Agilent 6210 tof lc ms system

Unless otherwise noted, the materials were obtained from commercial suppliers and used without any purification. D₂O was obtained from Sigma-Aldrich. 2′,5′-Diacetyl-3′-deoxy-3′-xylobromoinosine 7 was synthesized as described in [18 ]. Recombinant E.coli PNP was obtained as described in [15 (link)].
Analytical HPLC was performed on the Waters system (Waters 1525, Waters 2489, Breeze 2), column Nova Pak C₁₈, 4.6 × 150 mm, 5 µm, flow rate 0.5 mL/min. Method (I): gradient H₂O → 25% MeOH/H₂O, 20 min. Method (II): gradient H₂O → 50% MeOH/H₂O, 10 min.
NMR spectra were recorded on Bruker Avance II 700 spectrometers (Bruker BioSpin, Rheinstetten, Germany) in DMSO-d6 at 30 °C. Chemical shifts in ppm (δ) were measured relative to the residual solvent signals as internal standards (2.50). Coupling constants (J) were measured in Hz.
Liquid chromatography-mass spectrometry was performed on an Agilent 6210 TOF LC/MS system (Agilent Technologies, Santa Clara, CA, USA).
UV spectra were recorded on Hitachi U-2900 spectrophotometer (Tokyo, Japan).

Ac-Gly-[Cys-Sec]-Gly-NH₂ tetrapeptide, mimicking the TrxR C-terminal redox-active site, was reduced by DTT prior to its addition to a reaction with 1.4 equivalents of EM23 for 30 min at room temperature. The reaction products were analyzed with an Agilent 6210 TOF LC/MS system (Agilent, Santa Clara, CA, USA) in positive ion mode.