Mechanistic insights into pulsed electric field-induced oxidative degradation of arginine and glutamic acid: Combined experimental characterization and DFT computation

Pulsed electric field accelerated oxidation of arginine and glutamic acid. • Arginine had higher susceptibility to electric field due to its charged guanidino. • Density functional theory revealed electric field-altered oxidation pathways. • Electric field reduced energy barriers of β-cleavage through electronic polarization. Pulsed electric field (PEF) processing promoted oxidation of charged residues of proteins, while its mechanism remained vague. In this study, polarization and oxidation of arginine (Arg) and glutamic acid (Glu) induced by PEF treatment (5–20 kV/cm for 4 h) was investigated through experimental characterization and density functional theory (DFT) computation. The results demonstrated that PEF treatment restrained the vibrational dipole moment of N H and C O within Arg and Glu side-chain, respectively. In Arg, H 4 -H 6 signals shifted to a lower magnetic field with pronounced broadening, while C 1 , C 4 , C 5 , and C 7 shifted to a higher magnetic field accompanied by the appearance of C=N-related resonances. In contrast, Glu's carbon skeleton shifted slightly to a lower magnetic field without structural conversion. Furthermore, residues were oxidatively degraded with electric field intensity extended, accompanied by impaired positive of Arg and negative charge of Glu. DFT revealed strong polarization of electron distribution within molecular framework, where 0.017 a.u. treatment partially detached the electrons from backbone of carbon-centered radicals. Thermodynamic calculations verified that electric-field alignment with molecular dipoles markedly reduced the energy barrier of β-cleavage, yielding distinct volatile profiles characterized by multi-site cleavage and N-heterocycle in Arg, and predominant aldehydes and acids in Glu. These findings clarified electric field-induced oxidation pathways and provided the theoretical guidance of PEF processing for improved quality stability. Download: Download high-res image (151KB) Download: Download full-size image