Dual agilent jet stream electrospray ionization ajs esi

The averaged molar ratio of DFO/ATZ in the prepared DFO-ATZ was determined by LC-MS. The sample was loaded to an Agilent 6540 Q-TOF LC-MS system equipped with an Agilent 300 SB-C3 RRHD 1.8 μm LC column, 2.1 × 100 mm. The HPLC gradient was set to: 90% to 80% A [0.1% formic acid (Sigma-Aldrich, #399388) in water] from 0 – 4 min, 80% to 10% A from 4 – 5 min, and then 90% to 100% B [0.1% formic acid in acetonitrile (Sigma-Aldrich, #AX0156)] from 5 – 10 min. Dual Agilent Jet Stream Electrospray Ionization (AJS ESI) was used as the time-of-flight (TOF) MS ion source, and the sample was run at the positive polarity mode. Profile MS data was acquired for protein deconvolution data analysis using the Agilent MassHunter Qualitative Analysis with BioConfirmProteinDigest version B06.00. From the deconvolution results, peaks corresponding to unmodified ATZ and DFO-ATZ were manually integrated. The area of each peak was obtained for the calculation of DFO number per ATZ: N = R₀ × 0 + R₁ × 1 + R₂ × 2 + ⋯ + R_n × n. (N is the chelator number per ATZ; R₀, R₁, R₂ or R_n is the percentage of the peak area corresponding to DFO-ATZ with 0, 1, 2, or n of DFO chelator), respectively.