title: A cytosine . cytosine base paired parallel DNA double helix with thymine . thymine bulges.
abstract: 500 MHz 1H NMR studies using 2D-NOESY indicate that the oligonucleotide d(CTCTCT) at low pH forms a parallel double helix with cytosine . cytosine base pairs and thymine . thymine bulges. This unusual structure may explain the hypersensitivity of S1 nuclease at low pH towards supercoiled plasmids containing d(CT)n inserts.
mesh_terms: D001482:Base Composition; D003201:Computers; D004247:DNA / Q000378:metabolism; D004278:DNA, Superhelical / Q000378:metabolism; D004720:Endonucleases / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D010957:Plasmids; D011089:Polydeoxyribonucleotides / Q000378:metabolism*; D015719:Single-Strand Specific DNA and RNA Endonucleases
chemical_list: D004278:DNA, Superhelical; D011089:Polydeoxyribonucleotides; C045717:poly d(C-T); D004247:DNA; D004720:Endonucleases; D015719:Single-Strand Specific DNA and RNA Endonucleases