Neptunium

DescriptionML300 is a selective non-covalent inhibitor of SARS-CoV 3CL protease (IC50 = 4.11 μM).1,2

OccurrenceAt one time, neptunium’s entire existence was synthesized by man. Sometime later, in themid-twentieth century, it was discovered that a very small amount is naturally produced inuranium ore through the actions of neutrons produced by the decay of uranium in the orepitchblende. Even so, a great deal more neptunium is artificially produced every year than everdid or does exist in nature. Neptunium is recovered as a by-product of the commercial productionof plutonium in nuclear reactors. It can also be synthesized by bombarding uranium-238with neutrons, resulting in the production of neptunium-239, an isotope of neptunium witha half-life of 2.3565 days.

HistoryNeptunium was first discovered in 1940 by Edwin Mattison McMillan and Philip Abelson during their research on nuclear fission. It is a decay product of uranium. When a uranium target is bombarded with slow neutrons, the target subsequently emits unusual beta rays, indicating the presence of a new isotope, thus generating its most famous isotope—neptunium-239.

UsesThe most important radioactive isotope of neptunium is Neptunium-237, with a half-lifeof 2.144×10+6years, or about 2.1 million years, and decays into protactinium-233 throughalpha decay. Neptunium’s most important use is in nuclear research and for instrumentsdesigned to detect neutrons.