entropy question and how it relates to protein folding states

[Tus Ojitis]

Since systems move from a low number number of states (lower entropy) to a high number of states (higher entropy)- following the second law of thermodynamics. How does the protein folding move from a high number of potential folding configurations to its theoretical local state follow the second law of thermodynamics? If possible, please explaining using scientific terminology.

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[JustinM88]

Since systems move from a low number number of states (lower entropy) to a high number of states (higher entropy)- following the second law of thermodynamics. How does the protein folding move from a high number of potential folding configurations to its theoretical local state follow the second law of thermodynamics? If possible, please explaining using scientific terminology.

Still reading this pdf, but heres a little snippet so far:
"It is possible to observe chemical reactions that are associated with a decrease
in entropy. If that occurs, however, there must be an increase in entropy
elsewhere in the universe. In the case of protein folding as you will see, the
system refers to the protein itself, and the surroundings refers to the water
around it."


I could be wrong, but I think this is like that Biochem concept you prolly learned in undergrad where we add oil to water and it naturally makes 1 blob rather than multiple blobs due to the 2nd law of thermodynamics. Naturally, most students (including myself) see the multiple blobs of oil becoming 1 big blog and think "oh, we are going from disorder to order", BUT we have to be looking at the hydration shell (the water surrounding the hydrophobic stuff)(aka the 'Solvation Layer'). The hydration shell is "ordered water molecules", so ultimately we want to reduce the surface area of which allows for this ordered hydration shell like so (going from right to left in my drawing here):

 

[aldol16]

The second law states that the entropy of a system always increases. A protein is never found in isolation. The protein always has a solvation shell around it and that is included in the system. So yes, protein folding results in fewer conformational states of the protein, but it results in a far greater increase in conformational states for the water molecules in the solvation shell. In other words, in the extended form of the protein, water has to form a very ordered solvation layer around the protein to try to stabilize it. But when the protein is folded, all those water molecules are released back into high-entropy states. This more than compensates for the loss of protein entropy with folding.

 

[Zenabi90]

These are both great posts and answer the question thoroughly.

I would just like to reiterate that physics questions must always be looked at from both a micro and a macro standpoint. Object + system.

This is an important idea that transfers to medicine as well. Disease state + patient, patient + support system, etc.