CD in Analyzing Peptide Secondary Structure

Circular Dichroism, CD, spectroscopy is a powerful technique used to analyze the secondary structure of peptides. By measuring the differential absorption of left- and right-circularly polarized light, CD provides valuable insights into the folding and conformation of peptides, particularly the presence of alpha-helices, beta-sheets, and random coils.

Principles of CD Spectroscopy

Peptides absorb circularly polarized light differently depending on their secondary structure. Alpha-helices typically produce a strong negative peak at 222 nm and a positive peak at 190 nm, while beta-sheets show a positive peak around 195 nm and a negative peak near 217 nm. Random coils exhibit a more neutral CD spectrum with less defined peaks. By comparing the CD spectrum of a peptide to known reference spectra, researchers can estimate the proportions of these structural elements in the peptide.¹

Applications in Peptide Research

CD spectroscopy is widely used in the study of peptide folding and protein-peptide interactions. For example, CD can be used to monitor the conformational changes of peptides in response to different environmental conditions, such as changes in pH, temperature, or the presence of binding partners. CD is also applied in the assessment of peptide stability and the analysis of folding kinetics, helping researchers understand how peptides adopt their functional structures.²

Conclusion

CD spectroscopy is an essential tool for the analysis of peptide secondary structure. Its ability to detect subtle changes in peptide conformation makes it invaluable in the study of peptide folding, stability, and interactions, providing critical insights into the structure-function relationships of peptides.

Citations and Links

1. Greenfield, Norman J. “Using Circular Dichroism Spectra to Estimate Protein Secondary Structure.” Nature Protocols, vol. 1, no. 6, 2006, pp. 2876–2890. doi:10.1038/nprot.2006.202.

2. Kelly, Sarah M., et al. “How to Study Proteins by Circular Dichroism.” Biochimica et Biophysica Acta (BBA) – Proteins and Proteomics, vol. 1751, no. 2, 2005, pp. 119–139. doi:10.1016/j.bbapap.2005.06.005.