Fig. 5.

Free-energy landscape. Shown is an energy funnel in molecular conformation space. For this representation, the entropy is reflected in the width whereas the enthalpy is given by the depth. With the T-jump, nonequilibrium macromolecular conformations are populated above the initial, ordered state, and a search for this initial state follows across entropic barriers. Also displayed are pictorial snapshots for representative macromolecular conformations, including: a low-temperature one showing rigid helicity with segmental motions being suppressed, a softened one with segmental motions prevalent and less helicity, another one with the loss of helicity and interchain orientations near melting, and, eventually, the amorphous state of conformations (liquid-like phase) with random coils. (Inset) Simplified free-energy surfaces showing (Left) the effect of initial equilibrium temperature when a T-jump experiment is carried out, and (Right) the order/disorder two-state representation as the order parameter changes (see text).