Note: this site last updated in 2006
An article from "The Molecules of HIV" (c) Dan Stowell
One kiloDalton (kD) is equal to approximately the weight of one thousand hydrogen atoms, and is equivalent to 1.66 x 10-21 grams. We use this unit to express the size of proteins.
I say approximately the weight of one thousand hydrogen atoms. In fact, to be more precise it's one-sixteenth of the weight of one thousand oxygen-16 atoms.
The Dalton was named after John Dalton, a pioneer in the development of an atomic theory of chemistry.