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These aldehydes then react with the Schiff reagent to give a purple-magenta color. A suitable basic stain is often used as a counterstain. • PAS diastase stain (PAS-D) is PAS stain used in combination with diastase, an enzyme that breaks down glycogen. • Alcian blue/periodic acid–Schiff (AB/PAS or AB-PAS) uses alcian blue before the PAS step.
Periodic acid (/ ˌ p ɜːr aɪ ˈ ɒ d ɪ k / per-eye-OD-ik) is the highest oxoacid of iodine, in which the iodine exists in oxidation state +7. It can exist in two forms: orthoperiodic acid, with the chemical formula H 5 IO 6 , and metaperiodic acid, which has the formula HIO 4 .
In organic chemistry, the Malaprade reaction or Malaprade oxidation is a glycol cleavage reaction in which a vicinal diol is oxidized by periodic acid or a periodate salt to give the corresponding carbonyl functional groups. [1] [2] The reaction was first reported by Léon Malaprade in 1928. [3] [4] Amino alcohols are also cleaved. [5]
Enzymatic hydrolysis has largely displaced acid-catalyzed hydrolysis reactions. [134] The result is glucose syrup (enzymatically with more than 90% glucose in the dry matter) [134] with an annual worldwide production volume of 20 million tonnes (as of 2011). [135] This is the reason for the former common name "starch sugar".
Iodine-based reagents such as periodic acid (HIO 4) and (diacetoxyiodo)benzene (PhI(OAc) 2) are commonly used. [3] Another reagent is lead tetraacetate (Pb(OAc) 4). [4] These I- and Pb-based methods are called the Malaprade reaction and Criegee oxidation, respectively. The former is favored for aqueous solutions, the latter for nonaqueous ...
The Criegee oxidation is a glycol cleavage reaction in which vicinal diols are oxidized to form ketones and aldehydes using lead tetraacetate. It is analogous to the use of periodate (Malaprade reaction) but uses a milder oxidant. This oxidation was discovered by Rudolf Criegee and coworkers and first reported in 1931 using ethylene glycol as ...
The structure of the fuchsin dye. The Schiff test is an early organic chemistry named reaction developed by Hugo Schiff, [1] and is a relatively general chemical test for detection of many organic aldehydes that has also found use in the staining of biological tissues. [2]
A chemical glycosylation reaction involves the coupling of a glycosyl donor, to a glycosyl acceptor forming a glycoside. [1] [2] [3] If both the donor and acceptor are sugars, then the product is an oligosaccharide. The reaction requires activation with a suitable activating reagent.