Thermo Fischer Scientific

Thermo Fischer Scientific Inc. Molecular Spectroscopy Microanalysis Madison, WI USA... 

Ion detection is carried out using image current detection with subsequent Fourier transform of the time-domain signal in the same way as for the Fourier transform ion cyclotron resonance (FTICR) analyzer (see Section 2.2.6). Because frequency can be measured very precisely, high m/z separation can be attained. Here, the axial frequency is measured, since it is independent to the first order on energy and spatial spread of the ions. Since the orbitrap, contrary to the other mass analyzers described, is a recent invention, not many variations of the instrument exist. Apart from Thermo Fischer Scientific s commercial instrument, there is the earlier setup described in References 245 to 247. 

The acquisition speed is, as for the FTICR, resolution dependent. With Thermo Fischer Scientific s orbitrap the desired mass resolving power can be selected. With the lowest setting (7500 FWHM) the acquisition time for one ion injection is 0.3 s and with the highest setting (100,000 FWHM) it is 1.9 s. 

In principle, it would be possible to perform multistage mass spectrometry like in an ICR analyzer although with no gas CID would of course not be possible, but other dissociation methods could be employed. There might, however, be technical issues. At the time of writing, fragmentation is performed in the linear QIT preceeding the orbitrap in Thermo Fischer Scientific s instrument. Both pulsed and continuous ion sources can be employed. There are several ion sources that can be employed with Thermo Fischer Scientific s orbitrap. 

Fluorescent dyes modified with maleimide (e.g., ATTO-labels, Atto-Tec.com Alexa Fluor, Thermo Fischer Scientific CG dyes, Sigma-Aldrich Cyanine Dyes, GE Healthcare)... 

Chemokines were produced as previously described (in E. coli, either as native proteins or as NusA fusions (MagistreUi et al., 2005 Proudfoot Borlat, 2000) or purchased from Peprotech (Rocky Hill, NJ). Biotinylated chemokines were obtained from Almac (Craigavon, Northern Ireland) and oligonucleotides from Thermo Fischer Scientific. 

SpeedVac concentrator (Thermo Fischer Scientific SPD131 DDA-230) fitted with ultralow temperature refiigerator (Thermo Fischer Scientific RVT4104-230) and oil-free Teflon vacuum pump (Thermo Fischer Scientific, OFP400-230). 

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