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Determination of the Gas-phase Acidities of Oligopeptides
Published on: June 24, 2013
Backbone conformational dependence of peptide acidity
Janet S Anderson1, Griselda Hernández, David M LeMaster
1Department of Chemistry, Union College, Schenectady, New York 12308, USA.
Biophysical Chemistry
|February 10, 2009
Summary
Protein surface electrostatics drive vast differences in amide hydrogen exchange rates. Neighboring peptide group orientation significantly impacts hydroxide-catalyzed exchange, explaining million-fold variations in peptides.
Area of Science:
- Biochemistry
- Chemical Physics
Background:
- Protein surface electrostatics create a billion-fold range in amide hydrogen exchange rates.
- This range matches the attenuation observed for buried amides, highlighting electrostatic influence.
Purpose of the Study:
- To investigate the impact of neighboring peptide group orientation on hydroxide-catalyzed hydrogen exchange rates.
- To analyze the acidities of various peptide conformers using continuum dielectric methods.
Main Methods:
- Continuum dielectric analysis was performed on Ala-Ala, Ala-Gly, Gly-Ala, and trans-Pro-Ala peptide conformers.
- Hydroxide-catalyzed hydrogen exchange rates were experimentally measured and theoretically predicted.
Main Results:
- Neighboring peptide group orientation accounts for a million-fold variation in exchange rates.
- An internal dielectric value of 3 was consistent for model peptides, suggesting rapid intermediate decay.
- Specific Ala-Ala conformers, despite low population, dominate the hydrogen exchange reaction.
Conclusions:
- Peptide conformation and electrostatic interactions are critical determinants of hydrogen exchange rates.
- Understanding these factors is key to interpreting hydrogen exchange data in proteins.
- The study accurately predicts experimental exchange rates despite significant conformer acidity variations.
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