Living matter, at the molecular scale, is different from usual matter. Biological macromolecules deform without breaking, couple reactions to motion, perform tasks. Stretching a point, we may say that at the molecular scale, life is the coupling of chemical reactions to conformational motion.
We are interested in the essence of life (Indiana-Jones fashion), thus in this mechano-chemical coupling. We use nanomechanical and optical techniques to study, provoke, perturb, conformational changes of biological macromolecules (proteins, DNA).
Coming from the Physics of Complex Systems, we seek properties which display a degree of universality, rather than step by step descriptions of system specific processes (for an application of this philosophy in a rather different context see the project "Shape of Clouds"). Where it exists, such universality usually translates into a simple mathematical description.