Intact protein mass analysis 0-250 kDa

Molecular Weight Determination by LC ESI-MS protein analysis

Molecular weight determination by LC ESI-MS protein analysis is the golden standard for proteins up to 250 kDa. This technology provides very accurate MW data.

We load the protein sample onto an HPLC column and elute it off into the mass spectrometer. The advantage compared to MALDI-MS is the ability to analyze larger proteins. Also, the accuracy is higher by ESI-MS protein analysis.

Choose your service

Our Fast Protein Analysis Services are without customization. You get quality results in easy to understand standard reports, at fixed prices.

Option 1

Intact mass by ESI-MS

  • Mass range 0-250 kDa
  • Sample amount >5 ug
  • Accuracy within 30 ppm
Per sample
Results in 4-8 days
Option 2

Intact mass by ESI-MS (compared to protein sequence)

  • Mass range 0-250 kDa, sample amount >5 ug
  • Accuracy within 30 ppm
  • Comparison with theoretical Mw
Per sample
Results in 4-8 days
Service includes
  • The accuracy is within 30 ppm (+/-3 Dalton for a 100 kDa protein).
  • You can expect your results in 4-8 days.


Raw and deconvoluted data from ESI-MS Intact mass determination

Raw and deconvoluted data from ESI-MS Intact mass determination


Determine the mass weight of peptides and proteins in your sample up to 250 kDa

Our customers typically use this analysis for the following applications:

Determine the mass weight of peptides and proteins in your sample up to 250 kDa.

Compare samples – batch to batch variation.

Determine purity of your sample.

Look for modification such as glycosylations, acetylations, oxidations, etc.

Technical details

By ESI-MS analysis, proteins and peptides in liquid phase are sprayed through a capillary at high voltage into the MS instrument where the mass over charge ratio (m/z) is measured. For large biomolecules the electrospray process results in multiply protonated molecules with a distribution of ion species at m/z range from 1-3000. The mass of the molecule is determined using a deconvolution algorithm that calculates the mass of the intact non-protonated protein or peptide. The ESI process requires that the sample preparation is quite pure without interfering salts or detergents.

The sample is purified by reversed phase HPLC (Agilent 1200 system) using a short C8 column before being analyzed on a Q-TOF mass spectrometer (Bruker Maxis Impact system). The mass of the sample is determined by deconvolution of the obtained raw spectra using the MaxEnt algorithm. The high resolution and accuracy of the Q-Tof instrument result in very accurate mass determination within 0-3 Da of the theoretical mass.

Sample requirements

Protein samples can be submitted in liquid or as lyophilized material.
The chromatographic protein purity should be >90%
Avoid detergents and keep buffer concentration at a minimum. LC-ESI MS  analysis can be done on samples containing small amounts of salts, urea or detergent, but the best result are obtained with low buffer strength in volatile solvents without detergents.
Minimum amount ~ 10-50 micrograms

Please note that MW determination of intact proteins by mass spectrometry CANNOT be conducted on samples from gels or PVDF membranes!

Have questions? We'd love to help.

We're always eager to help. Please send us your question or request and we will get back to you as soon as possible.

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