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Raman spectroscopy of Z-form poly[d(A-T)].poly[d(A-T)]
J P Ridoux1, J Liquier, E Taillandier
1Laboratoire de Spectroscopie Biomoléculaire, UFR de Médecine Université Paris XIII, Bobigny, France.
Biochemistry
|May 17, 1988
Summary
Raman spectroscopy reveals that nickel ions induce a B-to-Z conformational change in double-stranded poly[d(A-T)] DNA. This transition, observed in high salt solutions, alters DNA helical structure and is characterized by specific spectral changes.
Area of Science:
- Molecular Biology
- Spectroscopy
- Biophysics
Background:
- DNA exists in various helical conformations, including the B-form and Z-form, which have distinct structural and functional properties.
- Poly(dA-dT) is a synthetic DNA polymer commonly used to study DNA structure and transitions.
- Raman spectroscopy is a powerful technique for analyzing molecular vibrations and elucidating structural details of biomolecules.
Purpose of the Study:
- To investigate the conformational transitions of double-stranded poly[d(A-T)] in solution using Raman spectroscopy.
- To characterize the Z-form spectrum of poly[d(A-T)] and compare it with known Z-form spectra of other DNA sequences.
- To elucidate the role of nickel ions in inducing the B-to-Z transition in poly[d(A-T)].
Main Methods:
- Raman spectroscopy was employed to analyze the helical structures of poly[d(A-T)] under varying ionic conditions.
- Spectra were recorded in sodium chloride solutions and upon addition of nickel ions at high salt concentrations.
- Comparative spectral analysis was performed with established Raman data for Z-form poly[d(G-C)], poly[d(A-C)].poly[d(G-T)], and specific DNA crystals.
Main Results:
- In sodium chloride solutions, poly[d(A-T)] exhibited spectra characteristic of the B-type (right-handed) conformation.
- Addition of nickel ions at high salt concentrations induced a Z-form Raman spectrum, indicating a transition to the left-handed Z-conformation.
- Detailed spectroscopic data revealed reorientation of purine-deoxyribose units, modifications in the phosphodiester backbone, and specific spectral shifts in adenosine regions.
Conclusions:
- Nickel ions play a crucial role in inducing the B-to-Z conformational transition in poly[d(A-T)] under specific ionic conditions.
- The observed spectral changes provide detailed insights into the structural alterations associated with the B-to-Z transition in this DNA sequence.
- This study contributes to understanding DNA conformational dynamics and the influence of metal ions on DNA structure.