AI Insight
This study evaluates sub-50 nm internal diameter quartz nanopipette emitters for native electrospray ionization mass spectrometry (nESI-MS), testing them across three distinct instrument platforms and a protein mass range spanning 17 to 800 kDa. Compared to conventional borosilicate emitters with 1-2 micrometer internal diameters, the quartz nanopipettes demonstrated higher signal-to-noise ratios, reduced sodium adduct formation, and better preservation of native protein states, including metal-bound complexes. The emitters also proved compatible with complex biological samples, successfully detecting alpha-synuclein directly from clarified bacterial lysate without extensive sample preparation.
Why it matters
Improving native mass spectrometry workflows by reducing adduct formation and enabling analysis at lower sample concentrations has direct relevance to structural biology and biopharmaceutical characterization, where accurate measurement of protein assemblies and modifications is critical. The instrument-portable nature of these emitters lowers the barrier to adopting gentler ionization conditions across different laboratory setups.
⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Native mass spectrometry (nMS) is well established for measuring protein masses and stoichiometries using nano-electrospray ionization (nESI), yet salt adduction and source activation energies can limit routine measurements. In this study, we benchmark submicron quartz nanopipette nESI emitters (<50 nm internal diameter) across three mass spectrometry platforms (quadrupole-time-of-flight, quadrupole-Orbitrap, and tribrid-Orbitrap platforms) and a wide protein mass range (17-800 kDa). We analysed holo-myoglobin (17 kDa) over a range of concentrations (10 M-10 nM) and capillary voltages to determine limits of detection and define a gentle operating regime. We additionally observe reduced Na+ adduction and preservation of the Zn2+ bound metalloproteoform of carbonic anhydrase II (29 kDa). Proteins and protein complexes spanning the mid-to-high mass range including ovalbumin (~44 kDa), malate dehydrogenase (~70 kDa), glutamate dehydrogenase (~350 kDa), {beta}-galactosidase (~465 kDa), and GroEL (~800 kDa), were readily detected using nanopipette emitters. Compared with conventional 1-2 m internal diameter borosilicate emitters, quartz nanopipettes provided higher signal-to-noise ratios and fewer adducts. Finally, direct analysis of clarified bacterial lysate expressing -synuclein yielded a clear monomeric charge-state distribution, demonstrating compatibility with complex biological matrices. Collectively, these results establish quartz nanopipette nESI as an instrument-portable, salt-tolerant approach suitable for routine nMS analysis across a broad range of protein molecular weights and sample complexities.