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Ultrafast surface hydration dynamics and expression of protein functionality: alpha -Chymotrypsin.
Samir Kumar Pal1, Jorge Peon, Ahmed H Zewail
1Laboratory for Molecular Sciences, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena 91125, USA.
Summary
Enzyme hydration dynamics at bovine pancreatic alpha-chymotrypsin differ between active and inactive states. Water mobility increases in the active state, impacting enzymatic function.
Area of Science:
- Biochemistry
- Physical Chemistry
- Enzymology
Background:
- Hydration dynamics are crucial for enzyme function.
- 1-anilinonaphthalene-8-sulfonate (ANS) probes protein surface hydration.
- Bovine pancreatic alpha-chymotrypsin exhibits distinct active and inactive states.
Purpose of the Study:
- Investigate hydration dynamics at the surface of bovine pancreatic alpha-chymotrypsin.
- Compare water molecule mobility at the enzyme's binding site in inactive (pH 3.6) and active (pH 6.7) states.
- Correlate hydration dynamics with enzymatic activity.
Main Methods:
- Femtosecond time-resolved spectroscopy using 1-anilinonaphthalene-8-sulfonate (ANS) as a fluorescent probe.
- X-ray crystallography to confirm probe binding site and protein structure.
- Analysis of hydration correlation function C(t) decay at different pH values.
Main Results:
- Hydration dynamics at the active site differ significantly between pH 3.6 and pH 6.7.
- Inactive state (pH 3.6): Ultrafast decay component with a dominant slow decay (tau = 43 ps).
- Active state (pH 6.7): Dominant ultrafast decay (90%) with a faster slow component (tau = 28 ps).
Conclusions:
- Water molecules in the hydration layer are more mobile in the active enzyme state.
- Water molecules are more rigidly structured in the inactive enzyme state.
- Altered hydration dynamics correlate with enzymatic function and substrate binding.