Surface Modified Nano-Electrospray Needles Improve Sensitivity for Native Mass Spectrometry

Abstract

Native mass spectrometry (MS) and charge detection-mass spectrometry (CD-MS) have become versatile tools for characterizing a wide range of proteins and macromolecular complexes. Both commonly use nano-electrospray ionization (nESI) from pulled borosilicate needles, but some analytes are known to nonspecifically adsorb to the glass, which may lower sensitivity and limit the quality of the data. To improve the sensitivity of native MS and CD-MS, we modified the surface of nESI needles with inert surface modifiers, including polyethylene-glycol. We found that the surface modification improved the signal intensity for native MS of proteins and for CD-MS of adeno-associated viral capsids. These surface modified needles provide a simple and inexpensive method for improving the sensitivity of challenging analytes.

Capillary Vibrating Sharp-Edge Spray Ionization Augments Field-Free Ionization Techniques to Promote Conformer Preservation in the Gas-Phase for Intractable Biomolecular Ions

“…The results show promise for field-free cVSSI as a new tool in an expanding repertoire for ionization techniques to be used in native MS analysis. 78,136,137 Admittedly, the method currently experiences limitations with regard to ion signal levels and spectral quality. The former may result from reduced droplet transmission into the mass spectrometer inlet.…”

“…For example, field-free cVSSI is readily coupled to emerging techniques such as the novel modification of nESI emitter tips. 137 One interesting area of research that may be impacted by the development of field-free cVSSI is that of protein flexibility studies. For example, the new cVSSI method offers the potential to determine relative flexibilities of different proteins by simply gradually increasing the DC voltage that is applied to the solution and observing differences in the CSDs.…”

Fundamentals: How Do We Calculate Mass, Error, and Uncertainty in Native Mass Spectrometry?

“…At a minimum, we propose that uncertainty from MS measurements should be determined from separate injections of replicate samples. The manual clipping of the homemade capillary needles that are common in native MS can introduce variance between injections due to different tip diameters, 25,38 so the use of replicate needles is a reasonable minimum to capture potential uncertainty in the measurement. Again, each researcher needs to define the appropriate replicates for their system, which may go beyond the minimum level proposed here.…”