Conventional MS Research Articles

Structure characterization of petroleum vacuum residues by in-beam EI Fourier transform ion cyclotron resonance mass spectrometry

A n-heptane soluble fraction (AH-VR-Sa) of Arabian heavy vacuum residues (AH-VR) has been analyzed by in-beam electron ionization Fourier transform ion cyclotron resonance mass spectrometry (EI FT-ICR MS). The probe temperature and the ionization energy of in-beam EI were independently adjusted to expand the detectable range of peaks originating from components of AH-VR-Sa and to prevent fragmentation of the molecular ions. The upper mass limit of the peaks was extended to m/ z=700 when the probe temperature and the ionization energy were set to 300 °C and 30 eV, respectively. The average molecular weight of the spectrum increased by an increase in the probe temperature. The molecular formulas of compounds in AH-VR-Sa were determined essentially based on accurate mass measurements. Major components of being characterized were hydrocarbons both with and without one sulfur atom. The compound type estimated on the basis of hydrogen-deficiency index Z (C n H 2 n+ Z ) was discussed. The strongest peaks of hydrocarbons with sulfur atom showed the Z value of −10. The compound type analysis indicates that sulfur atom may be located at an aromatic ring but not at a side chain. The effect of experimental conditions on the detectable compound type distribution was also discussed. The present results demonstrate that the characterization of vacuum residues by in-beam EI FT-ICR MS is advantageous over the conventional EI FT-ICR MS in the detectable range of peaks and in the versatility for samples. In-beam EI FT-ICR MS is useful as a complementary method to characterize vacuum residues by electrospray ionization (ESI) FT-ICR MS, since ESI cannot ionize hydrocarbons with high Z values.

Tc1/Tc2 and Th1/Th2 balance in Asian and Western types of multiple sclerosis, HTLV-I-associated myelopathy/tropical spastic paraparesis and hyperIgEaemic myelitis

CD8 + T cells, like CD4 + T cells, can differentiate into at least two subsets with distinct cytokine patterns: Tc1 cells produce Th1-like cytokines and Tc2 cells produce Th2-like cytokines. To clarify the immunopathological roles of Tc1 and Tc2 cells in central nervous system (CNS) inflammation, we examined intracellular cytokines in CD8 + and CD4 + T cells by flow cytometry and analyzed the Tc1/Tc2 balance as well as the Th1/Th2 balance in 80 patients with various CNS inflammatory diseases, including 20 with optico-spinal multiple sclerosis (OS-MS), 21 with conventional MS (C-MS), 22 with human T-lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and 17 with hyperIgEaemic myelitis. Twenty-two healthy subjects were also examined as controls. Patients with OS-MS showed a significantly higher percentage of INF-γ +IL-4 − CD8 + T cells as well as CD4 + T cells and a significantly higher intracellular interferon-γ (IFN-γ)/interleukin-4 (IL-4) ratio both in CD8 + and CD4 + T cells throughout the relapse and remission phases than the healthy controls. Furthermore, the patients with OS-MS showed a significantly lower percentage of INF-γ -IL-4 + CD4 + T cells as well as CD8 + T cells during the relapse phase than the healthy controls. On the other hand, the patients with C-MS showed a significantly higher percentage of IFN-γ −IL-4 + CD8 + T cells in addition to more IFN-γ +IL-4 − CD4 + T cells during the relapse phase than the healthy controls. The HAM/TSP patients showed a significantly higher percentage of INF-γ +IL-4 − CD8 + T cells and a significantly higher intracellular IFN-γ/IL-4 ratio in CD8 + T cells than the healthy controls. In contrast, in hyperIgEaemic myelitis, in addition to a significantly lower intracellular IFN-γ/IL-4 ratio in CD4 + T cells, a tendency toward a lower intracellular IFN-γ/IL-4 ratio in CD8 + T cells in comparison to the healthy controls was observed. These results clarified for the first time the distinct Tc1/Tc2 balance in each disease condition as follows: Tc1 cell response is predominant in OS-MS and HAM/TSP, while Tc2 cell response is predominant in hyperIgEaemic myelitis and at relapse phase of C-MS. Furthermore, our results suggest that CD8 + T cells play an adjunctive role in disease induction and the clinical course of MS.

Atomic spectrometry update. Atomic mass spectrometry

The review this year is dominated by the large number of publications on AMS, ICP-MS and SIMS. The increasing number of new AMS installations bears witness to the increasing interest in the technique now that smaller and simpler systems are becoming more widely available. Although high-energy systems still have an important role to play, each of the new systems was compact and of relatively low-energy. The development of ion sources that can accept gaseous samples has lowered the sample size requirement for radiocarbon analysis such that it is now little more than the background level. Contamination therefore has become a major issue. The numerous papers on improvements to SIMS analysis demonstrate the important role the technique plays in materials science. Unlike for most of the techniques covered, fundamental studies on SIMS analysis abound with particular attention being paid to understanding the ionization processes and the representativeness of the measured ion beam. Quantum chemistry calculations have been used to determine the fundamental processes occurring in cell ICP-MS. This approach contrasted with the empirical studies that are normally undertaken. Although many applications are still being published using collision and/or reaction cell ICP-MS, there were fewer novel or fundamental studies than in previous years. This suggests that cell ICP-MS is becoming a more routine method of analysis. The same can probably also be said of hyphenated ICP-MS methods for speciation, which continues to grow in importance but which is very much at the applied end of the spectrum. Speciation is notable in that it cuts across a number of MS techniques and conventional organic MS techniques are increasingly being investigated for structure determination of organometallic species. Each year seems to find further expansion of MC-ICP-MS into ‘non-traditional’ isotope analysis. This was the year for Ti isotope analysis. This Update is the 21st and last annual review on atomic mass spectrometry and follows the same format as last year's.1 Although an attempt is made to consider all relevant refereed papers, conference abstracts, reports, book chapters and patents for inclusion, the content of the review is highly selective. The selection of papers is based on criteria applied to focus sharply on the most significant developments in instrumentation and methodology or improved understanding of the fundamental phenomena involved in the MS process. The main ruling criterion for all speciation papers is that the work should involve or be intended for the study of natural systems. For example, the study of synthetic metal clusters is generally not included whereas the determination of organometallic compounds in environmental samples is. Applications of atomic MS are not covered in this Update and readers are referred to the Updates on Industrial Analysis: Metals, Chemicals and Advanced Materials,2 Environmental Analysis3 and Clinical and Biological Materials, Food and Beverages.4 Other, fundamental, reviews appear on X-ray fluorescence spectrometry5 and atomic emission, absorption and fluorescence spectrometries.6 Throughout this review, the term molecular ion will be restricted to denote only the positive or negative radical ion formed by removal or capture, respectively, of an electron. In contrast, addition of a proton or cation to a neutral molecule gives molecular adduct ions. Deprotonated molecules are considered as fragments. Although reproducibility or precision is a key figure of merit in MS, there is no agreed format for quoting it. The reader can assume that values of precision given in this Update as a percentage correspond to the RSD unless otherwise specified. For isotope ratios, however, values of precision are generally given as the SD of a permil value. It is a widespread phenomenon that analytical techniques in general and MS in particular spawn a large number of abbreviations and acronyms. A glossary of all abbreviations used in this Update appears at the end of the review. Most abbreviations are not defined in the text but those which are unlikely to be commonly known are defined in the text when used first and again in the glossary. It should be noted that throughout the text the letter C denotes the element carbon and not the unit of charge, the coulomb. The writing team would welcome feedback from readers of this review and invite you to complete the Atomic Spectrometry Updates questionnaire on http://www.asureviews.org.

Thermostability of endo-1,4-β-xylanase II from Trichoderma reesei studied by electrospray ionization Fourier-transform ion cyclotron resonance MS, hydrogen/deuterium-exchange reactions and dynamic light scattering

Endo-1,4-β-xylanase II (XYNII) from Trichoderma reesei is a 21kDa enzyme that catalyses the hydrolysis of xylan, the major plant hemicellulose. It has various applications in the paper, food and feed industries. Previous thermostability studies have revealed a significant decrease in enzymic activity of the protein at elevated temperatures in citrate buffer [Tenkanen, Puls and Poutanen (1992) Enzyme Microb. Technol. 14, 566–574]. Here, thermostability of XYNII was investigated using both conventional and nanoelectrospray ionization Fourier-transform ion cyclotron resonance MS and hydrogen/deuterium (H/D)-exchange reactions. In addition, dynamic light scattering (DLS) was used as a comparative method to observe possible changes in both tertiary and quaternary structures of the protein. We observed a significant irreversible conformational change and dimerization when the protein was exposed to heat. H/D exchange revealed two distinct monomeric protein populations in a narrow transition temperature region. The conformational change in both the water and buffered solutions occurred in the same temperature region where enzymic-activity loss had previously been observed. Approx. 10–30% of the protein was specifically dimerized when exposed to the heat treatment. However, adding methanol to the solution markedly lowered the transition temperature of conformational change as well as increased the dimerization up to 90%. DLS studies in water confirmed the change in conformation observed by electrospray ionization MS. We propose that the conformational change is responsible for the loss of enzymic activity at temperatures over 50°C and that the functioning of the active site in the enzyme is unfeasible in a new, more labile solution conformation.

Thermostability of endo-1,4-beta-xylanase II from Trichoderma reesei studied by electrospray ionization Fourier-transform ion cyclotron resonance MS, hydrogen/deuterium-exchange reactions and dynamic light scattering.

Endo-1,4-beta-xylanase II (XYNII) from Trichoderma reesei is a 21 kDa enzyme that catalyses the hydrolysis of xylan, the major plant hemicellulose. It has various applications in the paper, food and feed industries. Previous thermostability studies have revealed a significant decrease in enzymic activity of the protein at elevated temperatures in citrate buffer [Tenkanen, Puls and Poutanen (1992) Enzyme Microb. Technol. 14, 566-574]. Here, thermostability of XYNII was investigated using both conventional and nanoelectrospray ionization Fourier-transform ion cyclotron resonance MS and hydrogen/deuterium (H/D)-exchange reactions. In addition, dynamic light scattering (DLS) was used as a comparative method to observe possible changes in both tertiary and quaternary structures of the protein. We observed a significant irreversible conformational change and dimerization when the protein was exposed to heat. H/D exchange revealed two distinct monomeric protein populations in a narrow transition temperature region. The conformational change in both the water and buffered solutions occurred in the same temperature region where enzymic-activity loss had previously been observed. Approx. 10-30% of the protein was specifically dimerized when exposed to the heat treatment. However, adding methanol to the solution markedly lowered the transition temperature of conformational change as well as increased the dimerization up to 90%. DLS studies in water confirmed the change in conformation observed by electrospray ionization MS. We propose that the conformational change is responsible for the loss of enzymic activity at temperatures over 50 degrees C and that the functioning of the active site in the enzyme is unfeasible in a new, more labile solution conformation.

SALSA: a pattern recognition algorithm to detect electrophile-adducted peptides by automated evaluation of CID spectra in LC-MS-MS analyses.

A pattern recognition algorithm called SALSA (scoring algorithm for spectral analysis) has been developed to rapidly screen large numbers of peptide MS-MS spectra for fragmentation characteristics indicative of specific peptide modifications. The algorithm facilitates sensitive and specific detection of modified peptides at low abundance in an enzymatic protein digest. SALSA can simultaneously score multiple user-specified search criteria, including product ions, neutral losses, charged losses, and ion pairs that are diagnostic of specific peptide modifications. Application of SALSA to the detection of peptide adducts of the electrophiles dehydromonocrotaline, benzoquinone, and iodoacetic acid permitted their detection in a complex tryptic peptide digest mixture. SALSA provides superior detection of adducted peptides compared to conventional tandem MS precursor ion or neutral loss scans.

Aboriginals with multiple sclerosis: HLA types and predominance of neuromyelitis optica.

MS is common in people of northern European ethnicity who live in northern geographic areas; however, MS is rarely identified among aboriginal peoples living in the same areas. To determine the prevalence, clinical features, HLA type, and viral infections associated with MS among aboriginals in Manitoba, Canada. A retrospective study was performed in which the clinical features of all aboriginal patients with MS together with HLA type and human herpesvirus-6, HIV-1, human T-cell lymphotropic virus-1, and endogenous retrovirus associated with MS (MSRV) infections were analyzed and compared with results from nonaboriginal patients with MS. Seven aboriginals with MS were identified with a period prevalence among aboriginals of 40:100,000. Clinical features included relapsing-remitting (n = 6) or primary progressive (n = 1) phenotypes with aggressive disease courses and frequent involvement of optic nerves and spinal cord (n = 5) compared with nonaboriginal patients. Autopsy of one patient showed necrosis and eosinophil infiltrates in a cervical spinal cord lesion and a demyelinated optic nerve. Analysis of HLA alleles at the DRB1 and DQB1 loci indicated that the HLA types detected were common in aboriginals, but there were no HLA alleles previously associated with the development of MS. Analysis of the copy number of MSRV did not show differences among aboriginals and nonaboriginals with or without MS. Aboriginals of Algonkian background are at increased risk for an aggressive type of MS, resembling neuromyelitis optica, which is resistant to conventional MS treatments and occurs independently of HLA alleles previously associated with MS.

Tracing terrestrial compounds leaching from two reservoir catchments as input to dissolved organic matter

Conventional pyrolysis—GC—MS,thermochemolysis and alkaline CuO oxidation were applied to determine differences between dissolved organic matter (DOM)from terrestrial plants,soil horizons and drinking water reservoirs in two catchments in South Australia.These two reservoir-catchment systems were selected on the basis of contrasting vegetation and land use.Pyrolysis of DOM yielded furans,aliphatic products and N-containing compounds,which are indicative of polysaccharides,lipids and proteins,respectively.Thermo-chemolysis enabled detection of methoxy-benzyl compounds derived from various sources of DOM,indicating that these compounds can be used as bio-markers of vascular plant sources.Vanillic acid was detected from DOM isolates from the vegetation,soils and reservoir waters of the two catchments,using CuO oxidation,and hence this compound also appears to be a suitable bio-marker for tracing allochthonous DOM input into the reservoirs. Each of the three techniques resulted in the formation of different compounds from the DOM isolates,which indicated the type of precursor bio-polymer and/or some of the methoxyphenol structures of lignin.

A multidimensional electrospray MS-based approach to phosphopeptide mapping.

A new, multidimensional electrospray MS-based strategy for phosphopeptide mapping is described which eliminates the need to radiolabel protein with 32P or 33P. The approach utilizes two orthogonal MS scanning techniques, both of which are based on the production of phosphopeptide-specific marker ions at m/z 63 and/or 79 in the negative ion mode. These scan methods are combined with liquid chromatography-electrospray mass spectrometry and nanoelectrospray MS/MS to selectively detect and identify phosphopeptides in complex proteolytic digests. Low-abundance, low-stoichiometry phosphorylation sites can be selectively determined in the presence of an excess of nonphosphorylated peptides, even in cases where the signal from the phosphopeptide is indistinguishable from background in the conventional MS scan. The strategy, which has been developed and refined in our laboratory over the past few years, is particularly well suited to phosphoproteins that are phosphorylated to varying degrees of stoichiometry on multiple sites. Sensitivity and selectivity of the method are demonstrated here using model peptides and a commercially available phosphoprotein standard. In addition, the strategy is illustrated by the complete in vitro and in vivo phosphopeptide mapping of Sic1p, a regulator of the G1/S transition in budding yeast.

Premonitory Martensitic Surface Relief Via Novel X-Ray Diffuse and Laser Light Reflectivity from The (001)-Surface of A Ni63Al37Single Crystal

AbstractBoth x-ray diffuse reflectivity and laser light scattering have been used to investigate the temperature-dependent surface behavior of a Ni63Al37single crystal on different length scales. In-situ experiments were performed above the conventional martensitic start temperature Ms to search for premartensitic phenomena. X-ray experiments showed the presence of a surface precursor with second-order (continuous) character several 10 K above Ms. This premonitory effect corresponds to a height-height-correlation function which changes on the nanometer scale as the martensitic transformation is approached. At the martensitic transformation, the surface morphology changed from nanoscopic roughness to macroscopic relief within a temperature interval of less than 1 K via intermediate stages. Laser light scattering was employed to study time-dependent aspects of the athermal martensitic transformation above Ms. The occurrence of a martensitic transformation on isothermal holding after a certain incubation period was observed in Ni-Al for the first time. The measured incubation times increased by four orders of magnitude within a temperature interval of 0.5 K.

The running gauge coupling in the exact renormalization group approach

We discuss the perturbative running Yang-Mills coupling constant in the Wilsonian exact renormalization group approach, and compare it to the running coupling in the more conventional MS scheme. The exact renormalization group approach corresponds to a particular renormalization scheme, and we relate explicitly the corresponding Λ parameters. The unambiguous definition of an exact renormalization group scheme requires, however, the use of a one-loop improved high energy effective action.

Conversion Reactions of Various Phenoxyalkanoic Acid Herbicides in Soil. 2. Elucidation of the Enantiomerization Process of Chiral Phenoxy Acids from Incubation in a D2O/Soil System

The enantiomerization of chiral phenoxyalkanoic acid herbicides in soil under laboratory conditions in the presence of D2O was investigated. The compounds studied were 2-(4-chloro-2-methylphenoxy)propionic acid (MCPP), 2-(2,4-dichlorophenoxy)propionic acid (DCPP) and, for comparison, the achiral 4-chloro-2-methylphenoxyacetic acid (MCPA) and 2,4-dichlorophenoxyacetic acid (2,4-D). Enantiomerization was studied by incubating racemic and enantiopure MCPP and DCPP in D2O/soil and following the formation of deuterated analogs using enantioselective high-resolution gas chromatography (HRGC) and mass spectrometry/mass spectrometry (MS/MS). MS/MS showed less interference from natural 13C isotopomers than conventional MS and allowed the exact localization of deuterium in the labeled compounds. The results indicated exclusive H-D exchange at C-2 (α-methin H) of MCPP and DCPP with formation of the 2-deuterio analogs. H-D exchange in MCPP proceeded with retention as well as inversion of config uration, forming both of the labeled enantiomers from each of the native ones at comparable rates. H-D exchange was also observed for MCPA and 2,4-D with formation of the 2-deuterio and 2,2-dideuterio analogs. The importance of racemization reactions of chiral compounds is discussed, and general conclusions are drawn on the environmental fate of chiral compounds and on consequences for the monitoring of such compounds in the environment using enantioselective techniques.

Ultra-trace-level determination of the antifouling agent Irgarol 1051 by gas chromatography with tandem mass spectrometric detection

The contamination level of the s-triazine herbicide Irgarol 1051, which is used as the active ingredient in antifouling paints, was studied in the Western Scheldt estuary. The combined use of large-volume injection gas chromatography and ion trap (MS–MS) detection, enabled identification and quantification at the 0.1–1 ng/l level. By using tandem mass spectrometric detection (MS–MS), rather than conventional MS, a great gain in selectivity was achieved. The concentration levels found ranged between 1 and 10 ng/l.

Improved callogenesis and plant regeneration from immature male flowers of East African highland banana cv. “Nakitembe” (AAA-EA)

Application of biotechnological tools in breeding, germplasm conservation and propagation of the East African bananas (Musa sp.) is limited by the crop’s recalcitrance to somatic embryogenesis. This study was undertaken to establish an efficient callus induction and plant regeneration protocol from immature male flowers in the most commercial and farmer preferred banana cultivar “Nakitembe”. Embryogenic callusing was improved from 2.9% on conventional MA1 culture medium to 4.2% with 500 mg L-1 L-Glutamine, 500 mg L-1 L-Proline and 300 mg L-1 casein hydrolysate supplements. A combination of the three amino acids with Chui N6 salts yielded the highest callusing of 10.2%. Cell suspensions were developed and maintained on conventional MS based MA2 medium. Subsequently, the highest efficiency of embryos germination (up to 80%) was achieved on MA4 medium, supplemented with 2.25 mg L-1 BAP and 0.2 mg L-1 IAA. The developed protocol has been successfully applied in Agrobacterium mediated genetic transformations of this variety.