NopM and NopD are rhizobial nodulation outer proteins: identification using LC-MALDI and LC-ESI with a monolithic capillary column.

We have explored the potential of commercial polystyrene-divinylbenzene monolithic capillary nanoLC-MS/MS for identifying Sinorhizobium fredii HH103 nodulation outer proteins. Monolithic nanoLC with off-line MALDI-TOF/TOF and on-line ESI-q-oTOF is fast and robust, generating complementary data and offering high-confidence protein identifications from gel bands too weak for successful analysis using traditional approaches. This has allowed identification of two proteins not previously described as being type III-secreted in rhizobia, NopM and NopD.