Parsing Thermo Finnigan RAW files

In a rare move, I’m going to largely copy across a post from my work blog, because I hope it contains useful information. For background, I’m trying to write a simple python script that extracts particular metadata from a .RAW file, produced by a Thermo Finnigan mass spectrometer. Tools that exist for parsing these files require access to proprietary XCalibur libraries, which I do not have.

Thermo provided a link to MSFileReader, a ‘freeware’ COM object that should allow interaction with RAW files without an XCalibur installation. They also sent a PDF guide to the COM object. Although this will allow XCalibur to be avoided, the work is still Windows-bound.

Python and COM objects

Python can talk to COM objects, through the win32com.client package. As a test, I installed Python and MSFileReader and the pywin32 libs on my netbook (which is a Windows 7 machine). Can import the required Python module, but need to extent the PATH somewhat:

The key thing here is “NAME”:

The provided PDF gives C snippets for each method available in the COM object. This only provides one clue as to the possible name of the COM object

XRawfileCtrl is used to call the Open() method. However, this and MSFileReader as “NAME” both fail (Invalid class string).

Found ‘multiplierz‘ which seems to use MSFileReader to create mzAPI – which focusses on access to the actual data, rather than the metadata. The code gives some good clues as to how to use the COM object. [doi:10.1186/1471-2105-10-364]

MSFileReader.XRawfile is used as “NAME” in this code.

So:

To be continued…