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Estimation of Peptide Helicity from Circular Dichroism Using the Ensemble Model
Uroš Zavrtanik1, Jurij Lah1, San Hadži1
1Department of Physical Chemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, 1000 Ljubljana, Slovenia.
The Journal of Physical Chemistry. B
|March 12, 2024
Summary
This study introduces a new ensemble-based analysis for peptide helicity using circular dichroism (CD), improving accuracy over the traditional linear model. The enhanced method provides a more realistic estimation of helix content and folding parameters.
Area of Science:
- Biophysical Chemistry
- Spectroscopy
- Computational Biology
Background:
- Quantifying peptide helix content traditionally uses circular dichroism (CD) with a linear spectroscopic model.
- This model applies an average helix-length correction, overlooking variations in helical segment lengths among peptide conformers.
Purpose of the Study:
- To evaluate the accuracy of the established linear model for peptide helicity quantitation.
- To introduce and validate a more physically realistic ensemble-based analysis for CD signal interpretation.
- To develop a computational tool for estimating peptide helicity using the ensemble model.
Main Methods:
- Assessed the validity of the linear spectroscopic model's average helix-length correction assumption.
- Developed and implemented an ensemble-based analysis assigning length corrections to individual conformers.
- Utilized CD data across a range of helicities to recalibrate baseline parameters and helix-coil parameters for an alanine-rich peptide.
Main Results:
- The linear model was found to underestimate peptide helicity, with discrepancies varying based on ensemble composition.
- The ensemble model successfully extracts more detailed information from experimental CD data.
- Quantities like nucleation constant and heat capacity change for helix folding were determined more accurately.
Conclusions:
- The ensemble-based treatment of CD signals offers a more physically realistic framework for analyzing peptide helix content.
- Recalibrated spectroscopic baseline parameters enhance the coherence of CD data analysis.
- This approach provides a robust method for determining various peptide folding parameters.
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