Human insulin, myoglobin
from equine skeletal
muscle, 1,5-diaminonaphtalene (1,5-DAN; handle with care, check material
safety data sheet), N-phenyl-p-phenylenediamine
(PPDA; handle with care, check material safety data sheet), sinapinic
acid (SA), and acetonitrile (ACN; MS grade) were purchased from Sigma-Aldrich.
Trifluoroacetic acid (TFA) was purchased from Thermo Fisher Scientific.
Formic acid (FA) was purchased from Honeywell. Ultrapure water (Milli-Q;
Merck) was used throughout this study. 2-Propanol was purchased from
Biosolve BV. NIST mAb standard (HzIgG1-kappa, NS0) was provided by
the Consortium for Top-Down Proteomics (CTDP).39 (link),59 A 5 mg/mL solution of human insulin was prepared in water/TFA,
99.95%:0.05%. A 2 mg/mL solution of myoglobin was prepared in water.
NIST mAb standard was diluted from an initial concentration of 10
mg/mL to a final concentration of 2 mg/mL using water. A saturated
solution of 1,5-DAN was prepared in water/ACN/FA, 50%:49.95%:0.05%.
A saturated solution of PPDA was prepared in water/2-propanol/TFA,
50%:49.95%:0.05%. A 10 mg/mL solution of SA was prepared in water/ACN,
50%:50%. MALDI matrices were freshly prepared prior to the analysis.