Characterization of cationic glycoporphyrins by electrospray tandem mass spectrometry

Abstract

Novel cationic porphyrin derivatives having a galactose or a bis(isopropylidene)galactose unit linked directly to a pyridine or to an aminophenyl group were characterized by electrospray tandem mass spectrometry (ESI-MS/MS). The electrospray mass spectra (ESI-MS) show the M(+) ions, since these porphyrins are already monocharged in solution. The fragmentation of these ions under ESI-MS/MS conditions was studied and it was found that elimination of the sugar residue as a radical (-163 or -243 Da) is a common fragmentation pathway. Loss of the sugar unit as a neutral fragment (-162 or -242 Da) and cross-ring fragmentations typical of glyco-derivatives are also observed for the pyridinium glycoporphyrins, but they are absent in the case of ammonium glycoporphyrins. The cationic beta-pyridiniumvinyl porphyrins show an atypical fragmentation due to the cleavage of the C(5)-C(6) bond of the sugar unit. Overall, the different patterns of fragmentation observed in the ESI-MS/MS spectra of the sugar pyridinium porphyrins and of the sugar ammonium phenyl porphyrins can give important information about the type of spacer between the porphyrin and the sugar unit.

Glycophthalocyanines: structural differentiation and isomeric differentiation by matrix‐assisted laser desorption/ionization tandem mass spectrometry

“…). All these fragmentation pathways have been reported in ESI‐MS/MS studies of glycoporphyrin derivatives functionalized with galactose units containing isopropylidene protecting groups and confirm the presence of protected galactose moieties in the molecule …”

“…Solid secondary ion mass spectrometry was used for the study of acetylated glycoporphyrins, and liquid chromatography coupled to electrospray ionization (ESI)‐MS and tandem mass spectrometry (MS/MS) were used for the analysis of protoporphyrin glycoconjugates . The ESI‐MS/MS technique has proved to be useful for the structural characterization of neutral and cationic glycoporphyrins and electrospray tandem mass spectrometry allowed the differentiation of α‐ and β‐glycoporphyrin stereoisomers . A literature search, however, indicates that there are no detailed studies on the MALDI‐MS or MALDI‐MS/MS of glycophthalocyanines.…”

dMyc expression in the fat body affects DILP2 release and increases the expression of the fat desaturase Desat1 resulting in organismal growth

“…Analysis of peptides was performed at the Quantitative Proteomics Center at Columbia University using an ultrahigh-pressure liquid chromatograph and a quadrupole-time-of-flight mass spectrometer using methods described previously (Oswald et al, 2011). This system uses a shotgun proteomics method called MS E in which mass spectra are recorded at alternate low (precursor) and high (product) fragmentation voltages (Silva et al, 2006), resulting in a more complete representation of the intensity of a peptide in a chromatographic peak. Peptides were analyzed in a LC/MS run on a 0.75 μm ID × 25 cm reverse phase 1.7-μm particle diameter C18 column at a flow rate of 300 nL/min with an acetonitrile/formic acid gradient on a NanoAcquity UPLC (Waters Corp.).…”

Chemical Synthesis and Medicinal Applications of Glycoporphyrins

“…Here, an example is Boyle et al 's synthesis of a series of 5-(N-alkyl-4-pyridyl)--10,15,20-tris(4-thioglycosyl-2,3,5,6-tetrafluorophenyl)porphyrins (Scheme 18) [248] . The synthesis of the key intermediate, 5-(4-pyridyl)- Deprotection of the sugar residue provided the water soluble glycosyl cationic porphyrins 461a-d. Cationic porphyrin monomers such as these have the potential to be characterized by electrospray ionization tandem mass spectrometry (ESI-MS/MS) [228,249] . For satisfactory clinical use a PDT agent must generate sufficient ROS in addition to efficient cellular uptake.…”