Sensitivity of Projections of Backbone 13 C α / 15 N Chemical Shielding Along Covalent Bonds to Protein Secondary Structure—An Ab Initio Study
Year: 2025
Type: article
Abstract: ABSTRACT Statistical analysis of backbone 13 C α and 15 N chemical shielding tensors (CST) computed using the DFT‐GIAO method is presented for 40 alanine residues located centrally in three‐residue segments extracted from α‐helical and β‐sheet regions of 12 proteins with high‐resolution crystal structures. Our results show that the projections of 13 C α shielding along the three covalent bond directions, C α –C β , C α –H α , and C α –N, exhibit significantly higher sensitivity to secondary structure than the principal components. The increased sensitivity is due to the changes in the orientation of 13 C α CST in the molecular frame of the two secondary structures. Similarly, the projections of backbone amide 15 N shielding along the covalent bonds N–H, N–C α and along the normal direction to the peptide plane have a reasonably higher sensitivity to the secondary structure than the principal components. Unlike 13 C α nuclei, the orientation of amide 15 N CST in the molecular frame is found to be invariant in the two secondary structures. The calculated amide 15 N chemical shielding anisotropies (CSA) are larger in helix than in sheet structure, consistent with the experimental 15 N chemical shift studies reported in the literature. Furthermore, two‐dimensional correlation plots of backbone 13 C α and 15 N CSA parameters show a clear distinction between the two major secondary structure elements.
Source: Magnetic Resonance in Chemistry
DOI: 10.1002/mrc.5533
Authors: Shaniya Sunny, Sivakumar Paramasivam
Institution: SRM Institute of Science and Technology
Language: English
Subfield: Spectroscopy
Field: Chemistry
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W4410522944