if delta s is high which means positive high entropy, then when a drug binds to a protein why is it negative delta s?
When a drug binds to a protein, the overall change in entropy (ΔS) is typically negative, which seems contrary to the concept of high entropy associated with positive ΔS. However, it's important to understand the context of ΔS in these different scenarios.
In thermodynamics, entropy refers to the measure of the disorder or the number of possible microstates (arrangements) that a system can have. An increase in entropy (positive ΔS) suggests an increase in disorder or a larger number of possible arrangements.
When a drug binds to a protein, it forms a complex with specific interactions and structural changes, which can reduce the number of possible arrangements compared to the unbound state of both the drug and the protein. This reduction in the number of possibilities leads to a decrease in entropy (negative ΔS). Essentially, the binding process creates a more ordered and limited set of arrangements, decreasing the system's overall disorder.
To calculate the ΔS for a drug-protein binding process, one can consider the initial entropy of the unbound drug and protein, and compare it with the final entropy of the drug-protein complex. This negative ΔS represents the decrease in entropy as the system moves from a more disordered state (unbound) to a more ordered state (bound complex).
In summary, although a high entropy system is associated with positive ΔS, the binding of a drug to a protein typically involves a decrease in the number of possible arrangements, resulting in a negative ΔS.