Apple-green birefringence of Congo red stained preparations under polarized light is indicative of the presence of amyloid fibrils. Additionally, Congo red is used for the diagnostics of the Shigella flexneri serotype 2a, where the dye binds the bacterium's unique lipopolysaccharide structure.
What is congcongo red?
Congo red was first synthesized in 1883 by Paul Bottiger who was working then for the Friedrich Bayer Company in Elberfeld, Germany. He was looking for textile dyes that did not require a mordant step. The company was not interested in this bright red color, so he filed the patent under his name and sold it to the AGFA company of Berlin.
What is Congo red stain used for?
In biochemistry and histology, congo red is used to stain microscopic preparates, especially as a cytoplasm and erythrocyte stain. Apple-green birefringence of Congo red stained preparates under polarized light is indicative for the presence of amyloid fibrils.
Is collagen refractile after Congo red?
Nonspecific red staining by Congo red can be seen with collagen, fibrin, or other protein deposits; collagen can be refractile but not usually green ± Congo red In contrast to fibrillar collagen, amyloid fibrils are only birefringent after Congo red
What are the spectrophotometric properties of Congo red?
As suggested by its intense red color, congo red has important spectrophotometric properties. Indeed, its UV-visible absorption spectrum shows a characteristic, intense peak around 498 nm in aqueous solution, at low dye concentration. Congo red molar extinction coefficient is about 45000 [L]/ [mol]. [cm] in these conditions.
Is Congo red soluble in water?
It is an azo dye. Congo red is water-soluble, yielding a red colloidal solution; its solubility is greater in organic solvents. However, the use of Congo red has long been abandoned, primarily because of its carcinogenic properties.
Which type of dye is Congo red?
azo dyesIntroduced in 1884, Congo red belongs to a group of azo dyes derived from benzidine. Congo red was formerly used to dye cotton but has been superseded by dyes more resistant to light and to washing.
Is Congo red hydrophilic?
Mounted in this carbohydrate-containing, hydrophilic medium, the Congo red molecules are oriented parallel to the surface of the amyloid filaments and the sign is linear positive, corresponding to an additive character of topo-optical staining reactions.
What is the structure of Congo red?
C32H22N6Na2O6S2Congo red / Formula
Why is it called Congo red?
It's believed that the marketing people at AGFA (a Berlin-based company, remember) came up with the name Congo Red for their new sensational dye because, to Europeans in 1885, the Congo was seen as an exotic place, a land of mystery, and the name 'Congo' was currently on the tip of every tongue due to the world-famous ...
What is the principle of Congo red stain?
PRINCIPLE: Amyloid is homogeneous and eosinophilic, the deposits are extracellular and may become sufficiently large enough to cause damage to surrounding tissues. when stained with the Congo Red Stain the amyloid, with the aide of polarizing lenses, will birefringe an apple green color. under the microscope.
What are the physical properties of Congo red?
Congo Red PropertiesMelting point>360 °C (lit.)Colour Index22120colorRed BrownPH Range3(blue)-5.2(red)PH6.7 (10g/l, H2O, 20℃)17 more rows
Is Congo red toxic?
Congo Red is an azo dye, it is toxic to many organisms and is a suspected carcinogen and mutagen. To give it its full name it is the disodium salt of 3,3'-(1E,1'E)-biphenyl-4,4'-diylbis(diazene-2,1-diyl)bis(4-aminonaphthalene-1-sulfonate). It is a benzidine-based anionic disazo dye.
Why is Congo red blue?
Congo red is also used as a pH indicator. The color transition is between pH 3.0 and 5.0. Below a pH of 3.0 (very acidic solutions), the indicator is blue.
How do you dissolve Congo red?
Preparing the solutions for staining Congo Red powder dye solution (for staining acc. to the Highman method): 1% solution of Congo Red powder dye: • Dissolve 0.5 g of Congo Red dye in 50 ml of distilled/demi water. Add 50 mL of 100% ethanol. Filter before use.
Who discovered Congo red?
In 1922, Bennhold was the first to discover that CR can be used for identification of amyloids in organisms after injecting the dye into blood [14,134,135].
How do you use Congo red paper?
The Congo Red test paper is used to test narrow-range acidic solutions....Congo Red Test PaperRemove one Congo Red test paper from the vial, being careful not to touch the strip anywhere other than where you grasp it with your fingertips.Dip the strip into the solution to be tested for 1-2 seconds and remove.More items...
Is Congo red an azo dye?
Congo red is one of the best known and used azo dyes which has two azo bonds (-N=N-) chromophore in its molecular structure. Its structural stability makes it highly toxic and resistant to biodegradation.
What type of dye is Alizarin?
Alizarin is an example of anthraquinone dye. It gives red colour with aluminium and blue colour with barium. Anthraquinone is a yellow coloured crystalline solid.
What is Congo red used for in microbiology?
Congo red is a diazo textile dye that has been used to visualize the production of amyloid fibers for nearly a century. Microbiological applications were later developed, especially in identifying strains that produce amyloid appendages called curli and overexpressing polysaccharides in the biofilm matrix.
Is Congo red carcinogenic?
For instance, the diazo dye Congo red is known to be carcinogenic because of the presence of aromatic amine groups [9].
What is Congo red?
Congo red, first of the synthetic dyestuffs of the direct type, that is, not requiring application of a mordant ...
What is direct dye?
Direct dye, any of a class of coloured, water-soluble compounds that have an affinity for fibre and are taken up directly, such as the benzidine derivatives. Direct dyes are usually cheap and easily applied, and they can yield bright colours. Washfastness is poor but may be…
When was Congo red dye invented?
Introduced in 1884, Congo red belongs to a group of azo dyes derived from benzidine. Congo red was formerly used to dye cotton but has been superseded by dyes more resistant to light and to washing.
What is amyloid eosinophilic?
Amyloid is a homogeneous amorphous eosinophilic material that binds the dye Congo red, appearing orange-red by conventional light microscopy (Figure 1). Under polarized light microscopy, amyloid exhibits apple-green birefringence. AA amyloid loses its Congo red-associated birefringence after oxidation in permanganate solution, whereas AL amyloid retains this feature. Amyloid also stains with sulfated alcian blue. Electron microscopic examination of amyloid reveals a dominant (95%) fibrillar component (Figure 2), with distinct periodicity. A glycoprotein component, derived from soluble amyloid protein (SAP), is also present. More than 15 types of amyloid, which share common morphological features, are recognized. Immunohistochemical techniques to detect κ and λ light chains, amyloid-associated protein, or transthyretin (TTR) can be done to classify the fibril type. Negative stains for serum amyloid A (SAA) protein and TTR exclude AA-type and TTR-type amyloidosis, but stains for κ and λ chains are positive in only 60% of cases of AL amyloidosis.
What are the causes of amyloid deposits?
Amyloid deposits occur in a variety of conditions, such as familial amyloidosis, cerebral amyloid angiopathy, Alzheimer's disease, familial Creutzfeldt-Jakob disease, Gerstmann-Straussler-Scheinker disease, fatal familial insomnia, inclusion body myopathies, as well as Mediterranean fever and other familial diseases 8 ( Table 66-1 ).
What is the term for a variety of conditions characterized by deposits of Congo red –positive materials in tissue?
Amyloidosis refers to a variety of conditions characterized by deposits of Congo red –positive materials in tissue; these are recognized by their apple-green birefringence under polarized light.
What causes protein misfolding in amyloidosis?
Protein misfolding in amyloidosis develops in different ways; for example, a protein may have a propensity to have the abnormal conformation that becomes evident with aging, or when they are in higher concentrations, such as in β 2 microglobulin accumulation in uremics, or caused by the replacement of a single amino acid, as in the familial amyloidosis. Another mechanism is remodeling of protein precursors, as in the case of β amyloid precursor protein (APP) in Alzheimer's disease. These mechanisms can act independently or in association. Other factors could also contribute to this propensity. 8
What is a Congo red negative fibril?
These are two related yet distinct glomerular diseases characterized by deposition of Congo red–negative fibrils and characterized by a variety of light microscopic features and progressive clinical course. Fibrillary GN is defined as Congo red-negative fibrils < 30 nm in diameter, whereas immunotactoid GN is defined by glomerular deposition of hollow stacked microtubules > 30 nm in diameter. Both entities are relatively uncommon, accounting for less than 1% of native renal biopsies. Recurrence of these diseases is common after transplantation.
What is the diameter of collagen?
Figure 2. Transmission electron microscopic imaging comparing collagen (upper left) with a diameter of 20–100 nm to amyloid fibrils (lower right) with a mean diameter of 100 Å.
What is the best stain for starch?
Starches can be stained with Congo red or Nile blue/Nile red; in both these cases the staining mechanism is probably similar to that with lipids in that the stain prefers to be in a less polar environment. However, with Congo red there is probably also some hydrogen bonding. With both stains penetration of intact starch grains is poor and the stains can be used as a diagnosis of starch damage. Congo red is also a stain for amyloid deposits in animal tissues. Periodic acid Schiff staining is the established method for polysaccharides. The method is based on the cleaving of 1 : 2 glycol groups by periodic acid and the subsequent recolouring of sulphite decolorized magenta solution by the resultant aldehyde groups. Acridine orange can be used instead of Schiff's reagent as the final stain. Lectin-coupled dyes can stain specific sugar residues in fluorescent mode, alternatively lectin-coated colloidal gold can be used with the CLSM in reflectance rather than fluorescence mode.
How does Congo red stain?
For many years the rationale of the reaction was unknown but it has been shown that staining of amyloid by Congo red is through hydrogen bonding as opposed to the electrochemical bonds formed between the dye and most other tissue components. In aqueous solution Congo red stains many tissue components, although there is always a greater affinity for amyloid. In retrospect, many of the early modifications to Bennhold's aqueous method, e.g. using alkaline alcoholic solvents ( Highman 1946 ), or using competitive inhibition by salt solutions ( Puchtler et al 1964 ), had the effect of suppressing the electrochemical staining of other tissue components, enhancing hydrogen bonding, and so improving selectivity for amyloid. Experiments on purified extracts of amyloid show that the uptake is stoichiometric and can be used as a quantitative test for the fibrils ( Pras et al 1968 ).
What color is Congo red?
Congo red shows red-orange deposits under nonpolarized light; apple-green birefringence under polarized light required for specificity. –. Nonspecific red staining by Congo red can be seen with collagen, fibrin, or other protein deposits; collagen can be refractile but not usually green ± Congo red. –. In contrast to fibrillar collagen, amyloid ...
What size sections are needed for Congo red staining?
9 μm sections recommended for Congo red staining to maximize detection of small quantities of amyloid
What is the thioflavin T activated by?
Thioflavin T activated by blue light to emit yellow fluorescence; sensitive, not specific
What disease is present with nephrotic syndrome?
Patients present with nephrotic syndrome in both minimal change disease and amyloid
How much sodium hydroxide to add to 100 ml of stock solution?
To 100 ml of stock solution A add 1 ml of 1% aqueous sodium hydroxide and filter.
Is amyloid fibril birefringent?
In contrast to fibrillar collagen, amyloid fibrils are only birefringent after Congo red stain. –. Important to have simultaneous positive control. –. Rather than “apple-green” birefringence, some advocate the term “anomalous colors”. ○. Red without polarization (called “congophilia”) –.
Why is Congo red used in pulp?
However, the use of congo red in the cellulose industries ( cotton textile, wood pulp & paper) has long been abandoned, primarily because of its tendency to change color when touched by sweaty fingers, to run and because of its toxicity. Additional recommended knowledge.
When was Congo red invented?
Congo red was first synthesized in 1883 by Paul Bottiger who was working then for the Friedrich Bayer Company in Elberfeld, Germany. He was looking for textile dyes that did not require a mordant step. The company was not interested in this bright red color, so he filed the patent under his name and sold it to the AGFA company of Berlin. AGFA marketed the dye under the name "Congo red", a catchy name in Germany at the time of the 1884 Berlin West Africa Conference, an important event in the Colonisation of Africa. The dye was a major commercial success for AGFA. In the following years, for the same reasons, other dyes were marketed using the "Congo" name: Congo rubine, Congo corinth, brilliant Congo, Congo orange, Congo brown, and Congo blue.
Abstract
Magnesium aluminate nanoparticles were prepared by the sol–gel autocombustion method using mixture of alanine and urea as a fuel. The sample was characterized using XRD, FE-SEM, EDS, and IR spectroscopy. XRD analysis confirmed the formation of single-phase spinel compound with average particle size of 28 nm estimated from FE-SEM analysis.
1. Introduction
Magnesium aluminate MgAl 2 O 4 is an inorganic coordination polymer, which is involved into large number of experimental and theoretical studies. Materials based on magnesium aluminate have excellent mechanical, optical, and refractory properties, chemical resistance to aggressive environments.
2. Experimental
The sample of MgAl 2 O 4 was prepared via sol–gel auto-combustion technique used mixture of alanine and urea as a fuel. Mg (NO 3) 2 ·6H 2 O, Al (NO 3) 3 ·9H 2 O, C 3 H 7 NO 2 and CH 4 N 2 O were used as starting materials and stoichiometric ratios of metal nitrate/fuel mixtures were used.
4. Conclusions
The magnesium aluminate spinel NPs has been synthesized by autocombustion sol–gel method with urea and alanine as fuel and reducing agents. The NPs composition and crystallite sizes were analyzed using X-ray diffraction, field-emission scanning electron microscopy and IR-spectroscopy.
Acknowledgements
The authors are grateful to the Ministry of Education and Science of Ukraine (Projects Number 0118U000258 and 0117U002408) for their financial support. The TT thankful to Benedykt R.
