Structural polymorphism of homopurine-homopyrimidine sequences at neutral pH.


Under superhelical strain and mildly acidic pH, polyd(GA).polyd(CT) sequences are known to adopt an H-y3 conformer of H-DNA. We studied the effects of the sequence length, metal ions, and pH on the structures formed by polyd(GA).polyd(CT) sequences in supercoiled plasmid DNA at bacterial superhelicity. The results from experiments that distinguish multiple… (More)