Determination of Collision Cross-Sections of Protein Ions in an Orbitrap Mass Analyzer

Collision cross-section measurements of small molecules via transient decay profiles observed in Orbitrap mass analyzers

Collision cross section (CCS) of organic compounds can be measured via Fourier transform-based mass spectrometry (MS) by modeling the decay rate of transient signals in the analyzer. Deriving CCS values of low-mass molecules (mass < 2000 Da and CCS < 500 Å2) with Orbitrap MS is challenging due to their high axial frequencies and small absolute variances in cross-sectional profiles. Here, we acquired mass spectra of progressively more complex low-mass analytes using commercial Orbitrap mass spectrometers. The transient signals were processed using Fast Fourier transform (FFT) and short-time Fourier transform (StFFT) to derive decay constants of multiple select ionic species from a single MS full-scan experiment. Decay constants were translated into CCS values using at least two internal standards in the same mass spectrum. Our results suggest target ionic species should have high S/N in order to derive CCS values with ≤0.5% uncertainty. Limitations in the precision of CCS measurements reflect local space charge effects that disturb ion motion in the analyzer. The derived CCS values of polymer like fragments of Ultramark 1621 and small molecules such as individual protonated amino acids can achieve average ±1% error with selection of internal standards across a wide mass range. Future studies need to optimize the strategy to select internal standards in order to improve the precision and accuracy of CCS measurements for small molecules via Orbitrap MS.

Investigating Lipid Transporter Protein and Lipid Interactions Using Variable Temperature Electrospray Ionization, Ultraviolet Photodissociation Mass Spectrometry, and Collision Cross Section Analysis

Gram-negative bacteria develop and exhibit resistance to antibiotics, owing to their highly asymmetric outer membrane maintained by a group of six proteins comprising the Mla (maintenance of lipid asymmetry) pathway. Here, we investigate the lipid binding preferences of one Mla protein, MlaC, which transports lipids through the periplasm. We used ultraviolet photodissociation (UVPD) to identify and characterize modifications of lipids endogenously bound to MlaC expressed in three different bacteria strains. UVPD was also used to localize lipid binding to MlaC residues 130-140, consistent with the crystal structure reported for lipid-bound MlaC. The impact of removing the bound lipid from MlaC on its structure was monitored based on collision cross section measurements, revealing that the protein unfolded prior to release of the lipid. The lipid selectivity of MlaC was evaluated based on titrimetric experiments, indicating that MlaC-bound lipids in various classes (sphingolipids, glycerophospholipids, and fatty acids) as long as they possessed no more than two acyl chains.

Adding Color to Mass Spectra of Biopolymers: Charge Determination Analysis (CHARDA) Assigns Charge State to Every Ion Peak

Traditionally, mass spectrometry (MS) output is the ion abundance plotted versus the ionic mass-to-charge ratio m/z. While employing only commercially available equipment, Charge Determination Analysis (CHARDA) adds a third dimension to MS, estimating for individual peaks their charge states z starting from z = 1 and color coding z in m/z spectra. CHARDA combines the analysis of ion signal decay rates in the time-domain data (transients) in Fourier transform (FT) MS with the interrogation of mass defects (fractional mass) of biopolymers. Being applied to individual isotopic peaks in a complex protein tandem (MS/MS) data set, CHARDA aids peptide mass spectra interpretation by facilitating charge-state deconvolution of large ionic species in crowded regions, estimating z even in the absence of an isotopic distribution (e.g., for monoisotopic mass spectra). CHARDA is fast, robust, and consistent with conventional FTMS and FTMS/MS data acquisition procedures. An effective charge-state resolution Rz ≥ 6 is obtained with the potential for further improvements.

Special Issue with Research Topics on "Recent Analysis and Applications of Mass Spectra on Biochemistry"

Analytical mass spectrometry applies irreplaceable mass spectrometric (MS) methods to analytical chemistry and chemical analysis, among other areas of analytical science [...].

Determining Collisional Cross Sections from Ion Decay with Individual Ion Mass Spectrometry

Collision cross section (CCS) measurements determined by ion mobility spectrometry (IMS) provide useful information about gas-phase protein structure that is complementary to mass analysis. Methods for determining CCS without a dedicated IMS system have been developed for Fourier transform mass spectrometry (FT-MS) platforms by measuring the signal decay during detection. Individual ion mass spectrometry (I2MS) provides charge detection and measures ion lifetimes across the length of an FT-MS detection event. By tracking lifetimes for entire ion populations, we demonstrate simultaneous determination of charge, mass, and CCS for proteins and complexes ranging from ∼8 to ∼232 kDa.

Expanding Orbitrap Collision Cross-Section Measurements to Native Protein Applications Through Kinetic Energy and Signal Decay Analysis

The measurement of collision cross sections (CCS, σ) offers supplemental information about sizes and conformations of ions beyond mass analysis alone. We have previously shown that CCSs can be determined directly from the time-domain transient decay of ions in an Orbitrap mass analyzer as ions oscillate around the central electrode and collide with neutral gas, thus removing them from the ion packet. Herein, we develop the modified hard collision model, thus deviating from the prior FT-MS hard sphere model, to determine CCSs as a function of center-of-mass collision energy in the Orbitrap analyzer. With this model, we aim to increase the upper mass limit of CCS measurement for native-like proteins, characterized by low charge states and presumed to be in more compact conformations. We also combine CCS measurements with collision induced unfolding and tandem mass spectrometry experiments to monitor protein unfolding and disassembly of protein complexes and measure CCSs of ejected monomers from protein complexes.

Nanohydrophobic Interaction Chromatography Coupled to Ultraviolet Photodissociation Mass Spectrometry for the Analysis of Intact Proteins in Low Charge States

The direct correlation between proteoforms and biological phenotype necessitates the exploration of mass spectrometry (MS)-based methods more suitable for proteoform detection and characterization. Here, we couple nano-hydrophobic interaction chromatography (nano-HIC) to ultraviolet photodissociation MS (UVPD-MS) for separation and characterization of intact proteins and proteoforms. High linearity, sensitivity, and sequence coverage are obtained with this method for a variety of proteins. Investigation of collisional cross sections of intact proteins during nano-HIC indicates semifolded conformations in low charge states, enabling a different dimension of separation in comparison to traditional, fully denaturing reversed-phase separations. This method is demonstrated for a mixture of intact proteins from Escherichia coli ribosomes; high sequence coverage is obtained for a variety of modified and unmodified proteoforms.

Integrated Top-Down and Bottom-Up Mass Spectrometry for Characterization of Diselenide Bridging Patterns of Synthetic Selenoproteins

With the rapid acceleration in the design and development of new biotherapeutics, ensuring consistent quality and understanding degradation pathways remain paramount, requiring an array of analytical methods including mass spectrometry. The incorporation of non-canonical amino acids, such as for synthetic selenoproteins, creates additional challenges. A comprehensive strategy to characterize selenoproteins should serve dual purposes of providing sequence confirmation and mapping of selenocysteine bridge locations and the identification of unanticipated side products. In the present study, a combined approach exploiting the benefits of both top-down and bottom-up mass spectrometry was developed. Both electron-transfer/higher-energy collision dissociation and 213 nm ultraviolet photodissociation were utilized to provide complementary information, allowing high quality characterization, localization of diselenide bridges for complex proteins, and the identification of previously unreported selenoprotein dimers.

Exploring the Conformations and Binding Location of HMGA2·DNA Complexes Using Ion Mobility Spectrometry and 193 nm Ultraviolet Photodissociation Mass Spectrometry

Although it is widely accepted that protein function is largely dependent on its structure, intrinsically disordered proteins (IDPs) lack defined structure but are essential in proper cellular processes. Mammalian high mobility group proteins (HMGA) are one such example of IDPs that perform a number of crucial nuclear activities and have been highly studied due to their involvement in the proliferation of a variety of disease and cancers. Traditional structural characterization methods have had limited success in understanding HMGA proteins and their ability to coordinate to DNA. Ion mobility spectrometry and mass spectrometry provide insights into the diversity and heterogeneity of structures adopted by IDPs and are employed here to interrogate HMGA2 in its unbound states and bound to two DNA hairpins. The broad distribution of collision cross sections observed for the apo-protein are restricted when HMGA2 is bound to DNA, suggesting that increased protein organization is promoted in the holo-form. Ultraviolet photodissociation was utilized to probe the changes in structures for the compact and elongated structures of HMGA2 by analyzing backbone cleavage propensities and solvent accessibility based on charge-site analysis, which revealed a spectrum of conformational possibilities. Namely, preferential binding of the DNA hairpins with the second of three AT-hooks of HMGA2 is suggested based on the suppression of backbone fragmentation and distribution of DNA-containing protein fragments.

Symmetry of 4-Oxalocrotonate Tautomerase Trimers Influences Unfolding and Fragmentation in the Gas Phase

The recent discovery of asymmetric arrangements of trimers in the tautomerase superfamily (TSF) adds structural diversity to this already mechanistically diverse superfamily. Classification of asymmetric trimers has previously been determined using X-ray crystallography. Here, native mass spectrometry (MS) and ultraviolet photodissociation (UVPD) are employed as an integrated strategy for more rapid and sensitive differentiation of symmetric and asymmetric trimers. Specifically, the unfolding of symmetric and asymmetric trimers initiated by collisional heating was probed using UVPD, which revealed unique gas-phase unfolding pathways. Variations in UVPD patterns from native-like, compact trimeric structures to unfolded, extended conformations indicate a rearrangement of higher-order structure in the asymmetric trimers that are believed to be stabilized by salt-bridge triads, which are absent from the symmetric trimers. Consequently, the symmetric trimers were found to be less stable in the gas phase, resulting in enhanced UVPD fragmentation overall and a notable difference in higher-order re-structuring based on the extent of hydrogen migration of protein fragments. The increased stability of the asymmetric trimers may justify their evolution and concomitant diversification of the TSF. Facilitating the classification of TSF members as symmetric or asymmetric trimers assists in delineating the evolutionary history of the TSF.

Frequency chasing of individual megadalton ions in an Orbitrap analyser improves precision of analysis in single-molecule mass spectrometry

To enhance the performance of charge-detection mass spectrometry, we investigated the behaviour of macromolecular single ions on their paths towards and within the Orbitrap analyser. Ions with a mass beyond one megadalton reach a plateau of stability and can be successfully trapped for seconds, travelling a path length of multiple kilometres, thereby enabling precise mass analysis with an effective resolution of greater than 100,000 at a mass-to-charge ratio of 35,000. Through monitoring the frequency of individual ions, we show that these high-mass ions, rather than being lost from the trap, can gradually lose residual solvent molecules and, in rare cases, a single elementary charge. We also demonstrate that the frequency drift of single ions due to desolvation and charge stripping can be corrected, which improves the effective ion sampling 23-fold and gives a twofold improvement in mass precision and resolution.

The mass precision and resolution in charge-detection mass spectrometry can be improved by correcting frequency drifts of single ions. Now, chasing these individual ions for seconds in an Orbitrap mass spectrometer has revealed the exceptional stability of ultra-high-mass ions, culminating in an effective resolution of greater than 100,000 at m/z = 35,000.

Ion-Ion Charge Reduction Addresses Multiple Challenges Common to Denaturing Intact Mass Analysis

Complete LC-MS-based protein primary sequence characterization requires measurement of intact protein profiles under denaturing and/or reducing conditions. To address issues of protein overcharging of unstructured proteins under acidic, denaturing conditions and sample heterogeneity (macro- and micro-scales) which often confound denaturing intact mass analysis of a wide variety of protein samples, we propose the use of broadband isolation of entire charge state distributions of intact proteins followed by ion-ion proton transfer charge reduction, which we have termed "full scan PTCR" (fsPTCR). Using rapid denaturing size exclusion chromatography coupled to fsPTCR-Orbitrap MS and time-resolved deconvolution data analysis, we demonstrate a strategy for method optimization, leading to significant analytical advantages over conventional MS1. Denaturing analysis of the flexible bacterial translation initiation factor 2 (91 kDa) using fsPTCR reduced overcharging and showed an 11-fold gain in S/N compared to conventional MS1. Analysis by fsPTCR-MS of the microheterogeneous glycoprotein fetuin revealed twice as many proteoforms as MS1 (112 vs 56). In a macroheterogeneous mixture of proteins ranging from 14 to 148 kDa, fsPTCR provided more than 10-fold increased sensitivity and quantitative accuracy for diluted bovine serum albumin (66 kDa). Finally, our analysis shows that collisional gas pressure is a key parameter which can be utilized during fsPTCR to retain or remove larger proteins from acquired spectra.

Multi-CRAFTI: Relative Collision Cross Sections from Fourier Transform Ion Cyclotron Resonance Mass Spectrometric Line Width Measurements

Determination of collision cross sections (CCS) using the cross-sectional areas by the Fourier transform ion cyclotron resonance (CRAFTI) technique is limited by the requirement that accurate pressures in the trapping cell of the mass spectrometer must be known. Experiments must also be performed in the energetic hard-sphere regime such that ions decohere after single collisions with neutrals; this limits application to ions that are not much more massive than the neutrals. To mitigate these problems, we have resonantly excited two (or more) ions of different m/z to the same center-of-mass kinetic energy in a single experiment, subjecting them to identical neutral pressures. We term this approach "multi-CRAFTI". This facilitates measurement of relative CCS without requiring knowledge of the pressure and enables determination of absolute CCS using internal standards. Experiments with tetraalkylammonium ions yield CCS in reasonable agreement with the one-ion-at-a-time CRAFTI approach and with ion mobility spectrometry (IMS) when differences in collision energetics are taken into account (multi-CRAFTI generally yields smaller CCS than does IMS due to the higher collision energies employed in multi-CRAFTI). Comparison of multi-CRAFTI and IMS results with CCS calculated from structures computed at the M06-2X/6-31+G* level of theory using projection approximation or trajectory method values, respectively, indicates that the computed structures have CCS increasingly smaller than the experimental CCS as m/z increases, implying the computational model overestimates interactions between the alkyl arms. For ions that undergo similar collisional decoherence processes, relative CCS reach constant values at lower collision energies than do absolute CCS values, suggesting a means of increasing the accessible upper m/z limit by employing multi-CRAFTI.

Integration of Mass Spectrometry Data for Structural Biology

Mass spectrometry (MS) is increasingly being used to probe the structure and dynamics of proteins and the complexes they form with other macromolecules. There are now several specialized MS methods, each with unique sample preparation, data acquisition, and data processing protocols. Collectively, these methods are referred to as structural MS and include cross-linking, hydrogen-deuterium exchange, hydroxyl radical footprinting, native, ion mobility, and top-down MS. Each of these provides a unique type of structural information, ranging from composition and stoichiometry through to residue level proximity and solvent accessibility. Structural MS has proved particularly beneficial in studying protein classes for which analysis by classic structural biology techniques proves challenging such as glycosylated or intrinsically disordered proteins. To capture the structural details for a particular system, especially larger multiprotein complexes, more than one structural MS method with other structural and biophysical techniques is often required. Key to integrating these diverse data are computational strategies and software solutions to facilitate this process. We provide a background to the structural MS methods and briefly summarize other structural methods and how these are combined with MS. We then describe current state of the art approaches for the integration of structural MS data for structural biology. We quantify how often these methods are used together and provide examples where such combinations have been fruitful. To illustrate the power of integrative approaches, we discuss progress in solving the structures of the proteasome and the nuclear pore complex. We also discuss how information from structural MS, particularly pertaining to protein dynamics, is not currently utilized in integrative workflows and how such information can provide a more accurate picture of the systems studied. We conclude by discussing new developments in the MS and computational fields that will further enable in-cell structural studies.

Ion Mobility Separation Using a Dual-LIT Miniature Mass Spectrometer

Ion mobility (IM) has been increasingly used in combination with mass spectrometry (MS) for chemical and biological analysis. While implementation of IM with MS usually requires complex instrumentation with delicate controls, in this study we explored the potential of performing IM separation using dual-linear ion traps (LITs) in a miniature mass spectrometer, which was originally developed for performing comprehensive MS/MS scan functions with a simple instrumentation configuration. The IM separation was achieved by ion transfer between the LITs with dynamic gas flow. Its performance was characterized for analysis of a broad range of chemical and biological compounds including small organic compounds such as trisaccharides, raffinose, cellotriose, and melezitose, as well as protein conformers. The demonstrated technique serves as another example of developing powerful hybrid instrument functions with simple configurations and miniaturized sizes.

Enhanced Characterization of Membrane Protein Complexes by Ultraviolet Photodissociation Mass Spectrometry

Development of chemical chaperones to solubilize membrane protein complexes in aqueous solutions has allowed for gas-phase analysis of their native-like assemblies, including rapid evaluation of stability and interacting partners. Characterization of protein primary sequence, however, has thus far been limited. Ultraviolet photodissociation (UVPD) generates a multitude of sequence ions for the E. coli ammonia channel (AmtB), provides improved localization of a possible post-translational modification of aquaporin Z (AqpZ), and surpasses previous reports of sequence coverage for mechanosensitive channel of large conductance (MscL). Variations in UVPD sequence ion abundance have been shown to correspond to structural changes induced upon some perturbation. Preliminary results are reported here for elucidating increased rigidity or flexibility of MscL when bound to various phospholipids.

Extracting biomolecule collision cross sections from FT-ICR mass spectral line shape

To extend the ion structure analysis capability of Fourier transform mass spectrometry (FT-MS), both time-domain and frequency-domain methods have been developed to extract ion collision cross sections (CCS) from high resolution mass spectra in Fourier transform ion cyclotron resonance (FT-ICR) cells. In this study, a new frequency-domain method, namely the line shape fitting method, was proposed to calculate ion CCSs from FT-ICR mass spectra line shape. Besides experimental data, simulated data with precisely controlled signal to noise levels and decay factors were also applied to characterize this method. Compared with the linewidth correction method previously proposed by our group, this line shape fitting method is more tolerant to noise, data length, and sampling rate, thus providing more consistent results. More importantly, CCS measurements of angiotensin I, bradykinin, ubiquitin and cytochrome c show that the resolving power is improved with the new method.

Importance of collision cross section measurements by ion mobility mass spectrometry in structural biology

The field of ion mobility mass spectrometry (IM-MS) has developed rapidly in recent decades, with new fundamental advances underpinning innovative applications. This has been particularly noticeable in the field of biomacromolecular structure determination and structural biology, with pioneering studies revealing new structural insight for complex protein assemblies which control biological function. This perspective offers a review of recent developments in IM-MS which have enabled expanding applications in protein structural biology, principally focusing on the quantitative measurement of collision cross sections and their interpretation to describe higher order protein structures.

Impact of charge state on 193 nm ultraviolet photodissociation of protein complexes

As applications in mass spectrometry continue to expand into the field of structural biology, there have been an increasing number of studies on noncovalent biological assemblies. Ensuring that protein complexes maintain native-like conformations and architectures during the transition from solution to the gas phase is a key aim. Probing composition and arrangement of subunits of multi-charged complexes via tandem mass spectrometry (MS/MS) may lead to protein unfolding and the redistribution of charges on the constituent subunits, leading to asymmetric charge partitioning and ejection of a high-charged monomer. Additionally, the overall dissociation efficiency of many ion activation methods is often suppressed for low charge states, hindering the effectiveness of MS/MS for complexes that have low charge density. Ultraviolet photodissociation (UVPD) of proteins using 193 nm photons is a high-energy alternative to collisional activation and demonstrates little to no charge state dependence. Here the symmetry of charge partitioning upon UVPD is evaluated for an array of multimeric protein complexes as a function of initial charge state. The results demonstrate that high laser energies (3 mJ) for UVPD induces more symmetric charge partitioning and ejection of low-charged, presumably compact monomers than higher-energy collisional dissociation (HCD).

Recommendations for reporting ion mobility Mass Spectrometry measurements

Here we present a guide to ion mobility mass spectrometry experiments, which covers both linear and nonlinear methods: what is measured, how the measurements are done, and how to report the results, including the uncertainties of mobility and collision cross section values. The guide aims to clarify some possibly confusing concepts, and the reporting recommendations should help researchers, authors and reviewers to contribute comprehensive reports, so that the ion mobility data can be reused more confidently. Starting from the concept of the definition of the measurand, we emphasize that (i) mobility values (K0 ) depend intrinsically on ion structure, the nature of the bath gas, temperature, and E/N; (ii) ion mobility does not measure molecular surfaces directly, but collision cross section (CCS) values are derived from mobility values using a physical model; (iii) methods relying on calibration are empirical (and thus may provide method-dependent results) only if the gas nature, temperature or E/N cannot match those of the primary method. Our analysis highlights the urgency of a community effort toward establishing primary standards and reference materials for ion mobility, and provides recommendations to do so. © 2019 The Authors. Mass Spectrometry Reviews Published by Wiley Periodicals, Inc.

Top-Down Analysis of Proteins in Low Charge States

The impact of charging methods on the dissociation behavior of intact proteins in low charge states is investigated using HCD and 193 nm UVPD. Low charge states are produced for seven different proteins using the following four different methods: (1) proton transfer reactions of ions in high charge states generated from conventional denaturing solutions; (2) ESI of proteins in solutions of high ionic strength to enhance retention of folded native-like conformations; (3) ESI of proteins in high pH solutions to limit protonation; and (4) ESI of carbamylated proteins. Comparison of sequence coverages, degree of preferential cleavages, and types and distribution of fragment ions reveals a number of differences in the fragmentation patterns depending on the method used to generate the ions. More notable differences in these metrics are observed upon HCD than upon UVPD. The fragmentation caused by HCD is influenced more significantly by the presence/absence of mobile protons, a factor that modulates the degree of preferential cleavages and net sequence coverages. Carbamylation of the lysines and the N-terminus of the proteins alters the proton mobility by reducing the number of proton-sequestering, highly basic sites as evidenced by decreased preferential fragmentation C-terminal to Asp or N-terminal to Pro upon HCD. UVPD is less dependent on the method used to generate the low charge states and favors non-specific fragmentation, an outcome which is important for obtaining high sequence coverage of intact proteins.

Surface-Induced Dissociation of Noncovalent Protein Complexes in an Extended Mass Range Orbitrap Mass Spectrometer

Native mass spectrometry continues to develop as a significant complement to traditional structural biology techniques. Within native mass spectrometry (MS), surface-induced dissociation (SID) has been shown to be a powerful activation method for the study of noncovalent complexes of biological significance. High-resolution mass spectrometers have become increasingly adapted to the analysis of high-mass ions and have demonstrated their importance in understanding how small mass changes can affect the overall structure of large biomolecular complexes. Herein we demonstrate the first adaptation of surface-induced dissociation in a modified high-mass-range, high-resolution Orbitrap mass spectrometer. The SID device was designed to be installed in the Q Exactive series of Orbitrap mass spectrometers with minimal disruption of standard functions. The performance of the SID-Orbitrap instrument has been demonstrated with several protein complex and ligand-bound protein complex systems ranging from 53 to 336 kDa. We also address the effect of ion source temperature on native protein-ligand complex ions as assessed by SID. Results are consistent with previous findings on quadrupole time-of-flight instruments and suggest that SID coupled to high-resolution MS is well-suited to provide information on the interface interactions within protein complexes and ligand-bound protein complexes.

Measurement of Individual Ions Sharply Increases the Resolution of Orbitrap Mass Spectra of Proteins

It is well-known that with Orbitrap-based Fourier-transform-mass-spectrometry (FT-MS) analysis, longer-time-domain signals are needed to better resolve species of interest. Unfortunately, increasing the signal-acquisition period comes at the expense of increasing ion decay, which lowers signal-to-noise ratios and ultimately limits resolution. This is especially problematic for intact proteins, including antibodies, which demonstrate rapid decay because of their larger collisional cross-sections, and result in more frequent collisions with background gas molecules. Provided here is a method that utilizes numerous low-ion-count spectra and single-ion processing to reconstruct a conventional m/ z spectrum. This technique has been applied to proteins varying in molecular weight from 8 to 150 kDa, with a resolving power of 677 000 achieved for transients of carbonic anhydrase (29 kDa) with a duration of only ∼250 ms. A resolution improvement ranging from 10- to 20-fold was observed for all proteins, providing isotopic resolution where none was previously present.

An Orbitrap-based laser desorption/ablation mass spectrometer designed for spaceflight

RATIONALE

The investigation of cryogenic planetary environments as potential harbors for extant life and/or contemporary sites of organic synthesis represents an emerging focal point in planetary exploration. Next generation instruments need to be capable of unambiguously determining elemental and/or molecular stoichiometry via highly accurate mass measurements and the separation of isobaric interferences.

METHODS

An Orbitrap™ analyzer adapted for spaceflight (referred to as the CosmOrbitrap), coupled with a commercial pulsed UV laser source (266 nm), was used to successfully characterize a variety of planetary analog samples via ultrahigh resolution laser desorption/ablation mass spectrometry. The materials analyzed in this study include: jarosite (a hydrous sulfate detected on Mars); magnesium sulfate (a potential component of the subsurface ocean on Europa); uracil (a nucleobase of RNA); and a variety of amino acids.

RESULTS

The instrument configuration tested here enables: measurement of major elements and organic molecules with ultrahigh mass resolution (m/Δm ≥ 120,000, FWHM); quantification of isotopic abundances with <1.0% (2σ) precision; and identification of highly accurate masses within 3.2 ppm of absolute values. The analysis of a residue of a dilute solution of amino acids demonstrates the capacity to detect twelve amino acids in positive ion mode at concentrations as low as ≤1 pmol/mm² while maintaining mass resolution and accuracy requirements.

CONCLUSIONS

The CosmOrbitrap mass analyzer is highly sensitive and delivers mass resolution/accuracy unmatched by any instrument sent into orbit or launched into deep space. This prototype instrument, which maps to a spaceflight implementation, represents a mission-enabling technology capable of advancing planetary exploration for decades to come.