Measurement of leucine enkephalin in caudate nucleus tissue with fast atom bombardment-collision activated dissociation-linked field scanning mass spectrometry

Evaluation of the quantitative analysis of a steroid sulphate using fast atom bombardment and tandem mass spectrometry

Dehydroepiandrosterone sulphate (DHAS) has been quantified in human blood serum by fast atom bombardment (FAB)/tandem mass spectrometry of immunoadsorption extracts. FAB of DHAS yielded abundant ions corresponding to the intact steroid sulphate; these were selected by a double-focusing mass spectrometer prior to collisionally activated decomposition in a quadrupole collision cell and mass analysis by a quadrupole mass filter. [HSO4]- (m/z 97) was the sole prominent daughter ion. For quadrupole mass filter was set to transmit m/z 97 and a narrow-range magnet scan yielded a spectrum of parents, including m/z 367 and 369, corresponding to DHAS and the (2H2)-analogue (used as internal standard), respectively. Serum concentrations by this procedure were in good agreement with data obtained by gas chromatographic/mass spectrometric analyses of DHA heptafluorobutyrate, formed by direct derivatization of the steroid sulphate.

Profiling of neuropeptides using gradient reversed-phase high-performance liquid chromatography with novel detection methodologies

Biological tissues and fluids are subjected to gradient reversed-phase high-performance liquid chromatography (RP-HPLC) separation and the neuropeptide profile of the collected fractions is obtained by radioreceptor assay (RRA) using a broad-based competing ligand. Radioimmunoassay (RIA) is also used to detect specific neuropeptides in the HPLC-purified fractions. Further confirmation of the identity of the peptides present in the tissue is obtained by mass spectrometry (MS) in the fast atom bombardment (FAB) mode. FAB-MS produces the protonated molecular ion of the peptide and allows direct measurement of underivatized peptides at the nanogram level, with increased molecular specificity. FAB-MS-MS identifies a unique amino acid sequence-determining ion in the mass spectrum of a peptide and offers maximum molecular specificity. This analytical chromatography methodology is applied to the study of the molecular basis of several disease states by monitoring several peptidergic pathways and individual peptides and their metabolic relationships. Molecular mechanisms involved in pain, stress, tumor formation, and neurological studies are studied.

Metabolic profiling of opioid peptides in canine pituitary and selected brain regions using HPLC with a radioreceptor assay detector

A combination of gradient reversed-phase high performance liquid chromatography (RP/HPLC) with a radioreceptor assay detector that uses two ligands is used to obtain effectively the metabolic profile of endogenous receptoractive opioid peptides in the canine pituitary and in seven selected brain regions including the hypothalamus, caudate nucleus, mid-brain, amygdala, thalamus, pons-medulla, and the hippocampus. Gradient RP/HPLC separates a mixture of endogenous peptides over a wide range of hydrophobicities. A novel opioid preparation from canine limbic system synaptosomes is utilized in a radioreceptorassay screen; tritiated etorphine (ET) or D-2ala, D-5leuleucine enkephalin (DADL) is used as the competitively displaced ligand. This receptor-rich preparation contains several receptor types, and thus serves well as a screen with the required low level of specificity. Subsequent analysis with other detectors of high specificity (MS, RIA) will follow this screen in other studies. Etorphine interacts with several of the opioid peptide-preferring receptors, whereas DADL is more specific towards the delta receptor that preferentially binds the smaller pentapeptides of the enkephalin family. The highest amount of peptide receptor activity found in this study is in the pituitary tissue, a smaller amount in the hypothalamus and caudate nucleus, and still lower amounts in the other five brain tissue extracts. This variation in peptide concentration most probably reflects three separate factors that operate in this biologic system: differential tissue-specific processing patterns of the large peptide precursors; distribution of the three opioid peptide systems; and the receptor preparation and the radioligand used in the assay. The structures of the receptoractive compounds in each RP/HPLC peak await mass spectrometric confirmation.

Fast atom bombardment mass spectrometry in the pharmaceutical analysis of drugs

The principles, techniques and value of fast atom bombardment mass spectrometry are summarized in this revïew. Applications of the method in such areas as molecular weight determination, standard and metabolic studies, and peptide sequencing, as well as direct quantitative analysis, are surveyed, with examples from several classes of compounds with pharmacological activity.

Metabolic profiling of radioreceptor-assayable opioid peptides in a human pituitary ACTH-secreting tumor

The profile of endogenous opioid peptides in the peptide-rich fraction obtained from a homogenate of an ACTH-secreting human pituitary tumor is presented. Gradient RP-HPLC is used to separate the mixture into peptide constituents. A preparation of opioid receptors is used in a radioreceptor assay with ethorphine - a relatively non-specific ligand that is used as a screen because it interacts with mu, sigma, and delta receptors - as the HPLC detector to detect a range of peptides that derive from proenkephalin A and POMC.

The differentiation of isomeric biological compounds using collision-induced dissociation of ions generated by fast atom bombardment

Though fast atom bombardment ionization makes possible the ionization and molecular weight determination of polar or thermally labile biological compounds, the resulting mass spectra commonly give few or no fragment ions which would allow detailed structural analysis. In particular, isomeric compounds often give identical spectra. Collision-induced dissociation of ions resulting from fast atom bombardment ionization is shown to be a powerful combination which can differentiate isomeric substances. The technique is applied to isomeric bile acid salts and steroid conjugates and is capable of differentiating structural isomers which have similar fast atom bombardment mass spectra. A range of isomeric cyclic nucleotides is also shown to be amenable to the method. Sensitivity limits are examined and the unequivocal identification of two 3',5'-cyclic nucleotides isolated from living systems is demonstrated.

Metabolic profiling of opioid peptides in tooth pulp by HPLC and radioreceptor assay

A analytical system using a combination of gradient RP-HPLC and radioreceptor assay as the HPLC-detector is used to analyze the peptide-rich fraction extracted from a canine tooth pulp homogenate and to provide a metabolic profile of endogenous receptoractive peptides. The gradient RP-HPLC effectively separates the endogenous peptide mixture into a range of hydrophobicities that corresponds to a spectrum of peptide sizes. The receptor preparation is derived from a canine limbic system synaptosome fraction. 3H-DADL serves as the ligand in the RRA. The RP-HPLC/RRA data indicate canine tooth pulp contains a wide range of peptides that interact with the opioid peptide receptor preparation and displace the delta-receptor preferring ligand D2-ala, D5-Leu leucine enkephalin.

Asymmetric behavior induced by enkephalinergic agents in the basal ganglia

The caudate-putamen (CDp) and the globus pallidus (GP) are sites rich in both leucine (LEU) and methionine-enkephalin (MET-ENK) and in ENK receptors. Since chemical and electrolytic lesions of the CDp and GP result in a reduction in ENKs and their receptors and in motor asymmetry, there may be a role for CDp and GP ENKs in rotational behavior and bodily asymmetry. To test this possibility, various doses of D-ALA-2-LEU-ENK, D-ALA-2-MET-ENK, naloxone and naltrexone were injected into the CDp and GP through chronically implanted cannulae. The injections of MET and LEU-ENK caused dose-dependent ipsiversive rotations while injections of naloxone and naltrexone caused contraversive rotations. All of the drug injections also caused bodily asymmetries which were in the same direction as the circling. Intraperitoneal injections of naloxone dose-dependently blocked the rotational behavior induced by the most effective dose of the ENKs used. ENK injections into sites adjacent to the CDp and GP (i.e., cortex, nucleus accumbens and the region bordering the bed nucleus of the stria terminalis and the bed nucleus of anterior commissure) failed to produce any significant circling. These results clearly suggest that CDp and GP ENKs cause ipsiversive rotational behavior and bodily asymmetry and must be considered as one element of the control exerted by the basal ganglia over the motor system.

Quantitative analysis of an N-oxide metabolite by fast atom bombardment tandem mass spectrometry

An assay for the N-oxide metabolite of a benzazepine drug by fast atom bombardment ionization with tandem mass spectrometric analysis on a triple quadrupole mass spectrometer has been developed and validated for urine and plasma samples. This methodology allows analysis of this metabolite directly in crude sample extracts, without the need for extensive chromatography or sample derivatization. Quantification was accomplished with the use of a stable isotope analog of the analyte as an internal standard, using the selected reaction monitoring mode of operation.

Collision-induced dissociation-mass-analysed ion kinetic energy (CID-MIKE) analysis of ions generated by fast atom bombardment of isomeric bile salts

Molecular protonated ions and alkali attachment ions, generated by fast atom bombardment of isomeric bile salts, were analysed by collision-induced dissociation-mass-analysed ion kinetic energy (CID-MIKE) spectroscopy. Within each series of isomers, CID-MIKE spectra were similar, but showed subtle differences in the middle mass region. The most abundant ions were formed by fragmentation of the side chain. The positive charge was found to reside on the sulfonate or carboxylate moiety of the ionized salts and did not seem to migrate to other functional groups. Ions in the middle mass region were probably formed by fragmentation in the steroid ring system and therefore reflected structural differences of the bile conjugates. The usefulness of CID-MIKE spectroscopy in the structural analysis of isomeric materials was demonstrated.

Measurement of enkephalin peptides in canine brain regions, teeth, and cerebrospinal fluid with high-performance liquid chromatography and mass spectrometry

Endogenous enkephalin pentapeptides are measured with unambiguous molecular specificity in canine and human tissue and fluid extracts. Both field desorption and fast atom bombardment mass spectrometry have been used to produce a protonated molecular ion of the peptide high-performance liquid chromatography fraction. The protonated molecular ion is subjected to collision-activated dissociation processes and a linked-field scan (B/E) selects a unique amino acid sequence-determining ion for monitoring and measurement. Stable isotope-incorporated peptide internal standards are used for quantification. Endogenous enkephalins are measured in hypothalamus, cerebrospinal fluid, pituitary, caudate nucleus, and tooth pulp extracts. Part-per-billion levels of endogenous peptide are measured.

Fast atom bombardment mass spectrometry of insulin, insulin A-chain, insulin B-chain, and glucagon

Fast atom bombardment mass spectral data are presented for the polypeptides insulin, oxidized insulin A-chain, carboxymethylated insulin B-chain, and glucagon. The doubly-charged molecular ion of the intact insulin molecule produced with fast atom bombardment with xenon atoms is observed at a reduced accelerating voltage (4 kV).