ANALYTICAL PROPERTIES OF THE NANOELECTROSPRAY ION-SOURCE

The nanoelectrospray ion source (nanoES) has recently been developed a nd described theoretically. It is different from conventional electros pray sources and from other miniaturized electrospray sources by (i) i ts 1-2 mu m spraying orifice achieved by pulling the spraying capillar y to a fine tip, (ii) its very low now rate of similar to 20 nL/min an d the small size of droplets it generates, and (iii) the absence of so lvent pumps and inlet valves. The fabrication and operation of nanoES needles is described in detail. Solutions with up to 0.1 M salt conten ts could be sprayed without sheath now or pneumatic assist. Improved d esolvation in nanoES led to instrument-limited resolution of the signa ls of a glycoprotein and the ability to signal average extensively all owed the C-terminal sequencing of a 40 kDa protein. Extensive mass spe ctrometric and tandem mass spectrometric investigation of the componen ts of an unseparated peptide mixture was demonstrated by verification of 93% of the sequence of carbonic anhydrase. A rapid and robust desal ting/concentration step coupled to the nanoES procedure allows the dir ect analysis of impure samples such as peptide mixtures extracted afte r in-gel digestion.