Mass spectrum electrospray

Positive-ion electrospray mass spectrum of human hemoglobin (a) as initially obtained with all the measured masses, and (b) after calculation of true mass, as in Figure 8.3. The spectrum transforms into two main peaks representing the main alpha and beta chains of hemoglobin with accurate masses as given. This transformation is fnlly automated. The letters A, B, C refer to the three chains of hemoglobin. Thus, A13 means the alpha chain with 13 protons added. 

How then do we determine the molecular weight of an analyte from an electrospray mass spectrum To do this, we must consider the processes that lead to the formation of the ions observed. Each ion is formed by the addition of a number of species, often protons, to the analyte molecule, with the number of charges residing on that ion being related to the number of species added. The measured m/z of an ion is thus related to the molecular weight of the analyte from which it is generated by the following equation ... 

Table 4.1 Molecular weight of horse heart myoglobin calculated from four adjacent pair of ions observed in its electrospray mass spectrum...

Figure 5.23 Electrospray mass spectrum of the tryptic peptide with a retention time of 41.81 min from intact CMY-2 -lactamase. Reprinted from Biochim. Biophys. Acta, 1547, Bonomo, R. A., Liu, J., Chen, Y., Ng, L., Hujer, A. M. and Anderson, V. E., Inactivation of CMY-2 0-lactamase by tazobactam initial mass spectroscopic characterization , 196-205, Copyright (2001), with permission from Elsevier Science.

Figure 5.38 LC-electrospray mass spectrum of warfarin obtained from an LC-MS system which allows eluate from four HPLC columns to be analysed simultaneously. From de Biasi, V., Haskins, N., Organ, A., Bateman, R., Giles, K. and Jarvis, S., Rapid Commun. Mass Spectrom., 13, 1165-1168, Copyright 1999. John Wiley Sons Limited. Reproduced with permission.

Two adjacent signals in an electrospray mass spectrum of a pure protein sample have m/z values of 893.9 and 834.3. Calculate the charge state of each signal and the mass of the neutral protein. (+14 and +15 12,500 Da). 

Fig. 19.3. Example of high-resolution experiments on complex mixtures, showing the multiple elemental compositions possible at a single nominal mass. Top panel four elemental compositions at m/z 225 in the positive ion electrospray mass spectrum of a diesel oil feedstock (from Wu et al. [17]). Bottom panel multiple compositions at m/z 455 in the negative ion electrospray spectrum of olive oil (from Marshall et al. [18]).

The electrospray mass spectrum of metabolite 2 indicates it has a molecular weight of 522 Da, while the MS-MS spectrum of the (M + H)+ ion contains an intense ion at m/z 422, 1 Da greater than the base peak of the MS-MS spectrum of the protonated molecular ion of the parent drug. If we assume a similar relationship between these ions as assumed for m/z 465 and m/z 466 above, it is not unreasonable to postulate the structure of metabolite 2 to be that shown in Figure 5.44. 

Figure 10 Electrospray Mass Spectrum of a Peptide Having a Molecular Weight of 1977 Daltons131...

The molecular ion in the electrospray mass spectrum of the Pfizer anti-depressant Lustral (sertraline hydrochloride), CiyHigNCb, contains the peaks shown in Figure 5.25. Explain the relative intensities of these peaks (given in brackets above each peak). 

Table 22-3 Analysis of electrospray mass spectrum of cytochrome c in Figure 22-23... 

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.

FIGURE 7.35 (a) Initial mass spectrum obtained from PMMA microchip device. The mass spectrum is characterized by a substantial chemical noise background most likely due to residual developer solution present in the microchannels, (b) Electrospray mass spectrum obtained with 10 pM angiotensin I (in 50 50 MeOH/H20 containing 1% acetic acid) after the PMMA microchip has been washed with 50 50 MeOH/H20. The simple solvent wash completely eliminates the residual chemical contamination arising from the microchip fabrication step [200]. Reprinted with permission from the American Chemical Society. 

Fig. 5. Electrospray mass spectrum of an authentic epoxidation reagent mixture obtained by adding PhIO to an acetonitrile solution of [(salen)Mn(CH3CN)]+...

Fig. 9. a Electrospray mass spectrum of a 10 4 mol l"1 solution of HC1 in H20 under mild declustering conditions, showing the presence of different clusters [(H30)(H20)n]+, the clusters with n=l, 2, and 3 being most prominent, b CID threshold curve (collision gas Ar), showing the dependence of the dissociation cross section against collision energy, and fit to Ar-mentrout s threshold function... 

Fig. 4. a Electrospray mass spectrum of a 100 mmol l-1 solution of L-serine extensive clustering of serine units is observed for charge states z=l, 2, and 3. b Ion mobility spectrum of ions with m/z=841 showing the three features assigned as protonated octamer, doubly protonated 16-mer, and triply protonated 24-mer... 

Figure 3 Tandem electrospray mass spectrum (positive mode) of lactosylceramide, which shows the neutral loss of two hexose residues.

Figure 13.6. (a) Partial negative ion electrospray mass spectrum of a 36-component library mixture. Both the measured mass and the difference between the measured and theoretical values (in ppm) are shown, (b) Negative ion electrospray spectrum of the 120-component library showing the resolution of three nominally isobaric peaks. (Reproducedfrom Ref. 24 ty permission of Bentham Science Publishers). 

Figure 13.9. Affinity capillary electrophoresis-UV-raass spectrometry of a 100-tetrapep-tide library screened for binding to vancomycin (104 fxM in the electrophoresis buffer), (a) The elution of peptides was monitored with UV absorbance during capillary electrophoresis, and the elution time irrieased with increasing affinity for vancomycin. (b) Positive ion electrospray mass spectrum with CID of the Tris adduct of the proton-ated peptide detected at —5 min in the electropherogram shown in a (Reproduced from Ref 52 by permission of the American Chemical ardety.)...

Figure 7. (Left) Total ion chromatogram of a waterborne clearcoat. (Right, Top) summed electrospray mass spectrum (19.68-19.98 min) (right, bottom) summed electrospray mass spectrum (22.48-23.38 min).

Figure 2. Electrospray mass spectrum of the 30 member library. Both doubly and singly protonated species are observed. Insert blown up region of singly charged species. For conditions, see text.

Figure 3. Electrospray mass spectrum of the selected compounds from the library. One letter code for the N-terminal tetrapeptide moiety represents corresponding peptides with the biotin on the lysine sidechain. Due to the presence of Na in the binding buffer, peptides are observed...

---