A temperature-dependent Z to B to single-strand transition in d(CGCG).
A thermally induced left- to right-handed helical interconversion for the self-complementary tetradeoxynucleotide d(CGCG) has been observed in the presence of NaCl at concentrations from 1.5 to 2.25M. Analysis of the Raman spectrum of d(CGCG) in aqueous solution as a function of temperature indicates that at low temperature a left-handed Z-helical form is the predominant species. An increase in temperature results in a decrease in the population of the left-handed form and an increase in the population of the right-handed form. Further elevation in temperature results in extensive disruption of base stacking and a loss of secondary structure. This unstacking presumably represents dissociation to a single-stranded structure. The data suggest that a temperature-dependent Z to B to single-strand transition occurs under the conditions employed. A direct Z to single-strand conversion was not identified. In contrast to previous examples, the thermally induced left- to right-handed helical conversion for d(CGCG) can occur in the absence of chemically modified nucleic acid bases, alcohol solutions, or divalent ions.
G A
GA
Thomas
W L
WL
Peticolas
D004277:DNA, Single-Stranded; D003841:Deoxycytidine; D003849:Deoxyguanosine; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D009838:Oligodeoxyribonucleotides; D012965:Sodium Chloride; D013059:Spectrum Analysis, Raman; D013696:Temperature; D014867:Water
D004277:DNA, Single-Stranded; D009838:Oligodeoxyribonucleotides; D014867:Water; D003841:Deoxycytidine; D012965:Sodium Chloride; D003849:Deoxyguanosine