Michael J Pastel

Comparative mass spectrometric analyses of Photofrin oligomers by fast atom bombardment mass spectrometry, UV and IR matrix-assisted laser desorption/ionization mass spectrometry, electrospray ionization mass spectrometry and laser desorption/jet-cooling photoionization mass spectrometry.

Photofrin (porfimer sodium) is a porphyrin derivative used in the treatment of a variety of cancers by photodynamic therapy. This oligomer complex and a variety of porphyrin monomers, dimers and trimers were analyzed with five different mass spectral ionization techniques: fast atom bombardment, UV and IR matrix-assisted laser desorption/ionization, electrospray ionization, and laser desorption/jet-cooling photoionization. All five approaches resulted in very similar oligomer distributions with an average oligomer length of 2.7 +/- 0.1 porphyrin units. In addition to the Photofrin analysis, this study provides a side-by-side comparison of the spectra for the five different mass spectrometric techniques.

Reactions of the trisulfide moiety in calicheamicin

Abstract Calicheamicin γ1I ( 1 ) reacts with Ph3P to form a dimeric trisulfide ( 3 ), MeSSMe, Ph3PS, and Ph3PO, as well as an aromatic degradation product ( 2 ). The oxygen of the Ph3PO is derived from O2. Calicheamicin also reacts with thiols to produce disulfides (eg. 4 ) with high selectivity. Dimeric trisulfide 3 is generated during this reaction.