Samarium is a chemical element; it has symbol Sm and atomic number 62. It is a moderately hard silvery metal that slowly oxidizes in air. Being a typical member of the lanthanide series, samarium usually has the oxidation state +3. Compounds of samarium(II) are also known, most notably the monoxide SmO, monochalcogenides SmS, SmSe and SmTe, as well as samarium(II) iodide. Discovered in 1879 by French chemist Paul-Émile Lecoq de Boisbaudran, samarium was named after the mineral samarskite from which it was isolated. The mineral itself was named after a Russian mine official, Colonel Vassili Samarsky-Bykhovets, who thus became the first person to have a chemical element named after him, albeit indirectly. Samarium is the 40th most abundant element in Earth's crust and more common than metals such as tin. It occurs in concentration up to 2.8% in several minerals including cerite, gadolinite, samarskite, monazite and bastnäsite, the last two being the most common commercial sources of the element. These minerals are mostly found in China, the United States, Brazil, India, Sri Lanka and Australia; China is by far the world leader in samarium mining and production. In biology, many times Samarium ions are used to replace Calcium within biological macromolecules, since both elements share similar coordination chemistry. This replacement allowed the scientists to solve structures and to understand the functions of Calcium ions as cofactors. Here you can see a good example of the replacement of Calcium by Samarium (magenta spheres) in the structure of mouse Netrin-1, as determined by X-ray crystallography (PDB code: 8SNP)

#molecularart ... #samarium ... #replacement ... #calcium ... #netrin ... #xray

Structure rendered with @proteinimaging and depicted with @corelphotopaint