Question

Electron impact ionization is one of the oldest and most common forms of ionization.

a. Why is it very uncommon to find it used in a proteomics experiment?

b. What ionization techniques are preferred for proteomics and why?

Answer 1

a) Proteomics is the large scale study of proteins. As we know, proteins are large molecular weight compoundsand as a result electron impact ionization cannot be used in proteomics. Electron impact ionisation is the use of high energy electrons to produce ions of a compound. But the technique is suitable only for those molecules whose molecular weight is <1000Da. Thus it cannot be used in proteomics as proteins have molecular masses that much higher than the allowed limit in the technique. Moreover the technique involves large scale ionisation and this will be difficult to analyse in case of biological molecules.

b) Generally soft ionisation techniques are preferred in proteomics. Soft techniques are those in which fragmentations are minimum. Techniques like electronspray ionisation, HPLC, MALDI etc are used in proteomics.