Maxis q tof

UV and IR spectra were measured on an UV-2401PC spectrometer (Shimadzu, Beijing, China) and IR Affinity-1 spectrometer (Shimadzu, Beijing, China), respectively. Optical rotations were performed on a Perkine Elmer 341 polarimeter, and CD spectra were measured with a chirascan circular dichroism spectrometer (Applied Photophysics, Surrey, UK). HR-ESIMS were determined with a Bruker maXis Q-TOF in positive/negative ion mode. The NMR spectra including (1D and 2D NMR) were recorded on a Bruker AC 500 MHz spectrometer using TMS as standard. All chemical shifts were assigned with δ-values. X-ray diffraction intensity data were collected on Agilent Xcalibur Nova single-crystal diffractometer using Cu Kα radiation. Column chromatography (CC) was performed on silica gel (200–300 mesh, 300–400 mesh), and Sephadex LH-20 (Amersham Biosciences, Sweden), respectively. TLC were carried out on silica gel GF254 (10–40 µm) plates (Qingdao Marine Chemical Factory, China). All solvents used were of analytical grade (Tianjin Fuyu Chemical and Industry Factory). Semipreparative HPLC (Agilent Technologies, 1260 infinity series) was performed using an ODS column (YMC-pack ODS-A, 10 × 250 mm, 5 µm, 1.5 mL/min).

The structures were elucidated based on ESI-MS, 1D, and 2D NMR. NMR spectra were recorded on a Bruker Avance III-600 NMR spectrometer (Bruker, Billerica, MA, USA) with TMS as an internal standard. Mass spectrometry analysis was performed using an XTerraMS (Waters, Milford, MA, USA) equipped with an electrospray ionization (ESI) source. HR-ESI-MS data were acquired in m/z by using a BioTOF^TM-Q mass spectrometer (Bruker, Billerica, MA, USA) and a Dionex Ultimate 3000 coupled to a Bruker Maxis Q-TOF.

A weighted amount of the HSA (delipidated, Sigma, St. Louis, MI, USA) was dissolved in 20 mM ammonium bicarbonate aqueous buffer to obtain a solution with concentration equal to 200 µM. A weighted amount of a given cage iron(II) complex was dissolved in methanol just prior to the corresponding MS experiment to obtain a 2 mM solution. The reaction mixture containing 20 μM of the above protein and 60 μM of the clathrochelate in 20 mM aqueous ammonium bicarbonate was incubated at room temperature for 15 min.
Electrospray ionization mass spectra were measured on a Maxis QToF (Bruker Daltonics, Germany) using the Q-Tof control (Version 3.2.31.0) and the DataAnalysis (Version 4.1.359.0) software packages. The samples were injected under native conditions into the mass-spectrometer using the following parameters: infusion rate 350 μL/min, capillary voltage 4 kV, end plate offset −500 V, dry temperature 210 °C, dry gas 6 L/min, nebulizer 0.8 bar, transfer time 120 μs, acquisition rate 1 Hz and rolling average 2. The instrument was tuned to the high-mass range. Signals of HSA were detected in the range of m/z 3000–5000. The mass spectra were acquired over 5 min and averaged. Then, each of these experimental spectra was smoothed using the Savitzky–Golay algorithm with 0.2 smoothing width in five cycles.