ESIprot Online enables the charge state determination and molecular weight calculation for low resolution electrospray ionization (ESI) mass spectrometry (MS) data of proteins.
This is the PHP based online version of ESIprot.
Input m/z values
* the example m/z values correspond to the active form of alpha-chymotrypsin from bovine pancreas, with five disulfide (S-S) bonds and attachment of TN[147-148] (reported in RCM, 2010).
Electrospray ionization (ESI) mass spectrometry (MS) devices with relatively low resolution are widely used for proteomics and metabolomics. Ion trap devices like the Agilent MSD/XCT ultra or the Bruker HCT ultra are typical representatives. However, even if ESI-MS data of most of the naturally ocurring proteins can be measured, the availability of data evaluation software for such ESI protein spectra with low resolution is quite limited.
Main characteristics of ESIprot
Algorithm based on standard deviation optimization (scatter minimization)
Suitable for peak lists. No raw data and peak intesities required, therefore suitable to re-evaluate "historical" data
Highly accurate calculation of molecular weights of proteins, even from low resolution data
Only two peaks of one protein required, extremly robust
Theoretically unlimited molecular weight range
Designed for the analysis of pure proteins
Open source license GPL v3: program and parts of it may be used for commercial and non-commerical purposes
Winkler R.: ESIprot: A universal tool for charge state determination and molecular weight calculation of proteins from electrospray ionization mass spectrometry data. Rapid Commun Mass Spectrom, 24(3), 285-294, 2010, Full text on RCM
The Microsoft Windows version of ESIprot, as well as the Python source code (License GPL v3) are available at the