculated again on the average distance by using GIAO with B3LYP and CCSD calculation. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Improvements of parametric quantum methods with new elementary parametric functionalsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 10 2008Fernando Ruette Abstract A series of elementary parametric functionals (EPFs) for resonance integral, electron-electron repulsion, electron-nucleus attraction, core-core interaction, and bond correlation correction were included in the new version of CATIVIC method [Int J Quantum Chem 2004, 96, 321]. In the present work, a systematic way to improve the precision of parametric quantum methods (PQMs) by using several EPFs in the parameterization of a set of molecules is proposed. Based on the fact that a linear combination of elementary functionals from the exact Hamiltonian is also a functional, a linear combination of EPFs has been proved that can enhance the accuracy of PQMs by considering the convex condition. A general formulation of simulation techniques for molecular properties is presented and a formal extension of the minimax principle to PQMs is also considered. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source] Modular chemical geometry and symbolic calculationINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2006Michael P. Barnett Abstract We discuss (a) the construction of formulas for the puckering of 4 and 5 atom rings from simple geometrical principles; (b) the application of these formulas to the study of cyclobutanes and heterocyclic analogues; (c) the way the derivations are represented (i.e., the style facilitates symbolic calculations for many more chemical topics; (d) interfacing the Gaussian package and Mathematica; and (e) some representations of molecular properties in Mathematica and algorithmic operations on these. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source] Resonances and pseudoresonances in a potential with attractive coulomb tail: A study using analytic-continuation techniquesINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 2 2003Imke B. Müller Abstract The performance of the complex absorbing potential (CAP) and the complex scaling (CS) methods in the detection and calculation of complex Siegert energies is studied using a 1-D long-range attractive model potential. This potential is constructed to mimic molecular properties, in particular an attractive Coulombic term, to allow one to draw conclusions on molecular ab initio studies. Analyzing the spectrum of the model potential, one compact bound state embedded in the manifold of Rydberg states is found that shows artificial resonance characteristics when applying the CAP and the CS methods. This pseudoresonance problem is less pronounced in the calculation using the CS method than in that using the CAP method. Despite this deficiency, the CAP method is shown to possess advantages over CS when dealing with physical resonances under conditions that simulate the application of standard basis sets in ab initio calculations. The accuracy of the Siegert energy is shown to be maintained when applying a subspace projection technique to the CAP method. This technique reduces the computational demand significantly and leads to an important improvement of the CAP method, which should be of particular significance in molecular applications. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003 [source] A phase-space method for arbitrary bimolecular gas-phase reactions: Theoretical descriptionINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 5 2001A. Gross Abstract A theoretical model for the calculation of rate constants for arbitrary bimolecular gas-phase reactions was developed. The method is based on the phase-space statistical method developed by Light and co-workers 1,6. In the present article this method is extended to arbitrary molecular systems. The new method requires knowledge of the molecular properties in the reaction and products channels of the chemical system. The properties are the vibrational frequencies, moments of inertia, and potential energy for the interacting species in their ground state equilibrium configuration. Furthermore, we have to calculate either the energy barrier or the long-range potential for the chemical system (if the reaction channel does not have an energy barrier). The usefulness of the method is that it can be applied to all bimolecular reactions, trimolecular reactions, and even reactions of higher orders. Therefore, it can be applied to cases where rate constants of complex chemical reactions are required, but reliable laboratory measurements or other means to estimate rate parameters are not yet possible. Even if spectroscopic data are not available for the reactants and products, it is possible to use electronic structure theory to calculate the required data. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001 [source] Fluorescent proteins for live cell imaging: Opportunities, limitations, and challengesIUBMB LIFE, Issue 11 2009Jörg Wiedenmann Abstract The green fluorescent protein (GFP) from the jellyfish Aequorea victoria can be used as a genetically encoded fluorescence marker due to its autocatalytic formation of the chromophore. In recent years, numerous GFP-like proteins with emission colors ranging from cyan to red were discovered in marine organisms. Their diverse molecular properties enabled novel approaches in live cell imaging but also impose certain limitations on their applicability as markers. In this review, we give an overview of key structural and functional properties of fluorescent proteins that should be considered when selecting a marker protein for a particular application and also discuss challenges that lie ahead in the further optimization of the glowing probes. © 2009 IUBMB IUBMB Life, 61(11): 1029,1042, 2009 [source] Searching for Neuroglobin's role in the brainIUBMB LIFE, Issue 8-9 2007Karin Nienhaus Abstract Neuroglobin is a small globin that plays an important role in the protection of brain neurons from ischemic and hypoxic injuries. The molecular mechanisms by which Ngb performs its physiological function are still under debate. Suggestions include oxygen storage and delivery, scavenging of NO and/or reactive oxygen species, oxygen sensing and signal transduction. In recent years, the molecular structures of Ngb with carbon monoxide bound to the heme iron and without an exogenous ligand have been solved, and interesting structural changes have been noticed upon ligand binding. Moreover, equilibrium and kinetic properties of the reactions with ligands have been examined in great detail. Here we summarize the molecular properties of Ngb and discuss them in relation to the potential physiological functions. [source] WinXPRO: a program for calculating crystal and molecular properties using multipole parameters of the electron densityJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2002Adam Stash The computer program WinXPRO enables the calculation of crystal and molecular properties using the multipole parameters of the electron density. The list of properties includes the electron density and its topological and electric field characteristics, the local kinetic and potential energies, the electron localization function, and the effective crystal potential. WinXPRO works under the Windows operating system and can utilize any existing graphics program to display output. [source] Fungal tyrosinases: new prospects in molecular characteristics, bioengineering and biotechnological applicationsJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2006S. Halaouli Abstract Tyrosinases are type-3 copper proteins involved in the initial step of melanin synthesis. These enzymes catalyse both the o -hydroxylation of monophenols and the subsequent oxidation of the resulting o -diphenols into reactive o -quinones, which evolve spontaneously to produce intermediates, which associate in dark brown pigments. In fungi, tyrosinases are generally associated with the formation and stability of spores, in defence and virulence mechanisms, and in browning and pigmentation. First characterized from the edible mushroom Agaricus bisporus because of undesirable enzymatic browning problems during postharvest storage, tyrosinases were found, more recently, in several other fungi with relevant insights into molecular and genetic characteristics and into reaction mechanisms, highlighting their very promising properties for biotechnological applications. The limit of these applications remains in the fact that native fungal tyrosinases are generally intracellular and produced in low quantity. This review compiles the recent data on biochemical and molecular properties of fungal tyrosinases, underlining their importance in the biotechnological use of these enzymes. Next, their most promising applications in food, pharmaceutical and environmental fields are presented and the bioengineering approaches used for the development of tyrosinase-overproducing fungal strains are discussed. [source] QSAR study of ,-lactam antibiotic efflux by the bacterial multidrug resistance pump AcrB,JOURNAL OF CHEMOMETRICS, Issue 5 2004Márcia M. C. Ferreira Abstract AcrAB-TolC is the most important efflux pump system of Gram-negative bacteria, responsible for their resistance to lipophilic and amphilic drugs. In this work, HCA,PCA studies were performed to investigate the relationship between efflux activities (negative logarithm of minial inhibitor concentration, pMIC) of three strains of S. thypimurium with respect to ,-lactams, and to analyze the relationship between lipophilicity parameters calculated by different methods. The analyses demonstrate that pMICs strongly depend on properties of both bacterial strains and drug molecules, and that lipophilicity parameters do not necessarily contain the same information about the drugs. QSAR studies have shown that the calculated lipophilicities, in some cases, are non linearly related to the pMICs originated by active AcrAB-TolC bacterial pumps, due to the existence of ,-lactams with nitrogen- and sulfur-rich substituents. Among the most important ,-lactam molecular properties quantitatively related to pMICs are lipophilicity and electronic and hydrogen,bonding properties. Parameters describing these properties were included in the QSAR study to obtain parsimonius regression models for MICs. ,-Lactams were classified as good, moderately good and poor AcrAB-TolC substrates. Their stereoelectronic molecular properties, especially the Y-component of the molecular dipole moment and hydrogen binding properties, reflected this classification. Copyright © 2004 John Wiley & Sons, Ltd. [source] Global physicochemical properties as activity discriminants for the mGluR1 subtype of metabotropic glutamate receptorsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 16 2001Marta Filizola Abstract Metabotropic glutamate receptors (mGluRs) are important as candidate therapeutic targets for many neurological disorders. In the present work, the focus has been on the mGluR1 subtype, where agonists have a proconvulsant profile while antagonists exert anticonvulsant activity. Identification of molecular determinants for the inhibition of mGluR1 provides a new avenue for the discovery and development of novel anticonvulsant drugs. Spatial configuration of key groups alone cannot explain activation selectivity at this specific receptor subtype. In fact, all known agonists and antagonists acting at mGluR1 can accommodate the same critical moieties in a similar geometric arrangement that corresponds to the extended conformation of glutamate. Therefore, other factors must account for the differences in activation. This study presents the results of an analysis of a large suite of steric, topological, electrostatic, and thermodynamic molecular properties calculated for a representative set of potent mGluR1 agonists and antagonists. Global steric parameters and the total nonpolar area provide discrimination between the mGluR1 agonists and antagonists considered in the present work. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 2018,2027, 2001 [source] Dual-mode reflectance and fluorescence near-video-rate confocal microscope for architectural, morphological and molecular imaging of tissueJOURNAL OF MICROSCOPY, Issue 1 2007ALICIA L. CARLSON Summary We have developed a near-video-rate dual-mode reflectance and fluorescence confocal microscope for the purpose of imaging ex vivo human specimens and in vivo animal models. The dual-mode confocal microscope (DCM) has light sources at 488, 664 and 784 nm, a frame rate of 15 frames per second, a maximum field of view of 300 × 250 ,m and a resolution limit of 0.31 ,m laterally and 1.37 ,m axially. The DCM can image tissue architecture and cellular morphology, as well as molecular properties of tissue, using reflective and fluorescent molecular-specific optical contrast agents. Images acquired with the DCM demonstrate that the system has the sub-cellular resolution needed to visualize the morphological and molecular changes associated with cancer progression and has the capability to image animal models of disease in vivo. In the hamster cheek pouch model of oral carcinogenesis, the DCM was used to image the epithelium and stroma of the cheek pouch; blood flow was visible and areas of dysplasia could be distinguished from normal epithelium using 6% acetic acid contrast. In human oral cavity tissue slices, DCM reflectance images showed an increase in the nuclear-to-cytoplasmic ratio and density of nuclei in neoplastic tissues as compared to normal tissue. After labelling tissue slices with fluorescent contrast agents targeting the epidermal growth factor receptor, an increase in epidermal growth factor receptor expression was detected in cancerous tissue as compared to normal tissue. The combination of reflectance and fluorescence imaging in a single system allowed imaging of two different parameters involved in neoplastic progression, providing information about both the morphological and molecular expression changes that occur with cancer progression. The dual-mode imaging capabilities of the DCM allow investigation of both morphological changes as well as molecular changes that occur in disease processes. Analyzing both factors simultaneously may be advantageous when trying to detect and diagnose disease. The DCM's high resolution and near-video-rate image acquisition and the growing inventory of molecular-specific contrast agents and disease-specific molecular markers holds significant promise for in vivo studies of disease processes such as carcinogenesis. [source] The role of tryptophan in the antibacterial activity of a 15-residue bovine lactoferricin peptideJOURNAL OF PEPTIDE SCIENCE, Issue 4 2001Bengt Erik Haug Abstract Bovine lactoferricin is a 25-residue antibacterial peptide isolated after gastric cleavage of the iron transporting protein lactoferrin. A 15-residue fragment, FKCRRWQWRMKKLGA of this peptide sustains most of the antibacterial activity. In this truncated sequence, the two Trp residues are found to be essential for antibacterial activity. The anchoring properties of Trp, as have been observed in membrane proteins, are believed to be important for the interaction of Trp containing antibacterial peptides with bacterial cell membranes. We have investigated the molecular properties which make Trp important for the antibacterial activity of the 15-residue peptide by replacing Trp with natural and unnatural aromatic amino acids. This series of peptides was tested for antibacterial activity against Echerichia coli and Staphylococcus aureus. We found that neither the hydrogen bonding ability nor the amphipathicity of the indole system are essential properties for the effect of Trp on the antibacterial activity of the peptides. Replacement of Trp with residues containing aromatic hydrocarbon side chains gave the most active peptides. We propose that aromatic hydrocarbon residues are able to position themselves deeper into the bacterial cell membrane, making the peptide more efficient in disrupting the bacterial cell membrane. From our results the size, shape and aromatic character of Trp seem to be the most important features for the activity of this class of Trp containing antibacterial peptides. Copyright © 2001 European Peptide Society and John Wiley & Sons, Ltd. [source] Estimation of melting points of organic compounds-IIJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2006Akash Jain Abstract A model for calculation of melting points of organic compounds from structure is described. The model utilizes additive, constitutive and nonadditive, constitutive molecular properties to calculate the enthalpy of melting and the entropy of melting, respectively. Application of the model to over 2200 compounds, including a number of drugs with complex structures, gives an average absolute error of 30.1°. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95:2562,2618, 2006 [source] Influence of amylases on the rheological and molecular properties of partially damaged wheat starchJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 11 2006Pedro Leman Abstract The effects of Bacillus subtilis, porcine pancreatic and Aspergillus oryzae ,-amylases, sweet potato ,-amylase and Bacillus stearothermophilus maltogenic amylase (BStA) on the rheological properties (measured with a Rapid Visco Analyser) of partially damaged wheat starch were studied and the accompanying changes in starch molecular properties were analysed by high-performance size exclusion chromatography. Pasting and gelation of starch slurries (with an increased level of damaged starch) were significantly affected by the supplemented amylases and greatly depended on the mode of action and properties of the enzymes added. In general, at low endo-amylase concentrations, peak, hot paste and cold paste viscosities were more reduced for enzyme-supplemented partially damaged starch than for enzyme-supplemented native wheat starch, demonstrating the significance of damaged starch levels in determining amylase functionality. Higher dosages of thermostable amylases ruled out most of the differences between amylase-supplemented native starch and partially damaged starches, except for BStA. Furthermore, the (limited) endo-action of BStA determines to a great extent the rheological properties of the starch paste. These results contribute to a better understanding of (maltogenic) amylase functionality in processing (damaged) starch-containing foods. Copyright © 2006 Society of Chemical Industry [source] On the Production of Polyolefins with Bimodal Molecular Weight and Copolymer Composition Distributions in Catalytic Gas-Phase Fluidized-Bed ReactorsMACROMOLECULAR THEORY AND SIMULATIONS, Issue 8 2007Christos Chatzidoukas Abstract A comprehensive mathematical model is developed for the dynamic calculation of the molecular distributed properties (i.e. MWD and CCD) in a gas-phase, catalytic, ethylene-1-butene copolymerization, FBR, taking into account the various kinetic, micro- and macroscopic phenomena in the reactor. The effects of the two single-site catalyst mass fractions and reactor operating conditions on the production of polyolefins with ,tailor-made' bimodal molecular properties are investigated. It is shown that PE grades with either a bimodal MWD or CCD can be produced in a single FBR, using a mixture of two single-site catalysts under properly selected operating conditions. [source] INVITED REVIEW: Plant self-incompatibility in natural populations: a critical assessment of recent theoretical and empirical advancesMOLECULAR ECOLOGY, Issue 10 2004VINCENT CASTRIC Abstract Self-incompatibility systems in plants are genetic systems that prevent self-fertilization in hermaphrodites through recognition and rejection of pollen expressing the same allelic specificity as that expressed in the pistils. The evolutionary properties of these self-recognition systems have been revealed through a fascinating interplay between empirical advances and theoretical developments. In 1939, Wright suggested that the main evolutionary force driving the genetic and molecular properties of these systems was strong negative frequency-dependent selection acting on pollination success. The empirical observation of high allelic diversity at the self-incompatibility locus in several species, followed by the discovery of very high molecular divergence among alleles in all plant families where the locus has been identified, supported Wright's initial theoretical predictions as well as many of its later developments. In the last decade, however, advances in the molecular characterization of the incompatibility reaction and in the analysis of allelic frequencies and allelic divergence from natural populations have stimulated new theoretical investigations that challenged some important assumptions of Wright's model of gametophytic self-incompatibility. We here review some of these recent empirical and theoretical advances that investigated: (i) the hypothesis that S -alleles are selectively equivalent, and the evolutionary consequences of genetic interactions between alleles; (ii) the occurrence of frequency-dependent selection in female fertility; (iii) the evolutionary genetics of self-incompatibility systems in subdivided populations; (iv) the evolutionary implications of the self-incompatibility locus's genetic architecture; and (v) of its interactions with the genomic environment. [source] Use of Topological Indices of Organic Sulfur Compounds in Quantitative Structure-Retention Relationship StudyMOLECULAR INFORMATICS, Issue 9 2005F. Safa Abstract Structure-gas chromatographic retention index models were developed for some organic sulfur compounds at four different temperatures (60, 80, 100 and 120,°C) using only topological descriptors. At first, regression models were generated for each temperature separately with high values of multiple correlation coefficient and Fisher-ratio statistics. The results of cross validation test using leave-one-out (Q2,0.956) and leave-two-out (Q2,0.953) methods showed good predictive ability of the models developed. Then, a single combined quantitative structure-retention relationship model, added temperature as a parameter, was also developed for all the temperatures, showing good statistical parameters (R=0.991 and F=728.474). The stability and validity of the combined model were verified by both internal (Q2>0.970) and external validation (Q=0.993) techniques. The results of the study indicated the efficiency of the classical topological descriptors in simultaneous prediction of retention index values of sulfur compounds at different temperatures. The topological descriptors well covered the molecular properties known to be relevant for gas chromatographic retention data, such as molecular size and degree of branching. [source] Analysis of water solubility data on the basis of HYBOT descriptorsMOLECULAR INFORMATICS, Issue 9-10 2003Part 2. Abstract Solubility data of 787 organic liquids (electrolytes and non-electrolytes) with diverse structures has been quantitatively described by physicochemical property descriptors. Special effects like intra - and intermolecular hydrogen bonds have been shown to be very important for water solubility. It is found that an important part of the solute-solvent interaction is neglected in all correlations of logS with (only) logP, as in this case the solute H-bond donor effect is not considered. As expected intramolecular hydrogen bonds lead to reduced solubility, whereas intermolecular hydrogen bonds (both HB donors and acceptors) of solutes result in higher solubility. An exception to the latter rule are carboxylic acids which due to intermolecular HB-induced dimerization in the pure liquid phase of acids show a three times lower solubility as expected on the basis of their molecular properties. A volume-related term (molecular polarizability ,) was found to have an essential negative contribution to solubility. For the first time the solubility increasing effect of partial ionization of weak acids and bases in saturated aqueous solutions has been quantitatively considered for sets of compounds by exact calculation of the pH determined by the solutes aqueous solubility and pKa value(s). [source] Identification of Diverse Database Subsets using Property-Based and Fragment-Based Molecular DescriptionsMOLECULAR INFORMATICS, Issue 6 2002Mark Ashton Abstract This paper reports a comparison of calculated molecular properties and of 2D fragment bit-strings when used for the selection of structurally diverse subsets of a file of 44295 compounds. MaxMin dissimilarity-based selection and k -means cluster-based selection are used to select subsets containing between 1% and 20% of the file. Investigation of the numbers of bioactive molecules in the selected subsets suggest: that the MaxMin subsets are noticeably superior to the k -means subsets; that the property-based descriptors are marginally superior to the fragment-based descriptors; and that both approaches are noticeably superior to random selection. [source] | |||||||||||||||||||||||||||||||