What does Congo Red staining do to the amyloid molecule?
What does Congo Red staining do to the amyloid molecule?
Staining with Congo Red dye (CR) is one of the major methods used to detect the amyloid structure of protein aggregates. However, a series of experiments have shown that CR staining is insufficient for confirmation of the amyloid nature of protein aggregates.
What does Congo Red test for?
Congo red is still the standard stain used in most histopathology laboratories to identify amyloid material in tissues. The identification of Congophilic amyloid material is challenging because of multiple interfering factors.
What does Congo Red bind to?
amyloid fibrils
The fact that Congo red binds to native, partially folded conformations and amyloid fibrils of several proteins shows that it must be used with caution as a diagnostic test for the presence of amyloid fibrils in vitro.
Is Congo Red an amyloid specific dye?
Congo red (CR) binding, monitored by characteristic yellow-green birefringence under crossed polarization has been used as a diagnostic test for the presence of amyloid in tissue sections for several decades. Our data suggest that Congo red is sandwiched between two protein molecules causing protein oligomerization.
Is Congo red acidic or basic?
Congo red is an acid-base indicator dye. In free solution the colour and absorption characteristics of Congo red depend not only on the pH but are also governed by the nature of the solvent environment.
Where is amyloid produced?
It most commonly happens when a protein made by your liver is abnormal. This protein is called transthyretin (TTR). Wild-type amyloidosis. This variety of amyloidosis occurs when the TTR protein made by the liver is normal but produces amyloid for unknown reasons.
How do you make Congo red dye?
Congo Red is synthesised by coupling bis-diazotised benzidine with two molecules of napthionic acid. The blue dye so obtained is converted into its red disodium salt during its salting out with sodium chloride (Fig.
What is the pH range of Congo red?
pH 5.0
Congo Red is an indicator dye that is blue-violet at pH 3.0 and red at pH 5.0.
Why is it called Congo red?
“Congo” red was introduced in Berlin in 1885 as the first of the economically lucrative direct textile dyes. Conclusions: The Congo red stain was named “Congo” for marketing purposes by a German textile dyestuff company in 1885, reflecting geopolitical current events of that time.
What kind of birefringence is in Congo red amyloid?
We studied 160 papers on Congo red–stained amyloid and found that virtually all reported just green birefringence or apple-green birefringence, even though only 31% of the illustrations showed a pure green color. 2. Discrepancies between descriptions and illustrations of colours in Congo red-stained amyloid, and explanation of discrepant colours.
What kind of birefringence does Congo red stain show?
Rather than showing ‘apple-green birefringence in polarized light’ as often reported, Congo red-stained amyloid, when examined between crossed polarizer and analyzer, should more accurately be said to show anomalous colors. Amyloid / metabolism* Birefringence
When was the birefringence of Congo red discovered?
Congo red was discovered to stain amyloid by accident in 1922, and Congo red-stained amyloid was shown to be birefringent on polarization microscopy in 1927. Colours, namely green and yellow, were reported under these conditions in 1945, although these are only two of various anomalous colours that may be seen, depending on the optical set-up.
Which is more sensitive Congo red or apple green?
Congo red, despite having lower sensitivity, is the standard agent used to identify amyloid in tissues. While the apple-green birefringence seen under crossed polarized light is specific for amyloid material, staining with Congo red is technically difficult resulting in inconsistent staining.