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Electro-switchable Biosurface
An electro-switchable biosurface is a biosensor that is based on an electrode (often gold) to which a layer of biomolecules (often DNA molecules) has been tethered. An alternating or fixed electrical potential is applied to the electrode which causes changes in the structure and position (movement) of the charged biomolecules. The biosensor is used in science, e.g. biomedical and biophysical research or drug discovery, to assess interactions between biomolecules and binding kinetics as well as changes in size or conformation of biomolecules. Technological background The general principle of a biosurface is a solid surface with an additional layer of biological macromolecules. Because this molecular layer will reversibly respond to changes in the environment of the surface, it is also called “stimuli-responsive monolayer”. The external stimuli can be for example changes in temperature, changes in magnetic fields, mechanical forces or changes in electric fields. Different st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biosensor
A biosensor is an analytical device, used for the detection of a chemical substance, that combines a biological component with a physicochemical detector. The ''sensitive biological element'', e.g. tissue, microorganisms, organelles, cell receptors, enzymes, antibodies, nucleic acids, etc., is a biologically derived material or biomimetic component that interacts with, binds with, or recognizes the analyte under study. The biologically sensitive elements can also be created by biological engineering. The ''transducer'' or the ''detector element'', which transforms one signal into another one, works in a physicochemical way: optical, piezoelectric, electrochemical, electrochemiluminescence etc., resulting from the interaction of the analyte with the biological element, to easily measure and quantify. The biosensor reader device connects with the associated electronics or signal processors that are primarily responsible for the display of the results in a user-friendly way. This ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. Almost all metabolic processes in the cell need enzyme catalysis in order to occur at rates fast enough to sustain life. Metabolic pathways depend upon enzymes to catalyze individual steps. The study of enzymes is called ''enzymology'' and the field of pseudoenzyme analysis recognizes that during evolution, some enzymes have lost the ability to carry out biological catalysis, which is often reflected in their amino acid sequences and unusual 'pseudocatalytic' properties. Enzymes are known to catalyze more than 5,000 biochemical reaction types. Other biocatalysts are catalytic RNA molecules, called ribozymes. Enzymes' specificity comes from their unique three-dimensional structures. Like all catalysts, enzymes increase the reaction ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methods To Investigate Protein–protein Interactions
There are many methods to investigate protein–protein interactions which are the physical contacts of high specificity established between two or more protein molecules involving electrostatic forces and hydrophobic effects. Each of the approaches has its own strengths and weaknesses, especially with regard to the sensitivity and specificity of the method. A high sensitivity means that many of the interactions that occur are detected by the screen. A high specificity indicates that most of the interactions detected by the screen are occurring in reality. Biochemical methods Co-immunoprecipitation is considered to be the gold standard assay for protein–protein interactions, especially when it is performed with endogenous (not overexpressed and not tagged) proteins. The protein of interest is isolated with a specific antibody. Interaction partners which stick to this protein are subsequently identified by Western blotting. Interactions detected by this approach are considered to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene Therapy
Gene therapy is a medical field which focuses on the genetic modification of cells to produce a therapeutic effect or the treatment of disease by repairing or reconstructing defective genetic material. The first attempt at modifying human DNA was performed in 1980, by Martin Cline, but the first successful nuclear gene transfer in humans, approved by the National Institutes of Health, was performed in May 1989. The first therapeutic use of gene transfer as well as the first direct insertion of human DNA into the nuclear genome was performed by French Anderson in a trial starting in September 1990. It is thought to be able to cure many genetic disorders or treat them over time. Between 1989 and December 2018, over 2,900 clinical trials were conducted, with more than half of them in phase I.Gene Therapy Cli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isothermal Titration Calorimetry
Isothermal titration calorimetry (ITC) is a physical technique used to determine the thermodynamic parameters of interactions in solution. It is most often used to study the binding of small molecules (such as medicinal compounds) to larger macromolecules (proteins, DNA etc.). It consists of two cells which are enclosed in an adiabatic jacket. The compounds to be studied are placed in the sample cell, while the other cell, the reference cell, is used as a control and contains the buffer in which the sample is dissolved. Thermodynamic measurements ITC is a quantitative technique that can determine the binding affinity (K_a), enthalpy changes (\Delta H), and binding stoichiometry (n) of the interaction between two or more molecules in solution. From these initial measurements, Gibbs free energy changes (\Delta G) and entropy changes (\Delta S) can be determined using the relationship: :::\Delta G = -RT\ln = \Delta H -T\Delta S (where R is the gas constant and T is the absolute ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Surface Plasmon Resonance
Surface plasmon resonance (SPR) is the resonant oscillation of conduction electrons at the interface between negative and positive permittivity material in a particle stimulated by incident light. SPR is the basis of many standard tools for measuring adsorption of material onto planar metal (typically gold or silver) surfaces or onto the surface of metal nanoparticles. It is the fundamental principle behind many color-based biosensor applications and lab-on-a-chip sensors. It should be stressed that SPR is not a resonance on the planar surface and it is a polariton or surface-wave like phenomenon. Explanation The surface plasmon polariton is a non-radiative electromagnetic surface wave that propagates in a direction parallel to the negative permittivity/dielectric material interface. Since the wave is on the boundary of the conductor and the external medium (air, water or vacuum for example), these oscillations are very sensitive to any change of this boundary, such as the adso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polymerase
A polymerase is an enzyme ( EC 2.7.7.6/7/19/48/49) that synthesizes long chains of polymers or nucleic acids. DNA polymerase and RNA polymerase are used to assemble DNA and RNA molecules, respectively, by copying a DNA template strand using base-pairing interactions or RNA by half ladder replication. A DNA polymerase from the thermophilic bacterium, ''Thermus aquaticus'' (''Taq'') ( PDBbr>1BGX EC 2.7.7.7) is used in the polymerase chain reaction, an important technique of molecular biology. A polymerase may be template dependent or template independent. Poly-A-polymerase is an example of template independent polymerase. Terminal deoxynucleotidyl transferase also known to have template independent and template dependent activities. Types By function *DNA polymerase (DNA-directed DNA polymerase, DdDP) **Family A: DNA polymerase I; Pol γ, θ, ν **Family B: DNA polymerase II; Pol α, δ, ε, ζ **Family C: DNA polymerase III holoenzyme **Family X: Pol β, λ, μ * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ligand (biochemistry)
In biochemistry and pharmacology, a ligand is a substance that forms a complex with a biomolecule to serve a biological purpose. The etymology stems from ''ligare'', which means 'to bind'. In protein-ligand binding, the ligand is usually a molecule which produces a signal by binding to a site on a target protein. The binding typically results in a change of conformational isomerism (conformation) of the target protein. In DNA-ligand binding studies, the ligand can be a small molecule, ion, or protein which binds to the DNA double helix. The relationship between ligand and binding partner is a function of charge, hydrophobicity, and molecular structure. Binding occurs by intermolecular forces, such as ionic bonds, hydrogen bonds and Van der Waals forces. The association or docking is actually reversible through dissociation. Measurably irreversible covalent bonding between a ligand and target molecule is atypical in biological systems. In contrast to the definition of lig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Drug Discovery
In the fields of medicine, biotechnology and pharmacology, drug discovery is the process by which new candidate medications are discovered. Historically, drugs were discovered by identifying the active ingredient from traditional remedies or by serendipitous discovery, as with penicillin. More recently, chemical libraries of synthetic small molecules, natural products or extracts were screened in intact cells or whole organisms to identify substances that had a desirable therapeutic effect in a process known as classical pharmacology. After sequencing of the human genome allowed rapid cloning and synthesis of large quantities of purified proteins, it has become common practice to use high throughput screening of large compounds libraries against isolated biological targets which are hypothesized to be disease-modifying in a process known as reverse pharmacology. Hits from these screens are then tested in cells and then in animals for efficacy. Modern drug discovery involves the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quenching (fluorescence)
Quenching refers to any process which decreases the fluorescence intensity of a given substance. A variety of processes can result in quenching, such as excited state reactions, energy transfer, complex-formation and collisional quenching. As a consequence, quenching is often heavily dependent on pressure and temperature. Molecular oxygen, iodide ions and acrylamide are common chemical quenchers. The chloride ion is a well known quencher for quinine fluorescence. Quenching poses a problem for non-instant spectroscopic methods, such as laser-induced fluorescence. Quenching is made use of in optode sensors; for instance the quenching effect of oxygen on certain ruthenium complexes allows the measurement of oxygen saturation in solution. Quenching is the basis for Förster resonance energy transfer (FRET) assays. Quenching and dequenching upon interaction with a specific molecular biological target is the basis for activatable optical contrast agents for molecular imaging. Many dyes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluorophore
A fluorophore (or fluorochrome, similarly to a chromophore) is a fluorescent chemical compound that can re-emit light upon light excitation. Fluorophores typically contain several combined aromatic groups, or planar or cyclic molecules with several π bonds. Fluorophores are sometimes used alone, as a tracer in fluids, as a dye for staining of certain structures, as a substrate of enzymes, or as a probe or indicator (when its fluorescence is affected by environmental aspects such as polarity or ions). More generally they are covalently bonded to a macromolecule, serving as a marker (or dye, or tag, or reporter) for affine or bioactive reagents (antibodies, peptides, nucleic acids). Fluorophores are notably used to stain tissues, cells, or materials in a variety of analytical methods, i.e., fluorescent imaging and spectroscopy. Fluorescein, via its amine-reactive isothiocyanate derivative fluorescein isothiocyanate (FITC), has been one of the most popular fluorophores. Fro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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