MALDI Mass Spectrometry Electrospray (ESI) Mass Spectrometry Contaminate Mass Spectrometers

Molecular weight determination of intact proteins and peptides by mass spectrometry requires sufficient sample amounts to obtain good data and relatively pure protein preparation.

MALDI mass spectrometry and works well for small and large proteins in a range of solvents. Alternatively, the analysis can be conducted using electrospray (ESI) mass spectrometry that can give very accurate Mw determinations but requires a very pure sample.

Samples for MALDI-TOF analysis need to meet certain requirements for obtaining good spectra. The more careful you prepare samples (including early steps of isolation and preparation) the more likely a successful analysis will be. Here are some guidelines of which kind of treatment is advantageous for mass spectrometric analysis.

Sample Preparation

Samples can be submitted in liquid or solid form.

Liquid or Solid Sample

1. Purify the protein/peptide
   1. The chromatographic protein/peptide purity should be >90%
   2. Avoid detergents and keep buffer concentration at a minimum MALDI analysis can be done on samples containing small amounts of salts (under 50 mmol and if possible largely without buffer) , urea or detergent but the best result are obtained with low buffer strength in volatile solvents without detergents
   3. Minimum amount ~ 10 micrograms
2. Put the protein/peptide into microcentrifuge tube
   1. Use the Eppendorf Safe Lock tube supplied with
      the kit or similar tubes from your lab
   2. Lyophilize or speed vac the protein to a solid sample to ensure protein stability during shipment
   3. Alternatively, freeze or refrigerate to +4oC for cold shipment of the liquid sample
3. Type of sample accepted and not accepted
   1. The protein is dissolved in water/acetonitrile and cleaned on a C4 or C18 micro-column before analysis by MALDI-TOF MS, alternatively by nano-ESI-MS if requested.
   2. Please note that Mw determination of intact proteins by mass spectrometry CANNOT be conducted on samples from gels or PVDF membranes!
   3. Please do not use polyethylene glycol (PEG) and polypropylene glycol (PPG).
   4. The sample must be glycerol-free.
   5. The samples should not contain non-volatile salts / butters, such as phosphates, sulfates, various metals, etc. Such salts / butters can completely suppress the analyte signals and badly contaminate mass spectrometers.

We do not accept organometallic compounds and polymers.