Figure 8. Labeling of the fragments DNA digested by tear lipocalin and the minor tear endonuclease. Kinetics of nicking plasmid DNA by nucleases, TL and minor endonuclease, were obtained as described under Methods. Aliquots were taken in different time intervals and supplemented with 2 U DNA-polymerase I for 5 min at room temperature. Heating at 70^◦C for 5 min terminated the reaction. The amount [α-³²P] DTP incorporated was calculated for each point time. Plasmid DNA digested by TL (A) or the minor endonuclease (B) were subjected to 3^’ (lanes 1, 3) or 5^’ (lanes 2, 4) end-labeling with (lanes 1, 2) or without (lanes 3, 4) pretreatment with alkaline phosphatase. Plasmid DNA was separated by 0.8% agarose gel electrophoresis and analyzed by autoradiography. The forms of plasmid DNA are indicated to the left of the panel: relaxed (r), linear (l).