Congo Red (CAS 573-58-0)

Congo Red, with the CAS number 573-58-0, is a synthetic diazo dye that has historically been used extensively in the textile industry for dyeing cotton, but it has also carved a niche in scientific research, particularly in the study of protein aggregation. Structurally, Congo Red is known for its ability to bind selectively to beta-sheet structures in amyloid fibrils, a class of protein aggregates associated with various amyloid diseases. This binding is facilitated through hydrogen bonding and hydrophobic interactions between the dye and the amyloid fibril, resulting in a characteristic red to blue shift in the dye′s absorption spectrum, a phenomenon that can be observed under polarized light and is termed birefringence. This specific interaction makes Congo Red a valuable tool in histochemical techniques for staining amyloid deposits in tissue samples, allowing researchers to visually differentiate amyloid-containing regions from non-amyloid areas. Beyond this, Congo Red′s interaction with amyloid fibrils has been used in biophysical studies to investigate the kinetics and mechanisms of fibril formation and stability, providing insights into the pathophysiology of amyloid diseases.