Figure 1: Quantitative in vivo crosslinking experimental flow chart.

Drug-sensitive HeLa (S) and drug-resistant HeLa/SN100 (R) cells were cultured in isotopically light and/or heavy stable isotope labeling by amino acids in cell culture (SILAC) media. Light and heavy cells were mixed at 1:1 ratio and either subjected to I. Traditional quantitative SILAC analysis to obtain relative global protein abundances or II. In vivo crosslinking with PIR crosslinker. Crosslinked proteins were extracted reduced, alkylated and digested. Crosslinked peptides were purified by a combination of strong cation exchange (SCX) and avidin affinity chromatography and analysed using ReACT¹⁰. Data from the traditional SILAC and crosslinking SILAC experiments were merged into a quantitative interaction network providing an edgotype for multidrug resistance in HeLa cells.