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- Jan 29, 2015
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Hi guys! I'm just a little bit confused on how entropy relates to the solvation layer that forms during hydrophobic interactions in tertiary protein structures.
My textbook (and EK) say:
When water surrounds a hydrophobic molecule, the optimal arrangement of hydrogen bonds results in a highly structured shell, or solvation layer, of water around the molecule. The increased order of the water molecules in the solvation layer correlates with an unfavorable decrease in the entropy of the water. However, when nonpolar groups cluster together, the extent of the solvation layer decreases because each group no longer presents its entire surface to the solution. The result is a favorable increase in entropy.
That last bolded part is what's confusing me since this is what Kaplan's BC book is saying:
However, when a hydrophobic side chain is placed in aqueous solution, the water molecules in the solvation layer cannot form hydrogen bonds with the side chain. This forces the nearby water molecules to rearrange themselves into specific arrangements to maximize hydrogen bonding—which means a negative change in entropy, ΔS. Remember that negative changes in entropy represent increasing order (decreasing disorder) and thus are unfavorable.
So I'm just confused as to how entropy truly does affect the solvation layer since both of my prep sources are saying different things! Will it increase or decrease in hydrophobic interactions? Wondering if anybody could clear this up? Thanks ahead of time!! 🙂
My textbook (and EK) say:
When water surrounds a hydrophobic molecule, the optimal arrangement of hydrogen bonds results in a highly structured shell, or solvation layer, of water around the molecule. The increased order of the water molecules in the solvation layer correlates with an unfavorable decrease in the entropy of the water. However, when nonpolar groups cluster together, the extent of the solvation layer decreases because each group no longer presents its entire surface to the solution. The result is a favorable increase in entropy.
That last bolded part is what's confusing me since this is what Kaplan's BC book is saying:
However, when a hydrophobic side chain is placed in aqueous solution, the water molecules in the solvation layer cannot form hydrogen bonds with the side chain. This forces the nearby water molecules to rearrange themselves into specific arrangements to maximize hydrogen bonding—which means a negative change in entropy, ΔS. Remember that negative changes in entropy represent increasing order (decreasing disorder) and thus are unfavorable.
So I'm just confused as to how entropy truly does affect the solvation layer since both of my prep sources are saying different things! Will it increase or decrease in hydrophobic interactions? Wondering if anybody could clear this up? Thanks ahead of time!! 🙂