experiments were
carried out on a Bruker Autoflex III MALDI-TOF mass spectrometer (Bruker
Daltonics, Bremen, Germany), equipped with a Smartbeam 2 Nd:YAG laser.
MALDI-MS operating conditions were as follows: ion source 1 = 19.00
kV, ion source 2 = 16.60 kV, lens voltage = 8.44 kV, reflector voltage
= 20.00 kV, reflector voltage 2 = 9.69 kV, and positive reflectron
mode in a mass range of m/z 400–3000.
A total of 200 laser shots was fired per measurement. The laser energy
was optimized to ∼40 μJ/pulse. Data processing was performed
using the Bruker flexAnalysis (version 3.3) software.