Esquire 3000 plus iontrap mass spectrometer

All reagents and solvents
were reagent grade and used as purchased from commercial sources.
Compound 1 was synthesized at the Institute of Inorganic
Chemistry, University of Vienna. The purity of the used batch of 1 was checked at the Microanalytical Laboratory of the University
of Vienna by both elemental analysis applying a PerkinElmer 2400 CHN
elemental analyzer and mass spectroscopy applying a Bruker Esquire
3000 Plus Ion Trap mass spectrometer. The results revealed a deviation
of ±0.9 and ±0.1%, respectively, from the calculated value,
thus confirming ≥95% purity for 1.
Protein
purification was performed by size-exclusion chromatography (SEC)
using the ÄKTA explorer system from GE Healthcare. The purity
of the protein samples was checked by SDS-PAGE using a 15% acrylamide-containing
gel and the Mini-PROTEAN Tetra Cell from Bio-Rad. For highly concentrated
protein samples (75–120 mg/mL) to be obtained, ultrafiltration
was performed using Vivaspin concentrators with a 30 kDa cutoff membrane
from Sartorius. For the determination of protein concentrations, the
protein’s absorbance at 280 nm was measured by UV–vis
spectroscopy (UV-1800 from Shimadzu), and the concentrations were
subsequently calculated applying the Beer–Lambert Law using
the molar extinction coefficient (at 280 nm) of 36500 M^–1 cm^–1 for HSA.^{74 (link)}