All reagents and solvents used were ACS reagent grade or better. Research-grade AAV2 was produced by Patheon by transient transfection in HEK293 cells. The NanoOrange™ Protein Quantitation Kit was obtained from Biosciences (Dublin, Ireland). IonHance DFA was purchased from Waters™ Corporation (Milford, MA, USA). Thermo Scientific™ SMART Digest™ pepsin kit was obtained from Thermo Fisher Scientific (Sunnyvale, CA, USA). Optima™ LC-MS grade acetonitrile (ACN), Thermo Scientific™ UHPLC-MS grade water, formic acid (FA), and Tris(2-carboxyethyl)phosphine hydrochloride (TCEP) were sourced from Fisher Scientific (Dublin, Ireland). All other chemicals or solvents were obtained from Merck Sigma (Wicklow, Ireland). Purified water was obtained from an Arium® pro Ultrapure Water System (Sartorius, Göttingen, Germany).