Fast atom bombardment-collision activated dissociation-linked field scanning mass spectrometry of the neuropeptide substance P

From large analogical instruments to small digital black boxes: 40 years of progress in mass spectrometry and its role in proteomics. Part I 1965-1984

As the title implies, the author undertakes a personal retrospective on the developments that since 1965 have shaped MS and taken it from a position of simply playing a role in protein chemistry to becoming an indispensable tool in proteomics, all in the past 40-year span. The article reviews the MS timeline of events, stopping at various time points where MS made significant contributions to protein chemistry or where the development of new instrumentation for MS represented a major advance for peptide and protein work. Major highlights in the field and their significance for peptide and protein characterization are covered, starting from the pioneering work carried out in the 1960s on peptide derivative formation and sequencing with instrumentation proper of that time, to later work done with triple, quad, and four-sector instruments, and on to the more recent work on the characterization of the proteome with ion traps, time-of-flight (TOF) instruments, and new ionization and tagging techniques.

Biomedical and biological mass spectrometry

This review focuses on biological and biomedical mass spectrometry, and covers a selection of publications in this area included in the MEDLINE database for the period 1987-2001. Over the last 15 years, biological and biomedical mass spectrometry has progressed out of all recognition. The development of soft ionization methods, such as electrospray ionization and matrix-assisted laser desorption ionization, has mainly contributed to the remarkable progress, because they can easily produce gas-phase ions of large, polar, and thermally labile biomolecules, such as proteins, peptides, nucleic acids and others. The innovations of ionization methods have led to remarkable progress in mass spectrometric technology and in biochemistry, biotechnology and molecular biology research. In addition, mass spectrometry is one of the powerful and effective technologies for drug discovery and development. It is applicable to studies on structural determination, drug metabolism, including pharmacokinetics and toxicokinetics, and de novo drug discovery by applying post-genomic approarches. In the present review, the innovative soft ionization methods are first discussed along with their features. Also, the characteristics of the mass spectrometers which are active in the biological and biomedical research fields are also described. In addition, examples of the applications of biological and biomedical mass spectrometry are provided.

Opioid and tachykinin peptides, and their precursors and precursor-processing enzymes, in human cerebrospinal fluid

Opioid and tachykinin neuropeptides, which were derived from two biological sources (intact, and released from their corresponding precursors by the action of human cerebrospinal fluid (CSF) neuropeptidases), were characterized in human CSF by using a combination of post-high-performance liquid chromatographic (HPLC) detection techniques. Peptides were separated using gradient and isocratic reversed-phase HPLC. Radioimmunoassay measured immunoreactivity corresponding to several different individual neuropeptides including methionine enkephalin, leucine enkephalin, substance P and beta-endorphin. Commercial enzymes (trypsin, carboxypeptidase B) were used to release methionine- and leucine-enkephalin from precursors. Human CSF also served as a source of endogenous neuropeptidases. Mass spectrometry produced fragment ions that corroborated the amino acid sequence of methionine enkephalin and of substance P derived from both sources (intact, from precursors). These results demonstrated the presence of endogenous intact neuropeptides, several different neuropeptide-containing precursors and appropriate precursor-processing enzymes in human CSF for precursors of methionine enkephalin, leucine enkephalin, beta-endorphin1-31 and substance P.

Application of fast atom bombardment mass spectrometry to posttranslational modifications of neuropeptides

FABMS is a powerful and sensitive analytical technique capable of providing structural information unattainable by standard methods of peptide analysis. Many posttranslational modifications are undetectable by other routine analytical methods. In addition, FABMS is capable of providing information regarding posttranslational modifications at levels of peptide comparable to those required for other methods of analysis (10-1000 pmol). FABMS has had the effect on protein structure analysis that structure determination of any neuropeptide might now be considered incomplete without some form of mass spectrometric analysis. Much of the recent explosive increase in the use of mass spectrometry for solving problems in peptide structure analysis can be traced to improvements in methods capable of producing molecular ions from nonvolatile species. With the development of these methods, it can be expected that refinements of existing methods and new ionization methods will continue to increase the mass range and sensitivity available for peptide structure determination. For a brief review of other mass spectrometric methods applicable to peptides, see Delgass and Cooks.

Chemical degradation of 3H-labeled substance P in tris buffer solution

Substance P (SP) is an important neuropeptide that has been implicated in several physiological processes, and it is necessary to devise an analytical procedure to measure endogenous SP with a combination of high sensitivity and maximum molecular specificity. However, the unique chemical nature of SP (polarity, chemical stability, ease of oxidation, peptide bond lability) plays a significant role in its analysis, such as in receptor assays, immunoassays, chromatography, and mass spectrometry. In this study, we evaluated in polypropylene and glass assay tubes the effects on the recovery and stability of tritiated SP ([3H]SP) of several pertinent experimental parameters such as buffer, pH, multiple freeze-thaw cycles, and incubation temperature and time. Bovine serum albumin (BSA) effectively reduced the absorption of [3H]SP to polypropylene and glass tube surfaces. Following multiple (6X) freeze-thaw cycles of solutions in BSA-precoated tubes, the recovery of radioactive [3H]SP remained high (greater than 75%) after the last cycle, whereas recovery was minimal in uncoated or siliconized glass tubes. A high level of radioactivity recovery was maintained for 14 days of storage of [3H]SP in triethylamine formate (TEAF) solution in BSA-precoated tubes at 4 and -20 degrees C, but decreased at 37 degrees C to less than 80% in only 3 h. Following storage in Tris-HCl (pH 7.4) buffer, a combination of HPLC and mass spectrometric analyses revealed that a significant amount of peptide bond cleavage occurred to produce the two peptides ArgProLys (RPK) and ArgProLysProGlnGln (RPKPQQ), with only a small amount of remaining intact SP. That decomposition was not observed in triethylamine formate TEAF (pH 3.14) buffer solutions.

Fast atom bombardment/tandem mass spectrometry of physalaemin-like peptides

Fragment ion spectra obtained from collision-induced decomposition of protonated molecular ions have been used to determine amino acid sequences of several physalaemin-like peptides which were recently purified from rabbit stomach. This technique was chosen because the peptides were available in microgram quantities and were anticipated to contain pyroglutamate as the blocked N-terminal residue. Such spectra of several synthetic analogs of the naturally occurring peptides were obtained and analyzed to confirm the veracity of this peptide sequencing strategy. In addition, methyl ester derivatives of these synthetic peptides provided a crucial test for the spectral interpretation via the mass shifts thus induced.

Canine limbic system substance P receptors

A canine limbic system preparation is utilized as a source of substance P receptor(s) to screen gradient RP-HPLC fractions for the presence of receptoractive-substance P activity, and to quantify endogenous receptoractive-substance p in biological extracts such as human tooth pulp. The binding characteristics, KD = 1.3 nM and Bmax = 11 fmol mg-1 protein, are similar to values obtained from receptors produced from other biological sources such as whole rat brain, minus cerebellum.

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.

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).