Richard T. Gallagher

Cyclodextrin—piroxicam inclusion complexes: analyses by mass spectrometry and molecular modelling

Abstract Mass spectrometry has been used to investigate the natures of non-covalent complexes formed between the anti-inflammatory drug piroxicam and α-, β- and γ-cyclodextrins. Energies of these complexes have been calculated by means of molecular modelling. There is a correlation between peak intensities in the mass spectra and the calculated energies.

Electrospray mass spectrometry of lanthanide β-diketone complexes Part 1. Ligand exchange processes involving acetate ions and Ln(thd)3 complexes (Ln=Eu, Gd, Yb; thd=2,2,6,6-tetramethyl-3,5-heptanedione)

Abstract The electrospray mass spectra of the lanthanide (Ln)2,2,6,6-tetramethyl-3,5-heptanedione (thd) complexes Eu(thd) 3 , Gd(thd) 3 and Yb(thd) 3 were obtained from a methanol/water solution containing acetic acid. Protonated molecular ions Ln(thd) 3 H + were obtained in each case. Extensive ligand exchange reactions in solution resulted in many mixed-ligand cationic species involving acetato ligands, H 2 O and H + . Tandem mass spectrometry of Ln(thd) 3 H + gave the fragment ions Ln(thd) + containing a lanthanide in the divalent state for Eu and Yb.

Glycosidase-catalysed oligosaccharide synthesis: Preparation of the N-acetylchitooligosaccharidespenta-N-acetylchitopentaose and hexa-N-acetylchitohexaose using the β-N-acetylhexosaminidase of Aspergillus oryzae

Abstract Using a crude β-N-acetylhexosaminidase from Aspergillus oryzae both tri-N-acetylchitotriose (GlcNAc)3 (1, n=1) and tetra-N-acetylchitotetraose (GlcNAc)4 (1, n=2) act respectively as both glycosyl donor and glycosyl acceptor to give product mixtures containing significant quantities of the corresponding penta- and hexasaccharides [1 (n=3) and 1 (n=4), respectively] which are readily isolated and purified by charcoal-Celite chromatography.

The mechanism of alkyl radical elimination from ionised γγ-disubstituted alkenyl methyl ethers

The mechanism of alkyl radical loss from ionised alkenyl methyl ethers containing two γ-alkyl substituents, R1R2C=CHCH2OCH3+•, has been studied by investigating the collision-induced dissociation spectra of the resultant C n H2n–1O+ oxonium ions (n = 5–7). Comparison of these spectra with one another and those of reference ions generated by dissociative ionisation of secondary allylic alkenyl methyl ethers indicates that expulsion of a γ-alkyl group occurs without isomerisation of the heavy atom skeleton via an allylic rearrangement. This finding is consistent with the occurrence of two consecutive 1,2-H shifts in R1R2C=CHCH2OCH3+•, followed by γ-cleavage of the ionised enol ether, R1R2CHCH=CHOCH3+•, to give R1CH=CHCH=OCH3+ or R2CH=CHCH=OCH3+. Thus, CH3CH2CH2(CH3CH2)C=CHCH2OCH3+• loses C2H5• and C3H7• to yield CH3CH2CH2CH=CHCH=OCH3+ and CH3CH2CH=CHCH=OCH3+, respectively.

Efficient clustering of cyclic sulfonium salts applying liquid secondary ion mass spectrometry

Salt-like cluster ions of the ([cation] n [anion]n–1)+ type are commonly composed of mono-atomic, inorganic components. Clusters containing organic ions are also known, with nitrogen-centred cations being particularly prominent. However, sulphur-centred analogues, such as organic sulphonium salts, represent a notable exception. Fast atom bombardment and liquid secondary ion mass spectrometry of such compounds show, in general, a low tendency towards the formation of clusters. The present study reveals that sputtering of cyclic sulphonium salts leads to the efficient formation of cluster ions beyond previous observations. Cluster ions are characterised by isotopic pattern analysis and collision-induced dissociation.

Low- and high-energy collision-induced dissociation of pyridinoline and deoxypyridinoline ions using Fourier transform ion cyclotron resonance electrospray and liquid secondary-ion magnetic sector mass spectrometry

Abstract The trifunctional collagen cross-link molecules pyridinoline and deoxypyridinoline have been structurally characterised by (1) low-energy collision-induced dissociation (CID) (ECOM ≈ 15 eV) using Fourier transform ion cyclotron resonance electrospray ionisation mass spectrometry (FT-ICR-ESI-MS), and (2) high-energy collision-induced dissociation (ECOM ≈ 400 eV) using liquid secondary-ion mass spectrometry (LSIMS) on a four-sector mass spectrometer. Both ESI and LSIMS ionisation readily produce the naturally occurring parent cations, although the LSIMS ionisation method is somewhat hampered by background ions from the matrix. Low-energy or high-energy collision-induced dissociation produces structurally informative fragmentations. The observed fragmentation patterns in the low- and high-energy CID spectra are, however, strikingly different. Both low- and high-energy CID are structurally informative and appear to be complementary in the characterisation of collagen cross-link molecules.

Evidence for the formation of transient CH4C60+˙ following high-energy collisions between C60+˙ radical cations and methane

High-energy collisions of the C60+˙ radical cation with methane produce CH2 C60+˙ and CHC60+, characterised by deficits in translational energy consistent with their formation from CH4 C60+˙.