Chemical element chemical bonds, they form chemical compounds. Only a minority of elements are found uncombined as relatively pure minerals. Among the more common of such native elements are copper, silver, gold, carbon (as coal, graphite, or diamonds), and sulfur. All but a few of the most inert elements, such as noble gases and noble metals, are usually found on Earth in chemically combined form, as chemical compounds. While about 32 of the chemical elements occur on Earth in native uncombined forms, most of these occur as mixtures. For example, atmospheric air is primarily a mixture of nitrogen, oxygen, and argon, and
CU-2010 and CU-2020 CU-2010 and CU-2020 CU-2010 and CU-2020 are synthetic compounds that act as serine protease inhibitors. These were developed in 2010 to replace the use of aprotinin during and after cardiac surgery, including surgeries with cardiopulmonary bypass which cause blood loss and hemorrhagic complications. CU-2010 and CU-2020 were developed to avoid many issues associated with the use of aprotinin, including the risk of an allergic reaction and infection. Since the isolation of aprotinin is expensive, a drug with a simpler synthesis was desired. CU-2010 has a molecular weight of 700 Da and binds to the active site of serine proteases, like