A spin labeling study of calf thymus DNA

Area of Science:

• Biochemistry
• Molecular Biology
• Physical Chemistry

Background:

• Electron Spin Resonance (ESR) spectroscopy is a powerful tool for studying molecular dynamics.
• Spin labeling allows for the investigation of macromolecular structure and interactions.
• Understanding DNA structural transitions is crucial for various biological processes.

Purpose of the Study:

• To investigate the spin labeling of DNA using 2,2,6,6-Tetramethyl-4-(bis-ethyleneimino) triazinamino-piperidine-1-oxyl.
• To characterize the structural properties and stability of the spin-labeled DNA (SL-DNA).
• To determine the quantity of spin labels bound to DNA and their distribution.

Main Methods:

• Electron Spin Resonance (ESR) spectroscopy was employed to analyze the spin-labeled DNA.
• Heat denaturation and acid degradation were used to quantify the bound spin labels.
• Variable temperature ESR measurements were performed to determine structural transition temperatures.

Main Results:

• ESR spectra of SL-DNA showed a predominance of strongly immobilized spin labels.
• Microwave saturation characteristics differed significantly between immobilized and weakly immobilized components.
• The number of labels bound per 1000 nucleotides ranged from 4.0 to 12.6.
• The structural transition temperature of SL-DNA was approximately 63°C.
• Increased salt concentration led to a rise in the structural transition temperature.

Conclusions:

• The spin labeling method provides valuable information on DNA structure and dynamics.
• SL-DNA exhibits distinct structural properties and thermal stability.
• Salt concentration influences the thermal stability of SL-DNA.