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Merocyanine
Merocyanines are a class of polymethine dyes which are clearly defined by set structural properties. Merycyanines belong to the group of dyes referred to as functional dyes, where their applications are not only determined by their colour, but also their valuable chemical properties. These dyes are usually intensely colored and have large extinction coefficients. Merocyanine 540 was the first fluorescent dye used for measuring membrane potential, while Brooker's merocyanine and related compounds are notable for their solvatochromatic properties. : Definition :Conventionally, merocyanine class includes streptocyanines and their analogues where both the nitrogen atom and carbonyl group (or any other electron-withdrawing group containing a multiple carbon-heteroatomic bond, e.g. amino group) can form part of a heterocyclic system. Like ionic cyanines, merocyanines contain two terminal heteroatoms and a polymethine chain in their chromophores. See also * Brooker's merocyan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brooker's Merocyanine
Brooker's merocyanine (1-methyl-4- oxocyclohexadienylidene)ethylidene1,4-dihydropyridine, MOED) is an organic dye belonging to the class of merocyanines. MOED is notable for its solvatochromic properties, meaning it changes color depending on the solvent in which it is dissolved. As shown in the structural formula, MOED can be depicted using two resonance structures: neutral and zwitterionic. Research indicates that the zwitterionic structure is the major contributor to resonance hybrid when the compound exists in polar solvents such as water, and the neutral form when it exists in nonpolar solvents such as chloroform. Solvatochromic effects When MOED is dissolved in various liquids, its colour will vary, depending on the solvent and its polarity. In general, the more polar the solvent, the shorter the wavelengths of the light absorbed will be, this is referred to as a hypsochromic shift. When light of a certain colour (wavelength) is absorbed, the solution will appear in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Merocyanine 540
Merocyanines are a class of polymethine dyes which are clearly defined by set structural properties. Merycyanines belong to the group of dyes referred to as functional dyes, where their applications are not only determined by their colour, but also their valuable chemical properties. These dyes are usually intensely colored and have large extinction coefficients. Merocyanine 540 was the first fluorescent dye used for measuring membrane potential, while Brooker's merocyanine and related compounds are notable for their solvatochromatic properties. : Definition :Conventionally, merocyanine class includes streptocyanines and their analogues where both the nitrogen atom and carbonyl group (or any other electron-withdrawing group containing a multiple carbon-heteroatomic bond, e.g. amino group) can form part of a heterocyclic system. Like ionic cyanines, merocyanines contain two terminal heteroatoms and a polymethine chain in their chromophores. See also * Brooker's merocyan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solvatochromism
In chemistry, solvatochromism is the phenomenon observed when the colour due to a solute is different when that solute is dissolved in different solvents. The solvatochromic effect is the way the spectrum of a substance (the solute) varies when the substance is dissolved in a variety of solvents. In this context, the dielectric constant and hydrogen bonding capacity are the most important properties of the solvent. With various solvents there is a different effect on the electronic ground state and excited state of the solute, so that the size of energy gap between them changes as the solvent changes. This is reflected in the absorption or emission spectrum of the solute as differences in the position, intensity, and shape of the spectroscopic bands. When the spectroscopic band occurs in the visible part of the spectrum solvatochromism is observed as a change of colour. This is illustrated by Reichardt's dye, as shown in the image. Negative solvatochromism corresponds to a hypsoc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
J-aggregate
A J-aggregate is a type of dye with an absorption band that shifts to a longer wavelength (bathochromic shift) of increasing sharpness (higher absorption coefficient) when it aggregates under the influence of a solvent or additive or concentration as a result of supramolecular self-organisation. The dye can be characterized further by a small Stokes shift with a narrow band. The J in J-aggregate refers to E.E. Jelley who discovered the phenomenon in 1936. The dye is also called a Scheibe aggregate after G. Scheibe who also independently published on this topic in 1937. Scheibe and Jelley independently observed that in ethanol the dye PIC chloride has two broad absorption maxima at around 19,000 cm−1 and 20,500 cm−1 (526 and 488 nm respectively) and that in water a third sharp absorption maximum appears at 17,500 cm−1 (571 nm). The intensity of this band further increases on increasing concentration and on adding sodium chloride. In the oldest aggreg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Opacity (optics)
Opacity is the measure of impenetrability to electromagnetic radiation, electromagnetic or other kinds of radiation, especially visible light. In radiative transfer, it describes the absorption and scattering of radiation in a transmission medium, medium, such as a plasma (physics), plasma, dielectric, radiation shield, shielding material, glass, etc. An opaque object is neither Transparency (optics), transparent (allowing all light to pass through) nor translucent (allowing some light to pass through). When light strikes an interface between two substances, in general some may be reflected, some absorbed, some scattered, and the rest transmitted (also see refraction). Reflection can be diffuse reflection, diffuse, for example light reflecting off a white wall, or specular reflection, specular, for example light reflecting off a mirror. An opaque substance transmits no light, and therefore reflects, scatters, or absorbs all of it. Both mirrors and carbon black are opaque. Opacity ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Membrane Potential
Membrane potential (also transmembrane potential or membrane voltage) is the difference in electric potential between the interior and the exterior of a biological cell. That is, there is a difference in the energy required for electric charges to move from the internal to exterior cellular environments and vice versa, as long as there is no acquisition of kinetic energy or the production of radiation. The concentration gradients of the charges directly determine this energy requirement. For the exterior of the cell, typical values of membrane potential, normally given in units of milli volts and denoted as mV, range from –80 mV to –40 mV. All animal cells are surrounded by a membrane composed of a lipid bilayer with proteins embedded in it. The membrane serves as both an insulator and a diffusion barrier to the movement of ions. Transmembrane proteins, also known as ion transporter or ion pump proteins, actively push ions across the membrane and establish concentration gradi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyanine
Cyanines, also referred to as tetramethylindo(di)-carbocyanines are a synthetic dye family belonging to the polymethine group. Although the name derives etymologically from terms for shades of blue, the cyanine family covers the electromagnetic spectrum from near IR to UV. Chemically, cyanines are a conjugated system between two nitrogen atoms; in each resonance structure, exactly one nitrogen atom is oxidized to an iminium. Typically, they form part of a nitrogenous heterocyclic system. The main application for cyanine dyes is in biological labeling. Nevertheless, there is a wide literature on both their synthesis and uses, and cyanines are common in some CD and DVD media. Structure Cyanines have been classified in many ways: * ''Streptocyanines'' or ''open chain cyanines'': : R2N+=CH H=CH'n''-NR2 (I) * ''Hemicyanines'': : Aryl=N+=CH H=CH'n''-NR2 (II) * ''Closed chain cyanines'': :Aryl=N+=CH H=CH'n''-N=Aryl (III) Additionally, these classes are recognized: * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polymethine
Polymethines are compounds made up from an ''odd'' number of methine groups (CH) bound together by alternating single and double bonds.Kachovski and Dekhtyar, ''Dyes and Pigments'', 22 (1983) 83-97. Compounds made up from an ''even'' number of methine groups are known as polyenes. Polymethine dyes Cyanines are synthetic dyes belonging to polymethine group. Anthocyanidins are natural plant pigments belonging to the group of the polymethine dyes. Polymethines are fluorescent dyes that may be attached to nucleic acid probes for different uses, ''e.g.'', to accurately count reticulocyte Reticulocytes are immature red blood cells (RBCs). In the process of erythropoiesis (red blood cell formation), reticulocytes develop and mature in the bone marrow and then circulatory system, circulate for about a day in the blood stream before ...s. References Alkenes {{alkene-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromophore
A chromophore is the part of a molecule responsible for its color. The color that is seen by our eyes is the one not absorbed by the reflecting object within a certain wavelength spectrum of visible light. The chromophore is a region in the molecule where the energy difference between two separate molecular orbitals falls within the range of the visible spectrum. Visible light that hits the chromophore can thus be absorbed by exciting an electron from its ground state into an excited state. In biological molecules that serve to capture or detect light energy, the chromophore is the moiety that causes a conformational change in the molecule when hit by light. Conjugated pi-bond system chromophores Just like how two adjacent p-orbitals in a molecule will form a pi-bond, three or more adjacent p-orbitals in a molecule can form a conjugated pi-system. In a conjugated pi-system, electrons are able to capture certain photons as the electrons resonate along a certain distance ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyanine Dyes
Cyanines, also referred to as tetramethylindo(di)-carbocyanines are a synthetic dye family belonging to the polymethine group. Although the name derives etymologically from terms for shades of blue, the cyanine family covers the electromagnetic spectrum from near IR to UV. Chemically, cyanines are a conjugated system between two nitrogen atoms; in each resonance structure, exactly one nitrogen atom is oxidized to an iminium. Typically, they form part of a nitrogenous heterocyclic system. The main application for cyanine dyes is in biological labeling. Nevertheless, there is a wide literature on both their synthesis and uses, and cyanines are common in some CD and DVD media. Structure Cyanines have been classified in many ways: * ''Streptocyanines'' or ''open chain cyanines'': : R2N+=CH H=CH'n''-NR2 (I) * ''Hemicyanines'': : Aryl=N+=CH H=CH'n''-NR2 (II) * ''Closed chain cyanines'': :Aryl=N+=CH H=CH'n''-N=Aryl (III) Additionally, these classes are recognized: * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benzoxazoles
Benzoxazole is an aromatic organic compound with a molecular formula C7H5NO, a benzene-fused oxazole ring structure, and an odor similar to pyridine. Although benzoxazole itself is of little practical value, many derivatives of benzoxazoles are commercially important. Being a heterocyclic compound, benzoxazole finds use in research as a starting material for the synthesis of larger, usually bioactive structures. Its aromaticity makes it relatively stable, although as a heterocycle, it has reactive sites which allow for functionalization. Occurrence and applications It is found within the chemical structures of pharmaceutical drugs such as flunoxaprofen and tafamidis. Benzoxazole derivatives are also of interest for optical brighteners in laundry detergents.E. Smulders, E. Sung "Laundry Detergents, 2. Ingredients and Products" in ''Ullmann's Encyclopedia of Industrial Chemistry'', Wiley-VCH, Weinheim, 2012. Benzoxazoles belong to the group of well-known antifungal agents with an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lactams
A lactam is a cyclic amide, formally derived from an amino alkanoic acid. The term is a portmanteau of the words ''lactone'' + ''amide''. Nomenclature Greek prefixes in alphabetical order indicate ring size: * α-Lactam (3-atom rings) * β-Lactam (4-atom rings) * γ-Lactam (5-atom rings) * δ-Lactam (6-atom rings) * ε-Lactam (7-atom rings) This ring-size nomenclature stems from the fact that a hydrolyzed α-Lactam leads to an α-amino acid and a β-Lactam to a β-amino acid, ''etc''. Synthesis General synthetic methods exist for the organic synthesis of lactams. Beckmann rearrangement Lactams form by the acid-catalyzed rearrangement of oximes in the Beckmann rearrangement. Schmidt reaction Lactams form from cyclic ketones and hydrazoic acid in the Schmidt reaction. Cyclization of amino acids Lactams can be formed from cyclisation of amino acids via the coupling between an amine and a carboxylic acid within the same molecule. Lactamization is most efficient in this wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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