Cresol Red

Cresol red is a pH indicator and molecular weight marker for agarose gels. Unlike bromophenol blue and xylene cyanol, cresol red does not inhibit Taq polymerase in PCRs.

Agarose molecular weight marker

advantage: much less shadow on EtBr pictures unlike xylene cyanol and bromophenol blue

• molecular weight 404 g/mol
• in 1% agarose at ~1000 bp (between xylene cyanol 5000bp and bromophenol blue 500bp)
• in 3% agarose at >100bp (xylene cyanol 300bp)

pH indicator

• amber - acidic pH
• yellow - neutral
• red - alkaline

External links

• Wendy Chao's loading dye recipe and discussion
• Cresol Red solution calculator
• Cresol red at Pubchem
• Cresol Red sodium salt - Sigma catalogue
• Stains and Dyes Letter C of the Sigma Aldrich online catalogue showing different Cresol varieties
• Cresol Red at Wikipedia