Dalton (Da)

Dalton (Da) is a newer unit of mass taken as identical to u  (the unified atomic mass unit), but not accepted as standard nomenclature by the IUPAC or IUPAP. The dalton or u is equal in mass to 1/12 the mass of a ¹²C atom. Mass is often expressed by biologists as kilodaltons and abbreviated  kDa, and this unit sometimes appears as the label on the  x-axis of a mass spectrum. d