Kinetics and thermodynamics of oxidation mediated reaction in l-cysteine and its methyl and ethyl esters in dimethyl sulfoxide-d6 by NMR spectroscopy

Abstract

L-Cysteine (L-Cys), L-Cysteine methyl ester (L-CysME) or L-Cysteine ethyl ester (L-CysEE), when dissolved in dimethyl sulfoxide, undergoes an oxidation process. This process is slow enough and leads to nuclear magnetic resonance (NMR) spectral changes that could be monitored in real time. The oxidation mediated transition is modeled as a pseudo-first order kinetics and the thermodynamic parameters are estimated using the Eyring's formulation. L-Cysteine and their esters are often used as biological models due to the remarkable thiol group that can be found in different oxidation states. This oxidation mediated transition is due to the combination of thiol oxidation to a disulfide followed be solvent-induced effects may be relevant in designing cysteine-based molecular models.

Incorporation of Complexation into a Coamorphous System Dramatically Enhances Dissolution and Eliminates Gelation of Amorphous Lurasidone Hydrochloride

“…In comparison to crystalline LH, the 13 C NMR spectrum of its amorphous counterpart showed slight changes in chemical shifts with broadening lines because of the conformational distribution after amorphization (Figure d) . For crystalline CYS, chemical shifts of the carbon atoms in the carboxyl group (C1, Figure b), adjacent to the carboxyl group and the amino group (C2), and connected to sulfydryl (C3), were observed 171.01, 54.88, and 23.98 ppm, respectively (Figure b) . The physical mixture exhibited a spectrum with overlapping carbon signals of crystalline LH and CYS (Figure c).…”

“…42 For crystalline CYS, chemical shifts of the carbon atoms in the carboxyl group (C1, Figure 1b), adjacent to the carboxyl group and the amino group (C2), and connected to sulfydryl (C3), were observed 171.01, 54.88, and 23.98 ppm, respectively (Figure 5b). 43 The physical mixture exhibited a spectrum with overlapping carbon signals of crystalline LH and CYS (Figure 5c). Coamorphous LH−CYS displayed some shifted signals with significantly broadening lines, which is distinguishable from the physical mixture (Figure 5e).…”

Solubility Behavior and Polymorphism of l-Cysteine Methyl Ester Hydrochloride in 14 Pure and a Binary Ethanol and Dichloromethane Solvent Systems

“…These metal complexes could serve as models for structural motifs such as zinc fingers . In the field of biology, l -cysteine methyl ester was regularly used for proposing biological models due to the remarkable thiol group that can be found in different oxidation states . It also offers several advantages as a surface labeling reagent for glycosylated plasma membrane molecules .…”

Molecular Thermodynamics Using Nuclear Magnetic Resonance (NMR) Spectroscopy

“…The experimental details regarding the measurement of the kinetic parameters of the oxidation process have been described previously [24]. Figure 1 (panel a) shows the oxidation reaction in L-Cys ethyl ester (EE).…”

“…The experimental measurements are shown as symbols, and the non-linear least square fit to the respective experimental data are shown as dashed lines (samples temperatures are given in the legends). Figure reproduced with permission [24].…”