Names | |
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Preferred IUPAC name 4-{Bis[4-(dimethylamino)phenyl]methylidene}-N,N-dimethylcyclohexa-2,5-dien-1-iminium chloride | |
Other names
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Identifiers | |
3D model (JSmol) | |
3580948 | |
ChEBI | |
ChEMBL | |
ChemSpider | |
DrugBank | |
ECHA InfoCard | 100.008.140 |
EC Number |
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KEGG | |
MeSH | Gentian+violet |
PubChem CID | |
RTECS number |
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UNII |
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UN number | 3077 |
CompTox Dashboard (EPA) | |
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Properties | |
C25H30ClN3 | |
Molar mass | 407.99 g·mol−1 |
Melting point | 205 °C (401 °F; 478 K) |
4 g/L at 25 °C [1] | |
Pharmacology | |
D01AE02 ( WHO ) G01AX09 ( WHO ) | |
Hazards | |
GHS labelling: | |
Danger | |
H302, H318, H351, H410 | |
P273, P280, P305+P351+P338, P501 | |
Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 1.2 g/kg (oral, mice) 1.0 g/kg (oral, rats) [2] |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Crystal violet or gentian violet, also known as methyl violet 10B or hexamethyl pararosaniline chloride, is a triarylmethane dye used as a histological stain and in Gram's method of classifying bacteria. Crystal violet has antibacterial, antifungal, and anthelmintic (vermicide) properties and was formerly important as a topical antiseptic. The medical use of the dye has been largely superseded by more modern drugs, although it is still listed by the World Health Organization.
The name gentian violet was originally used for a mixture of methyl pararosaniline dyes (methyl violet), but is now often considered a synonym for crystal violet. The name refers to its colour, being like that of the petals of certain gentian flowers; it is not made from gentians or violets.
A number of possible routes can be used to prepare crystal violet. [3] [4] The original procedure developed by the German chemists Kern and Caro involved the reaction of dimethylaniline with phosgene to give 4,4′-bis(dimethylamino)benzophenone (Michler's ketone) as an intermediate. [5] This was then reacted with additional dimethylaniline in the presence of phosphorus oxychloride and hydrochloric acid. [6]
The dye can also be prepared by the condensation of formaldehyde and dimethylaniline to give a leuco dye: [3] [4] [7]
Second, this colourless compound is oxidized to the coloured cationic form (hereafter with oxygen, but a typical oxidizing agent is manganese dioxide, MnO2):
Crystal violet(pH indicator) | ||
below pH −1.0 | above pH 2.0 | |
−1.0 | ⇌ | 2.0 |
When dissolved in water, the dye has a blue-violet colour with an absorbance maximum at 590 nm and an extinction coefficient of 87,000 M−1 cm−1. [8] The colour of the dye depends on the acidity of the solution. At a pH of +1.0, the dye is green with absorption maxima at 420 nm and 620 nm, while in a strongly acidic solution (pH −1.0), the dye is yellow with an absorption maximum at 420 nm.[ citation needed ]
The different colours are a result of the different charged states of the dye molecule. In the yellow form, all three nitrogen atoms carry a positive charge, of which two are protonated, while the green colour corresponds to a form of the dye with two of the nitrogen atoms positively charged. At neutral pH, both extra protons are lost to the solution, leaving only one of the nitrogen atoms positive charged. The pKa for the loss of the two protons are approximately 1.15 and 1.8. [8]
In alkaline solutions, nucleophilic hydroxyl ions attack the electrophilic central carbon to produce the colourless triphenylmethanol or carbinol form of the dye.[ citation needed ] Some triphenylmethanol is also formed under very acidic conditions when the positive charges on the nitrogen atoms lead to an enhancement of the electrophilic character of the central carbon, which allows the nucleophilic attack by water molecules. This effect produces a slight fading of the yellow colour.[ citation needed ]
Crystal violet is used as a textile and paper dye, and is a component of navy blue and black inks for printing, ball-point pens, and inkjet printers. Historically, it was the most common dye used in early duplication machines, such as the mimeograph and the ditto machine. [9] It is sometimes used to colourize diverse products such as fertilizer, antifreeze, detergent, and leather.[ citation needed ] Marking blue, used to mark out pieces in metalworking, is composed of methylated spirits, shellac, and gentian violet. [10]
When conducting DNA gel electrophoresis, crystal violet can be used as a nontoxic DNA stain as an alternative to fluorescent, intercalating dyes such as ethidium bromide. Used in this manner, it may be either incorporated into the agarose gel or applied after the electrophoresis process is finished. Used at a 0.001% concentration and allowed to stain a gel after electrophoresis for 30 minutes, it can detect as little as 16 ng of DNA. Through use of a methyl orange counterstain and a more complex staining method, sensitivity can be improved further to 8 ng of DNA. [11] When crystal violet is used as an alternative to fluorescent stains, it is not necessary to use ultraviolet illumination; this has made crystal violet popular as a means of avoiding UV-induced DNA destruction when performing DNA cloning in vitro.[ citation needed ]
In biomedical research, crystal violet can be used to stain the nuclei of adherent cells. [12] In this application, crystal violet works as an intercalating dye and allows the quantification of DNA which is proportional to the number of cells.[ citation needed ]
The dye is used as a histological stain, particularly in Gram staining for classifying bacteria. [13]
In forensics, crystal violet was used to develop fingerprints. [14]
Crystal violet is also used as a tissue stain in the preparation of light microscopy sections. [15] In laboratory, solutions containing crystal violet and formalin are often used to simultaneously fix and stain cells grown in tissue culture to preserve them and make them easily visible, since most cells are colourless. It is also sometimes used as a cheap way to put identification markings on laboratory mice; since many strains of lab mice are albino, the purple colour stays on their fur for several weeks. [16]
Crystal violet can be used as an alternative to Coomassie brilliant blue (CBB) in staining of proteins separated by SDS-PAGE, reportedly showing a 5x improved sensitivity vs CBB. [17]
Gentian violet has antibacterial, antifungal, antihelminthic, antitrypanosomal, antiangiogenic, and antitumor properties. [18] [19] It is used medically for these properties, in particular for dentistry, and is also known as "pyoctanin" (or "pyoctanine"). [20] It is commonly used for:
In resource-limited settings, gentian violet is used to manage burn wounds, [21] inflammation of the umbilical cord stump (omphalitis) in the neonatal period, [22] oral candidiasis in HIV-infected patients [23] and mouth ulcers in children with measles. [24]
In body piercing, gentian violet is commonly used to mark the location for placing piercings, including surface piercings.[ citation needed ]
Because of its antimicrobial activity, it is used to treat ich in fish. However, it usually is illegal to use in fish intended for human consumption. [25]
Crystal violet is one of the components of methyl violet, a dye first synthesized by Charles Lauth in 1861. [26] From 1866, methyl violet was manufactured by the Saint-Denis-based firm of Poirrier et Chappat and marketed under the name "Violet de Paris". It was a mixture of the tetra-, penta- and hexamethylated pararosanilines. [27]
Crystal violet itself was first synthesized in 1883 by Alfred Kern (1850–1893) working in Basel at the firm of Bindschedler and Busch. [6] To optimize the difficult synthesis which used the highly toxic phosgene, Kern entered into a collaboration with the German chemist Heinrich Caro at BASF. [5] Kern also found that by starting with diethylaniline rather than dimethylaniline, he could synthesize the closely related violet dye now known as C.I. 42600 or C.I. Basic violet 4. [28]
The name "gentian violet" (or Gentianaviolett in German) is thought to have been introduced by the German pharmacist Georg Grübler, who in 1880 started a company in Leipzig that specialized in the sale of staining reagents for histology. [29] [30] The gentian violet stain marketed by Grübler probably contained a mixture of methylated pararosaniline dyes. [31] The stain proved popular and in 1884 was used by Hans Christian Gram to stain bacteria. He credited Paul Ehrlich for the aniline-gentian violet mixture. [32] Grübler's gentian violet was probably very similar, if not identical, to Lauth's methyl violet, which had been used as a stain by Victor André Cornil in 1875. [33]
Although the name gentian violet continued to be used for the histological stain, the name was not used in the dye and textile industries. [34] The composition of the stain was not defined and different suppliers used different mixtures. In 1922, the Biological Stain Commission appointed a committee chaired by Harold Conn to look into the suitability of the different commercial products. [29] In his book Biological Stains, Conn describes gentian violet as a "poorly defined mixture of violet rosanilins". [34]
The German ophthalmologist Jakob Stilling is credited with discovering the antiseptic properties of gentian violet. [35] He published a monograph in 1890 on the bactericidal effects of a solution that he christened "pyoktanin", which was probably a mixture of aniline dyes similar to gentian violet. [36] He set up a collaboration with E. Merck & Co. to market "Pyoktanin caeruleum" as an antiseptic. [37]
In 1902, Drigalski and Conradi found that although crystal violet inhibited the growth of many bacteria, it has little effect on Bacillus coli ( Escherichia coli ) and Bacillus typhi ( Salmonella typhi ), which are both gram-negative bacteria. [38] A much more detailed study of the effects of Grübler's gentian violet on different strains of bacteria was published by John Churchman in 1912. [39] He found that most gram-positive bacteria (tainted) were sensitive to the dye, while most gram-negative bacteria (not tainted) were not, and observed that the dye tended to act as a bacteriostatic agent rather than a bactericide.[ citation needed ]
One study in mice demonstrated dose-related carcinogenic potential at several different organ sites. [40] [41] The Food and Drug Administration in the US (FDA) has determined that gentian violet has not been shown by adequate scientific data to be safe for use in animal feed. Use of gentian violet in animal feed causes the feed to be adulterated and is a violation of the Federal Food, Drug, and Cosmetic Act in the US. On June 28, 2007, the FDA issued an "import alert" on farm raised seafood from China because unapproved antimicrobials, including gentian violet, had been consistently found in the products. The FDA report states:
"Like MG (malachite green), CV (crystal violet) is readily absorbed into fish tissue from water exposure and is reduced metabolically by fish to the leuco moiety, leucocrystal violet (LCV). Several studies by the National Toxicology Program reported the carcinogenic and mutagenic effects of crystal violet in rodents. The leuco form induces renal, hepatic and lung tumor in mice." [42] [43]
In 2019, Health Canada found medical devices that use gentian violet to be safe for use but recommended to stop using all drug products that contain gentian violet, including on animals, causing Canadian engineering schools to revisit the usage of this dye during orientation. [44] [45]
Agarose gel electrophoresis is a method of gel electrophoresis used in biochemistry, molecular biology, genetics, and clinical chemistry to separate a mixed population of macromolecules such as DNA or proteins in a matrix of agarose, one of the two main components of agar. The proteins may be separated by charge and/or size, and the DNA and RNA fragments by length. Biomolecules are separated by applying an electric field to move the charged molecules through an agarose matrix, and the biomolecules are separated by size in the agarose gel matrix.
Gram stain, is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria. It may also be used to diagnose a fungal infection. The name comes from the Danish bacteriologist Hans Christian Gram, who developed the technique in 1884.
Molecular biology is a branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions.
N,N-Dimethylaniline (DMA) is an organic chemical compound, a substituted derivative of aniline. It is a tertiary amine, featuring a dimethylamino group attached to a phenyl group. This oily liquid is colourless when pure, but commercial samples are often yellow. It is an important precursor to dyes such as crystal violet.
Gel electrophoresis of nucleic acids is an analytical technique to separate DNA or RNA fragments by size and reactivity. Nucleic acid molecules are placed on a gel, where an electric field induces the nucleic acids to migrate toward the positively charged anode. The molecules separate as they travel through the gel based on the each molecule's size and shape. Longer molecules move more slowly because they the gel resists their movement more forcefully than it resists shorter molecules. After some time, the electricity is turned off and the positions of the different molecules are analyzed.
Methylthioninium chloride, commonly called methylene blue, is a salt used as a dye and as a medication. As a medication, it is mainly used to treat methemoglobinemia by chemically reducing the ferric iron in hemoglobin to ferrous iron. Specifically, it is used to treat methemoglobin levels that are greater than 30% or in which there are symptoms despite oxygen therapy. It has previously been used for treating cyanide poisoning and urinary tract infections, but this use is no longer recommended.
Methyl violet is a family of organic compounds that are mainly used as dyes. Depending on the number of attached methyl groups, the color of the dye can be altered. Its main use is as a purple dye for textiles and to give deep violet colors in paint and ink. It is also used as a hydration indicator for silica gel. Methyl violet 10B is also known as crystal violet and has medical uses.
Staining is a technique used to enhance contrast in samples, generally at the microscopic level. Stains and dyes are frequently used in histology, in cytology, 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, cell populations, or organelles within individual cells.
Two-dimensional gel electrophoresis, abbreviated as 2-DE or 2-D electrophoresis, is a form of gel electrophoresis commonly used to analyze proteins. Mixtures of proteins are separated by two properties in two dimensions on 2D gels. 2-DE was first independently introduced by O'Farrell and Klose in 1975.
Protein electrophoresis is a method for analysing the proteins in a fluid or an extract. The electrophoresis may be performed with a small volume of sample in a number of alternative ways with or without a supporting medium, namely agarose or polyacrylamide. Variants of gel electrophoresis include SDS-PAGE, free-flow electrophoresis, electrofocusing, isotachophoresis, affinity electrophoresis, immunoelectrophoresis, counterelectrophoresis, and capillary electrophoresis. Each variant has many subtypes with individual advantages and limitations. Gel electrophoresis is often performed in combination with electroblotting or immunoblotting to give additional information about a specific protein.
Coomassie brilliant blue is the name of two similar triphenylmethane dyes that were developed for use in the textile industry but are now commonly used for staining proteins in analytical biochemistry. Coomassie brilliant blue G-250 differs from Coomassie brilliant blue R-250 by the addition of two methyl groups. The name "Coomassie" is a registered trademark of Imperial Chemical Industries.
Malachite green is an organic compound that is used as a dyestuff and controversially as an antimicrobial in aquaculture. Malachite green is traditionally used as a dye for materials such as silk, leather, and paper. Despite its name the dye is not prepared from the mineral malachite; the name just comes from the similarity of color.
Fuchsine (sometimes spelled fuchsin) or rosaniline hydrochloride is a magenta dye with chemical formula C20H19N3·HCl. There are other similar chemical formulations of products sold as fuchsine, and several dozen other synonyms of this molecule.
Nile blue is a stain used in biology and histology. It may be used with live or fixed cells, and imparts a blue colour to cell nuclei.
In pathology, silver staining is the use of silver to selectively alter the appearance of a target in microscopy of histological sections; in temperature gradient gel electrophoresis; and in polyacrylamide gels.
Pararosaniline, Basic Red 9, or C.I. 42500 is an organic compound with the formula [(H2NC6H4)3C]Cl. It is a magenta solid with a variety of uses as a dye. It is one of the four components of basic fuchsine. (The others are rosaniline, new fuchsine and magenta II.) It is structurally related to other triarylmethane dyes called methyl violets including crystal violet, which feature methyl groups on nitrogen.
Antimicrobials destroy bacteria, viruses, fungi, algae, and other microbes. The cells of bacteria (prokaryotes), such as salmonella, differ from those of higher-level organisms (eukaryotes), such as fish. Antibiotics are chemicals designed to either kill or inhibit the growth of pathogenic bacteria while exploiting the differences between prokaryotes and eukaryotes in order to make them relatively harmless in higher-level organisms. Antibiotics are constructed to act in one of three ways: by disrupting cell membranes of bacteria, by impeding DNA or protein synthesis, or by hampering the activity of certain enzymes unique to bacteria.
Methyl green is a cationic or positive charged stain related to Ethyl Green that has been used for staining DNA since the 19th century. It has been used for staining cell nuclei either as a part of the classical Unna-Pappenheim stain or as a nuclear counterstain ever since.
In recent years, its fluorescent properties, when bound to DNA, have positioned it as useful for far-red imaging of live cell nuclei. Fluorescent DNA staining is routinely used in cancer prognosis. Methyl green also emerges as an alternative stain for DNA in agarose gels, fluorometric assays, and flow cytometry. It has also been shown that it can be used as an exclusion viability stain for cells. Its interaction with DNA has been shown to be non-intercalating, in other words, not inserting itself into the DNA, but instead electrostatic with the DNA major groove. It is used in combination with pyronin in the methyl green–pyronin stain, which stains and differentiates DNA and RNA.
SDS-PAGE is a discontinuous electrophoretic system developed by Ulrich K. Laemmli which is commonly used as a method to separate proteins with molecular masses between 5 and 250 kDa. The combined use of sodium dodecyl sulfate and polyacrylamide gel eliminates the influence of structure and charge, and proteins are separated by differences in their size. At least up to 2012, the publication describing it was the most frequently cited paper by a single author, and the second most cited overall.
Methyl violet 6B is a violet triarylmethane dye from the group of cationic dyes and an essential component of C.I. Basic Violet 1. The compound is sometimes equated with methyl violet in the literature.
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