14+ 13+ 12 15 16 11+ 10+ 十 8025 8000 9000 10000 11000 12000 m/z ESI mass spectrum of a protein, cytochrome c, molecular weight approximately 12360Da), examined (a) at low resolution and(b) at high resolution over a narrow rangeESI mass spectrum of a protein, cytochrome c, (molecular weight approximately 12360Da), examined (a) at low resolution and (b) at high resolution over a narrow range