Related Experiment Videos
Isotope effects in peptide group hydrogen exchange
G P Connelly1, Y Bai, M F Jeng
1Johnson Research Foundation, Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia 19104-6059.
Proteins
|September 1, 1993
Summary
Kinetic isotope effects in peptide hydrogen exchange are small due to non-bond-breaking pathways. Solvent isotope effects significantly influence reaction rates, with implications for protein studies.
Area of Science:
- Biophysical Chemistry
- Chemical Kinetics
- Isotope Effects
Background:
- Peptide hydrogen exchange is crucial for understanding protein dynamics.
- Kinetic and equilibrium isotope effects provide insights into reaction mechanisms.
Purpose of the Study:
- To evaluate kinetic and equilibrium isotope effects in peptide group hydrogen exchange.
- To establish reference rates for protein hydrogen exchange studies.
Main Methods:
- Investigated acid- and base-catalyzed hydrogen exchange reactions.
- Measured rate constants for NH, ND, and NT exchange in H2O and D2O.
- Utilized poly-DL-alanine as a model for random coil polypeptides.
Main Results:
- Small kinetic isotope effects observed due to non-bond-breaking exchange pathways.
- Solvent isotope effects significantly alter reaction rates (e.g., doubling in D2O).
- Base-catalyzed exchange rates decrease in the order NH > ND > NT.
- Small equilibrium isotope effects favor heavier isotope accumulation.
Conclusions:
- Peptide hydrogen exchange mechanisms are distinct from typical bond-breaking reactions.
- Solvent composition plays a critical role in modulating exchange rates.
- Established reference rates aid in interpreting protein hydrogen exchange data.