INTERACTIONS OF METAL IONS WITH POLYNUCLEOTIDES AND RELATED COMPOUNDS, V. THE UNWINDING AND REWINDING OF DNA STRANDS UNDER THE INFLUENCE OF COPPER (II) IONS

"Banks, C. V., and D. W. Klingman, Anal. Chim. Acta, 15, 356 (1956). 12 Similar MCD results have been obtained by J. G. Foss and M. E. McCarville [J. Am. Chem. Soc., 87, 228 (1965)] who also discuss the relation of MCD to Zeeman splitting (see also refs. 5c and 6a). The reversal in sign reported by Foss for praseodymium chloride is due to the fact that the authors have measured the magnetic field in the reverse manner to that usually employed (see, for instance, Partington, J. R., An Advanced Treatise on Physical Chemistry (London: Longmans, Green and Co., 1953), vol. 4, p. 593. Verdet constants of the rare earths in Corning glasses have been measured in the visible spectral range by Borrelli, N. F., J. Chem. Phys., 41, 3289 (1964). '3 Bunnenberg, E., C. Djerassi, K. Mislow, and A. Moscowitz, J. Am. Chem. Soc., 84, 2823 (1962). 14 Gray, H. B., and E. Billig, J. Am. Chem. Soc., 85, 2019 (1963). We are indebted to Prof. H. B. Gray (Columbia University) for the specimen.