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 a substrate, due to its peptide-like properties. After intravenous infusion, CU-2010 is quickly cleared as it has a half-life of about 20 minutes (in rats and dogs). Polymerization and covalent attachment of polymer chains of polyethylene glycol (PEG) or pegylation results in the formation of CU-2020, which has a longer half-life of 45 minutes. The advantage of the short half-life of CU-2010 is that it allows it to work in an “on-off” mode, hence being able to adapt to the haemostatic situation of the moment. CU-2010 and CU-2020 have the ability to inhibit plasmin to a similar extent as aprotinin,