pUC12-W1: a plasmid vector for the study of cloned DNA conformation.

pUC12-W1 is a new cloning vector for the study of torsion-induced structural transitions of insert DNA. It was derived from pUC12 by deleting three A + T-rich sequences which can undergo structural transitions when torsionally stressed. Transitions at these sites have low energy of activation and undefined structures. They complicate studies on transitions of DNA inserts by diverting torsional force and causing the vector to be undefined in helical and energetic terms. The new vector pUC12-W1, from which these segments have been deleted, will facilitate studies of torsion-induced structural transitions of insert DNA.