Melting fine structure of DNA fragments of known base sequence from ΦX174


THERE is much experimental evidence of discrete unfolding of double-stranded DNA, revealed as fine structures in the melting profile (refs 1–4 and refs therein). Although this is believed to reflect aspects of the nature of the base sequence through the instability of AT and GC base pairs5, detailed quantitative analysis is hindered by factors such as the highly cooperative nature of double-helix stabilisation by base stacking and the long-range correlation of helical states through the entropy effect of the unfolded loop. Furthermore, the lack of appropriate nomenclature for the base sequence has complicated discussion. Fortunately, essentially the whole base sequence of the DNA of bacteriophage ΦX174 has been determined6, and we present here melting profiles of two fragments obtained from the replicative form by means of the restriction enzyme HapII, and examine them with reference to their base sequence.

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WADA, A., TACHIBANA, H., UENO, S. et al. Melting fine structure of DNA fragments of known base sequence from ΦX174. Nature 269, 352–353 (1977).

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