ABSTRACT
An important feature of proteins is their stable equilibrium conformations. A protein has a given native structure under given native conditions, and it has a given denatured structure under given denaturing conditions. That structure does not depend on the kinetic process by which the protein reached that state. So, a protein that was folded on a ribosome in a cell is in the same state as a protein that was refolded from an unfolded structure in a test tube, as long as it is under the same conditions. That means that protein properties can usually be expressed by equilibrium thermodynamics, without the need for pathway information. There are some exceptions, however. The structures of protein crystals or aggregates sometimes do depend on the initial conditions or how fast they were formed. Here, we explore some stable states of proteins and the forces that stabilize them.
