title: Destabilization of the duplex and the high-salt Z-form of poly(dG-methyl5dC) by substitution of ethyl for the 5-methyl group.
abstract: The B-to-Z conformational transition of poly(dG-dC) is highly promoted by 5-methyl substitution of the dC moiety, i.e. in poly(dG-methyl5dC). By the synthesis of a new poly(dG-dC) analogue, poly(dG-ethyl5dC), the effect of a longer alkyl-chain substituent of dC on structure and conformation has been studied with ultraviolet absorption melting profiles and circular dichroism spectroscopy. The 5-ethyl substituent in poly(dG-ethyl5dC) destabilizes the duplex structure against thermal denaturation compared with both poly(dG-methyl5dC) and poly(dG-dC). C.d. studies also reveal that for the high-salt B-Z transition of poly(dG-ethyl5dC) a higher NaCl concentration is required than for that of poly(dG-methyl5dC), although much lower than for poly(dG-dC). However low-salt Z-DNA in poly(dG-ethyl5dC) shows unique features, e.g. it needs no divalent cations to be stable. The low-salt B-Z transition of poly(dG-ethyl5dC) can also be observed by the absorption-temperature melting profile, in contrast to both poly(dG-methyl5dC) and poly(dG-dC). The effects of MgCl2 concentration, temperature, acid pH and trifluorethanol on the conformation of poly(dG-ethyl5dC) have also been determined.
authors.affiliation: Central Research Institute for Chemistry, Hungarian Academy of Sciences, Budapest.
authors.forename: J
authors.initials: J
authors.lastname: Sági
authors.forename: A
authors.initials: A
authors.lastname: Szemzö
authors.forename: L
authors.initials: L
authors.lastname: Otvös
authors.forename: M
authors.initials: M
authors.lastname: Vorlícková
authors.forename: J
authors.initials: J
authors.lastname: Kypr
mesh_terms: D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D003853:Deoxyribonucleosides / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009690:Nucleic Acid Conformation; D011089:Polydeoxyribonucleotides / Q000737:chemistry; D012965:Sodium Chloride / Q000737:chemistry; D013696:Temperature; D014270:Trifluoroethanol / Q000737:chemistry
chemical_list: D003853:Deoxyribonucleosides; D011089:Polydeoxyribonucleotides; C062463:poly(deoxyguanosyl-5-ethyldeoxycytidine); C019530:poly(dC-dG); D012965:Sodium Chloride; C029988:poly(dG-m(5)dC).poly(dG-m(5)dC); D014270:Trifluoroethanol; D004247:DNA