Native mass spectrometry aims to identify and characterize proteins in their native (intact) state. Thermo Fisher Scientific first introduced the Thermo Scientific™ Exactive™ Plus EMR LC-MS instrument for native mass spectrometry with targets including monoclonal antibodies, antibody-drug conjugates (ADC), glycoforms, etc. The instrument provides an extended m/z range of 350-20,000, improved transmission of higher-mass ions and high-resolution, accurate-mass capabilities.
The Q Exactive UHMR (Ultra-High Mass Range) mass spectrometer is designed for large intact protein and protein complexes analysis. What are the differences compared to the Exactive Plus EMR mass spectrometer?
For starters, the Q Exactive UHMR mass spectrometer provides an extended mass range of up to m/z 80,000. Thus, the instrument can enable native mass spectrometry analysis of large protein-nucleic acid assemblies that require very efficient transmission in the ultrahigh mass range as depicted in Figure 1.
Figure 1: Native MS and MS/MS analysis of hepatitis B virus particles.
The Q Exactive UHMR mass spectrometer can release intact membrane protein assemblies in the source region of the mass spectrometer (as opposed to the HCD cell in its predecessor) through a process called ”in-source trapping.“ This process not only enables desolvation of noncovalent protein complexes, but also reduces their kinetic energy, which improves their transmission through the bent flatapole. Lastly, the Q Exactive UHMR mass spectrometer’s quadrupole mass filter has ultrahigh precursor selection capability. Hence, the quadrupole can select up to m/z 25,000 ions for selection ion monitoring (SIM) and MS/MS experiments.
Dr. Albert Heck at Utrecht University has used both the Exactive Plus EMR mass spectrometer and the Q Exactive UHMR mass spectrometer. The Heck lab develops mass spectrometry methods for the structural characterization of proteins but also for better understanding protein complexes and their interactions. Dr. Heck called out two additional primary benefits of the Q Exactive UHMR Orbitrap Mass Spectrometer: “With the introduction … of the Q Exactive UHMR, it’s really been a game changer for, I think, mostly two reasons. First, the sensitivity in the mass resolution has increased a lot. We can now record in a matter of seconds or let’s say minutes. So, we use much less sample, and the data looks therefore also better. Another major benefit is that we can do now, MS/MS and pseudo-MS3 on the Q Exactive UHMR, even on these very large protein assemblies, and that’s really a key benefit for identification and analysis of protein assemblies.”
Check out this Nature Methods publication by Utrecht University, which talks about these benefits in more detail.