Fig. 1. Melting curves of DNA 3WJs, L1L2L3 (circles) and S1S2S3 (squares), in the absence (white) and presence of Ni^II ions (black). [DNA strand] = 1.0 μM each, [EDTA] = 10 μM or [Ni^II] = 1.0 μM in 10 mM MOPS buffer (pH 7.0), 100 mM NaCl, 0.2 °C min^–1. All the samples were annealed before the measurements.