*4.7. Synapt G2S Instrument Settings and Data Aquisition*

Nano-ESI-MS measurements were performed using a Synapt G2S instrument (Waters MS-Technologies, Manchester, UK). ITEM-TWO measurements of the Troponin I peptide—antiTroponin I complex were performed with the following instrumental settings: source temperature, 50 ◦C; capillary voltage, 1.8 kV; sample cone voltage, 110 V; source offset voltage, 110 V; trap gas flow, 8.0 mL/min; cone gas flow, 100 L/h. All mass spectra were acquired in positive-ion mode applying a mass window of *m*/*z* 200–8000. The *m*/*z* axis was calibrated using 1 mg/mL sodium iodide dissolved in an isopropanol/water solution (50:50, *v*/*v*). The quadrupole analyzer was used to block transmission of lower molecular weight ions: M1 = 4000 with dwell time of 25% and ramp time of 25%; M2 = 5000 with dwell time of 25% and ramp time of 25%; M3 = 6000. The surviving antibody-peptide complexes were dissociated in the first collision cell (TRAP) by increasing the collision cell voltage difference in a stepwise manner (2–10 V/step). Data were acquired and processed with MassLynx software version 4.1 (Waters MS-Technologies, Manchester, UK). At each collision cell

voltage difference setting a mass spectrum was recorded for 1 min, each. All scans for a given collision cell voltage difference were combined to generate an average spectrum. From each spectrum the ion intensities (in arbitrary units) were deduced.
