Ultraviolet Resonance Raman Marker Bands of the Right to Left Helix Structure Transitions in DNA and Polynucleotide Model Compounds

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Abstract
The right to left helix structural transition in purine-pyrimidine alternating copolymers has been extensively studied by vibrational spectroscopies, amongst many other experimental approaches. Here, the use of resonance Raman spectroscopy in the ultraviolet region (223-, 257- and 281 nm excitation wavelengths) to monitor such structural changes is reviewed in the light of new results obtained on poly(dA-dC) · poly(dG-dT) on one hand, and the previous results obtained on poly(dG-dC)2, poly(dA-dT)2 and natural DNA (Chicken erythrocytes) on the other. It is now possible to define B → Z transition marker bands involving the proper bases, which show a similar behaviour on structural transition whatever the composition of alternating purine-pyrimidine sequences : the 1580 - and 1487 cm−1 lines of the purines, the 1486- and 1294 cm−1 lines of the pyrimidines are good markers in the vibrational spectra recorded at various UV excitation wavelengths.