quaternary /kwot″əner′ē, kwətur″nərē/ [L, quattuor, four] , 1. adj., pertaining to a chemical compound in which four atoms or groups of elements are bonded to one atom, such as a quaternary ammonium compound in which four organic radicals are substituted for the four hydrogen molecules on an ammonium ion. 2. n., fourth-level structure in proteins, as in the structure of hemoglobin made up of two alpha-globulins and two beta-globulins.
