Abstract:

Recent structural investigations of triple helices by NMR, vibration spectroscopy and molecular modelling suggest that their conformation in solution contain sugars with more than one type of pucker. In this paper, the conformation of triple helices dA10•2dT10 and duplex dA10•dT10 have been investigated by near infrared Fourier transform Raman spectroscopy at excited wavelength 1064nm. In the case of triplex DNA, FT-Raman spectra obtained clearly reveal the existence of both C3’-endo/anti (A-type) and C2’-endo/ anti (B-type), moreover, a relatively intensive band at 823cm－1 suggests the existence of an intermediate conformation between C2’-endo/ anti and C3’-endo/anti sugar puckers. The analysis of the characteristic bands at around 1218cm-1 and 638cm-1 of thymine residues that are sensitive to sugar puckers gives evidences for the existence of a significant displacement from the C2’-endo conformer. In the case of duplex DNA dA10•dT10, FT-Raman spectra obtained show the existence of both A-like and B-like conformations in the solution.

Key words: Triplex , dA₁₀ 2DT₁₀, Fourier transform Raman spectra, Conformation