Lesson Summary

This lesson explains the chemical mechanism behind PAS staining.

Learning Objectives

• Describe the oxidation reaction.
• Explain Schiff reagent chemistry.
• Understand the formation of the magenta reaction product.

Content

Step 1: Oxidation

Periodic acid oxidizes vicinal glycol groups into aldehydes.

Reaction:

Vicinal glycol
      ↓ Periodic Acid
Aldehyde groups

Step 2: Schiff Reaction

Schiff reagent reacts with aldehydes.

Result:

Aldehyde + Schiff Reagent
             ↓
Magenta Color

Counterstain

Hematoxylin stains nuclei blue.

Key Takeaway

PAS staining depends on oxidation of carbohydrates to aldehydes followed by reaction with Schiff reagent.