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Multivalent ions are necessary for poly[d(AC) · d(GT)] to assume the Z form: A CD study
Author(s) -
RiazanceLawrences Jeannine H.,
Johnson W. Curtis
Publication year - 1992
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360320307
Subject(s) - chemistry , ion , biophysics , organic chemistry , biology
In previous work, it was shown that poly [d(AC) · d(GT)] could be forced into the Z form by strong dehydrating conditions, provided EDTA was not present. Presumably multivalent impurities were also necessary for the transition. In order to gain control over the B to Z transition for this DNA, we carefully removed all divalent contaminants from the sample and asked the obvious question: What ions are necessary for the transition under dehydrating conditions? We systematically investigated the effect of various multivalent ions. The common contaminants Ca 2+ , Mg 2+ , and Fe 3+ will not cause the transition, but Co 2+ and Ni 2+ facilitate the transition, undoubtedly because of their well‐known propensity to bind to purine N7. Since the transition also depends on the synergistic dehydrating action of sodium perchlorate and ethanol, we include CD spectra for the independent variations of these two factors. In addition, vacuum‐uv CD spectra for the A form and various B forms of poly [d (AC) · d (GT)] are presented for the first time.