Mass Determination by MALDI-MS
Mass determination by MALDI-TOF is recommended when the available amount is lower than 2 nmol or if the protein is very heterogeneously modified (for example: pegylated proteins).
What is delivered?
The mass of the protein is given with a 500 ppm measure uncertainty. Report will be sent by email. Results are usually available in 10 working days.
What is needed for these analyses?
Protein amount must be at least 100 pmol in the sample with a concentration of at least 50 μM, otherwise a pre-concentration step will be needed).
Suitable buffer conditions are water, ammonium acetate up to 100 mM or ammonium bicarbonate up to 100 mM.
Sample purity is critical and contaminants not compatible with MS, especially like salts, detergents, chaotrops, etc. must be eliminated before MS analysis. In this case, a ZipTip C4 (see Sample Preparation Section for more details) is performed and proteins are resuspended in the matrix solution. While performing these extra steps, sample must be stable (no degradation, neither aggregation nor precipitation).
