An atomic mass unit (abbreviated amu) was a unit of atomic mass equal to 1/12 the mass of the most abundant isotope of carbon, carbon-12, which contains six protons, six neutrons, and six electrons.
In 2372, B'Elanna Torres ordered 0.57 amus of antiproton radiation be bled from the USS Voyager's warp core to treat Tom Paris, who had experienced hyper-evolution due to a warp 10 flight. (VOY: "Threshold")
Torres seems to use amu as a unit of radiation rather than mass, which conflicts with the 21st-century definition.
In 2374, Neelix attempted to beam 10,000 amus of protomatter from a class 1 nebula. However, the transporter beam ignited the protomatter. (VOY: "Mortal Coil")