Charge-deconvoluted spectrum

Example The ESI mass spectrum and the charge-deconvoluted molecular weights (inset) of bovine serum albumine (BSA) as obtained from a quadrupole ion trap instrument are compared below (Fig. 11.19). Ion series A belongs to the noncovalent BSA dimer, series B results from the monomer. [24]... 

Fig. 11.19. Partial ESI mass spectrum of BSA and molecular weights after charge deconvolution (inset). Charge states are assigned to both series of peaks. Reproduced from Ref. [24] by permission. John Wiley Sons, 2000.

Since incubation of the protease with a large excess of DFP could nonspecifically phosphorylate tyrosine residues (10), the control and inactivated protease samples were analyzed by ES mass spectrometry (8). The ES mass spectrum of a fully active control sample of CMV protease is shown in Figure 1, where a series of multiply charged ions (from +12 to +34) provided an average Mf value of 27,910 (calculated Mr=27,909). The deconvoluted spectrum (Fig. 1, inset), shows that only 30% of the protease was full length (observed... 

Figure 1. A, SDS-PAGE analysis. From the left- standard (45, 31, 21 and 14 kDa, from the top), DTT-reduced rhSCF, DTT-reduced dimer, nonreduced rhSCF, and nonreduced dimer. B, RP-HPLC of wild type rhSCF and the SDS-nondissociable dimer. C. ESI-MS analysis of wild type rhSCF and the dimer. The multiply charged ions are indicated and the molecular masses of each form obtained from the respective deconvoluted spectrum are 18,658.5 2.3 and 37,315.2+3.6, respectively.

Figure 5.5 RPLC-MS of pi fractions. A-G represent pi ranges of 9.2-8.1, 8.1-7.0, 7.0 5.9, 5.9-4.8, 4.8-3.7, 3.7-2.6 and 2.6-1.5, respectively. Left panel, extracted mass chromatogram of each protein in the fraction middle panel, raw spectrum of each protein averaged over the top 80% of the LC peak right panel, deconvoluted spectrum (singly charged) by MaxEntl. Only the total ion chromatogram is shown for fraction F no deconvoluted spectrum is shown for fraction G. Reprinted with permission from F. Zhou and M. Johnston, Analytical Chemistry 76, 2734—2740, Copyright 2004 American Chemical Society...

Fig. 10. Mass spectra of from MALDIMS, and from ESIMS. For MALDIMS the mass scale was calibrated with myoglobin ions as an internal standard. For ESIMS the mass scale was calibrated externally using the doubly charged and singly charged ions of gramicidin S. The right hand panel of the ESIMS spectrum shows the deconvoluted spectrum, giving measured molecular weights for the mtgor species, which differ by one hexose. Deviations from the calculated values are shown in parentheses.

Figure 18 Nano-ESI MS/MS analysis of a triply protonated Man9GlcNAc2 A-linked gly-copeptide. (A) The mass spectrum with peptide y ions indicated and (B) the singly charged deconvoluted mass spectrum of panel A where the sugar-loss ion series is indicated (61).

Fig. 5.12 The mass spectrum of myoglobin showing multiply charged ions (upper trace) and the deconvoluted spectrum showing the molecular weight (lower trace).

The extracted ion mobility plot for the [M-f5H] ion of the fibril preparation is presented in Figure 15.5a and b together with the drift scope of the 5+, 6+, and 7+ charged ions. The resulting deconvoluted spectrum of the fibril preparation is shown in Figure 15.6. From the mass spectrometric data of the ion mobility profiles, modifications of Ap by oxidation and loss of one water molecule could be identified, in addition to the intact AP(l-40) ion. The oxidation at the MeF residue of AP was confirmed by MS/MS sequence determination (data not shown). 

Note The output of computerized charge deconvolution can often be customized to either display the mass spectrum as it would appear with singly charged ions or to deliver the molecular weights of the corresponding neutrals (as in the above example). The output of neutral represents the only case where the abscissa has to be labeled mass [u] , while mass spectra strictly require m/z on thex-axis ... 

Fig. 12.35. ESI-FT-ICR IRMPD spectrum of negative ions of the phosphorothioate deoxyoligonucleotide 5 -GCCCAAGCTGGCATCCGTCA-3. (a) The mass spectrum as obtained and (b) after charge deconvolution. Only the

The central engine of this data workflow is the process of spectral deconvolution. During spectral deconvolution, sets of multiply charged ions associated with particular proteins are reduced to a simplified spectrum representing the neutral mass forms of those proteins. Our laboratory makes use of a maximum entropy-based approach to spectral deconvolution (Ferrige et al., 1992a and b) that attempts to identify the most likely distribution of neutral masses that accounts for all data within the m/z mass spectrum. With this approach, quantitative peak intensity information is retained from the source spectrum, and meaningful intensity differences can be obtained by comparison of LC/MS runs acquired and processed under similar conditions. 

Figure 2.22 Charge attribution (a) and deconvolution (b) of the electrospray positive ion mass spectrum of cytochrome c (see Figure 2.21)...

Fig. 20 Deconvolution of the transient spectrum obtained upon the application of a 25-ps laser pulse to a solution of [hexamethylbenzene, NO+] charge-transfer complex showing the Wheland intermediate (430 nm) and the hexamethylbenzene cation radical (495 nm). Courtesy of S.M. Hubig and J.K. Kochi, unpublished results.

Figure 7.5 Deconvoluted, zero charge state mass spectrum demonstrating a hit from a DCL-targeting metallo-[3-lactamase (Bell). The dominant peak corresponds to anrora A kinase linked to extender 23, which is in turn linked to fragment 24 to give 25 (dynamic hit ). Reprinted from Reference 27, with permission from Elsevier, Copyright (2008).

Figure 3-12 Positive ion electrospray mass spectrum of horse apomyoglobin (Mr 16,950.4). The net charge on each ion as well as the mass to charge ratio m/z is indicated at the top of each peak. The inset shows a computer "deconvolution" of the spectrum with the calculated value of molecular mass. Courtesy of Kamel Harrata.

Fig. 12. Band analysis of the (rans-[IrCl4F2]2 charge transfer absorption spectrum (10 K in KC1 discs) by deconvolution into Gaussians (points, experimental, solid line superposition of components)...

If the protein molecular weight is unknown, then the charge states are also not known. The process of determining the molecular weight for an unknown protein from such a mass spectrum is known as deconvolution and is based on simple algebra. If MW is the... 

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