DNA hydration studied by pressure perturbation scanning microcalorimetry

Area of Science:

• Biophysical Chemistry
• Structural Biology
• Thermodynamics

Background:

• Understanding DNA thermal transitions is crucial for molecular biology.
• Differential scanning calorimetry (DSC) is a key technique for studying biomolecular thermodynamics.
• The role of hydration water in DNA structural stability is an active area of research.

Purpose of the Study:

• To quantify temperature-induced volume changes in DNA duplexes with varying GC/AT content.
• To investigate the influence of hydration on DNA thermal expansion coefficients.
• To explore the thermodynamic properties of ordered water in DNA minor grooves.

Main Methods:

• Pressure perturbation differential scanning calorimetry (PPDSC) was employed.
• Thermal expansion coefficients and partial volumes of DNA duplexes were determined.
• Data were analyzed in relation to DNA sequence composition (GC/AT content).

Main Results:

• DNA duplex unfolding correlates with increased thermal expansion coefficients and partial volumes.
• AT-rich DNA dodecamers showed unusually large, temperature-induced partial volume changes.
• Ordered water molecules in the minor groove of AT-rich DNA were found to be denser than bulk water.

Conclusions:

• Hydration water in AT-rich DNA minor grooves significantly impacts thermal expansion.
• The observed ordered water exhibits properties similar to high-pressure ice, not normal ice.
• These findings provide insights into DNA hydration and its role in thermal stability.