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Formation of hybrid molecules from two alternating DNA copolymers

1962; Elsevier BV; Volume: 5; Issue: 2 Linguagem: Inglês

10.1016/s0022-2836(62)80083-7

1089-8638

Ross B. Inman, Robert L. Baldwin,

Nanopore and Nanochannel Transport Studies

Hybrid double helices can be formed from the alternating DNA copolymers dAT† and dABU¯ by slowly cooling a solution through the random coil-helix transition in high salt, where both polymers have nearly the same melting temperature. Very high concentrations are needed to form hybrids. This indicates that at low concentrations single strands fold back on themselves, by means of the alternating base sequence, instead of uniting with other strands. Formation of hybrid double helices rather than end-to-end aggregates is shown by the failure of sonic breakage to release dAT and dABU¯ from the hybrid and by the existence of a hybrid melting zone when the melting curve is measured in low salt, where the melting zones for dAT : dAT and dABU¯ : dABU¯ are sharp and separated by 9°C. The amount melting in the hybrid zone measures the number of hybrid base-pairs. As a test for hybrid double helices, melting curves are more reliable than density gradient analysis : it is possible to produce materials which sediment with a hybrid density but show no hybrid melting zone. Studies with hybrid molecules show that dAT and dABU¯ have considerable configurational mobility in the temperature zone preceding the optical density transition. Hybrid molecules also have been used to study strand disentanglement after melting. The results show that these are separate processes, melting being much more rapid, when the hybrids are melted in low salt, at relatively low temperatures.