Related Experiment Videos
The denaturation of DNA
1Laboratoire de Génétique, Faculté des Sciences, Université Libre de Bruxelles, Rhode-St-Genèse, Belgium.
Gene
|December 15, 1993
Summary
Native DNA exhibits a lower ultraviolet absorption than expected, revealing a secondary structure. Mild treatments cause this structure to collapse, increasing DNA absorbance.
Area of Science:
- Biochemistry
- Molecular Biology
- Spectroscopy
Background:
- Nucleic acids have a characteristic UV absorption spectrum with a peak around 260 nm.
- Native DNA's UV spectrum is lower than predicted by its constituent nucleotides.
- This difference was observed in 1950 and is linked to DNA's structure.
Purpose of the Study:
- To investigate the cause of the reduced UV absorbance in native DNA.
- To understand the structural basis of DNA's spectral properties.
- To explore the phenomenon of hyperchromicity in DNA.
Main Methods:
- Ultraviolet (UV) absorption spectroscopy.
- Analysis of native and hydrolyzed DNA samples.
- Comparison of observed absorbance with calculated values from nucleotides.
Main Results:
- Native DNA shows significantly lower UV absorbance compared to its constituent nucleotides.
- Mild treatments (low pH, high temperature, low salt) increase DNA absorbance (hyperchromic effect).
- These treatments do not break phosphoester bonds or significantly alter molecular weight.
Conclusions:
- Native DNA possesses a secondary structure stabilized by nitrogen base interactions.
- DNA denaturation, triggered by mild conditions, involves the collapse of this secondary structure.
- The hyperchromic effect is a direct consequence of DNA secondary structure disruption.