Unified atomic mass unit
Orange Book Entry
This unit (u) is based on the standard that the mass of 12C is exactly 12 u. The older symbol, amu, using the standard based on the mass of 16O is no longer recommended. In biochemistry the term dalton, symbol Da, is sometimes used but is not here recommended.
Gold Book Entry
unified atomic mass unit
Non-SI unit of mass (equal to the atomic mass constant), defined as one twelfth of the mass of a carbon-12 atom in its ground state and used to express masses of atomic particles, u = 1.660 5402(10) x 10??????????????????????????27 kg.
Proposed New Entry
Non-SI unit of mass, defined as 1/12 of the mass of the carbon-12 atom in its ground state. The name unified atomic mass unit and its symbol u are not widely used in mass spectrometry, partly because of the clumsy name "unified atomic mass unit" which gets even worse when used with a SI prefix, e.g. "kilo unified atomic mass unit". Therefore it is recomendet to use the supplementary name Dalton. The Dalton is defined as
- 1 Da = 1 u = 1.660 5402(10) x 10??????????????????????????27 kg = 1/12 m(12C).
The dalton already is widely used in bio mass spec.
