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Streptavidin
Streptavidin is a 66.0 (tetramer) kDa protein purified from the bacterium '' Streptomyces avidinii''. Streptavidin homo-tetramers have an extraordinarily high affinity for biotin (also known as vitamin B7 or vitamin H). With a dissociation constant (Kd) on the order of ≈10−14 mol/L, the binding of biotin to streptavidin is one of the strongest non-covalent interactions known in nature. Streptavidin is used extensively in molecular biology and bionanotechnology due to the streptavidin-biotin complex's resistance to organic solvents, denaturants (e.g. guanidinium chloride), detergents (e.g. SDS, Triton X-100), proteolytic enzymes, and extremes of temperature and pH. Structure The crystal structure of streptavidin with biotin bound was reported by two groups in 1989. The structure was solved using multi wavelength anomalous diffraction by Hendrickson et al. at Columbia University and using multiple isomorphous replacement by Weber et al. at E. I. DuPont Central Research ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biotinylation
In biochemistry, biotinylation is the process of covalently attaching biotin to a protein, nucleic acid or other molecule. Biotinylation is rapid, specific and is unlikely to disturb the natural function of the molecule due to the small size of biotin (MW = 244.31 g/mol). Biotin binds to streptavidin and avidin with an extremely high affinity, fast on-rate, and high specificity, and these interactions are exploited in many areas of biotechnology to isolate biotinylated molecules of interest. Biotin-binding to streptavidin and avidin is resistant to extremes of heat, pH and proteolysis, making capture of biotinylated molecules possible in a wide variety of environments. Also, multiple biotin molecules can be conjugated to a protein of interest, which allows binding of multiple streptavidin, avidin or neutravidin protein molecules and increases the sensitivity of detection of the protein of interest. There is a large number of biotinylation reagents available that exploit t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biotin
Biotin (or vitamin B7) is one of the B vitamins. It is involved in a wide range of metabolic processes, both in humans and in other organisms, primarily related to the utilization of fats, carbohydrates, and amino acids. The name ''biotin'', borrowed from the German , derives from the Ancient Greek word (; 'life') and the suffix "-in" (a suffix used in chemistry usually to indicate 'forming'). Chemical description Biotin is classified as a heterocyclic compound, with a sulfur-containing ring fused ureido and tetrahydrothiophene group. A C5-carboxylic acid side chain is appended to one of the rings. The ureido ring, containing the −N−CO−N− group, serves as the carbon dioxide carrier in carboxylation reactions. Biotin is a coenzyme for five carboxylase enzymes, which are involved in the catabolism of amino acids and fatty acids, synthesis of fatty acids, and gluconeogenesis. Biotinylation of histone proteins in nuclear chromatin plays a role in chromatin stability and g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Strep-tag
The Strep-tag system is a method which allows the purification and detection of proteins by affinity chromatography. The Strep-tag II is a synthetic peptide consisting of eight amino acids (Tryptophan, Trp-Serine, Ser-Histidine, His-Proline, Pro-Gln-Phenylalanine, Phe-Glutamic acid, Glu-Lysine, Lys). This peptide sequence exhibits intrinsic affinity towards Strep-Tactin, a specifically engineered streptavidin, and can be N- or C- terminally fused to recombinant proteins. By exploiting the highly specific interaction, ''Strep''-tagged proteins can be isolated in one step from crude cell lysates. Because the ''Strep''-tag elutes under gentle, physiological conditions, it is especially suited for generation of functional proteins. Development and biochemistry of the Strep-tag Streptavidin is a tetrameric protein expressed in ''Streptomyces avidinii''. Because of Streptavidin's high affinity for vitamin H (biotin), Streptavidin is commonly used in the fields of molecular biology a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homotetramer
A tetrameric protein is a protein with a protein quaternary structure, quaternary structure of four subunits (tetrameric). Homotetramers have four identical Protein subunit, subunits (such as glutathione S-transferase), and heterotetramers are Multiprotein complex, complexes of different subunits. A tetramer can be assembled as dimer of dimers with two homodimer subunits (such as sorbitol dehydrogenase), or two heterodimer subunits (such as hemoglobin). Subunit interactions in tetramers The interactions between subunits forming a tetramer is primarily determined by non covalent interaction. Hydrophobic effects, hydrogen bonds and electrostatic interactions are the primary sources for this binding process between subunits. For homotetrameric proteins such as Sorbitol dehydrogenase (SDH), the structure is believed to have evolved going from a monomeric to a dimeric and finally a tetrameric structure in evolution. The binding process in SDH and many other tetrameric enzymes can be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Streptomyces Avidinii
''Streptomyces avidinii'' is a bacterium species from the genus of ''Streptomyces'' which produces streptavidin. See also * List of Streptomyces species, List of ''Streptomyces'' species References Further reading * * * * * * * * * * External linksType strain of ''Streptomyces avidinii'' at Bac''Dive'' - the Bacterial Diversity Metadatabase Streptomyces, avidinii Bacteria described in 1964 {{Streptomyces-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Western Blot
The western blot (sometimes called the protein immunoblot), or western blotting, is a widely used analytical technique in molecular biology and immunogenetics to detect specific proteins in a sample of tissue homogenate or extract. Besides detecting the proteins, this technique is also utilized to visualize, distinguish, and quantify the different proteins in a complicated protein combination. Western blot technique uses three elements to achieve its task of separating a specific protein from a complex: separation by size, transfer of protein to a solid support, and marking target protein using a primary and secondary antibody to visualize. A synthetic or animal-derived antibody (known as the primary antibody) is created that recognizes and binds to a specific target protein. The electrophoresis membrane is washed in a solution containing the primary antibody, before excess antibody is washed off. A secondary antibody is added which recognizes and binds to the primary antibody ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horseradish Peroxidase
The enzyme horseradish peroxidase (HRP), found in the roots of horseradish, is used extensively in biochemistry applications. It is a metalloenzyme with many isoforms, of which the most studied type is C. It catalyzes the oxidation of various organic substrates by hydrogen peroxide. Structure The structure of the enzyme was first solved by X-ray crystallography in 1997; and has since been solved several times with various substrates. It is a large alpha-helical glycoprotein which binds heme as a redox cofactor. Substrates Alone, the HRP enzyme, or conjugates thereof, is of little value; its presence must be made visible using a substrate that, when oxidized by HRP using hydrogen peroxide as the oxidizing agent, yields a characteristic color change that is detectable by spectrophotometric methods. Numerous substrates for horseradish peroxidase have been described and commercialized to exploit the desirable features of HRP. These substrates fall into several distinct cat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanobiotechnology
Nanobiotechnology, bionanotechnology, and nanobiology are terms that refer to the intersection of nanotechnology and biology. Given that the subject is one that has only emerged very recently, bionanotechnology and nanobiotechnology serve as blanket terms for various related technologies. This discipline helps to indicate the merger of biological research with various fields of nanotechnology. Concepts that are enhanced through nanobiology include: nanodevices (such as biological machines), nanoparticles, and nanoscale phenomena that occurs within the discipline of nanotechnology. This technical approach to biology allows scientists to imagine and create systems that can be used for biological research. Biologically inspired nanotechnology uses biological systems as the inspirations for technologies not yet created. However, as with nanotechnology and biotechnology, bionanotechnology does have many potential ethical issues associated with it. The most important objectives that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanoscopic Scale
The nanoscopic scale (or nanoscale) usually refers to structures with a length scale applicable to nanotechnology, usually cited as 1–100 nanometers (nm). A nanometer is a billionth of a meter. The nanoscopic scale is (roughly speaking) a lower bound to the mesoscopic scale for most solids. For technical purposes, the nanoscopic scale is the size at which fluctuations in the averaged properties (due to the motion and behavior of individual particles) begin to have a significant effect (often a few percent) on the behavior of a system, and must be taken into account in its analysis. The nanoscopic scale is sometimes marked as the point where the properties of a material change; above this point, the properties of a material are caused by 'bulk' or 'volume' effects, namely which atoms are present, how they are bonded, and in what ratios. Below this point, the properties of a material change, and while the type of atoms present and their relative orientations are still importan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbon Nanotube
A scanning tunneling microscopy image of a single-walled carbon nanotube Rotating single-walled zigzag carbon nanotube A carbon nanotube (CNT) is a tube made of carbon with diameters typically measured in nanometers. ''Single-wall carbon nanotubes'' (''SWCNTs'') are one of the allotropes of carbon, intermediate between fullerene cages and flat graphene, with diameters in the range of a nanometre. Although not made this way, single-wall carbon nanotubes can be idealized as cutouts from a two-dimensional Hexagonal tiling, hexagonal lattice of carbon atoms rolled up along one of the Bravais lattice vectors of the hexagonal lattice to form a hollow cylinder. In this construction, periodic boundary conditions are imposed over the length of this roll-up vector to yield a helical lattice of seamlessly bonded carbon atoms on the cylinder surface. ''Multi-wall carbon nanotubes'' (''MWCNTs'') consisting of nested single-wall carbon nanotubes weakly bound together by van der Waals ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ribbon Diagram
Ribbon diagrams, also known as Richardson diagrams, are three-dimensional space, 3D schematic representations of protein structure and are one of the most common methods of protein depiction used today. The ribbon shows the overall path and organization of the protein backbone in 3D, and serves as a visual framework on which to hang details of the full atomic structure, such as the balls for the oxygen atoms bound to the active site of myoglobin in the adjacent image. Ribbon diagrams are generated by interpolating a smooth curve through the polypeptide backbone. Alpha helix, α-helices are shown as coiled ribbons or thick tubes, Beta strand, β-strands as arrows, and non-repetitive coils or loops as lines or thin tubes. The direction of the Peptide, polypeptide chain is shown locally by the arrows, and may be indicated overall by a colour ramp along the length of the ribbon. Ribbon diagrams are simple yet powerful, expressing the visual basics of a molecular structure (twist, fold ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SpyCatcher
''Spycatcher: The Candid Autobiography of a Senior Intelligence Officer'' (1987) is a memoir written by Peter Wright, former MI5 officer and Assistant Director, and co-author Paul Greengrass. He drew on his own experiences and research into the history of the British intelligence community. Published first in Australia, the book was banned in England (but not Scotland) due to its allegations about government policy and incidents. These efforts ensured the book's notoriety, and it earned considerable profit for Wright. In 2021, the Cabinet Office was still blocking freedom of information requests for files on the ''Spycatcher'' affair despite the rule that documents should be released after 30 years. Content In ''Spycatcher'', Wright says that one of his assignments was to unmask a Soviet mole in MI5, who he says was Roger Hollis, a former MI5 Director General. His book also discusses other candidates who may have or may not have been the mole. He explores the history o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
