# 11.16. Proteins in aqueous solution fold to unique three-dimensional structures atambient conditions. However, they also have a first-order-like transition to astate of less-structured, floppy configurations that can be accomplished in anumber of ways. The most common is by increasing T past the folding tempera-ture at ambient pressure. They can also be unfolded by extreme compression,cooling, and expansion into the negative-pressure regime, at least in theoryFigure 11.8 gives a schematic of the "phase" behavior and these four mechanismsof unfolding.(a) For each mechanism, indicate the signs of the volume and entropy changesassociated with the folded-to-unfolded transition, namely AV VunfoldedVfolded and AS Sunfolded SfoldedFigure 11.8. Proteins can exist in folded andunfolded states depending on the pressure andtemperature. The gray line denotes the boundarybetween the two, called the folding curve. Theindicates ambient conditions.compressionfoldedheatcold-Tunfoldedexpansion/stretching (b) Explain why the cooling and stretching mechanisms might be difficultor impossible to realize in an experiment. Hint: what would happen if thesolution contained no proteins?

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This problem is (11.16) from a book  "Thermodynamics and Statistical Mechanics An Integrated Approach by M. Scott Shell"

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Step 1

(a) Proteins in aqueous solution become larger in the size due to accumulation of fluid therefore proteins in aqueous solution fold to unique three-dimensional structure at ambient conditions.

Proteins structure changes from structured to less structured, floppy configuration that can be accomplished in a number of ways.

Step 2

Folding and unfolding of protein is due to change in structure with change in temperature and pressure.

As the temperature is increased, protein becomes less viscous, therefore volume will increase.

In folded structure molecules are arranged so closely which results more viscous solution and volume is less than that of unfolded structure.

Therefore, change in volume associated with the folded to unfolded transition is positive which is shown below:

Step 3

Entropy is thermodynamic property which describes randomness of system. In case of folded structure molecules are well arranged while in case of unfolded structure molecules are randomly arranged. Therefore...

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