What is a Electrospray MS?
The Mass of Proteins can be Precisely Determined Electrospray mass spectrometry
The very low volatility of proteins was a barrier for many years to using mass spectrometry, an estazblished analytical technique in organic chemistry. This difficulty has been circumvented by the recent introduction of electrospray ionization mass spectrometry. A protein sample in an acidic volatile solvent is sprayed into a mass spectrometer. The solvent surrounding individual droplets evaporates rapidly in the vacuum chamber of the instrument, leaving unfragmented bare protein molecules carrying multiple positive charges. These charged protein molecules are accelerated by an electric field and then deflected by a magnetic field. They are separated according to the ratio of their mass to their charge. The mass spectrum of a pure protein shows a set of peaks corresponding to different numbers of bound protons. Because adjacent peaks in the mass sopectrum arise from proteins containing n-1, n, and n+1 bound protons, the mass of the parent protein molecule can be deduced. Mass spectrometric determinations are accurate to about 1 part in 104, which means that the mass of a 1-kd protein can be measured to within 1 dalton.