Side-Chain Protonation States of a Fluorescent Arginine.
J Org Chem
; 84(22): 14407-14413, 2019 11 15.
Article
in En
| MEDLINE
| ID: mdl-31608637
An arginine derivative with a fluorescent side-chain, Boc-Arg(Nap)-OH, was prepared by palladium(0)-catalyzed coupling of Boc-Arg-OH with a 4-bromonaphthalimide. The presence of the fluorophore lowers the pKa of the side-chain guanidinium group by several orders of magnitude, to 9.0 (±0.1), allowing the derivative to access an electrically neutral protonation state that is not generally available to arginine itself. Computational modeling (DFT) predicts that protonation takes place at the side-chain CâN atom that bears the fluorophore. Calculated electronic absorptions for the protonated (356 nm) and neutral species (440 nm) are in good agreement with experiment. When irradiated with light, excited-state proton transfer (ESPT) occurs from cationic side-chains to suitably basic solvents, resulting in fluorescence emission from the neutral species. Arg(Nap) can be incorporated into peptides with sterically accessible N-termini using specially adapted conditions of solid-phase peptide synthesis.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Type of study:
Prognostic_studies
Language:
En
Journal:
J Org Chem
Year:
2019
Document type:
Article
Affiliation country:
United States
Country of publication:
United States