UCLA Physics & Astronomy
A straight rod compressed along its axis buckles at a finite critical compression force (the Euler instability). What happens if the rod in question is a molecule of double stranded DNA ? I will describe measurements of the elastic energy of short (6 nm) DNA molecules in solution constrained into a sharply bent conformation. We find that the molecule develops a kink at a critical torque τc ≈ 27 pN × nm. This system is related in several ways to the Euler instability.