Ruthenium red
The inorganic dye ammoniated ruthenium oxychloride, also known as ruthenium red, is used in histology to stain aldehyde fixed mucopolysaccharides.
Ruthenium red has also been used as a pharmacological tool to study specific cellular mechanisms. Selectivity is a significant issue in such studies as RR is known to interact with many proteins. These include mammalian ion channels TRPP3, a plant ion channel, Ca2+-ATPase, mitochondrial Ca2+ uniporter, tubulin, myosin light-chain phosphatase, and Ca2+ binding proteins such as calmodulin. Ruthenium red displays nanomolar potency against several of its binding partners. For example, it is a potent inhibitor of intracellular calcium release by ryanodine receptors . As a TRPA1 blocker, it assists in reducing the airway inflammation caused by pepper spray.
RR has been used on plant material since 1890 for staining pectins, mucilages, and gums. RR is a stereoselective stain for pectic acid, insofar as the staining site occurs between each monomer unit and the next adjacent neighbor.
