Temperature effect on poly(dA).poly(dT): molecular dynamics simulation studies of polymeric and oligomeric...

Area of Science:

• Biophysics
• Computational Biology
• Molecular Biology

Background:

• DNA unwinding and melting are crucial for biological processes like replication and transcription.
• Melting thermodynamics are vital for identifying promoter regions, but studies often focus on short DNA fragments.

Purpose of the Study:

• To investigate the melting thermodynamics and dynamic properties of homopolymeric poly(dA).poly(dT) using molecular dynamics (MD) simulations.
• To differentiate between the melting behavior of DNA oligonucleotides and their polymeric counterparts, eliminating end-effects.

Main Methods:

• MD simulations of poly(dA).poly(dT) oligomers and polymers at temperatures from 300 to 400 K.
• Analysis of dynamic properties including basepairing, stacking geometry, groove width, backbone conformation, and counterion distribution.
• Simulations designed to mimic infinite DNA length by mitigating end-effects.

Main Results:

• Oligomers displayed terminal fraying above 340 K, while polymers showed partial melting at elevated temperatures without complete denaturation.
• Increased temperature led to an increase in N-H···O hydrogen bonds and a decrease in C-H···O hydrogen bond frequencies.
• Counterion restructuring in the minor groove was observed as an initial step in duplex melting.

Conclusions:

• Polymeric DNA exhibits distinct melting behavior compared to short oligonucleotides, with partial melting occurring at higher temperatures.
• Temperature-dependent changes in hydrogen bonding and counterion distribution play significant roles in initiating DNA duplex melting.
• MD simulations provide valuable insights into the sequence-dependent melting thermodynamics of DNA relevant to biological functions.