A novel intramolecular G-quartet-containing fold of single-stranded d(GT)8 and d(GT)16 oligonucleotides

Human genome is shown to be enriched with (GT)n stretches of lengths from 8 to 20 dinucleotides. Low temperature (T ≤ 10 °C) conformations of d(GT)n oligonucleotides (n = 7, 8, 12, 16, 20) were studied by means of circular dichroism (CD), thermal melting, ethidium bromide (EtBr) probing and single nucleotide substitutions. Rotational relaxation times for EtBr:d(GT)n complexes confirmed a monomolecular state of the oligonucleotides. CD spectra indicated involvement of all guanines of d(GT)8 and d(GT)16 in G-quartets, while dT(GT)7, d(GT)12 and d(GT)20 were shown to be only partially ordered. The schemes of the d(GT)8 and d(GT)16 folds are suggested.