Related Experiment Videos
Does DNA acid fixation produce left-handed Z structure?
H A Tajmir-Riahi1, J F Neault, M Naoui
1Centre de recherche en photobiophysique, Université du Québec à Trois-Rivère, Canada.
FEBS Letters
|August 14, 1995
Summary
Acetic acid alters calf-thymus DNA structure by protonating bases, causing G-C and A-T base pair unpairing and unstacking. This leads to non-B-DNA structures, including the Z-conformation, at acidic pH.
Area of Science:
- Biochemistry
- Molecular Biology
- Spectroscopy
Background:
- DNA's double helix structure is crucial for genetic information storage.
- Understanding DNA structural transitions under varying conditions is vital for molecular biology.
- Acid-induced DNA modifications can impact its biological functions.
Purpose of the Study:
- To investigate the effects of acetic acid on calf-thymus DNA structure.
- To correlate spectral changes with DNA base protonation and conformational transitions.
- To elucidate the formation of acid-DNA complexes and their structural consequences.
Main Methods:
- Fourier Transform Infrared (FTIR) difference spectroscopy was employed.
- Studies were conducted across a pH range of 7.3-2.5.
- Various acid/DNA phosphate molar ratios (r) were analyzed.
Main Results:
- Cytosine protonation and G-C base pair unpairing initiated at pH 4-3, completing by pH 2.5.
- A-T base pair protonation and unstacking also occurred between pH 4-3 and 2.5.
- G-C base pair protonation led to Hoogsteen-type H-bonding before disruption.
- Protonation induced non-B-DNA structures, including the left-handed Z-conformation.
Conclusions:
- Acetic acid induces significant structural changes in calf-thymus DNA at acidic pH.
- Base protonation, unpairing, and unstacking are key events in acid-DNA interactions.
- DNA can transition to non-B-DNA forms, such as the Z-conformation, under acidic conditions.