High pressure Fourier transform infrared spectroscopy of poly(dA)poly(dT),poly(dA) and poly(dT)

The effect of hydrostatic pressure upon the DNA duplex, poly(dA)poly(dT), a nd its component single strands, poly(dA) and poly(dT) has been studied by fourier-transform infrared spectroscopy (FT-IR). The spectral data indicate that at 28 degrees C and pressures up to 12 kbar (1200 MPa) all three poly mers retain the B conformation. Pressure causes the band at 967 cm(-1), ari sing from water-deoxyribose interactions, to shift to higher frequencies, a result consistent with increased hydration at elevated pressures. A larger pressure-induced frequency shift in this band is observed in the single st randed polymers than in the double stranded molecule, suggesting that the e ffect of pressure on the hydration of single strands may be greater than up on a double stranded complex. A pressure-dependent hypochromicity in the ba nds attributed to base stacking indicates that pressure facilitates the bas e stacking in the three polymers, in agreement with previous assessments of the importance of stacking in the stabilization of DNA secondary structure at ambient and high pressures. (C) 1999 Elsevier Science B.V. All rights r eserved.