Open AccessStabilization of the Z′ form of poly(dGdC):poly(dGdC) in solution by multivalent ions relates to the Z¶form in crystals
Author(s) -
Mark E. Harder,
W. Curtis Johnson
Publication year - 1990
Publication title -
nucleic acids research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 9.008
H-Index - 537
eISSN - 1362-4954
pISSN - 0305-1048
DOI - 10.1093/nar/18.8.2141
Subject(s) - polynucleotide , circular dichroism , crystallography , ion , stereochemistry , biology , chemistry , biochemistry , organic chemistry
Both multivalent ions and 85% ethanol are required to produce the original Z' form of poly(dGdC):poly(dGdC) in solution. When multivalent impurities are removed by dialysis against 0.5 M NaCl and 1 mM EDTA, the circular dichroism retains features of the standard Z form. Addition of Ca+2 nearly reverses this effect. Analysis by singular value decomposition of near-ultraviolet circular dichroism spectra collected during titrations of polynucleotide in 60% ethanol with multivalent ions reveal that, at concentrations below .5 per nucleotide, they stabilize Z'-like forms in a two-state equilibrium with the Z form. Differences among the Z' spectra produced by the different ions suggest that at least three families of Z' structures exist. Furthermore, comparison with crystal data indicates that the Z' form in solution is related to the ZII form in crystals.