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Biological Environments (biological + environment)
Selected AbstractsComplete high-density lipoproteins in nanoparticle coronaFEBS JOURNAL, Issue 12 2009Erik Hellstrand In a biological environment, nanoparticles immediately become covered by an evolving corona of biomolecules, which gives a biological identity to the nanoparticle and determines its biological impact and fate. Previous efforts at describing the corona have concerned only its protein content. Here, for the first time, we show, using size exclusion chromatography, NMR, and pull-down experiments, that copolymer nanoparticles bind cholesterol, triglycerides and phospholipids from human plasma, and that the binding reaches saturation. The lipid and protein binding patterns correspond closely with the composition of high-density lipoprotein (HDL). By using fractionated lipoproteins, we show that HDL binds to copolymer nanoparticles with much higher specificity than other lipoproteins, probably mediated by apolipoprotein A-I. Together with the previously identified protein binding patterns in the corona, our results imply that copolymer nanoparticles bind complete HDL complexes, and may be recognized by living systems as HDL complexes, opening up these transport pathways to nanoparticles. Apolipoproteins have been identified as binding to many other nanoparticles, suggesting that lipid and lipoprotein binding is a general feature of nanoparticles under physiological conditions. [source] 980-nm Laser-Driven Photovoltaic Cells Based on Rare-Earth Up-Converting Phosphors for Biomedical ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 23 2009Zhigang Chen Abstract A prerequisite for designing and constructing wireless biological nanorobots is to obtain an electrical source that is continuously available in the operational biological environment. Herein the first preparation of 980-nm laser-driven photovoltaic cells (980LD-PVCs) by introducing of a film of rare-earth up-converting nanophosphors in conventional dye-sensitized solar cells is reported. Under the irradiation of a 980-nm laser with a power of 1,W, the visible up-converting luminescence of rare-earth nanophosphors can be efficiently absorbed by the dyes in 980LD-PVCs so that they exhibit a maximal output power of 0.47 mW. In particular, after being covered with 1 to 6 layers of pig intestines (thickness: ca. 1,mm per layer) as a model of biological tissues, 980LD-PVCs still possess a maximal output power of between 0.28 and 0.02,mW, which is efficient enough to drive many kinds of biodevices. This research opens up the possibility of preparing and/or developing novel electrical sources for wireless biological nanorobots and many other biodevices. [source] Biofiltration of nuisance sulfur gaseous odors from a meat rendering plantJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 12 2002Zarook Shareefdeen Abstract This paper presents a case study of a commercial biofilter, treating air streams contaminated with several odorous compounds including dimethyl sulfide, ammonia, methanethiol, hydrogen sulfide and ethylamine. The biofilter is packed with a proprietary wood-based (BIOMIXÔ) medium which is designed to provide a good biological environment, pH buffer capacity, low pressure drop and resistance to compaction. This commercial biofilter treats a contaminated air volume of 15,000 actual cubic feet per minute (acfm) from a meat rendering and wastewater treatment operation with a 30-s empty bed residence time. The case study includes a novel gas sampling procedure and characterization of biofilter air streams through a mobile Fourier transform infrared system and olfactometer analysis. The results confirmed the good distribution of air, moisture and bacterial population across the medium. Four years of consistent performance of this commercial biofilter with >99% removal of 24,500 odor units demonstrates that biofilters can be successfully applied for the removal of highly odorous gaseous sulfur compounds. © 2002 Society of Chemical Industry [source] MALDI-TOF mass spectrometric analysis for the characterization of the 5,10,15,20-tetrakis- (m -hydroxyphenyl)bacteriochlorin (m -THPBC) photoproducts in biological environmentJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2005Henri-Pierre Lassalle Abstract Photoproducts formation upon irradiation (739 nm) of 5,10,15,20-tetrakis(m -hydroxyphenyl)bacteriochlorin (m -THPBC) in phosphate buffer saline (PBS) supplemented with human serum albumin (HSA) were studied by means of absorption spectroscopy and MALDI-TOF mass spectrometry. The experiments were performed with a freshly prepared PBS,HSA solution of m -THPBC and with a PBS,HSA m -THPBC solution incubated for 6 h at 37 °C. The incubation of m -THPBC solution leads to the dye monomerisation, whereas in the freshly prepared solution, m -THPBC is under an aggregated form. Regardless of the incubation condition, photobleaching experiments carried out by absorption spectroscopy demonstrate the degradation of the photosensitizer and its phototransformation in m -THPC. Moreover, m -THPC was the sole photoproduct detected using absorption spectroscopy. Together with a degradation of m -THPBC and formation of m -THPC, MALDI-TOF mass spectrometry evidenced several other photoinduced modifications. Photoproducts such as dihydroxy m -THPBC and dihydroxy m -THPC were detected in both conditions; however, the formation of hydroxylated photoproducts was significantly greater in incubated solution. In addition, small molecules arising from the degradation of the photosensitizer and identified as dipyrin derivatives and dipyrrolic synthon were observed. Copyright © 2005 John Wiley & Sons, Ltd. [source] A potential role for isothermal calorimetry in studies of the effects of thermodynamic non-ideality in enzyme-catalyzed reactions,JOURNAL OF MOLECULAR RECOGNITION, Issue 5 2004Thierry G. A. Lonhienne Abstract Attention is drawn to the feasibility of using isothermal calorimetry for the characterization of enzyme reactions under conditions bearing greater relevance to the crowded biological environment, where kinetic parameters are likely to differ significantly from those obtained by classical enzyme kinetic studies in dilute solution. An outline of the application of isothermal calorimetry to the determination of enzyme kinetic parameters is followed by considerations of the nature and consequences of crowding effects in enzyme catalysis. Some of those effects of thermodynamic non-ideality are then illustrated by means of experimental results from calorimetric studies of the effect of molecular crowding on the kinetics of catalysis by rabbit muscle pyruvate kinase. This review concludes with a discussion of the potential of isothermal calorimetry for the experimental determination of kinetic parameters for enzymes either in biological environments or at least in media that should provide reasonable approximations of the crowded conditions encountered in vivo. Copyright © 2004 John Wiley & Sons, Ltd. [source] An overview of factors affecting the disposition of intramammary preparations used to treat bovine mastitisJOURNAL OF VETERINARY PHARMACOLOGY & THERAPEUTICS, Issue 4 2006R. GEHRING The administration of antimicrobial drugs by the intramammary route offers a convenient option for the treatment of bovine mastitis. The goal of antimicrobial treatment is to achieve effective drug concentrations at the site of infection. Drug concentrations must also decrease to safe levels before the milk is harvested for human consumption. The rate of change of drug concentrations in the milk and udder tissues over time is dependent on the physicochemical characteristics of the drug and how these interact with the biological environment, affecting the rate and extent of absorption, distribution and elimination. Studies reported in the literature have identified various pathophysiological and pharmaceutical factors that may influence these processes. This review summarizes current understanding of factors affecting the disposition of drugs following intramammary administration. Areas of incomplete knowledge requiring further research have been identified. [source] Unusual Photoinduced Response of mTHPC Liposomal Formulation (Foslip)PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2009Dzmitry Kachatkou Liposomal formulations of meso-tetra(hydroxyphenyl)chlorin (mTHPC) have already been proposed with the aim to optimize photodynamic therapy. Spectral modifications of these compounds upon irradiation have not yet been investigated. The objective of this study was to evaluate photobleaching properties of mTHPC encapsulated into dipalmitoylphosphatidylcholine (DPPC) liposomes, Foslip. Fluorescence measurements in DPPC liposomes with different DPPC:mTHPC ratios demonstrated a dramatic decrease in fluorescence anisotropy with increasing local mTHPC concentration, thus suggesting strong interactions between mTHPC molecules in lipid bulk medium. Exposure of Foslip suspensions to small light doses (<50 mJ/cm2) resulted in a substantial drop in fluorescence, which, however, was restored after addition to the sample of a non-ionic surfactant Triton X-100. We attributed this behavior to photoinduced fluorescence quenching. This effect depended strongly on the molar DPPC:mTHPC ratio and was revealed only for high local mTHPC concentrations. The results were interpreted supposing energy migration between closely located mTHPC molecules with its subsequent dissipation by the molecules of photoproduct acting as excitation energy traps. We further assessed the effect of photoinduced quenching in plasma protein solution. Relatively slow kinetics of photoinduced Foslip response during incubation in the presence of proteins was attributed to mTHPC redistribution from liposomal formulations to proteins. Therefore, changes in mTHPC distribution pattern in biological systems would be consistent with changes in photoinduced quenching and would provide valuable information on mTHPC interactions with a biological environment. [source] Electro-synthesized PEDOT/glutamate chemically modified electrode: a combination of electrical and biocompatible featuresPOLYMER INTERNATIONAL, Issue 5 2008Jianfei Che Abstract BACKGROUND: Neural prosthetic devices have been developed that can facilitate the stimulation and recording of electrical activity when implanted in the central nervous system. The key parts of the devices are metal (gold) electrodes; however, surface modification of the gold electrode is desired. Conducting polymers are promising candidates for this purpose. RESULTS: A conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), was electro-polymerized onto gold electrodes with a neural transmitter of glutamate (Glu) as dopant. A protocol of ion exchange was employed due to the difficulty of direct incorporation of Glu into PEDOT. Sodium p -toluenesulfonate (TSNa) was chosen as the first dopant and subsequent incorporation of Glu was accomplished via ion exchange. The electrochemical properties of the resultant PEDOT/Glu were studied using electrochemical impedance spectroscopy and cyclic voltammetry. The purpose of incorporating Glu was to improve the biocompatibility of the coated electrode. The PEDOT/Glu-coated electrode showed better cell attachment compared with a PEDOT/TSNa-coated electrode in in vitro cell culture of PC12. The stability of PEDOT was studied by immersing the coated electrode in a biologically relevant reducing agent of glutathione. CONCLUSION: The charge capacity of the coated electrode had an initial slight decrease and then remained unchanged. Good electro-activity was conserved, indicating the superior stability of PEDOT in the biological environment. Copyright © 2007 Society of Chemical Industry [source] Generation of a Hydroperoxidochromium Complex from Nitratochromium(III) Ions and Hydrogen PeroxideEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 30 2008Mingming Cheng Abstract Accelerated substitution at chromium(III) in CraqONO22+ provides the basis for a novel route to the corresponding hydroperoxidochromium complex in aqueous solutions. Despite the great concentration advantage of water, the reaction of CraqONO22+ with 10,100 mM H2O2 generates >50,% yields of CraqOOH2+, which makes this reaction useful for preparative purposes, and may also represent a potential source of high-valent chromium in biological environments. In a minor, parallel path, small concentrations of a superoxidochromium(III) complex, CraqOO2+, are also produced. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Electrochemical Nanotransistor from Mixed-Polymer BrushesADVANCED MATERIALS, Issue 16 2010Tsz Kin Tam Reversible switching of the electrode interface between OFF/ON states is achieved by electrochemically triggered reorganization of a nanostructured polymer brush associated with the interface. The switching process is accomplished by local interfacial pH changes allowing operation in buffered biological environments (see figure). The fabricated device mimics the performance of switching electronic devices such as transistors. [source] Dynamically Restructuring Hydrogel Networks Formed with Reversible Covalent Crosslinks,ADVANCED MATERIALS, Issue 18 2007C. Roberts Dynamically restructuring hydrogel networks are formed from two water-soluble polymers by functionalization with phenylboronic acid (PBA) and salicylhydroxamic acid (SHA) moieties that interact through pH-sensitive and reversible covalent crosslinks (see figure). The networks can be tuned to display a wide range of pH-responsive properties, which can potentially be exploited for drug delivery systems in biological environments where similar acidic changes occur. [source] A potential role for isothermal calorimetry in studies of the effects of thermodynamic non-ideality in enzyme-catalyzed reactions,JOURNAL OF MOLECULAR RECOGNITION, Issue 5 2004Thierry G. A. Lonhienne Abstract Attention is drawn to the feasibility of using isothermal calorimetry for the characterization of enzyme reactions under conditions bearing greater relevance to the crowded biological environment, where kinetic parameters are likely to differ significantly from those obtained by classical enzyme kinetic studies in dilute solution. An outline of the application of isothermal calorimetry to the determination of enzyme kinetic parameters is followed by considerations of the nature and consequences of crowding effects in enzyme catalysis. Some of those effects of thermodynamic non-ideality are then illustrated by means of experimental results from calorimetric studies of the effect of molecular crowding on the kinetics of catalysis by rabbit muscle pyruvate kinase. This review concludes with a discussion of the potential of isothermal calorimetry for the experimental determination of kinetic parameters for enzymes either in biological environments or at least in media that should provide reasonable approximations of the crowded conditions encountered in vivo. Copyright © 2004 John Wiley & Sons, Ltd. [source] Multiscale observation of biological interactions of nanocarriers: From nano to macroMICROSCOPY RESEARCH AND TECHNIQUE, Issue 9 2010Su-Eon Jin Abstract Microscopic observations have played a key role in recent advancements in nanotechnology-based biomedical sciences. In particular, multiscale observation is necessary to fully understand the nano-bio interfaces where a large amount of unprecedented phenomena have been reported. This review describes how to address the physicochemical and biological interactions of nanocarriers within the biological environments using microscopic tools. The imaging techniques are categorized based on the size scale of detection. For observation of the nanoscale biological interactions of nanocarriers, we discuss atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). For the micro to macro-scale (in vitro and in vivo) observation, we focus on confocal laser scanning microscopy (CLSM) as well as in vivo imaging systems such as magnetic resonance imaging (MRI), superconducting quantum interference devices, and IVIS®. Additionally, recently developed combined techniques such as AFM-CLSM, correlative light and electron microscopy (CLEM), and SEM spectroscopy are also discussed. In this review, we describe how each technique helps elucidate certain physicochemical and biological activities of nanocarriers such as dendrimers, polymers, liposomes, and polymeric/inorganic nanoparticles, thus providing a toolbox for bioengineers, pharmaceutical scientists, biologists, and research clinicians. Microsc. Res. Tech. 73:813,823, 2010. © 2010 Wiley-Liss, Inc. [source] Biomedical applications of 10B and 11B NMRNMR IN BIOMEDICINE, Issue 2 2005Peter Bendel Abstract This review focuses mainly on the detection and investigation of molecules used for boron neutron capture therapy (BNCT) by 10B and 11B NMR. In this binary radiation treatment, boron-containing molecules (also called ,BNCT agents') enriched in the 10B isotope, are targeted to the tumor, and irradiated with thermal or epithermal neutrons. Capture of these neutrons by 10B nuclei generates cell-damaging radiation, confined to single cell dimensions. NMR research efforts have primarily been applied in two directions: first, to investigate the metabolism and pharmaco-kinetics of BNCT agents in-vivo, and second, to use localized NMR spectroscopy and/or MRI for non-invasive mapping of the administered molecules in treated animals or patients. While the first goal can be pursued using 11B NMR for natural-abundance samples (80% 11B / 20% 10B), molecules used in the actual treatment are >,95% enriched in 10B, and must therefore be detected by 10B NMR. Both 10B (spin 3) and 11B (spin 3/2) are quadrupolar nuclei, and their typical relaxation times, in common BNCT agents in biological environments, are rather short. This poses some technical challenges, particularly for MRI, which will be reviewed, along with possible solutions. The first attempts at 11B NMR and MRI detection of BNCT agents in biological tissue were conducted over a decade ago. Since then, results from 11B MRI in laboratory animals and in humans have been reported, and 11B NMR spectroscopy provided interesting and unique information about the metabolism of some BNCT agents in cultured cells. 10B NMR was applied either ,indirectly' (in double-resonance experiments involving coupled protons), but also by direct 10B MRI in mice. However, no results involving the NMR detection of 10B-enriched compounds in treated patients have been reported yet. Copyright © 2005 John Wiley & Sons, Ltd. [source] MACROEVOLUTION AND MACROECOLOGY THROUGH DEEP TIMEPALAEONTOLOGY, Issue 1 2007NICHOLAS J. BUTTERFIELD Abstract:, The fossil record documents two mutually exclusive macroevolutionary modes separated by the transitional Ediacaran Period. Despite the early appearance of crown eukaryotes and an at least partially oxygenated atmosphere, the pre-Ediacaran biosphere was populated almost exclusively by microscopic organisms exhibiting low diversity, no biogeographical partitioning and profound morphological/evolutionary stasis. By contrast, the post-Ediacaran biosphere is characterized by large diverse organisms, bioprovinciality and conspicuously dynamic macroevolution. The difference can be understood in terms of the unique escalatory coevolution accompanying the early Ediacaran introduction of eumetazoans, followed by their early Cambrian (Tommotian) expansion into the pelagic realm. Eumetazoans reinvented the rules of macroecology through their invention of multitrophic food webs, large body size, life-history trade-offs, ecological succession, biogeography, major increases in standing biomass, eukaryote-dominated phytoplankton and the potential for mass extinction. Both the pre-Ediacaran and the post-Ediacaran biospheres were inherently stable, but the former derived from the simplicity of superabundant microbes exposed to essentially static, physical environments, whereas the latter is based on eumetazoan-induced diversity and dynamic, biological environments. The c. 100-myr Ediacaran transition (extending to the base of the Tommotian) can be defined on evolutionary criteria, and might usefully be incorporated into the Phanerozoic. [source] Bioactive polyurethanes in clinical applications,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9-10 2006G. Ciardelli Abstract Biomaterials play an important role in most tissue engineering strategies. They can serve as substrates on which cell populations can attach and migrate, can be used as cell delivery vehicles and as bioactive factor carriers to activate specific cellular functions. A series of biodegradable polyurethanes (PUs) with tunable chemical, physical and degradation properties, showing an adequate response to in vitro tests was proposed for applications in soft tissue engineering. Three-dimensional scaffolds of superimposed square meshed grids were prepared by using a rapid prototyping technique (pressure activated microsyringe, PAM) and tested in vivo. Functionalization of PU systems was performed in order to control the chemistry of the materials for the promotion of highly specific binding interactions between materials and biological environments. Two different approaches were used for the coupling of bioactive molecules such as gelatin. The first involved the modification of the polymer chain through a novel monomer and the second one consisted in a surface modification by plasma-induced graft copolymerization of acrylic acid. Copyright © 2006 John Wiley & Sons, Ltd. [source] Key amino acid residues required for aryl migration catalysed by the cytochrome P450 2-hydroxyisoflavanone synthaseTHE PLANT JOURNAL, Issue 5 2002Yuji Sawada Summary Isoflavonoids are distributed predominantly in leguminous plants, and play pivotal roles in the interaction of host plants with biological environments. Isoflavones in the diet also have beneficial effects on human health as phytoestrogens. The isoflavonoid skeleton is constructed by the CYP93C subfamily of cytochrome P450s in plant cells. The reaction consists of hydroxylation of the flavanone molecule at C-2 and an intramolecular 1,2-aryl migration from C-2 to C-3 to yield 2-hydroxyisoflavanone. In this study, with the aid of alignment of amino acid sequences of CYP93 family P450s and a computer-generated putative stereo structure of the protein, candidates for key amino acid residues in CYP93C2 responsible for the unique aryl migration in 2-hydroxyisoflavanone synthase reaction were identified. Microsomes of recombinant yeast cells expressing mutant proteins of CYP93C2 were prepared, and their catalytic activities tested. The reaction with the mutant in which Ser 310 in the centre of the I-helix was converted to Thr yielded increased formation of 3-hydroxyflavanone, a by-product of the 2-hydroxyisoflavanone synthase reaction, in addition to the major isoflavonoid product. More dramatically, the mutant in which Lys 375 in the end of ,-sheet 1,4 was replaced with Thr produced only 3-hydroxyflavanone and did not yield the isoflavonoid any longer. The roles of these amino acid residues in the catalysis and evolution of isoflavonoid biosynthesis are discussed. [source] Intermediates in the Autoxidation of Nitrogen MonoxideCHEMISTRY - A EUROPEAN JOURNAL, Issue 25 2009Benedikt Galliker Abstract ONOO. is an important intermediate in the autoxidation of nitrogen monoxide by dioxygen. A formerly unknown red isomer of N2O4, ONOONO (see figure), formed in 2-methylbutane at 113,K from nitrogen monoxide and dioxygen, is converted to O2NNO2 upon warming. We have identified two intermediates in the autoxidation of NO.: ONOO., which was detected by EPR spectroscopy at 295,K and atmospheric pressure in the gas phase, and ONOONO, a red substance produced at 113,K in 2-methylbutane. The red compound is diamagnetic and absorbs maximally at 500,nm. The ONOONO intermediate is unstable above the melting point of 2-methylbutane and rapidly converts to O2NNO2. From the semiquantitative determination of mole fractions present in the gas phase by EPR spectroscopy, we estimated the rate constants for the steps that lead to ONOO. and ONOONO, from the known overall rate constant of the autoxidation reaction, by assuming that a quasi-stationary mechanism applies. The rate constant for the rate-determining formation of ONOO. is about 3.1×10,18,cm3,molecule,1,s,1 (or 80,s,1 in mole fractions), the dissociation rate constant of ONOO. is about 6.5×103,s,1, and ONOONO is formed with a rate constant of k=7.7×10,14,cm3,molecule,1,s,1 (1.9×106,s,1 in mole fractions). From these constants, we estimate that the equilibrium constant for the formation of ONOO. from NO. and O2 (K) is 4.8×10,22,cm3,molecule,1 (1.2×10,2), and, therefore, ,G=+11.0,kJ,mol,1. In water, the Gibbs energy change is close to zero. The presence of ONOO. at steady-state concentrations under dioxygen excess may be important not only for reactions in the atmosphere, but especially for reactions in aerosols and biological environments, because the rate constant for formation in solution is higher than that in the gas phase, and, therefore, the half-life of ONOO. is longer. [source] | |||||||||||||||||||