Extended Data Fig. 1: Graphic scheme of the trapping nano-LC system.

A large-i.d. trapping column (300 μm i.d.) and 65-cm-long, 75 μm i.d. C18 separation column, heated at 50 °C, are connected and operated by a six-port valve. The unique selective trapping-delivery strategy consists of three stages, including sample injection, cleanup and delivery. The red lines and arrows indicate the flow of the peptide sample in each stage.