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Figure 7. Curie-point pyrolysis mass spectra of two closely related dipeptides, differing only in the amino acid sequence. Note changes in relative intensities at m/z 79, 92, 94, 104, 108, 117 and 120. The difference in intensity at m/z 60 may be unrelated to structural features and probably represents acetic acid derived from the acetate counter-ion of the terminal amino group. Conditions: sample 10 ug; Tc 510°C; Eel 14 eV.

Figure 7. Curie-point pyrolysis mass spectra of two closely related dipeptides, differing only in the amino acid sequence. Note changes in relative intensities at m/z 79, 92, 94, 104, 108, 117 and 120. The difference in intensity at m/z 60 may be unrelated to structural features and probably represents acetic acid derived from the acetate counter-ion of the terminal amino group. Conditions: sample 10 ug; Tc 510°C; Eel 14 eV.

preferring faster filament pyrolysis techniques over slow furnace pyrolysis techniques such as direct probe pyrolysis - fast laser pyrolysis might help to produce larger building blocks in protein pyrolysis. Preliminary experiments by Kistemaker et al. (ref. 29), however, failed to demonstrate these larger fragments.

In summing up the present situation, we have the distinct impression that, because of the limited success obtained and the availability of powerful alternative techniques, Py-MS techniques may not gain as much momentum in the chemical characterisation of proteins as for some other biopolymers. However, it should be kept in mind that some important classes of proteins, such as glycoproteins, are less amenable to conventional techniques and may therefore constitute an important potential field of application. Also, Py-MS may prove to be of value in the rapid characterisation of protein preparations, when only a limited amount of chemical interpretation is desired (ref. 96). Alternatively, the sensitivity of Py-MS might perhaps allow its use in tandem with conventional protein characterisation techniques, e.g. for the analysis of electrophoretic bands or spots. Finally, Py-MS has proved to be of value in the characterisation of unusual oligopeptide structures such as those encountered in some antibiotics (ref. 61). An example of the Py-MS spectra of two closely related dipeptides is shown in Figure 7, demonstrating the sensitivity of the Curie-point Py-MS technique to minor structural details.

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