chemistry

Periodic acid–Schiff stain

Periodic acid–Schiff stain is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Periodic acid–Schiff stain rather than just read about it. In short: Periodic acid–Schiff (PAS) is a staining method used to detect polysaccharides (such as glycogen) and mucosubstances (such as glycoproteins, glycolipids and mucins) in tissues. The reaction of periodic acid oxidizes vicinal diols in these sugars, usually breaking up the bond between two adjacent carbons not involved in the glycosidic linkage or ring closure in the ring of monosaccharide units that are part of the lo…

Key takeaways

Periodic acid–Schiff stain belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Periodic acid–Schiff stain to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Periodic acid–Schiff stain from memory before moving on to harder problems.

Reference excerpt

Periodic acid–Schiff (PAS) is a staining method used to detect polysaccharides (such as glycogen) and mucosubstances (such as glycoproteins, glycolipids and mucins) in tissues. The reaction of periodic acid oxidizes vicinal diols in these sugars, usually breaking up the bond between two adjacent carbons not involved in the glycosidic linkage or ring closure in the ring of monosaccharide units that are part of the long polysaccharides and creating a pair of aldehydes at the two free tips of each broken monosaccharide ring. The oxidation condition has to be sufficiently regulated so as to not further oxidize the aldehydes. 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.

Uses

PAS staining is mainly used for staining structures containing a high proportion of carbohydrate macromolecules (glycogen, glycoprotein, proteoglycans), typically found in e.g. connective tissues, mucus, the glycocalyx, and basal laminae. PAS staining can be used to assist in the diagnosis of several medical conditions:

Glycogen storage disease (versus other storage disorders). Adenocarcinomas, which often secrete neutral mucins. Paget disease of the breast. Alveolar soft part sarcoma. Staining macrophages in Whipple's disease. It can be used to diagnose α1-antitrypsin deficiency if periportal liver hepatocytes stain positive. Aggregates of PAS-positive lymphocytes are present in epidermis in Mycosis fungoides and Sézary syndrome, called Pautrier microabscesses. Ewing sarcoma Erythroleukemia, a leukemia of immature red blood cells. These cells stain a bright fuchsia. Pulmonary alveolar proteinosis. Fungal infection, the cell walls of fungi stain magenta; this only works on living fungi. In contrast, Grocott's methenamine silver stain (GMS) will stain both living and dead fungal organisms. It is used to identify glycogen in lung biopsy specimens of infants with pulmonary interstitial glycogenosis (PIG). It can be used to highlight super cross-linked lipids inclusions in ceroid lipofuscinosis (NCL). Presence of glycogen can be confirmed on a section of tissue by using diastase to digest the glycogen from a section, then comparing a diastase digested PAS section with a normal PAS section. The diastase negative slide will show a magenta staining where glycogen is present within a section of tissue. The slide that has been treated with diastase will lack any positive PAS staining in those locations on the slide PAS staining is also used for staining cellulose. One example would be looking for implanted medical devices composed of nonoxidized cellulose. If the PAS stain will be performed on tissue, the recommended fixative is 10% neutral-buffered formalin or Bouin solution. For blood smears, the recommended fixative is methanol. Glutaraldehyde is not recommended because free aldehyde groups may be available to react with the Schiff reagent, which may result in false positive staining.

Illustrations

Worked examples

Example 1 — a first encounter with Periodic acid–Schiff stain

Start with the simplest possible case. Write down what Periodic acid–Schiff stain claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Periodic acid–Schiff stain before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Periodic acid–Schiff stain ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Periodic acid–Schiff stain

In research: Periodic acid–Schiff stain appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Periodic acid–Schiff stain in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Periodic acid–Schiff stain is common in secondary-school and first-year university syllabi. It links to neighbouring topics Biochemistry detection methods, Carbohydrate methods, Staining dyes, so understanding it makes those chapters shorter.
In everyday life: Look for Periodic acid–Schiff stain outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Periodic acid–Schiff stain” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Periodic acid–Schiff stain in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Periodic acid–Schiff stain means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Periodic acid–Schiff stain out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Periodic acid–Schiff stain in simple terms?

Why does Periodic acid–Schiff stain matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Periodic acid–Schiff stain?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Periodic acid–Schiff stain.