| A strategy for the structural elucidation of selected biological molecules has been devised using several mass spectrometry (MS) techniques. A combination of tandem MS and high-resolution, accurate mass measurements has been employed in the study of spirolide marine toxins and paralytic shellfish poisons (PSPs). The toxin profiling of a crude algal extract containing several known and unknown spirolides provided a good example for the use of mass spectrometry in the structural characterization of small molecules. Through the detailed study of the fragmentation behavior of these compounds, some structures of unknown compounds were proposed. In addition, several other compounds were recognized as having similar structural features, thus potentially possessing a biogenetic link to the spirolides. Two PSP toxins, saxitoxin and neosaxitoxin, exhibit extremely complex collision-induced dissociation spectra and their fragmentation patterns were elucidated with ion trap MSn and high-resolution mass spectrometry. A detailed understanding of gas-phase dissociation behavior was afforded by the collection of MS data as well as computational calculations of their gas-phase proton affinities. The PSP toxins also provided an excellent example for the comparison of mass resolution and accuracy requirements of complex spectra. High-resolution Fourier transform-ion cyclotron resonance and medium-resolution quadrupole-time-of-flight instruments were compared for elemental formula assignments from these measurements. Likewise, the study of anthracycline antibiotics involved the detailed study of the fragmentation behavior of doxorubicin and three structural analogs, supported by accurate mass measurements. Furthermore, using the information gained from these experiments, metabolites of doxorubicin were elucidated.;Additionally, growing interest in the ability to conduct rapid quantitative assays for small molecules by matrix-assisted laser desorption/ionization (MALDI) has been the driving force for several recent studies. The combination of a high repetition rate MALDI source with a triple quadrupole has been employed in several fundamental studies involving some technical aspects of high-throughput quantitative MALDI. Also, certain physicochemical properties were assessed for understanding the importance of internal standard selection. The potential of the MALDI-triple quadrupole system has been further demonstrated in a study of the spirolides, both in utilizing its abilities as a high-throughput quantitative instrument and a rapid screening tool. |
