In this paper we show that for a Grothendieck category A and a complex E in
C(A) there is an associated localization endofunctor l in D(A). This means
that l is idempotent tin a natural way) and that the objects that go to 0
by l are those of the smallest localizing (= triangulated and stable for co
products) subcategory of D(A) that contains E. As applications, we construc
t K-injective resolutions for complexes of objects of A and derive Brown re
presentability for D(A) from the known result for D(R-mod), where R is a ri
ng with unit.