The inorganic dye ammoniated

ruthenium Ruthenium is a chemical element with the symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is inert to most other chemic ...

oxychloride, also known as ruthenium red, is used in

histology Histology, also known as microscopic anatomy or microanatomy, is the branch of biology which studies the microscopic anatomy of biological tissues. Histology is the microscopic counterpart to gross anatomy, which looks at larger structures vi ...

stain A stain is a discoloration that can be clearly distinguished from the surface, material, or medium it is found upon. They are caused by the chemical or physical interaction of two dissimilar materials. Accidental staining may make materials app ...

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group ...

fixed

mucopolysaccharides Glycosaminoglycans (GAGs) or mucopolysaccharides are long, linear polysaccharides consisting of repeating disaccharide units (i.e. two-sugar units). The repeating two-sugar unit consists of a uronic sugar and an amino sugar, except in the case ...

. Ruthenium red (RR) 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 ( CatSper1, TASK,

RyR1 Ryanodine receptor 1 (RYR-1) also known as skeletal muscle calcium release channel or skeletal muscle-type ryanodine receptor is one of a class of ryanodine receptors and a protein found primarily in skeletal muscle Skeletal muscles (commonly ...

RyR2 Ryanodine receptor 2 (RYR2) is one of a class of ryanodine receptors and a protein found primarily in cardiac muscle. In humans, it is encoded by the ''RYR2'' gene. In the process of cardiac calcium-induced calcium release, RYR2 is the major med ...

, RyR3, TRPM6,

TRPM8 Transient receptor potential cation channel subfamily M (melastatin) member 8 (TRPM8), also known as the cold and menthol receptor 1 (CMR1), is a protein that in humans is encoded by the ''TRPM8'' gene. The TRPM8 channel is the primary molecular ...

, TRPV1, TRPV2, TRPV3,

TRPV4 Transient receptor potential cation channel subfamily V member 4 is an ion channel protein that in humans is encoded by the ''TRPV4'' gene. The ''TRPV4'' gene encodes TRPV4, initially named "vanilloid-receptor related osmotically activated channe ...

TRPV5 Transient receptor potential cation channel subfamily V member 5 is a calcium channel protein that in humans is encoded by the ''TRPV5'' gene. Function The ''TRPV5'' gene is a member of the transient receptor family and the TRPV subfamily. T ...

, TRPV6,

TRPA1 Transient receptor potential cation channel, subfamily A, member 1, also known as transient receptor potential ankyrin 1, TRPA1, or The Wasabi Receptor, is a protein that in humans is encoded by the ''TRPA1'' (and in mice and rats by the ''Trpa1' ...

, mCa1, mCa2, CALHM1) TRPP3, a plant ion channel, Ca²⁺-ATPase, mitochondrial Ca²⁺ uniporter,

tubulin Tubulin in molecular biology can refer either to the tubulin protein superfamily of globular proteins, or one of the member proteins of that superfamily. α- and β-tubulins polymerize into microtubules, a major component of the eukaryotic cytosk ...

myosin light-chain phosphatase Myosin light-chain phosphatase, also called myosin phosphatase (EC 3.1.3.53; systematic name yosin-light-chainphosphate phosphohydrolase), is an enzyme (specifically a serine/threonine-specific protein phosphatase) that dephosphorylates the re ...

, and Ca²⁺ binding proteins such as

calmodulin Calmodulin (CaM) (an abbreviation for calcium-modulated protein) is a multifunctional intermediate calcium-binding messenger protein expressed in all eukaryotic cells. It is an intracellular target of the secondary messenger Ca2+, and the bi ...

. Ruthenium red displays nanomolar potency against several of its binding partners (e.g. TRPV4, ryanodine receptors,...). For example, it is a potent inhibitor of intracellular

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...

release by ryanodine receptors (Kd ~20 nM). As a TRPA1 blocker, it assists in reducing the airway inflammation caused by

pepper spray Pepper spray, oleoresin capsicum spray, OC spray, capsaicin spray, or capsicum spray is a lachrymatory agent (a compound that irritates the eyes to cause a burning sensation, pain, and temporary blindness) used in policing, riot control, ...

. RR has been used on plant material since 1890 for staining pectins,

mucilage Mucilage is a thick, gluey substance produced by nearly all plants and some microorganisms. These microorganisms include protists which use it for their locomotion. The direction of their movement is always opposite to that of the secretion of ...

s, and

gums The gums or gingiva (plural: ''gingivae'') consist of the mucosal tissue that lies over the mandible and maxilla inside the mouth. Gum health and disease can have an effect on general health. Structure The gums are part of the soft tissue l ...

. RR is a stereoselective stain for pectic acid, insofar as the staining site occurs between each monomer unit and the next adjacent neighbor.Mariani Colombo P, Rascio N. "Ruthenium red staining for electron microscopy of plant material". ''Journal of Ultrastructure Research'' Volume 60, Issue 2, August 1977, Pages 135–139

References

{{Transient receptor potential channel modulators Staining dyes Ruthenium complexes Ammine complexes