Mechanics of DNA: Sequence Dependent Elasticity

We have used constant force axial optical tweezers to understand the subtle effects of sequence variations on the mechanical properties of DNA. Using designed sequences of DNA with nearly identical curvatures, but varied AT content, we have shown the persistence length to be highly dependent on the elasticity of DNA. The persistence length varies by almost thirty percent between sequences containing 61% AT and 45% AT. The biological implications of this can be substantial, as the need to bend DNA is involved in a host of regulatory schemes, ranging from nucleosome positioning to the formation of protein-mediated repressor and enhancer loops.