Mass spectrum hemoglobin

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. 

An electrospray/transmission quadrapole mass spectrum of the a chain of hemoglobin from acidic solution exhibits nine peaks corresponding to MH"+. Find the charge, n, for peaks A-I. Calculate... 

A MALDI-TOF mass spectrum of human hemoglobin Hb Miyazono. Two p-globins (one normal and one mutant) are detected. B MALDI spectrum of the tryptic cleavage of the (3-globin from Hb Miyazono mutant of human hemoglobin. Mutated peptides T9m and T8+T9m are detected. By tandem mass spectrometry, the mutation is characterized as the substitution 79D-E. Reproduced (modified) from Wada Y., Journal of Chromatography B, 781, 291-301, 2002, with permission. 

Pyrolysis does not provide always the desired information on materials from this group. For example, several pyrolysis studies on hemoglobin [15,16], showed that the heme prosthetic group is not revealed in the mass spectrum due to its low contribution to the total mass of the molecule (about 1% [15]), The Py-MS result for hemoglobin from bovine erythrocytes obtained by Curie point pyrolysis at 510° C from a sample applied as a methanol suspension and analyzed by MS with El ionization at 14 eV [15] is shown in Figure 12.4.1. 

Intact hemoglobin variants can also be detected with ESI-MS. The ESI mass spectrum contains a series of multiply charged ions that usually complicate the detection of a protein mixture. The data can, however, be software-transformed to provide a single peak that is unique to a specific protein. This approach has been used to identify hemoglobin from a blood sample from a newborn sickle-cell carrier [46]. 

FIGURE 4.14 Mass spectrum of hemoglobin in buffered ammonium acetate at pH 9.5 from 1500 to 4500 mlz- All observed peaks are annotated. The elevated pH stabilizes tetramer signal with the [Q+17H+] + tetramer dominating the spectrum. Holoheterodimer and a are also present. 

Fig. 2. Five fragment masses determined from the mass spectrum of the mock unknown protein (human hemoglobin a chain) tryptic digest form the basis of peptide mapping. The mass-to-charge ratio is labeled nih on the horizontal axis.

Fig. 5. MS/MS mass spectrum reveals the partial sequence of a ttyptic peptide from the human hemoglobin a subunit This information is sufficient to successfully perform a sequence tag search and identify the protein. L/I stands for leucine or isoleucine, whereas and X denote unknown sequences.

Figure 5.8 ESI product ion mass spectrum of the aT9 peptide characterizing the a-chain of bovine hemoglobin, measured on a QTrap 4000 system.

Figure 4 Mass spectrometry analysis of difference peptides from the dehydroascorbate modified p-globin subunit. Dehydroascorbate modified deoxy recombinant hemoglobin was prepared as described in Fig. 2. Trypsin digestion was performed as described in materials and methods and the p-globin N-terminal peptide (see upper panel Fig. 3) and the difference peptide (see lower panel Fig. 3) analyzed hy LC-MS. The spectrum in the upper panel represents the P-globin N-terminal peptide and the spectrum in the lower panel represents the difference peptide. A summary of the data is presented in Table 1.

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