Is a folded protein's conformation subject to thermal fluctuations?

Question

In biology class we learn that proteins are folded, and that the shape the protein takes affects its bioactivity. Typically we don't go much further into protein shape from that, at least not at the level of biology I've taken. Now, my biophysicist friends who are working on protein folding tell me that their typical approach to that problem is a statistical mechanics one. I know that typically a statistical mechanical system fluctuates between its various microstates. This lead me to wonder if the conformation of a protein also oscillates around its equilibrium conformation.

Thanks and regards.

Answer 1

Yes folded proteins do fluctuate even in their native/folded state. They do not fluctuate like a polymer chain in good solvent for example but rather like atoms in a solid, where the concept of neighbours in 3 dimensions is well defined enabling one to give labels to the residues if needed.

For that reason people in the community call these states "ordered states" as opposed to another type of proteins called "intrinsically disordered proteins" which do not fold in bulk but need to interact with other biomolecules or substrates to fold into particular states.

Answer 2

Take an egg, crack it and pour it out on a hot pan. The proteins are subjected to heat and they change their conformational shape. The heat causes these proteins to thermally vibrate more violently until these vibrations are sufficient to push the proteins into a different shape. In general the cooking of meat does much the same.