Updated project metadata. We have enabled ultrasensitive proteomics of limited protein digests by developing a tapered-tip nanoelectrospray ionization (nanoESI) interface for microanalytical capillary electrophoresis (CE) high resolution mass spectrometry (HRMS). CE-nanoESI-HRMS allowed us to detect 260 zmol angiotensin II (lower limit of detection) and identify 1 pg of bovine serum albumin and cytochrome c. A 1 ng protein digest from the mouse posterior cortex yielded 217 nonredundant protein groups, including many gene products that are used as classical neuronal markers.