A SODIUM-POTASSIUM SWITCH IN THE FORMATION OF 4-STRANDED G4-DNA

Single-stranded complex guanine-rich DNA sequences from chromosomal telomeres and else-where can associate to form stable parallel four-stranded structures termed G4-DNA by a process that is anomalously dependent on the particular alkali metal cation that is present. The anomaly, which is not found in the formation of G4-DNA by oligonucleotides containing short, single runs of three or more guanines, is caused by potassium cations excessively stabilizing fold-back intermedi-ate structures, or pathway by-products. © 1990 Nature Publishing Group.