Collision-induced Tandem Mass Spectrometry Research Articles

Unusual Class I Lanthipeptides from the Marine Bacteria Thalassomonas viridans.

A novel class I lanthipeptide produced by the marine bacterium Thalassomonas viridans XOM25T was identified using genome mining. The putative lanthipeptides were heterologously coexpressed in Escherichia coli as GFP-prepeptide fusions along with the operon-encoded class I lanthipeptide modification machinery VdsCB. The core peptides, VdsA1 and VdsA2, were liberated from GFP using the NisP protease, purified, and analyzed by collision-induced tandem mass spectrometry. The operon-encoded cyclase and dehydratase, VdsCB, exhibited lanthipeptide synthetase activity via post-translational modification of the VdsA1 and VdsA2 core peptides. Modifications were directed by the conserved double glycine leader containing prepeptides of VdsA1 and VdsA2.

Tandem mass spectrometric analysis of novel caffeine scaffold-based bifunctional compounds for Parkinson's disease.

Novel bifunctional compounds composed of a caffeine scaffold attached to nicotine (C8 -6-N), 1-aminoindan (C8 -6-I), or caffeine (C8 -6-C8 ) were designed as therapeutics or diagnostics for Parkinson's disease (PD). In order to probe their pharmacological and toxicological profile, an appropriate analytical method is required. The goal of this study is to establish a tandem mass spectrometric fingerprint for the development of quantitative and qualitative methods that will aid future assessment of the in vitro and in vivo absorption, distribution, metabolism, excretion (ADME) and pharmacokinetic properties of these lead bifunctional compounds for PD. Accurate mass measurement was performed using a hybrid quadrupole orthogonal time-of-flight mass spectrometer while multistage MS/MS and MS3 analyses were conducted using a triple quadrupole linear ion trap mass spectrometer. Both instruments are equipped with an electrospray ionization (ESI) source and were operated in the positive ion mode. The source and compound parameters were optimized for all three tested bifunctional compounds. The MS/MS analysis indicates that the fragmentation of C8 -6-N and C8 -6-I is driven by the dissociation of the nicotine and 1-aminoindan moieties, respectively, but not caffeine. A significant observation in the MS/MS fragmentation of C8 -6-C8 suggests that a previously reported loss of acetaldehyde during caffeine dissociation is instead a loss of CO2 . The collision-induced tandem mass spectrometry (CID-MS/MS) analysis of these novel bifunctional compounds revealed compound-specific diagnostic product ions and neutral losses for all three tested bifunctional compounds. The established MS/MS fingerprint will be applied to the future development of qualitative and quantitative methods.

Structural elucidation of palytoxin analogs produced by the dinoflagellate Ostreopsis ovata IK2 strain by complementary use of positive and negative ion liquid chromatography/quadrupole time‐of‐flight mass spectrometry

The ovatoxins are palytoxin analogs of a dinoflagellate origin implicated in human intoxication. The structures of ovatoxin-a, ovatoxin-d, and ovatoxin-e produced by the IK2 strain of Ostreopsis ovata collected in Japan were elucidated using liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/QTOFMS). The novel structures and a new insight into the spectral data are presented. The structural elucidations were carried out by complementary use of positive and negative ion LC/QTOFMS. Ostreocin-D (C127H219N3O53), another palytoxin congener previously elucidated by negative fast-atom bombardment collision-induced tandem mass spectrometry (FAB CID MS/MS), was used as a reference. Positive ion spectra allowed deduction of hydroxyl positions based on the conjugated polyene structures produced, while the negative ion spectra allowed assignments of cleavage sites of C-C bonds. The analysis could be performed using a small sample without extensive purification. Ovatoxin-a IK2 (C129H223N3O52), ovatoxin-d IK2 (C129H223N3O53), and ovatoxin-e IK2 (C129H223N3O53) were tentatively assigned to 42-hydroxy-17,44,70-trideoxypalytoxin, 42-hydroxy-17,70-dideoxypalytoxin and 42,82-dihydroxy-17,44,70-trideoxypalytoxin, respectively. The wide applicability of the method was suggested.

Probing deamidation in therapeutic immunoglobulin gamma (IgG1) by ‘bottom‐up’ mass spectrometry with electron transfer dissociation

Aspartic acid formed by nonenzymatic deamidation of asparagine often isomerizes to isoaspartic acid through a succinimide intermediate. Accumulation of isoaspartic acid initiates aggregation and degradation in proteins. Deamidation at the antigen-binding region reduces the efficacy and also upregulates immunogenicity of monoclonal antibodies. We report an improved 'bottom-up' tandem mass spectrometric method to detect and decipher the position of isoaspartate formation in therapeutic immunoglobulin gamma in a single chromatographic run. Differentiation between aspartate and isoaspartate residues through collision-induced tandem mass spectrometry is formidable due to their identical mass. Signature backbone cleavage ions, c(n) + 57 and z(l-n) - 57, produced upon radical-mediated fragmentation, were used to delineate the site of isomerization. It is more conclusive than monitoring the relative peak intensity and the decrease in hydrophobicity of the isoaspartate-containing peptide in a chromatographic elution. Collectively, this methodology provides a useful tool to monitor deamidation and isomerization in biopharmaceuticals during their production, downstream processing and storage.

Can mass dissociation patterns of transition‐metal complexes be predicted from electrochemical data?

The Cooks kinetic method has been very convenient to correlate the relative dissociation rates obtained by collision-induced fragmentation experiments with the energies of two related bonds in molecules and complexes in the gas phase. Reliable bond energy data are, however, not always available, particularly for polynuclear transition-metal complexes, such as the triruthenium acetate clusters of the general formula [Ru(3) (micro(3)-O)(micro-CH(3)COO)(6)(py)(2)(L)](+), where L = ring substituted N-heterocyclic ligands. Accordingly, their gas-phase collision-induced tandem mass spectrometry (CID MS/MS) dissociation patterns have been analyzed pursuing a relationship with the more easily accessible redox potentials (E(1/2)) and Lever's E(L) parameters. In fact, excellent linear correlations of ln(1/2A(L)/A(py)), where A(py) and A(L) are the abundance of the fragments retaining the pyridine (py) and L ligand, respectively, with E(1/2) and E(L) were found. This result shows that those electrochemical parameters are correlated with bond energies and can be used in the analysis of the dissociation data. Such modified Cooks method can be used, for example, to determine the electronic effects of substituents on the metal-ligand bonds for a series of transition-metal complexes.

Coupling of fully automated chip electrospray to Fourier transform ion cyclotron resonance mass spectrometry for high‐performance glycoscreening and sequencing

The NanoMate robot has been coupled to a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer at 9.4 T and implemented for the first time for complex carbohydrate analysis. It was optimized in the negative ion mode to achieve automated sample delivery on the chip along with increased sensitivity, ultra-high resolution and accurate mass determination. A novel bracket has been designed to allow a reliable mounting of the NanoMate to the Apollo electrospray ionization (ESI) source of an APEX II instrument. The notably higher efficiency of ionization for compositional mapping of complex mixtures and feasibility for fragmentation analysis of components by sustained off-resonance irradiation collision-induced tandem mass spectrometry (SORI-CID MS2) has been demonstrated on a glycoconjugate mixture containing O-glycosylated sialylated peptides from urine of a patient suffering from a hereditary N-acetylhexosaminidase deficiency (Schindler's disease), previously analyzed by capillary-based nanoESI-FTICRMS, and of a healthy control person. Due to its potential to generate highly charged ionic species, reduce the in-source fragmentation, increase sensitivity, reproducibility and ionization efficiency, along with the ability to generate a sustained and constant electrospray, this method can be considered as a new platform for advanced glycomics.

Copper and iron interactions with angiotensin-converting enzyme inhibitors. A study by fast-atom bombardment tandem mass spectrometry.

Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd.

Fast-atom bombardment mass spectrometry and low energy collision-induced tandem mass spectrometry of tauroconjugated bile acid anions

Fragmentation of negative ions produced by fast-atom bombardment (FAB) from 14 tauroconjugated bile acids and some of their deuterated analogs has been studied by mass spectrometry and by collision-induced dissociation (CED) tandem mass spectrometry at low energy.Low energy collision-induced dissociation of the deprotonated molecules [M - H](-) of these tauroconjugated bile acids leads to both charge-driven and charge-remote fragmentations (CRF). The former yields neutral loss from the side chain with charge migration during the fragmentation process. These fragments dominate the CID spectra, but are absent from the FAB spectra. Their relative abundances are dependent on the number and the positions of the hydroxyl groups in the steroid nucleus and thus permit distinction among some positional isomers.The CRF fragments correspond to cleavages in the side chain up to fragmentations across the steroid rings with charge retention on the sulfonate group. These CRF fragments, which also are useful for structural identification, are less intense in CID than in FAB spectra. It appears that these charge-remote fragments are favored by unsaturation in the steroid rings, either as keto groups or as endocyclic double bonds. Tandem mass spectrometry combined with the use of deuterated analogs demonstrates that the structures of the survivor pseudomolecular ions and of the CRF fragments are not rearranged.