Sample Preparation Guidelines

Services Protein in Solution / Solid  Gel Slice from SDS PAGE  PVDF membrane
Protein identification by MS - MALDI-TOF/TOF
  • Pure protein: 100ng to 1ug, <250uL
  • Best to freeze-dry or air-dry in 1.5mL tube
  • Free of interfering buffers and salts (Client must declare what buffers and salts were used prior to sample drying.  If a result of extraction, it will help to provide extraction procedure, eg HPLC, Protein preciptation, MWCO.)
  • NOTE:                                             
    Buffers containing primary amines, such as TRIS and HEPES, should be removed. Low concentrations of SDS (up to 0.3%) and PBS can be tolerated. There may be other interferring buffers not common to these, thus always provide buffer composition prior to drying.
  • De Novo service, same as the above         
  • De Novo service, Pure protein: Normally 10ng-100ng. Again, for freeze-dried or powdered: 50µg 
  • Yes. Cut into 1.5mL tube and dried.

    NOTE: no water or buffer!
  • Minimum 2 spots: Commassive Blue; or MS compatible Silver Stain (1 month). (Each spot contain minimum 100ng)
  • Minimum 4 spots: SYPRO Ruby; or Cy dyes.                                                               MALDI-TOF/TOF: Sample size >20kDa LC/MS/MS: sample size <20kDa
  • De Novo service, same as the above 
Protein identification by MS - Electrospray (LC/MS/MS) 
De Novo Protein Sequencing 
iTRAQ analysis 
  • 200-500µg of sample                   
  • Cell lysates, secreted protein samples, but not radioactive samples.                                    
  • Ship sample with dry ice  
    NOTE: Please make sure that all serum or related culture medium are washed off before lysing cells. For any questions, please write-in to enquire.
Never Never
Protein Mass analysis
  • Pure protein, must be freeze dried from low salt buffer.      
  • The protein concentration before drying must be at least 0.1mg/ml.
  • The solution must be a low salt buffer, e.g. 50mM ammonium hydrogen carbonate; for TRIS or phosphate buffers the maximum salt strength is 20mM. NaCl and surfactants (e.g. SDS) cannot be present.
Never Never
Amino Acid Analysis (AAA)
  • The minimum amounts are:
    High sensitivity AAA – 10 μg (5μg in duplicate)
    Cys – 20μg (10μg in duplicate)
    Trp – 1mg (0.5mg in duplicate)
  • Sample must be freeze dried.   
  • Information needed:
    (1) The volume of the liquid before drying.
    (2) Solvent/buffer used before drying.
    (3) Known or estimated concentration of sample.
Never Never
N-Terminal Protein Sequencing 
  • Diluting the sample with a small amount (25 ul for up to 100 ug of protein) of SDS boiling buffer without reducing agents (5% SDS, 10% glycerol and 60 mM Tris, pH 6.8) and freeze drying by lyophilization.
  • Solution sample: with dry ice shipment. (Additional charges apply for run gel & PVDF membrane blotting services)
  • Should be stained with
    Coomassie Blue, and the target band must then be visible by eye. Blots must be free of any particulate material.
  • Attach gel photo to indicate the exact band to be cut (by us) and sequenced.


Please be reminded that to avoid evaporation, leakage or lost of samples, all sample tubes MUST be wrapped with para-film before shipping them to our lab.