Chapter 1 - DNA Molecules Mechanical Properties and Models

Abstract

In this chapter, we discuss effective deoxyribonucleic acid (DNA) elasticity models based on discrete statistical mechanics, atomistic, continuum, and transition approximation methods. We analyze their advantages and limitations in representing such a complicated structure as the double helix B-DNA molecule with a right-handed helix, and its transition to S-DNA without strands’ separation, and single-stranded DNA (ssDNA) with single strands separated forms. There also exist Z-DNA molecules with left-handed helix and A-DNA molecules with right-handed helix and a shorter pitch. At approximately 65 pN, the B form (double-stranded DNA – dsDNA) has a transition to S-DNA. The S-DNA picture is consistent with the observation of unpeeling during overstretching, unlike in the case of ssDNA. In 1953, Watson and Crick discovered the structure of the DNA double helix that opened the area of molecular biology. The double helix model not only provided proof of the structure of dsDNA, but also helped to reveal its replication mechanism in linear and nonlinear elasticity. In connection with this, we show the necessity to develop a more comprehensive explicit functional helicoidal model (EFHM) of DNA molecule, given that elasticity plays an important role in all functions of this molecule.