The non-covalent interactions which maintain protein-RNA complexes such as U1 snRNP in human spliceosome were investigated using nanoflow ESI-MS technique. The reconstituted U1 snRNP complex comprised core domain of Sm proteins and snRNA. The instrument pressure was varied by partial closure of rotary pump isolation valve and combination of cone, extractor and collision cell voltages were used to control extent of dissociation. The results show that when present in complex under similar instr...