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Updated: Jan 12, 2026
11:19
Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels
Published on: July 4, 2016
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Characterising Side Chain Conformations in Proteins Using 19F-ENDOR and New Fluorinated Amino Acid Spin Labels
Martyna Judd1,2, Elwy H Abdelkader3, Haocheng Qianzhu1
1Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|October 31, 2025
Summary
This study precisely locates protein side chain conformations using Fluorine-19 ENDOR (Electron Nuclear Double Resonance) spectroscopy. The method accurately determines side chain positions and conformational space in solution.
Area of Science:
- Biophysical Chemistry
- Structural Biology
- Spectroscopy
Background:
- Electron Nuclear Double Resonance (ENDOR) spectroscopy can measure distances between spin labels and labels in proteins.
- Previous studies demonstrated distance measurements > 20 Å using 19F-ENDOR at 94 GHz.
Purpose of the Study:
- To examine the precision of 19F-ENDOR for locating amino acid side chain positions in proteins.
- To determine the conformational space sampled by solvent-exposed protein chains using simulation tools.
- To demonstrate the utility of 19F-ENDOR constraints in pinpointing side chain conformations.
Main Methods:
- Incorporation of novel fluorinated phenylalanine amino acids into the metalloprotein Calbindin D9k binding Gd3+.
- Triangulation of 19F-ENDOR determined distances to identify side chain conformations.
- Utilizing splittings, lineshapes, and integrated intensities of 19F-ENDOR signals to constrain conformational space.
- Employing comprehensive rotamer simulations.
Main Results:
- Triangulation precisely identified the conformation of buried side chains, agreeing with crystal structure data.
- 19F-ENDOR constraints accurately pinpointed side chain conformations in proteins.
- The study successfully used differently fluorinated amino acids to refine conformational analysis.
Conclusions:
- 19F-ENDOR spectroscopy, combined with novel fluorinated amino acids, provides precise determination of protein side chain conformations.
- This method advances the ability to study protein dynamics and conformational landscapes in solution.
- The findings offer a powerful tool for structural biology and biophysical chemistry research.
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