Radial mechanical properties of deoxyribonucleic acid molecules

Given the small diameter of deoxyribonucleic acid (DNA), the difficulty in studying its radial mechanical properties laid in the challenge of applying a precise and controlled small force. In this work, the radial mechanical properties of DNA were measured in the AFM. DNA adhesion properties were analyzed through force-distance curves and adhesion images. The adhesion force values applied on DNA obtained from the force-distance curves were consistent with those obtained from the adhesion images. The Young's modulus of DNA was determined by collecting the data of indentation depth and the force applied on DNA and using the Hertz model for calculation. At the same compression speed, the Young's moduli increased with increasing forces, but exhibited a nonlinear growth. This reflected the complex stress-strain behavior of DNA. The impact of speeds on mechanical properties of DNA was explored. Higher speed resulted in greater Young's moduli and adhesion. This study not only deepens the understanding the mechanical properties of DNA, but also provides a strategy for investigating the mechanical properties of other thin and soft materials.