SOFTWARE FOR MASS SPECTROMETRY
Members of the Trace Analysis Research Centre have written computer programs that do a variety of calculations helpful for mass spectrometrists. These include the calculation of isotope cluster patterns for simple and tandem mass spectra, accurate masses of noncovalently bonded cluster ions, atom enrichment levels, and all formulae of ions with a specific mass-to-charge ratio. These can be downloaded gratis as explained below.
Isotope Cluster Patterns
IsoPatrn is a program that calculates the isotope cluster pattern of an ion in simple or tandem mass spectra (MSn for n up to 4). The ion may contain any of the atoms in the Periodic Table with stable isotopes. Six user-defined elements may also be introduced. Calculation of isotope patterns for product ion, precursor ion, or constant neutral loss mass spectra is supported.
The code, written for Windows-based personal computers in Microsoft Visual C++, employs the "classical" polynomial expansion algorithm and uses 80-bit floating point math routines to improve accuracy for very large molecules. IsoPatrn requires a 32-bit operating system, Windows 98 or later or Windows NT V4.0. There are no large memory or disk space requirements.
IsoPatrn provides regular Windows features including online help, hard-copy output, and the ability to save the results to simple text files, the data in which are comma-delimited for ease of importing into spreadsheet programs. The most recent edition of IsoPatrn is Version 2.10. This version contains several features not included in previous editions (V1.xx). These include the ability to list the individual components that make up eack peak in the isotope cluster and the ability to plot the resulting cluster spectrum at a resolution chosen by the user. The individual peak components can be saved to a file as well as the data used to generate the graph. IsoPatrn V2.00 could print the actual spectrum, but it could not save the spectrum in a graphical format. The latest version has the ability to export the spectrum in graphical format as an enhanced metafile, which can be imported easily and directly into word processor, spreadsheet, and presentation applications.
IsoPatrn is provided in compressed or "zipped" form in a package of 292 kB. Download IsoPatrn.
I_Clustr, a program that performs many of the same calculations as IsoPatrn (see above) but for use with 16-bit DOS or Windows operating systems, is no longer offered for downloading, since it lacks many of the features offered by IsoPatrn and since there is no longer much need for 16-bit programs.
Accurate Mass, Formula, Enrichment Calculations
The ISOMABS program will calculate ISOtopic Masses and ABundanceS found in mass spectral isotope patterns, as well as give possible formulae and classify ions as even- or odd-electron for a given m/z value.
Essentially all compounds containing elements with two or more natural or user-enriched isotopes exhibit mass spectra having isotope cluster ions. Most of the ISOMABS Program is designed to assist with understanding and dealing with the features arising from these clusters of ions.
The suite of programs will allow for:
- calculation of isotope cluster patterns from naturally-occurring species,
- calculation of isotope patterns from ions having user-specified isotopic enrichment,
- calculation of atom enrichment levels from the mass spectrum of a compound enriched in a specific isotope,
- calculation of accurate mass-to-charge ratios of noncovalently bonded cluster ions,
- calculation of all possible formulae for ions of a given m/z ratio, which can be very helpful in interpreting fragmentation patterns in a mass spectrum,
- correction of peak intensities for ions having intense [M-1] ions.
The menu-driven Program is written in a simple format using QuickBasic and will run on any PC. To retain simplicity, all input to the program is by way of the keyboard. Output is to the screen or it can be saved to a text file for further processing.
The most recent edition of ISOMABS is Version 5.1. It is provided in compressed or "zipped" form in a package of 587 kB. Download ISOMABS.