|
| ||
|
|
||
Biomolecules
Kinds of Biomolecules Selected AbstractsFunctionalization Strategies for Protease Immobilization on Magnetic NanoparticlesADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Dan Li Abstract A comprehensive study on the general functionalization strategies for magnetic nanoparticles (MNPs) is presented in this work. Using well-established techniques as well as modified protocols, the wide range of functional moieties grafted on ,-Fe2O3 (maghemite) nanosurfaces include those of amine, aldehyde, carboxylic, epoxy, mercapto, and maleimide ends. Among the modified protocols are the one-step water-catalyzed silanization with mercaptopropyltrimethoxysilane, resulting in dense distal thiols, and the direct functionalization with a heterogeneous bifunctional linker N -[p-maleimidophenyl]isocynanate (PMPI). The former results in a protective Stöber type coating while simultaneously reducing the iron oxide core to magnetite (Fe3O4). The conjugation of trypsin, hereby chosen as model biomolecule, onto the differently functionalized MNPs is further demonstrated and assessed based on its activity, kinetics, and thermo-/long-term stability as well as reusability. Besides aqueous stability and ease in recovery by magnetic separation, the immobilized trypsin on MNPs offers superior protease durability and reusability, without compromising the substrate specificity and sequence coverage of free trypsin. The MNP-based proteases can be used as valuable carriers in proteomics and miniaturized total analysis devices. The applicability of the functional surfaces devised in the current study is also relevant for the conjugation of other biomolecules beyond trypsin. [source] In Situ Bioconjugation: Single Step Approach to Tailored Nanoparticle-Bioconjugates by Ultrashort Pulsed Laser AblationADVANCED FUNCTIONAL MATERIALS, Issue 8 2009Svea Petersen Abstract A single step approach to tailored nanoparticle-bioconjugates, enabling the generation of gold nanoparticles by laser ablation and their in situ conjugation with any biomolecule bearing an electron donating function (e.g., thiolated oligonucleotides) is established. The integrity of oligonucleotides after conjugation and the stability of bioconjugates in physiological media are investigated. Their size is tailorable via process parameters. This rapid and universal method may provide biochemists with various nanoparticle-bioconjugates for screening the often unpredictable structure,function relationship. [source] Supported Lipid Bilayer on Nanocrystalline Diamond: Dual Optical and Field-Effect Sensor for Membrane DisruptionADVANCED FUNCTIONAL MATERIALS, Issue 1 2009Priscilla Kailian Ang Abstract It is demonstrated that a good biomimetic model lipid membrane with dynamic fluidity can be established on optically transparent nanocrystalline diamond (OTND) with surface roughness below 10,nm. Maigainin II, an antimicrobial peptide, is chosen to investigate the permeation of artificial bacterial membranes constructed on OTND. Due to the unique combination of optical transparency and highly sensitive surface conducting channel, intrinsic OTND affords the possibility of dual-mode sensing based on optical and field effect properties. This opens up new possibilities for making integrated biomolecule,semiconductor microdevices, or sensors where the binding of biomolecules can be tracked using confocal microscopy whilst the associated changes in charge density during membrane perforation can be tracked using the space charge effect in the semiconductor. Such a synergistic approach may provide a powerful methodology for the screening of specific bactericidal activity on biomimetic membrane systems. [source] Bacteriorhodopsin-Monolayer-Based Planar Metal,Insulator,Metal Junctions via Biomimetic Vesicle Fusion: Preparation, Characterization, and Bio-optoelectronic Characteristics,ADVANCED FUNCTIONAL MATERIALS, Issue 8 2007D. Jin Abstract A reliable and reproducible method for preparing bacteriorhodopsin (bR)-containing metal,biomolecule,monolayer-metal planar junctions via vesicle fusion tactics and soft deposition of Au top electrodes is reported. Optimum monolayer and junction preparations, including contact effects, are discussed. The electron-transport characteristics of bR-containing membranes are studied systematically by incorporating native bR or artificial bR pigments derived from synthetic retinal analogues, into single solid-supported lipid bilayers. Current,voltage (I,V) measurements at ambient conditions show that a single layer of such bR-containing artificial lipid bilayers pass current in solid electrode/bilayer/solid electrode structures. The current is passed only if retinal or its analogue is present in the protein. Furthermore, the preparations show photoconductivity as long as the retinal can isomerize following light absorption. Optical characterization suggests that the junction photocurrents might be associated with a photochemically induced M-like intermediate of bR. I,V measurements along with theoretical estimates reveal that electron transfer through the protein is over four orders of magnitude more efficient than what would be estimated for direct tunneling through 5,nm of water-free peptides. Our results furthermore suggest that the light-driven proton-pumping activity of the sandwiched solid-state bR monolayer contributes negligibly to the steady-state light currents that are observed, and that the orientation of bR does not significantly affect the observed I,V characteristics. [source] From Molecular Machines to Microscale Motility of Objects: Application as "Smart Materials", Sensors, and NanodevicesADVANCED FUNCTIONAL MATERIALS, Issue 5 2007I. Willner Abstract Machinelike operations are common functions in biological systems, and substantial recent research efforts are directed to mimic such processes at the molecular or nanoscale dimensions. The present Feature Article presents three complementary approaches to design machinelike operations: by the signal-triggered mechanical shuttling of molecular components; by the signal-triggering of chemical processes on surfaces, resulting in mechanical motion of micro/nanoscale objects; and by the fuel-triggered motility of biomolecule,metal nanowire hybrid systems. The shuttling of molecular components on molecular wires assembled on surfaces in semirotaxane configurations using electrical or optical triggering signals is described. The control of the hydrophilic/hydrophobic surface properties through molecular shuttling or by molecular bending/stretching processes is presented. Stress generated on microelements, such as cantilevers, results in the mechanical deflection of the cantilever. The deposition of a redox-active polyaniline film on a cantilever allows the reversible electrochemically induced deflection and retraction of the cantilever by the electrochemical oxidation or reduction of the polymer film, respectively. A micro-robot consisting of the polypyrrole (PPy) polymer deposited on a multi-addressable configuration of electrodes is described. Au magnetic core/shell nanoparticles are incorporated into a polyaniline film, and the conductivity of the composite polymer is controlled by an external magnet. Finally, the synthesis of a hybrid nanostructure consisting of two actin filaments tethered to the two ends of a Au nanowire is described. The adenosine triphosphate (ATP)-fueled motility of the hybrid nanostructure on a myosin monolayer associated with a solid support is demonstrated. [source] Chemical-to-Electrical-Signal Transduction Synchronized with Smart Gel Volume Phase TransitionADVANCED MATERIALS, Issue 43 2009Akira Matsumoto A stimulus-responsive polymer gel designed on a field-effect transistor gate undergoes a reversible volume phase transition in response to a specific biomolecule. An abrupt permittivity change at the gel/gate interface during the transition gives rise to a chemical to electrical signal conversion; the signal is thus detectable via a transistor without the limit of the Debye length. [source] Structural refinement by restrained molecular-dynamics algorithm with small-angle X-ray scattering constraints for a biomoleculeJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2004Masaki Kojima A new algorithm to refine protein structures in solution from small-angle X-ray scattering (SAXS) data was developed based on restrained molecular dynamics (MD). In the method, the sum of squared differences between calculated and observed SAXS intensities was used as a constraint energy function, and the calculation was started from given atomic coordinates, such as those of the crystal. In order to reduce the contribution of the hydration effect to the deviation from the experimental (objective) curve during the dynamics, and purely as an estimate of the efficiency of the algorithm, the calculation was first performed assuming the SAXS curve corresponding to the crystal structure as the objective curve. Next, the calculation was carried out with `real' experimental data, which yielded a structure that satisfied the experimental SAXS curve well. The SAXS data for ribonuclease T1, a single-chain globular protein, were used for the calculation, along with its crystal structure. The results showed that the present algorithm was very effective in the refinement and adjustment of the initial structure so that it could satisfy the objective SAXS data. [source] Strategies to model the near-solute solvent molecular density/polarizationJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 5 2009Pei-Kun Yang Abstract The solvent molecular distribution significantly affects the behavior of the solute molecules and is thus important in studying many biological phenomena. It can be described by the solvent molecular density distribution, g, and the solvent electric dipole distribution, p. The g and p can be computed directly by counting the number of solvent molecules/dipoles in a microscopic volume centered at r during a simulation or indirectly from the mean force F and electrostatic field E acting on the solvent molecule at r, respectively. However, it is not clear how the g and p derived from simulations depend on the solvent molecular center or the solute charge and if the gF and pE computed from the mean force and electric field acting on the solvent molecule, respectively, could reproduce the corresponding g and p obtained by direct counting. Hence, we have computed g,p,gF, and pE using different water centers from simulations of a solute atom of varying charge solvated in TIP3P water. The results show that gF and pE can reproduce the g and p obtained using a given count center. This implies that rather than solving the coordinates of each water molecule by MD simulations, the distribution of water molecules could be indirectly obtained from analytical formulas for the mean force F and electrostatic field E acting on the solvent molecule at r. Furthermore, the dependence of the g and p distributions on the solute charge revealed provides an estimate of the change in g and p surrounding a biomolecule upon a change in its conformation. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009 [source] A pyrazolylamine-phosphonate monoester chelator for the fac -[M(CO)3]+ core (M = Re, 99mTc): synthesis, coordination properties and biological assessmentJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 13 2007Elisa Palma Abstract Aiming to develop new strategies for the labeling of hydroxyl-containing biomolecules with the organometallic core fac -[99mTc(CO)3]+, we have prepared a new model bifunctional chelator, L4 (ethyl hydrogen (2-{[2-(3,5-dimethyl-1H -pyrazol-1-yl)ethyl]amino}ethyl)phosphonate), combining a pyrazolyl-amine chelating group and a monophosphonate ethyl ester function (,P(O)OHOEt). The phosphonate group allows metal stabilization, and, simultaneously, can be considered as a potential attachment site for a biomolecule. Reaction of L4 with the precursor [99mTc(H2O)3(CO)3]+ gave the model radiocomplex [99mTc(CO)3(k3 -L4)] (6a). This radiocomplex was identified by comparing its chromatographic profile with that of the corresponding Re analog (6) under the same conditions, also prepared and fully characterized by the usual analytical techniques. Radiocomplex 6a is moderately lipophilic (log Po/w = 1.07), presenting high stability in vitro without any measurable decomposition or ligand exchange, even in the presence of strong competing chelators such as histidine and cysteine (37°C, 24 h). Biodistribution studies of the complex in CD-1 mice indicated a rapid blood clearance, and a rapid clearance from main organs, occurring primarily through the hepatobiliary pathway. Complex 6a presents also a high robustness in vivo, demonstrated by its resistance to metabolic degradation in blood, and intact excretion into the urine, after RP-HPLC analysis of blood and urine samples. Copyright © 2007 John Wiley & Sons, Ltd. [source] Direct atomic force microscopy observations of monovalent ion induced binding of DNA to micaJOURNAL OF MICROSCOPY, Issue 3 2004J. S. ELLIS Summary Multivalent ions in solution are known to mediate attraction between two like-charged molecules. Such attraction has proved useful in atomic force microscopy (AFM) where DNA may be immobilized to a mica surface facilitating direct imaging in liquid. Theories of DNA immobilization suggest that either ,salt bridging' or fluctuation in the positions of counter ions about both the mica surface and DNA backbone secure DNA to the mica substrate. Whilst both theoretical and experimental evidence suggest that immobilization is possible in the presence of divalent ions, very few studies identify that such immobilization is possible with monovalent ions. Here we present direct AFM evidence of DNA immobilized to mica in the presence of only monovalent ions. Our data depict E. coli plasmid pBR322 adsorbed onto the negatively charged mica both after short (10 min) and long (24 h) incubation periods. These data suggest the need to re-explore current theories of like-charge attraction to include the possibility of monovalent interactions. We suggest that this DNA immobilization strategy may offer the potential to image natural processes with limited immobilization forces and hence enable maximum conformational freedom of the immobilized biomolecule. [source] Protein adsorption drastically reduces surface-enhanced Raman signal of dye moleculesJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2010Dongmao Zhang Abstract There is an increasing interest in developing surface enhancement Raman spectroscopy methods for intracellular biomolecule and for in vitro protein detection that involve dye or protein,dye conjugates. In this work, we have demonstrated that protein adsorption on silver nanoparticle (AgNP) can significantly attenuate the surface-enhanced Raman spectroscopy (SERS) signal of dye molecules in both protein/dye mixtures and protein/dye conjugates. SERS spectra of 12 protein/dye mixtures were acquired using 4 proteins [bovine serum albumin (BSA), lysozyme, trypsin, and concanavalin A] and three dyes [Rhodamine 6G, adenine, and fluorescein isothiocyanate (FITC)]. Besides the protein/dye mixtures, spectra were also obtained for the free dyes and four FITC-conjugated proteins. While no SERS signal was observed in protein/FITC mixtures or conjugates, a significantly reduced SERS intensity (up to 3 orders of magnitude) was observed for both R6G and adenine in their respective protein mixtures. Quantitative estimation of the number of dye molecules absorbed onto AgNP implied that the degree of R6G SERS signal reduction in the R6G/BSA sample is 2 to 3 orders of magnitude higher than what could be accounted for by the difference in the amount of the absorbed dyes. This finding has significant implications for both intracellular SERS analyses and in vitro protein detection using SERS tagging strategies that rely on Raman dyes as reporter molecules. Copyright © 2009 John Wiley & Sons, Ltd. [source] Stimuli-responsive properties of aminophenylboronic acid-carrying thermosensitive copolymersPOLYMER INTERNATIONAL, Issue 5 2003Abstract Thermosensitive copolymers of N -isopropylacrylamide (NIPA) and N -acryloxysuccinimide (NASI) were obtained by solution polymerization using azobisisobutyronitrile as the initiator in a tetrahydrofuran,toluene mixture at 65,°C. A boronic acid-carrying ligand, m -aminophenylboronic acid (APBA) was covalently attached to the thermosensitive copolymer via the reaction between amino and succinimide groups. APBA-coupled thermosensitive copolymer exhibited both temperature and pH sensitivity. Thermally reversible phase transitions were observed both in the acidic and alkaline pH region for the APBA-modified copolymers obtained with different NASI feed concentrations. In our study, ribonucleic acid (RNA) was selected as a biomolecule having reactive groups which could potentially interact with the boronic acid functionality. The response of boronic acid-carrying thermosensitive copolymer against RNA was investigated in aqueous media in the pH range 4,9. In the acidic pH region, an increase was observed in the lower critical solution temperature (LCST) of the APBA-coupled thermosensitive copolymer with increasing RNA concentration. However, LCST decreased with increasing RNA concentration at both neutral and alkaline pH values. The LCST of the APBA-attached copolymer varied linearly with the RNA concentration at pH of 3, 4 and 7. © 2003 Society of Chemical Industry [source] Efficient UV detection of protein crystals enabled by fluorescence excitation at wavelengths longer than 300,nmACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 4 2010Karsten Dierks It is well known that most proteins and many other biomolecules fluoresce when illuminated with UV radiation, but it is also commonly accepted that utilizing this property to detect protein crystals in crystallization setups is limited by the opacity of the materials used to contain and seal them. For proteins, this fluorescence property arises primarily from the presence of tryptophan residues in the sequence. Studies of protein crystallization results in a variety of setup configurations show that the opacity of the containment hardware can be overcome at longer excitation wavelengths, where typical hardware materials are more transparent in the UV, by the use of a powerful UV-light source that is effective in excitation even though not at the maximum of the excitation response. The results show that under these circumstances UV evaluation of crystallization trials and detection of biomolecular crystals in them is not limited by the hardware used. It is similarly true that a deficiency in tryptophan or another fluorescent component that limits the use of UV light for these purposes can be effectively overcome by the addition of fluorescent prostheses that bind to the biomolecule under study. The measurements for these studies were made with a device consisting of a potent UV-light source and a detection system specially adapted (i) to be tunable via a motorized and software-controlled absorption-filter system and (ii) to convey the excitation light to the droplet or capillary hosting the crystallization experiment by quartz-fibre light guides. [source] Labeling of proteins with fluorescent probes: Photophysical characterization of dansylated bovine serum albumin,BIOCHEMISTRY AND MOLECULAR BIOLOGY EDUCATION, Issue 5 2003Valeria Levi Abstract Fluorescence spectroscopy is a widely used technique in biophysical studies. One of the strategies frequently used consists of labeling biomolecules with fluorescent probes, which have distinctive photophysical properties. This methodology allows the study of a wide variety of structural features of the biomolecule. We describe a simple laboratory activity for undergraduate Biophysical Chemistry courses. The experimental work includes two activities: labeling BSA with dansyl chloride and analyzing the resulting absorption and fluorescence spectra. The discussion of these activities helps students to understand the basis of fluorescence spectroscopy with emphasis in the application to biological systems. [source] The biomolecule ubiquinone exerts a variety of biological functions,BIOFACTORS, Issue 1-4 2003Hans Nohl Abstract The chemistry of ubiquinone allows reversible addition of single electrons and protons. This unique property is used in nature for aerobic energy gain, for unilateral proton accumulation, for the generation of reactive oxygen species involved in physiological signaling and a variety of pathophysiological events. Since several years ubiquinone is also considered to play a major role in the control of lipid peroxidation, since this lipophilic biomolecule was recognized to recycle ,-tocopherol radicals back to the chain-breaking form, vitamin E. Ubiquinone is therefore a biomolecule which has increasingly focused the interest of many research groups due to its alternative pro- and antioxidant activity. We have intensively investigated the role of ubiquinone as prooxidant in mitochondria and will present experimental evidences on conditions required for this function, we will also show that lysosomal ubiquinone has a double function as proton translocator and radical source under certain metabolic conditions. Furthermore, we have addressed the antioxidant role of ubiquinone and found that the efficiency of this activity is widely dependent on the type of biomembrane where ubiquinone exerts its chain-breaking activity. [source] Baculovirus P35 protein: An overview of its applications across multiple therapeutic and biotechnological arenasBIOTECHNOLOGY PROGRESS, Issue 2 2010Sudhir Sahdev Abstract Baculovirus immediate early P35 protein is well known for its anti-apoptotic as well as anti-oxidant properties. Mechanism of action of P35 involves inhibition of a vast range of initiator to executioner class of caspases. In addition, P35's role in inhibiting oxidant-induced mitochondrial damage, primarily in the apoptotic pathway, has also been extensively investigated. Elucidation of P35's functions during regulation of programmed cell death (PCD) has led to a renewed focus on exploiting this basic knowledge for clinical and other related applications. This review outlines specific biochemical and genetic pathways where P35 intervenes and regulates rate-limiting steps in the apoptotic signaling cascade. Research efforts are underway to utilize P35 as an agent in regulating apoptosis and under certain circumstances, also explore the therapeutic potential of its anti-oxidant features. One of the major outcomes of recent studies include significantly improved effectiveness of cytochrome P450 directed enzyme pro-drug delivery tools when used in conjunction with P35, which may help in alleviating drug resistance in tumor cells and simultaneously prolonging the cytotoxic effects of anti-cancer drugs. Moreover, applied research carried out recently in the fields of diabetes, ischemia-induced neuronal cell death, experimental autoimmune encephalomyelitis (EAE), multiple sclerosis (MS), inflammatory arthritis, cardiovascular and ocular disorders illustrate P35's utilization across diverse therapeutic areas and will certainly make it an attractive biomolecule for the discovery research. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] Enzyme immobilization via silaffin-mediated autoencapsulation in a biosilica supportBIOTECHNOLOGY PROGRESS, Issue 2 2009Wesley D. Marner II Abstract Enzymes and other biomolecules are often immobilized in a matrix to improve their stability or to improve their ability to be reused. Performing a polycondensation reaction in the presence of a biomolecule of interest relies on random entrapment events during polymerization and may not ensure efficient, homogeneous, or complete biomolecule encapsulation. To overcome these limitations, we have developed a method of incorporating autosilification activity into proteins without affecting enzymatic functionality. The unmodified R5 silaffin peptide from Cylindrotheca fusiformis is capable of initiating silica polycondensation in vitro at ambient temperatures and pressures in aqueous solution. In this study, translational fusion proteins between R5 and various functional proteins (phosphodiesterase, organophosphate hydrolase, and green fluorescent protein) were produced in Escherichia coli. Each of the fusion proteins initiated silica polycondensation, and enzymatic activity (or fluorescence) was retained in the resulting silica spheres. Under certain circumstances, the enzymatically-active biosilica displayed improved stability relative to free enzyme at elevated temperatures. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Interpreting Experimental Data by Using Molecular Simulation Instead of Model BuildingCHEMISTRY - A EUROPEAN JOURNAL, Issue 26 2009Zrinka Gattin Abstract A proper description of the conformational equilibrium of polypeptides or proteins is essential for a correct description of their function. The conformational ensembles from 16 molecular dynamic simulations of two ,- heptapeptides were used to interpret the primary NMR data, which were also compared to a set of NMR model structures (see graphic). One of the most used spectroscopic techniques for resolving the structure of a biomolecule, such as a protein or peptide, is NMR spectroscopy. Because only NMR signal intensities and frequencies are measured in the experiment, a conformational interpretation of the primary data, that is, measured data, is not straightforward, especially for flexible molecules. It is hampered by the occurrence of conformational and/or time-averaging, by insufficient number of experimental data and by insufficient accuracy of experimental data. All three problematic aspects of structure refinement based on NMR nuclear Overhauser effect (NOE) intensities and 3J coupling data are illustrated by using two ,-heptapeptides in methanol as an example. We have performed 16 molecular dynamics (MD) simulations between 20 to 100,ns in length of unrestrained and NOE distance-restrained cases (instantaneous and time-averaged) of two ,-heptapeptides with a central ,-HAla(,-OH) amino acid in methanol at two different temperatures using two different GROMOS force-field parameter sets, 45,A3 and 53,A6. The created conformational ensembles were used to interpret the primary NMR data on these molecules. They also were compared to a set of NMR model structures derived by single-structure refinement in vacuo by using standard techniques. It is shown that the conformational interpretation of measured experimental data can be significantly improved by using unrestrained, instantaneous and time-averaged restrained MD simulations of the peptides by using a thermodynamically calibrated force field and by explicitly including solvent degrees of freedom. [source] Aryloxy Phosphoramidate Triesters: a Technology for Delivering Monophosphorylated Nucleosides and Sugars into CellsCHEMMEDCHEM, Issue 11 2009Youcef Mehellou Dr. Abstract Prodrug technologies aimed at delivering nucleoside monophosphates into cells (protides) have proved to be effective in improving the therapeutic potential of antiviral and anticancer nucleosides. In these cases, the nucleoside monophosphates are delivered into the cell, where they may then be further converted (phosphorylated) to their active species. Herein, we describe one of these technologies developed in our laboratories, known as the phosphoramidate protide method. In this approach, the charges of the phosphate group are fully masked to provide efficient passive cell-membrane penetration. Upon entering the cell, the masking groups are enzymatically cleaved to release the phosphorylated biomolecule. The application of this technology to various therapeutic nucleosides has resulted in improved antiviral and anticancer activities, and in some cases it has transformed inactive nucleosides to active ones. Additionally, the phosphoramidate technology has also been applied to numerous antiviral nucleoside phosphonates, and has resulted in at least three phosphoramidate-based nucleotides progressing to clinical investigations. Furthermore, the phosphoramidate technology has been recently applied to sugars (mainly glucosamine) in order to improve their therapeutic potential. The development of the phosphoramidate technology, mechanism of action and the application of the technology to various monophosphorylated nucleosides and sugars will be reviewed. [source] Observation of Protein Domain Motions by Neutron SpectroscopyCHEMPHYSCHEM, Issue 6 2010Michael Monkenbusch Dr. Abstract High-resolution inelastic neutron scattering, which is available with neutron spin-echo spectroscopy (NSE) is introduced as a tool for the analysis of biomolecule ,exibility. Coherent scattering in a range where it is sensitive to length scales of nanometers and covering a time range from picoseconds to several 100 ns makes the motion of larger subdomains within proteins visible. We show that and how the internal domain motion within a protein in solution can be measured. Comparison with displacement patterns from normal mode analysis provides further insight into the nature of the geometry of the motions that lead to the oberved dynamic signature. The NSE experiment on alcohol dehydrogenase (ADH) is used as example to illustrate the general principles of the method. [source] 68Ga-PET: a powerful generator-based alternative to cyclotron-based PET radiopharmaceuticalsCONTRAST MEDIA & MOLECULAR IMAGING, Issue 2 2008Melpomeni Fani Abstract PET (positron emission tomography) is a powerful diagnostic and imaging technique which requires short-lived positron emitting isotopes. The most commonly used are accelerator-produced 11C and 18F. An alternative is the use of metallic positron emitters. Among them 68Ga deserves special attention because of its availability from long-lived 68Ge/68Ga generator systems which render 68Ga radiopharmacy independent of an onsite cyclotron. The coordination chemistry of Ga3+ is dominated by its hard acid character. A variety of mono- and bifunctional chelators have been developed which allow the formation of stable 68Ga3+complexes and convenient coupling to biomolecules. 68Ga coupling to small biomolecules is potentially an alternative to 18F- and 11C-based radiopharmacy. In particular, peptides targeting G-protein coupled receptors overexpressed on human tumour cells have shown preclinically and clinically high and specific tumour uptake. Kit-formulated precursors along with the generator may be provided, similar to the 99Mo/99mTc-based radiopharmacy, still the mainstay of nuclear medicine. Copyright © 2008 John Wiley & Sons, Ltd. [source] Graphene Based Electrochemical Sensors and Biosensors: A ReviewELECTROANALYSIS, Issue 10 2010Yuyan Shao Abstract Graphene, emerging as a true 2-dimensional material, has received increasing attention due to its unique physicochemical properties (high surface area, excellent conductivity, high mechanical strength, and ease of functionalization and mass production). This article selectively reviews recent advances in graphene-based electrochemical sensors and biosensors. In particular, graphene for direct electrochemistry of enzyme, its electrocatalytic activity toward small biomolecules (hydrogen peroxide, NADH, dopamine, etc.), and graphene-based enzyme biosensors have been summarized in more detail; Graphene-based DNA sensing and environmental analysis have been discussed. Future perspectives in this rapidly developing field are also discussed. [source] Application of Nanoparticles in Electrochemical Sensors and BiosensorsELECTROANALYSIS, Issue 4 2006Xiliang Luo Abstract The unique chemical and physical properties of nanoparticles make them extremely suitable for designing new and improved sensing devices, especially electrochemical sensors and biosensors. Many kinds of nanoparticles, such as metal, oxide and semiconductor nanoparticles have been used for constructing electrochemical sensors and biosensors, and these nanoparticles play different roles in different sensing systems. The important functions provided by nanoparticles include the immobilization of biomolecules, the catalysis of electrochemical reactions, the enhancement of electron transfer between electrode surfaces and proteins, labeling of biomolecules and even acting as reactant. This minireview addresses recent advances in nanoparticle-based electrochemical sensors and biosensors, and summarizes the main functions of nanoparticles in these sensor systems. [source] Contactless Conductivity Detection in Capillary Electrophoresis: A ReviewELECTROANALYSIS, Issue 24 2004Pavel Kubá Abstract The popularity of contactless conductivity detection in capillary electrophoresis has been growing steadily over the last few years. Improvements have been made in the design of the detector in order to facilitate its handling, to allow easy incorporation into available instruments or to achieve higher sensitivity. The understanding of its fundamental working principles has been advanced and the detection approach has also been transferred to lab-on-chip devices. The range of applications has been extended greatly from the initial work on small inorganic ions to include organic species and biomolecules. Concurrent determination of cations and anions by dual injection from opposite ends has been demonstrated as well as sample introduction by using flow-injection systems for easy automation of the process. [source] Electrocatalytic Properties and Sensor Applications of Fullerenes and Carbon NanotubesELECTROANALYSIS, Issue 9 2003Bailure Abstract The electrochemical behavior of fullerene and fullerene derivatives are reviewed with special reference to their catalytic and sensor applications. Recent work on carbon nanotubes, used as catalyst supports in heterogeneous catalysis and sensor development is also presented. An overview of recent progress in the area of fullerene electrochemistry is included. Several cases of electrocatalytic dehalogenation of alkyl halides, assisted by the electrode charge transfer to fullerenes, are discussed. Research work on the electrocatalysis of biomolecules, such as hemin, cytochrome c, DNA, coenzymes, glucose, ascorbic acid, dopamine, etc. have also been considered. Based on the studies of the interaction of fullerenes, fullerene derivatives, and carbon nanotubes with other molecules and biomolecules in particular, the possibilities for the preparation of electrochemical sensors and their application in electroanalytical chemistry are highlighted. [source] Decreasing effective nanofluidic filter size by modulating electrical double layers: Separation enhancement in microfabricated nanofluidic filtersELECTROPHORESIS, Issue 23 2008Hansen Bow Abstract Conventional methods for separating biomolecules are based on steric interactions between the biomolecules and randomly oriented gel fibers. The recently developed artificial molecular sieves also rely on steric interactions for separation. In this work, we present an experimental investigation of a method that can be used in these sieves to increase separation selectivity and resolution. This method exploits the electrostatic repulsion between the charged molecules and the charged nanofluidic structure. Although this method has been mentioned in the previous work, it has not been examined in detail. We characterize this method by comparing the selectivity with that achieved in devices with different dimensions. The results of this study are relevant to the optimization of chip-based gel-free biomolecule separation and analysis. [source] Behavior of interacting species in vacancy affinity capillary electrophoresis described by mass balance equationELECTROPHORESIS, Issue 16 2008Ying Sun Abstract Vacancy ACE (VACE) is one of the ACE methods, and has been used to study binding interactions between different biomolecules. Thermodynamic binding constants can be estimated with nonlinear regression methods. With a highly efficient computer simulation program (SimDCCE), it is possible to demonstrate the detailed behaviors of each species during the interaction process under different conditions. In this work, thirteen scenarios in four different combinations of migration orders of the free protein, free drug, and complex formed are studied. The detailed interaction process between protein and ligand is discussed and illustrated based on the mass balance equation, also called mass transfer equation. By properly setting the parameters in the simulation model, the influence of different factors during the interaction process can be well understood. [source] Effect of mangiferin on radiation-induced micronucleus formation in cultured human peripheral blood lymphocytesENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 1 2005Ganesh Chandra Jagetia Abstract Irradiation causes a variety of lesions in important biomolecules of the cell through generation of free radicals leading to genomic instability. DNA strand breaks, acentric fragments, or defective kinetochores are manifested as micronuclei after the first cell division. Chemicals that can trap free radicals may reduce the deleterious effects of ionizing radiation. Mangiferin (MGN), a glucosylxanthone derived from Mangifera indica (mango), was investigated for its ability to reduce the frequency of radiation-induced micronucleated binucleate cells (MNBNCs) in cultured human peripheral blood lymphocytes (HPBLs). HPBL cultures were pretreated with 0, 5, 10, 20, 50, and 100 ,g/ml of MGN for 30 min before exposure to 3 Gy of 60Co ,-radiation. The maximum decline in radiation-induced micronuclei was observed at a concentration of 50 ,g/ml MGN; thereafter, a nonsignificant elevation in MNBNC frequency was observed at 100 ,g/ml MGN. Since the lowest MNBNC frequency was observed for 50 ,g/ml MGN, dose-response studies were undertaken using this concentration. Irradiation of HPBLs with 0, 1, 2, 3, or 4 Gy of ,-radiation caused a dose-dependent elevation in the MNBNC frequency, while treatment of HPBLs with 50 ,g/ml MGN 30 min before radiation resulted in significant declines in these frequencies. MGN alone did not alter the proliferation index. Irradiation caused a dose-dependent decline in the proliferation index, while treatment of HPBLs with 50 ,/ml MGN significantly elevated the proliferation index in irradiated cells. MGN treatment reduced hydrogen peroxide-induced lipid peroxidation in HPBLs in a concentration-dependent fashion. In cell-free studies, MGN inhibited the induction of ·OH (hydroxyl), O2·, (superoxide), DPPH (1,1-diphenyl-2-picrylhydrazyl), and ABTS·+ (2,2-azino-bis-3-ethyl benzothiazoline-6-sulphonic acid) radicals in a dose-dependent manner. The results of this study indicate that MGN possesses radioprotective properties by suppressing the effects of free radicals. Environ. Mol. Mutagen. 45:000,000, 2005. © 2005 Wiley-Liss, Inc. [source] Limits of life in MgCl2 -containing environments: chaotropicity defines the windowENVIRONMENTAL MICROBIOLOGY, Issue 3 2007John E. Hallsworth Summary The biosphere of planet Earth is delineated by physico-chemical conditions that are too harsh for, or inconsistent with, life processes and maintenance of the structure and function of biomolecules. To define the window of life on Earth (and perhaps gain insights into the limits that life could tolerate elsewhere), and hence understand some of the most unusual biological activities that operate at such extremes, it is necessary to understand the causes and cellular basis of systems failure beyond these windows. Because water plays such a central role in biomolecules and bioprocesses, its availability, properties and behaviour are among the key life-limiting parameters. Saline waters dominate the Earth, with the oceans holding 96.5% of the planet's water. Saline groundwater, inland seas or saltwater lakes hold another 1%, a quantity that exceeds the world's available freshwater. About one quarter of Earth's land mass is underlain by salt, often more than 100 m thick. Evaporite deposits contain hypersaline waters within and between their salt crystals, and even contain large subterranean salt lakes, and therefore represent significant microbial habitats. Salts have a major impact on the nature and extent of the biosphere, because solutes radically influence water's availability (water activity) and exert other activities that also affect biological systems (e.g. ionic, kosmotropic, chaotropic and those that affect cell turgor), and as a consequence can be major stressors of cellular systems. Despite the stressor effects of salts, hypersaline environments can be heavily populated with salt-tolerant or -dependent microbes, the halophiles. The most common salt in hypersaline environments is NaCl, but many evaporite deposits and brines are also rich in other salts, including MgCl2 (several hundred million tonnes of bischofite, MgCl2·6H2O, occur in one formation alone). Magnesium (Mg) is the third most abundant element dissolved in seawater and is ubiquitous in the Earth's crust, and throughout the Solar System, where it exists in association with a variety of anions. Magnesium chloride is exceptionally soluble in water, so can achieve high concentrations (> 5 M) in brines. However, while NaCl-dominated hypersaline environments are habitats for a rich variety of salt-adapted microbes, there are contradictory indications of life in MgCl2 -rich environments. In this work, we have sought to obtain new insights into how MgCl2 affects cellular systems, to assess whether MgCl2 can determine the window of life, and, if so, to derive a value for this window. We have dissected two relevant cellular stress-related activities of MgCl2 solutions, namely water activity reduction and chaotropicity, and analysed signatures of life at different concentrations of MgCl2 in a natural environment, namely the 0.05,5.05 M MgCl2 gradient of the seawater : hypersaline brine interface of Discovery Basin , a large, stable brine lake almost saturated with MgCl2, located on the Mediterranean Sea floor. We document here the exceptional chaotropicity of MgCl2, and show that this property, rather than water activity reduction, inhibits life by denaturing biological macromolecules. In vitro, a test enzyme was totally inhibited by MgCl2 at concentrations below 1 M; and culture medium with MgCl2 concentrations above 1.26 M inhibited the growth of microbes in samples taken from all parts of the Discovery interface. Although DNA and rRNA from key microbial groups (sulfate reducers and methanogens) were detected along the entire MgCl2 gradient of the seawater : Discovery brine interface, mRNA, a highly labile indicator of active microbes, was recovered only from the upper part of the chemocline at MgCl2 concentrations of less than 2.3 M. We also show that the extreme chaotropicity of MgCl2 at high concentrations not only denatures macromolecules, but also preserves the more stable ones: such indicator molecules, hitherto regarded as evidence of life, may thus be misleading signatures in chaotropic environments. Thus, the chaotropicity of MgCl2 would appear to be a window-of-life-determining parameter, and the results obtained here suggest that the upper MgCl2 concentration for life, in the absence of compensating (e.g. kosmotropic) solutes, is about 2.3 M. [source] The Chemistry of Technetium,Water Complexes within the Manganese Triad: Challenges and PerspectivesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2009Roger Alberto Abstract The chemistry of technetium is essentially driven by radiopharmaceutical applications. These comprise the syntheses of novel complexes but, moreover, the combination of targeting biomolecules with metal complexes. Aqua ions are especially convenient for facilitatating the introduction of metal cations into biomolecules, but are nonexistent for Tc and Re in the Mn triad. This microreview will discuss the chemistry of those Tc complexes that contain H2O as ligands. Special attention will be payed to organometallic aqua ions, i.e. complexes that are typically organometallic with water as ligand. Of particular interest is the coordination chemistry of [M(OH2)3(CO)3]+ (M = Mn, Tc, Re) complexes in water since it is the origin of the widely applied radiopharmaceutical research with 99mTc and 188Re. The chemistry of organometallic aqua ions is not confined to Werner-type ligands, hence, a further emphasis will be placed on pure organometallic chemistry in water.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] | |||||||||||||||||||||||||||||||||||||||||||