Charge detection mass spectrometry (CDMS) is a single-particle technique where the masses of individual ions are determined from simultaneous measurement of each ion’s mass-to-charge ratio (m/z) and ...charge. CDMS has many desirable features: it has no upper mass limit, no mass discrimination, and it can analyze complex mixtures. However, the charge is measured directly, and the poor accuracy of the charge measurement has severely limited the mass resolution achievable with CDMS. Since the charge is quantized, it needs to be measured with sufficient accuracy to assign each ion to its correct charge state. This goal has now been largely achieved. By reducing the pressure to extend the trapping time and by implementing a novel analysis method that improves the signal-to-noise ratio and compensates for imperfections in the charge measurement, the uncertainty has been reduced to less than 0.20 e rmsd (root-mean-square deviation). With this unprecedented precision peaks due to different charge states are resolved in the charge spectrum. Further improvement can be achieved by quantizing the charge (rounding the measured charge to the nearest integer) and culling ions with measured charges midway between the integral values. After ions with charges more than one standard deviation from the mean are culled, the fraction of ions assigned to the wrong charge state is estimated to be 6.4 × 10–5 (i.e., less than 1 in 15 000). Since almost all remaining ions are assigned to their correct charge state, the uncertainty in the mass is now almost entirely limited by the uncertainty in the m/z measurement.
An Orbitrap-based ion analysis procedure determines the direct charge for numerous individual protein ions to generate true mass spectra. This individual ion mass spectrometry (I
MS) method for ...charge detection enables the characterization of highly complicated mixtures of proteoforms and their complexes in both denatured and native modes of operation, revealing information not obtainable by typical measurements of ensembles of ions.
Charge detection mass spectrometry (CDMS) of low-level signals is currently limited to the analysis of individual ions that generate a persistent signal during the entire observation period. Ions ...that disintegrate during the observation period produce reduced frequency domain signal amplitudes, which lead to an underestimation of the ion charge state, and thus the ion mass. The charge assignment can only be corrected through an accurate determination of the time of ion disintegration. The traditional mechanisms for temporal signal analysis have severe limitations for temporal resolution, spectral resolution, and signal-to-noise ratios. Selective Temporal Overview of Resonant Ions (STORI) plots provide a new framework to accurately analyze low-level time domain signals of individual ions. STORI plots allow for complete correction of intermittent signals, the differentiation of single and multiple ions at the same frequency, and the association of signals that spontaneously change frequency.
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•A simple electrospray interface consisting of a long drift region followed by a DC ion carpet is described.•The performance is optimized by trajectory calculations and ...experiments.•Trajectory calculations indicate >90% transmission efficiency for thermalized ions.•m/z discrimination at the DC ion carpet is minimized.
We describe a simple electrospray interface incorporating a long drift region and a DC ion carpet. The function of the drift region is to thermalize and desolvate the ions. It has a series of ring electrodes supplied with RF and DC voltages, which radially confine and transport ions towards the DC ion carpet. The DC ion carpet consists of a series of concentric rings on a planar printed circuit board, which provide a DC potential gradient that funnels ions through a central aperture. The design and operating parameters were optimized by trajectory calculations and experiments. According to calculations, the transmission efficiency for thermalized ions exceeds 90%, and there is little m/z discrimination at the exit aperture.
Charge detection mass spectrometry (CDMS) of low-level signals is currently limited to the analysis of individual ions that generate a persistent signal during the entire observation period. Ions ...that disintegrate during the observation period produce reduced frequency domain signal amplitudes, which lead to an underestimation of the ion charge state, and thus the ion mass. The charge assignment can only be corrected through an accurate determination of the time of ion disintegration. The traditional mechanisms for temporal signal analysis have severe limitations for temporal resolution, spectral resolution, and signal-to-noise ratios. Selective Temporal Overview of Resonant Ions (STORI) plots provide a new framework to accurately analyze low-level time domain signals of individual ions. STORI plots allow for complete correction of intermittent signals, the differentiation of single and multiple ions at the same frequency, and the association of signals that spontaneously change frequency.
Reactions of CO 2 on Solid and Liquid Al 100 Leslie, Katheryne L.; Shinholt, Deven; Jarrold, Martin F.
The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory,
02/2013, Letnik:
117, Številka:
6
Journal Article
Reactions of CO sub(2) on Solid and Liquid Al sub(100) super(+) Leslie, Katheryne L; Shinholt, Deven; Jarrold, Martin F
The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory,
02/2013, Letnik:
117, Številka:
6
Journal Article
Recenzirano
The reactions of CO sub(2) on the Al sub(100) super(+) cluster have been investigated as a function of cluster temperature (300-1100 K) and relative kinetic energy (0.2-10 eV). Two main products are ...observed at low cluster temperature: Al sub(100)O super(+) (which is believed to result from a stripping reaction) and Al sub(100)CO sub(2) super( +) from complex formation. As the cluster temperature is raised, both products dissociate by loss of Al sub(2)O. Al sub(100)O super(+) forms Al sub(98) super(+), while Al sub(100)CO sub(2) super( +) forms Al sub(98)CO super(+) and Al sub(96)C super(+). In both cases, loss of Al sub(2)O turns-on above the melting temperature of Al sub(100) super(+). This presumably occurs because the overall reaction leading to the loss of Al sub(2)O is significantly less endothermic for the liquid cluster than for the solid.
Reactions of CO2 on Solid and Liquid Al100 Leslie, Katheryne L; Shinholt, Deven; Jarrold, Martin F
The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory,
02/2013, Letnik:
117, Številka:
6
Journal Article
Recenzirano
The reactions of CO2 on the Al100 + cluster have been investigated as a function of cluster temperature (300–1100 K) and relative kinetic energy (0.2–10 eV). Two main products are observed at low ...cluster temperature: Al100O+ (which is believed to result from a stripping reaction) and Al100CO2 + from complex formation. As the cluster temperature is raised, both products dissociate by loss of Al2O. Al100O+ forms Al98 +, while Al100CO2 + forms Al98CO+ and Al96C+. In both cases, loss of Al2O turns-on above the melting temperature of Al100 +. This presumably occurs because the overall reaction leading to the loss of Al2O is significantly less endothermic for the liquid cluster than for the solid.
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