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DAPI
DAPI (pronounced 'DAPPY', /ˈdæpiː/), or 4′,6-diamidino-2-phenylindole, is a fluorescent stain that binds strongly to adenine– thymine-rich regions in DNA. It is used extensively in fluorescence microscopy. As DAPI can pass through an intact cell membrane, it can be used to stain both live and fixed cells, though it passes through the membrane less efficiently in live cells and therefore provides a marker for membrane viability. History DAPI was first synthesised in 1971 in the laboratory of Otto Dann as part of a search for drugs to treat trypanosomiasis. Although it was unsuccessful as a drug, further investigation indicated it bound strongly to DNA and became more fluorescent when bound. This led to its use in identifying mitochondrial DNA in ultracentrifugation in 1975, the first recorded use of DAPI as a fluorescent DNA stain. Strong fluorescence when bound to DNA led to the rapid adoption of DAPI for fluorescent staining of DNA for fluorescence microscopy. It ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Staining (biology)
Staining is a technique used to enhance contrast in samples, generally at the microscopic level. Stains and dyes are frequently used in histology (microscopic study of biological tissues), in cytology (microscopic study of cells), and in the medical fields of histopathology, hematology, and cytopathology that focus on the study and diagnoses of diseases at the microscopic level. Stains may be used to define biological tissues (highlighting, for example, muscle fibers or connective tissue), cell populations (classifying different blood cells), or organelles within individual cells. In biochemistry, it involves adding a class-specific (DNA, proteins, lipids, carbohydrates) dye to a substrate to qualify or quantify the presence of a specific compound. Staining and fluorescent tagging can serve similar purposes. Biological staining is also used to mark cells in flow cytometry, and to flag proteins or nucleic acids in gel electrophoresis. Light microscopes are used for vi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hoechst Stain
Hoechst stains are part of a family of blue fluorescent dyes used to stain DNA. These bis-benzimides were originally developed by Hoechst AG, which numbered all their compounds so that the dye Hoechst 33342 is the 33,342nd compound made by the company. There are three related Hoechst stains: Hoechst 33258, Hoechst 33342, and Hoechst 34580. The dyes Hoechst 33258 and Hoechst 33342 are the ones most commonly used and they have similar excitation– emission spectra. Molecular characteristics Both dyes are excited by ultraviolet light at around 350 nm, and both emit blue-cyan fluorescent light around an emission spectrum maximum at 461 nm. Unbound dye has its maximum fluorescence emission in the 510–540 nm range. Hoechst stains can be excited with a xenon- or mercury-arc lamp or with an ultraviolet laser. There is a considerable Stokes shift between the excitation and emission spectra that makes Hoechst dyes useful in experiments in which multiple fluo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluorescence Microscopy
A fluorescence microscope is an optical microscope that uses fluorescence instead of, or in addition to, scattering, reflection, and attenuation or absorption, to study the properties of organic or inorganic substances. A fluorescence microscope is any microscope that uses fluorescence to generate an image, whether it is a simple setup like an epifluorescence microscope or a more complicated design such as a confocal microscope, which uses optical sectioning to get better resolution of the fluorescence image. Principle The specimen is illuminated with light of a specific wavelength (or wavelengths) which is absorbed by the fluorophores, causing them to emit light of longer wavelengths (i.e., of a different color than the absorbed light). The illumination light is separated from the much weaker emitted fluorescence through the use of a spectral emission filter. Typical components of a fluorescence microscope are a light source (xenon arc lamp or mercury-vapor lamp are com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flow Cytometry
Flow cytometry (FC) is a technique used to detect and measure the physical and chemical characteristics of a population of cells or particles. In this process, a sample containing cells or particles is suspended in a fluid and injected into the flow cytometer instrument. The sample is focused to ideally flow one cell at a time through a laser beam, where the light scattered is characteristic to the cells and their components. Cells are often labeled with fluorescent markers so light is absorbed and then emitted in a band of wavelengths. Tens of thousands of cells can be quickly examined and the data gathered are processed by a computer. Flow cytometry is routinely used in basic research, clinical practice, and clinical trials. Uses for flow cytometry include: * Cell counting * Cell sorting * Determining cell characteristics and function * Detecting microorganisms * Biomarker detection * Protein engineering detection * Diagnosis of health disorders such as blood cancers * Me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Netropsin
Netropsin (also termed congocidine or sinanomycin) is a polyamide with antibiotic and antiviral activity. Netropsin was discovered by Finlay ''et al.'', and first isolated from the actinobacterium '' Streptomyces netropsis''. It belongs to the class of pyrrole-amidine antibiotics. DNA binding properties Netropsin binds to the minor groove of AT-rich sequences of double stranded DNA. In contrast, netropsin does not bind single stranded DNA or double stranded RNA. Crystallographic structures of DNA-bound Netropsin have been obtained and elucidate details of how the drug binds in the minor groove. In the bound structure, the drug makes hydrogen bonding interactions with four subsequent base pairs of the DNA duplex, locally displacing the water molecules of the spine of hydration. Using gel mobility and analytical ultracentrifugation, it was shown that Netropsin binding to DNA increases the twist per base by similar to 9˚ per molecule bound. Thus, it removes supercoils when ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time-dependent Density Functional Theory
Time-dependent density-functional theory (TDDFT) is a quantum mechanical theory used in physics and chemistry to investigate the properties and dynamics of many-body systems in the presence of time-dependent potentials, such as electric or magnetic fields. The effect of such fields on molecules and solids can be studied with TDDFT to extract features like excitation energies, frequency-dependent response properties, and photoabsorption spectra. TDDFT is an extension of density-functional theory (DFT), and the conceptual and computational foundations are analogous – to show that the (time-dependent) wave function is equivalent to the (time-dependent) electronic density, and then to derive the effective potential of a fictitious non-interacting system which returns the same density as any given interacting system. The issue of constructing such a system is more complex for TDDFT, most notably because the time-dependent effective potential at any given instant depends on t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Cultures
Cell culture or tissue culture is the process by which cells are grown under controlled conditions, generally outside of their natural environment. After cells of interest have been isolated from living tissue, they can subsequently be maintained under carefully controlled conditions. They need to be kept at body temperature (37 °C) in an incubator. These conditions vary for each cell type, but generally consist of a suitable vessel with a substrate or rich medium that supplies the essential nutrients (amino acids, carbohydrates, vitamins, minerals), growth factors, hormones, and gases ( CO2, O2), and regulates the physio-chemical environment ( pH buffer, osmotic pressure, temperature). Most cells require a surface or an artificial substrate to form an adherent culture as a monolayer (one single-cell thick), whereas others can be grown free floating in a medium as a suspension culture. This is typically facilitated via use of a liquid, semi-solid, or solid growth me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mycoplasma
''Mycoplasma'' is a genus of bacteria that, like the other members of the class ''Mollicutes'', lack a cell wall, and its peptidoglycan, around their cell membrane. The absence of peptidoglycan makes them naturally resistant to antibiotics such as the beta-lactam antibiotics that target cell wall synthesis. They can be parasitic or saprotrophic. In casual speech, the name ''"mycoplasma"'' (plural ''mycoplasmas'' or ''mycoplasms'') generally refers to all members of the class Mollicutes. In formal scientific classification, the designation ''Mycoplasma'' refers exclusively to the genus, a member of the Mycoplasmataceae, the only family in the order Mycoplasmatales (see "scientific classification"). In 2018, ''Mycoplasma'' was split with many clinically significant species moved to other genera in Mollicutes; see the page Mollicutes for an overview. Etymology The term "mycoplasma", from the Greek μύκης, ' (fungus) and πλάσμα, ' (formed), was first used by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Growth Medium
A growth medium or culture medium is a solid, liquid, or semi-solid designed to support the growth of a population of microorganisms or cells via the process of cell proliferation or small plants like the moss ''Physcomitrella patens''. Different types of media are used for growing different types of cells. The two major types of growth media are those used for cell culture, which use specific cell types derived from plants or animals, and those used for microbiological culture, which are used for growing microorganisms such as bacteria or fungi. The most common growth media for microorganisms are nutrient broths and agar plates; specialized media are sometimes required for microorganism and cell culture growth. Some organisms, termed fastidious organisms, require specialized environments due to complex nutritional requirements. Viruses, for example, are obligate intracellular parasites and require a growth medium containing living cells. Types The most common growth media ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluorescence
Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with colored visible light. The color of the light emitted depends on the chemical composition of the substance. Fluorescent materials generally cease to glow nearly immediately when the radiation source stops. This distinguishes them from the other type of light emission, phosphorescence. Phosphorescent materials continue to emit light for some time after the radiation stops. This difference in duration is a result of quantum spin effects. Fluorescence occurs when a photon from incoming radiation is absorbed by a molecule, exciting it to a higher energy level, followed by the emission of light as the molecule returns to a lower energy state. The emitted light may have a longer wavelength and, therefore, a lower photon energy than the absorbed radi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polarizable Continuum Model
The polarizable continuum model (PCM) is a commonly used method in computational chemistry to model solvation effects. When it is necessary to consider each solvent molecule as a separate molecule, the computational cost of modeling a solvent-mediated chemical reaction becomes prohibitively high. Modeling the solvent as a polarizable continuum, rather than individual molecules, makes ''ab initio'' computation more readily achievable. Two types of PCMs have been popularly used: the dielectric PCM (D-PCM), in which the continuum is polarizable (see dielectrics), and the conductor-like PCM (C-PCM), in which the continuum is conductor-like, similar to the COSMO Solvation Model.Jacopo Tomasi, Benedetta Mennucci, and Roberto Cammi (2005). "Quantum Mechanical Continuum Solvation Models." Chem. Rev. 105(8): 2999-309/ref> The molecular Gibbs free energy, free energy of solvation is computed as the sum of three terms: :''G''sol = ''G''es + ''G''dr + ''G''cav ::''G''es = electrostatic ::' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intercalation (biochemistry)
In biochemistry, intercalation is the insertion of molecules between the planar bases of deoxyribonucleic acid (DNA). This process is used as a method for analyzing DNA and it is also the basis of certain kinds of poisoning. There are several ways molecules (in this case, also known as ''ligands'') can interact with DNA. Ligands may interact with DNA by covalently binding, electrostatically binding, or intercalating. Intercalation occurs when ligands of an appropriate size and chemical nature fit themselves in between base pairs of DNA. These ligands are mostly polycyclic, aromatic, and planar, and therefore often make good nucleic acid stains. Intensively studied DNA intercalators include berberine, ethidium bromide, proflavine, daunomycin, doxorubicin, and thalidomide. DNA intercalators are used in chemotherapeutic treatment to inhibit DNA replication in rapidly growing cancer cells. Examples include doxorubicin (adriamycin) and daunorubicin (both of which are used in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
