ESIprot Online

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

m/z 1 (e.g. 1019.0):
m/z 2 (e.g. 1061.4):
m/z 3 (e.g. 1107.5):
m/z 4 (e.g. 1157.8):
m/z 5 (e.g. 1212.9):
m/z 6 (e.g. 1273.5):
m/z 7 (e.g. 1340.4):
m/z 8 (e.g. 1414.8):
m/z 9 (e.g. 1498.0):
min charge (default: 1):
max charge (default: 100):

At least m/z 1 and m/z 2 must be provided

* 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.
Deconvoluted ESI mass spectrum

Main characteristics of ESIprot


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 ESIprot webpage.