Fig. 2.
Quantitative CLMS analysis of C3, C3b and C3(H2O) in solution. A, The strategy of QCLMS using differentially isotope-labeled cross-linkers for comparing protein conformations. B, SDS-PAGE shows that BS3 (light cross-linker) and BS3-d4 (heavy cross-linker) cross-link C3, C3(H2O) and C3b with roughly equivalent overall efficiencies, and that broadly similar sets of cross-linked products were obtained. C, Sample identifiers and color coding used in this study. For example sample I-1 consists of an equimolar mixture of BS3-cross-linked C3 (blue) and BS3-d4-cross-linked C3(H2O) (green). Pair-wise comparisons of C3(H2O) against C3 (I-1 and I-2), and C3(H2O) against C3b (red) (II-1 and II-2).