Isoindoline-Based Nitroxides as Bioresistant Spin Labels for Protein Labeling via Cysteines and Alkyne Bearing Noncanonical Amino Acids.

Isoindoline-Based Nitroxides as Bioresistant Spin Labels for Protein Labeling via Cysteines and Alkyne Bearing Noncanonical Amino Acids. Chembiochem. 2019 Oct 28;: Authors: Braun TS, Widder P, Osswald U, Groß L, Williams L, Schmidt M, Helmle I, Summerer D, Drescher M Abstract Electron paramagnetic resonance (EPR) spectroscopy in combination with site-directed spin labeling (SDSL) is a powerful tool in protein structural research. Nitroxides are highly suitable spin labeling reagents, but suffer from limited stability in particular in cellular environment. Here, we present the synthesis of a maleimid- and an azide-modified tetraethyl-shielded isoindoline-based nitroxide (M- and Az-TEIO) for labeling of cysteines or the noncanonical amino acid para -ethynyl-l-phenylalanine ( p ENF). We demonstrate high stability of TEIO  site-specifically attached to the protein thioredoxin (TRX) towards reduction in prokaryotic and eukaryotic environments, and conduct double electron-electron resonance (DEER) measurements. We further generate a rotamer library for the new residue p ENF-Az-TEIO that affords a distance distribution that is in agreement with the measured distribution. PMID: 31657498 [PubMed - as supplied by publisher]
Source: Chembiochem - Category: Biochemistry Authors: Tags: Chembiochem Source Type: research