Question

can we record MSMS of doubly charged ions in MALDI-ToF

Answer 1

Even with these added difficulties, MS can still be an invaluable tool for the analysis of chemokine oligomerization. In 2005, Yu et al. performed native spray analysis of various chemokine ligands of CCR2 in the presence and absence of heparin sulfate octasaccharides. In native spray analysis, MCP-1 (CCL2) and MCP-2 (CCL8) were found to exist in solution in an equilibrium between homodimer and monomer. However, using native spray MS, it was shown that only the dimer bound to the heparan sulfate octasaccharide. Similar studies of other CCR2 chemokines did not reveal any oligomers by native spray, and additionally showed heparan sulfate octasaccharide binding to the chemokine monomer. In all cases, the native spray MS results confirmed previous solution-phase analysis results.157 Further work by Crown et al.examined heterodimerization of these CCR2 chemokine ligands. Using native spray MS, the authors were able to measure apparent equilibriums between homodimer and heterodimer complexes of these CCR2 ligand chemokines. Heterodimerization dominated in mixtures of CCL2 and CCL8 in the absence of Arixtra, a heparan sulfate pentasaccharide derivative. All other combinations of CCL2, CCL8, and other CCR2 chemokine ligands examined revealed only homodimerization of CCL2 or CCL8, with the other paired chemokines existing only as monomers. However, upon addition of Arixtra, all pairs tested were observed to generate significant amounts of heterodimer, with the exception of CCL2–CCL13.158 More recently, Carlson et al. have examined the heterodimerization of CXCL4 and CXCL7 with other platelet-derived chemokines. Using native spray MS, the authors were able to screen 24 different combinations of CC and CXC chemokines and their ability to form heterodimers with CXCL4 and CXCL7.159 This screening process is made possible by the relative speed and sensitivity of native spray MS when compared to other analytical techniques used for oligomerization analysis, such as NMR and analytical ultracentrifugation.