DNA Volume 4, Number 2, 1985 Mary Ann Liebert, Inc., Publishers ... JM83 (Vieira and Messing, 1982), (ii) recombinant pBR322 derivatives (de Boer et al., 1983; Hui et al., 1984) from E ... For alkali denaturation, 2 p% of supercoiled DNA is dis- solved in 20 pi of 0.2 M NaOH, 0.2 ...