5.gif) |
The HD exchange rate (kex) ia obtained by 1st
order decay fitting of the intensity of time-dependent 15N-1H HSQC spectra.
This requires two-state folding process assumption [NOTE] |
| Euqilibrium HD Ecchange Experiment |
| Equilibrium HD exchange of amide protons with solvent is
a probe for local structural stability. Under EX2 conditions (kf
>> krc), the free energy for the opening reaction that leads
to exchange of individual protons can be obtained from the measured rates
of exchange (kex) and an estimate of the random-coil exchange
rate (krc): |
 G HD
= -RT ln (k ex/k rc) |
|
[NOTE]
|
| Two-State Folding
Process: |
- Nearly superimposable equilibrium denaturation
curves followed by fluorescence and CD;
- Single-exponential folding and unfolding kinetics;
- Agreement between kinetically and thermodynamically
determined deltaGU and m values.
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|
GHD values
at 295 K for amide protons in 0 M GdmCl (A) and 0.7 M GdmCl (B).
Solid lines at 4.67 kcal/mol (A) and 3.47 kcal/mol (B) indicate
the free energy of unfolding in D2O, GU
D2O.
S, strand; 310,310 helix.
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