Received August 27, 1997
Experimental and theoretical studies of protein folding have led now to understanding some basic principles of this process. In the simplest case of two-state folding it starts from the formation of the folding nucleus which immediately grows up embracing the whole protein molecule. However, typically folding occurs through a compact intermediate which has some native-like features of its 3D-structure. It is possible that also in these cases the folding nucleus is involved in the transition state between unfolded chain and compact intermediate.
KEY WORDS: protein folding, nucleation--growth mechanism, intermediate states, molten globule, transition states