MCB 124 mt 2 part 1, protien stability + 1st half of mutant portein stablility

importance of afinsen's egg white experiment
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importance of afinsen's egg white experiment
1.) proved 3-D structure is required for function
2.)protein sequence is all the information necessary to form its own structure
Why do proteins need to fold? (3 reasons)
1*. Orient chemical groups precisely
in 3-D => "activity"
2. Protect from degradation
3. Prevent aggregation
What is stability?
free energy change difference between the folded and unfolded proteins / (under the assumption that there are only two states and that the process is fully reversible
How do you measure Kf (amount of foldedness) of a protein?
Problem: is that at room temperature it is challenging to measure K accurately as its not the suitable temp from many proteins.

Solution: perturb the equilibrium to destabilize folded so that Kf can be measurable. Done using heat & denaturants.
thermal melting
method for determining Kf near Tm( where K=1), Then Extract Kf as a function of T
total heat capacity of F and U states with the environmental factor included
U- a. lower heat capacity from U structure, 10x (clatherate coating on hydrophobic residue increases heat capacity) = higher Heat capacity than F

F- higher heat capacity from F structure. Lowered heat capacity from "free" water due to no exposed hydrophobic residues.
generic change in heat capacity per residue,going F->U
-12.5cal/(mol*K)
▲G transfer=

▲G protein=
▲G transfer= ▲G for H2O molecules upon removing hydrophobic residues from the protein and burying it within the protein core.

▲G protein = ▲ G for protein molecules due to folding the protein within water
▲H transfer=

▲H protein=
▲H transfer =the difference in interactions of h20 molecules liquid water vs. clatherate water.

▲H protein= difference in intraprotein interactions.
at 20 °C Th=
areas where energy of clatherate=H20