Convert from grain to dalton

Unit Definition (grain)
The grain is a traditional unit of weight. The grain, equal to 1/480 troy ounce, or exactly 64.798 91 milligrams, was the legal foundation of traditional English weight systems, with various pounds being defined as a specified number of grains: 5760 grains in a troy pound and 7000 grains in an avoirdupois pound, for example. In the version of the troy system used by jewelers, there are 24 grains in a pennyweight and 20 pennyweight in an ounce. In the version used by apothecaries, there are 20 grains in a scruple, 3 scruples in a dram, and 8 drams in an ounce. Originally the grain was defined in England as the weight of a barleycorn. This made the English grain larger the corresponding grain units of France and other nations of the Continent, because those units were based on the weight of the smaller wheat grain.

Unit Definition (dalton)
The dalton is an alternate name for the unified atomic mass unit (u or amu). The dalton is often used in microbiology and biochemistry to state the masses of large organic molecules; these measurements are typically in kilodaltons (kDa). It seems necessary to have such a unit, since "kilo-amu" would be such a clumsy name. The SI accepts the dalton as an alternate name for the unified atomic mass unit and specifies Da as its proper symbol. The unit honors the English chemist John Dalton (1766-1844), who proposed the atomic theory of matter in 1803.