Ponceau S (Acid Red 112) is an azo protein dye commonly used as a stain in spot blotting assays for protein quantification.

1. Use in Western Blot
1. Material preparation:
1) Ponceau S solution: generally prepared as a 0.1% solution, Ponceau S can be dissolved in water or 1% ethanol.
2) Transfer membrane: usually PVDF or nitrocellulose membrane, on which the protein in the sample is transferred.
3) Decontamination buffer (TBST or other suitable buffer): used to remove excess dye.
2. Steps:
1) Staining: Soak the transferred membrane in Ponceau S solution, usually staining for 5-10 minutes, until the protein band appears obvious red.
2) Washing: Wash the membrane with decontamination buffer to remove excess dye, usually washing several times until the background of the protein band is clearer.
3) Detection: Use a scanner or camera to shoot the stained membrane, observe the position and intensity of the protein band, and perform quantitative analysis.
2. Protein quantitative analysis
By comparing the intensity of standard protein bands (such as β-actin, GAPDH, etc.), a preliminary estimate of the protein concentration in unknown samples can be made.