Mass spectrometric analysis of hydroxyproline glycans

Mass spectrometric techniques are presented which allow one to analyze the sugar part bound to hydroxyproline in hydroxyproline-rich glycoproteins. The hydroxyproline (Hyp) glycans obtained by alkaline hydrolysis give abundant [M + Na](+) ions by electrospray ionization which after collision-induced dissociation (CID) yield inter alia [Hyp - H + Na](+). In mixtures a parent ion scan of this species will indicate the various molecular species which can then be analyzed by MS(n) after CID in an ion trap, where successive losses of the sugar units are observed. Methylation techniques allow one to distinguish between linear and branched isomeric structures.     

Mass spectrometric analysis of halogenated polymers

Controlled pyrolysis—electron impact mass spectrometry is a general method for the identification of polymers. It is shown here to be useful for the diagnosis of commercial halogen-containing polymers. The application of the technique both in a purely fingerprinting role, and by rationalising spectra in terms of structure and generalised thermal degradation pathways, is demonstrated. Inorganic oxides can have a secondary effect on degradative behaviour and spectral form.     

Mass spectrometric analysis of protein phosphorylation

Phosphorylation is one of the most common posttranslational modifications of proteins in eukaryotic cells; it plays an important role in a wide spectrum of biological processes. This makes its study an important task for understanding cell functioning mechanisms. The aim of phosphoproteomics is a global mass spectral analysis of the phosphoprotein composition of cells, i.e., phosphoproteome. Nowadays, new effective methods are actively developed, which succeed not only in the detection of phosphorylated proteins but also in the determination of phosphorylated amino acid residues (phosphorylation sites) and in the quantitative comparison of phosphorylation among several specimens. Despite the analysis of protein phosphorylation remains a complicated problem, the available methods nowadays allow the detection of thousands of phosphorylation sites in the very same experiment. The present review covers the main methods utilized in contemporary phosphoproteomics: phosphoprotein and phosphopeptides enrichment as well as the mass spectrometric analysis of protein phosphorylation.     

Mass spectrometric analysis of high-purity carbon dioxide

A high-vacuum, low-temperature, continuous separation technique has been used in conjunction with a mass spectrometer for the analysis of carbon dioxide containing vpm amounts of H(2), He, CH(4), Ne, N(2), CO, O(2) and Ar. The method relies on the condensation of carbon dioxide on the walls of a glass U-tube, cooled in liquid nitrogen, connected between an inlet and the ion source. A high-pressure carbon dioxide sample thus enters the inlet leak but only the impurities pass through the U-tube and reach the ion source, resulting in considerable gain in sensitivity and elimination of interference from carbon dioxide. The sensitivity of the method is several orders of magnitude better than the normal mass spectrometric method.     

Mass spectrometric analysis of carbon monoxide-nitrogen mixtures

A method for the analysis of gas mixtures containing both carbon monoxide and nitrogen, by using a single-focussing mass spectrometer, is described. It involves measurement of the mass spectrum of a gas sample before and after conversion of the carbon monoxide present into carbon dioxide by means of the Schütze catalyst.     

Mass spectrometric analysis of mixtures without separation

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, p. 1450, June, 1989.     

Mass spectrometric analysis of N-substituted cyclohexene-1,2-dicarboximides

Both low and high resolution mass spectra of cis-4-cyclohexene-1,2-dicarboximide, its N-methyl, N-ethyl, N-n-propyl and N-n-butyl derivatives, and cyclohexane-1,2-dicarboximide were obtained at 70 eV. Each of the spectra exhibited characteristic nominal ions at masses 151, 136, 123 and a group of ions at masses 77, 78, 79, 80 and 81 of which m/e 80 was always the base peak except for the unsubstituted cyclohexane compound. The m/e 77 to 81 fragments are composed of carbon and hydrogen and derived from the cyclohexene ring. The ions possessing higher masses are heterocyclic and certain of them show doublets and triplets. Evidence for a 1,3 hydrogen migration was supplied by studies with the N-(ethyl-2-d₃) derivative and evidence for a 1,4 migration by the N-(n-propyl-3-d₃) derivative.     

Mass spectrometric isotopic and trace analysis of187Os

The application of mass spectrometric methods in the determination of isotopic abundance and of trace elements in highly enriched¹⁸⁷Os is described. The capability of ICP-MS in comparison with solid-state mass spectrometric techniques (SIMS, SNMS and GDMS) for the precise isotopic analysis of highly-enriched osmium has been investigated. The formation of cluster ions in several plasma types has been measured, and the problems of possible interferences from molecular and cluster ions is discussed.     

Mass spectrometric identification of peptide hormones in doping-control analysis

The identification power of mass spectrometry has enabled the determination of hundreds of prohibited drugs in doping-control analysis. A few years ago, its utility was extended to peptide hormones such as erythropoietins, synthetic insulins and corticotrophins detectable in blood or urine. New assays have been established to improve the fight against doping, employing highly selective and sensitive detection methods based on chromatographic and tandem mass spectrometric techniques. In particular, in light of recent scandals related to assumed peptide hormone misuse and attempts at the alteration of urine, sophisticated analytical tools are essential for obtaining unequivocal results in sports drug testing.     

Mass spectrometric approach for the analysis of food proteins

In the study of food proteins, the need for accurate protein structural analysis has been acknowledged because of the fact that nucleotide sequencing alone is of limited analytical value if not combined with relevant information regarding the specific protein expressed and the occurrence of phosphorylation, glycosylation and disulphide bridges, and with the modification induced by the technological treatment. Mass spectrometry, whether used alone or to complement the traditional molecular-based techniques has become fundamental to the structural analysis of proteins. It is, moreover, virtually irreplaceable in determining post-translational modifications as conventional methods cannot deliver reliable data. What lies at the root of this methodological breakthrough is the combination of high-resolution separation techniques such as two-dimensional electrophoresis or capillary reverse- phase high-performance liquid chromatography with mass spectrometric analysis, what is termed "proteomic" analysis. Thus, it appears appropriate to state that the new mass spectrometric techniques have been established as a valuable and efficient tool for protein and peptide analysis in complex mixtures, like those from food matrices, enabling us therefore to provide accurate information on molecular weight and also to put forth a structural assessment at a low-picomole level of material. Thus, a series of alternative approaches have been developed based on advanced mass spectrometric analysis in conjunction with classic protein chemistry in order to provide an in-depth view of food protein structure. This review outlines several of these novel methodologies as they apply to structural characterization of food products.     

Comparison of bovine and porcine beta-lactoglobulin: a mass spectrometric analysis

Nano-electrospray-ionization mass spectrometry (nano-ESI-MS) is applied to comparison of bovine and porcine beta-lactoglobulin (BLG and PLG). The conformational and oligomeric properties of the two proteins under different solvent and experimental conditions are analyzed. The pH-dependence of dimerization is described for the pH range 2-11. The results indicate maximal dimer accumulation at pH 6 for BLG and pH 4 for PLG, as well as a lower stability of the PLG dimer at pH 4 compared to BLG at pH 6. Conformational stability appears to be higher for BLG at acidic pH, but higher for PLG at basic pH. The higher stability of BLG at low pH is revealed by means of either chemical or thermal denaturation. Equilibrium folding intermediates of both proteins are detected. Finally, conditions are found that promote dissociation of the BLG dimer at pH 6 into folded monomers.     

Mass spectrometric analysis of carbohydrates labeled with a biotinylated tag

A derivatization method for mass spectrometric analysis of oligosaccharides is presented. Small saccharides, complex, high‐mannose‐type oligosaccharides and oligosaccharides released from hen ovalbumin were converted into their biotin derivatives by incubating them with biotinamidocaproyl hydrazide (BACH). Improved sensitivity of mass spectrometric analysis of labeled glycans in comparison with their natural counterparts was achieved after derivatization. The labeling reagent contains a biotin handle at one end and a hydrazide group at the other. Hence, the key feature of biotinylated sugars is that in addition to their usefulness in functional studies (e.g. analysis of the interaction between lectins and biotin‐derivatized oligosaccharides) they might be utilized also for structural analysis of oligosaccharides. Mass spectrometric studies were performed by matrix‐assisted laser desorption/ionization time‐of‐flight and electrospray ionization mass spectrometry. Copyright © 2009 John Wiley & Sons, Ltd.     

Mass spectrometric detection of the Gibbs reaction for phenol analysis

This paper describes a new method for detecting phenols, by reaction with Gibbs reagent to form indophenols, followed by mass spectrometric detection. Unlike the standard Gibbs reaction, which uses a colorometric approach, the use of mass spectrometry allows for simultaneous detection of differently substituted phenols. The procedure is demonstrated to work for a large variety of phenols without para‐substitution. With para‐substituted phenols, Gibbs products are still often observed, but the specific product depends on the substituent. For para groups with high electronegativity, such as methoxy or halogens, the reaction proceeds by displacement of the substituent. For groups with lower electronegativity, such as amino or alkyl groups, Gibbs products are observed that retain the substituent, indicating that the reaction occurs at the ortho or meta position. In mixtures of phenols, the relative intensities of the Gibbs products are proportional to the relative concentrations, and concentrations as low as 1 μmol/L can be detected. The method is applied to the qualitative analysis of commercial liquid smoke, and it is found that hickory and mesquite flavors have significantly different phenolic composition.     

Mass spectrometric analysis of ceramics after decomposition with elemental fluorine

The features of a combustion with elementary fluorine for the case of compact SiC ceramics and model substances for boron containing ceramics (H₃BO₃ and Na₂B₄O₇) were investigated with the aim of their decomposition and analysis. On-line detection of the gaseous decomposition products by quadrupole mass spectrometry using electron impact ionisation was studied. Limitations by blanks and transport interferences were investigated. Standard addition as well as the isotope dilution technique were used for calibration in the case of B, C and W at the trace and major component level.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthdayDeceased May 1995.     

Mass spectrometric analysis of recombinant human α-2 interferon

Mass spectrometry (MS) was used for the characterization of recombinant human α-2 interferon (α-2 IFN) produced in E. coli. After purification by monoclonal antibody affinity chromatography, α-2 IFN showed two major peaks in reversed-phase liquid chromatography (RP- LC). Each component was digested with trypsin and Staphylococcus aureus protease V8, separately or in tandem, and the peptide mixture was analysed by MS without further purification. The first peak corresponded to the 165 amino acid sequence of human α-2 IFN and the main component of the second peak was the acetylated Cys₁ α-2 IFN. It was also possible to verify by MS the location of the SS bonds in α-2 IFN and the occurrence of incorrect SS bridges in the products of some renaturation processes. The best renaturation process for obtaining a product without adducts or scrambling of disulphide bonds could be found by using RP-LC and fast atom bombardment MS.     

Mass spectrometric investigation of benzyliderieaniline

The mass spectral fragmentation of benzylideneaniline has been studied by deuterium labelling. Under electron impact, molecular ions undergo simple fission at the phenyl–N, phenyl–C and C?N bonds, hydrogen migration reactions, and skeletal rearrangement fragmentations. Except in the skeletal rearrangement reactions, hydrogen scrambling does not feature in benzylideneaniline upon electron impact.     

Mass spectrometric investigation of carbohydrates

Conclusions The pathways of the fragmentation of completely methylated- methyl-L-arabopyranoside were studied in detail. The data obtained will serve as a basis for establishing the structure of the partially methylated pentopyranosides.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 277–283, February, 1967.The authors would like to express their deep gratitude to R. A. Khmel'nitskii and A. A. Polyakova for kindly permitting the use of a mass spectrometer, equipped with a multiloop oscillograph.