[Spectral analysis of DNA solution treated with acid at various pH for different time].

The Raman spectra of DNA in acidic solution at pH 3.0, pH 2.0 and pH 1.0 after 1, 2, 12 and 24 h treatment were measured. The results showed that the protonation of DNA occurred and the Raman characteristic shift and intensity changed to different extent at various pH and after different time. At pH 3.0 there were weak bands of A-DNA and strong bands of B-DNA just after one hour acid treatment. The band of C-DNA appeared at the same time and showed a gradual enhancement. At pH 2.O0 the band of A-DNA disappeared. With increasing time, the band intensity of B-DNA became weaker and the C-DNA stronger. Approching to pH 1.0, the bands B-DNA and C-DNA almost disappeared, the new bands at 891, 1265 and 1418 cm(-1) appeared at the same time and the intensity of 891 and 1265 cm(-1) increased, but the intensity of 1418 cm(-1) became weaker. This fact indicated the formation of Z-DNA. The protonation of DNA proceeded gradually deeper from pH 3.0 to pH 1.0. Up to pH 1. 0, the conformation of original double helix was modified and changed.