Periodic acid–Schiff stain

Periodic acid–Schiff (PAS) is a <a href="/facts/Staining/jqGqWEE1">staining</a> method used to detect <a href="/facts/Polysaccharides/lqXq2cJU">polysaccharides</a> (such as <a href="/facts/Glycogen/kWa8fPFE">glycogen</a>) and mucosubstances (such as <a href="/facts/Glycoproteins/bKPzzW7m">glycoproteins</a>, <a href="/facts/Glycolipids/QUR36mXd">glycolipids</a> and mucins) in tissues. The reaction of <a href="/facts/Periodic_acid/DIucS68e">periodic acid</a> oxidizes <a href="/facts/Diol/pmaVtfKx">vicinal diols</a> in these <a href="/facts/Sugar/jb5KXRHT">sugars</a>, 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 <a href="/facts/Aldehyde/xSIRkW03">aldehydes</a> at the two free tips of each broken <a href="/facts/Monosaccharide/yzs2d6Eq">monosaccharide</a> ring. The oxidation condition has to be sufficiently regulated so as to not further oxidize the aldehydes. These aldehydes then react with the <a href="/facts/Schiff_reagent/k3UtSlBq">Schiff reagent</a> to give a purple-magenta color. A suitable basic stain is often used as a <a href="/facts/Counterstain/k4UBK1Iu">counterstain</a>.
<a href="/facts/PAS_diastase_stain/jJsBTp5w">• PAS diastase stain</a> (PAS-D) is PAS stain used in combination with <a href="/facts/Diastase/NY0EQvrK">diastase</a>, an <a href="/facts/Enzyme/DSI1Fh7y">enzyme</a> that breaks down glycogen.
• Alcian blue/periodic acid–Schiff (AB/PAS or AB-PAS) uses <a href="/facts/Alcian_blue_stain/qUlFzm21">alcian blue</a> before the PAS step.

Periodic acid–Schiff stain open-in-new

Periodic acid–Schiff stain