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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of kerogens by matrix-assisted laser desorption ionization mass spectroscopy (1994)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 823-828 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Two kerogen samples from shales of different geological age, selected from each of Types I, II and III, have been characterized by matrix-assisted laser desorption ionization mass spectroscopy (MALDI-MS). A Kratos Kompact MALDI III time-of-flight mass spectrometer equipped with a nitrogen laser operated at 337 nm was used on samples mounted in a matrix of sinapinic acid. The spectrometer was used in linear mode with a mass range up to 270 000 u and an ion extraction voltage of 20 kV. Individual spectra from 50 laser shots at low laser fluence were summed for each spectrum. The present study is a first attempt at characterizing kerogens by MALDI-MS. At low mass (200-500 u) families of peaks consisting of overlapping homologous series of apparently polar compounds have been observed: these peaks appear to be distinct from those due to the matrix material. In higher mass regions of the spectra, continua of masses extending from 1000 u up to around 10 000 u were observed; ions at higher masses were separated to baseline up to masses of 50 000 u. Evidence was found for a relationship between the minimum laser power sufficient for activating the MALDI-ionization process and the geological age of the kerogens; the laser power decreased as the geological age increased. In the case of one kerogen, a high laser fluence was used to generate molecular ions up to the detection limit of the mass spectrometer, in excess of 260 000 u. This paper presents results from a preliminary study of kerogens which requires an in-depth examination of the desorption process in complex mixtures.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290081006
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of coal by matrix-assisted laser desorption ionization mass spectrometry. I. The argonne coal samples (1994)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 808-814 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The Argonne set of coals cover the rank range from lignite to semi-anthracite; these samples have been studied by matrix-assisted laser desorption mass spectrometry (MALDI-MS) in a time-of-flight mass spectrometer equipped with a nitrogen laser at 337 nm, using sinapinic acid as matrix. The coal particle size was less than 5 microns. The characteristics of the MALDI-MS spectra of the set of coals were found to be rank-related; desorption from high-rank coals was found to take place with greater relative ease than from low-rank coals. Two major features were found in all spectra: a homologous series of peaks in the 200-500 u mass range and an intense peak between 1000 and 5000 u, the particular shape of the peak depending on coal rank. A continuum of lower intensity peaks extending to very large molecular masses was found in all spectra, the upper limit of molecular masses increasing with coal rank at the same laser fluence. The effect of changes in laser power on spectra was investigated: upper mass limits were found to increase with power up to the detection limit of the instrument but low-mass parts of spectra were found to distort, possibly due to detector overloading. A maximum laser fluence value acceptable over the coal-rank range represented by these samples could therefore not be easily defined. None of the mass spectra showed evidence of the presence of either carbon clusters or fullerene formation, indicating that laser fluences did not reach intensities high enough to induce substantial secondary reactions. Comparing molecular mass distributions detected by MALDI of coal pyrolysis tars and directly from coals suggests the MALDI and pyrolytic mechanisms of volatile release to be structurally different; in particular, the preferential evaporation of lighter species which occurs during pyrolytic tar evolution (and during field-ionization mass spectroscopy) appears to evole material with a more restricted range of molecular masses compared to laser desorption mechanisms.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290081004
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization of coal by matrix-assisted laser desorption mass spectrometry. II. Pyrolysis tars and liquefaction extracts from the argonne coal samples (1994)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 815-822 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Coal pyrolysis tars and liquefaction extracts prepared from the set of eight Argonne coal samples have been characterized by MALDI-MS. A Kratos Kompact MALDI III linear time-of-flight mass spectrometer was used, with a nitrogen laser operating at 337 nm and sinapinic acid as matrix. Spectra were collected by summing 50 laser pulses at low laser fluence to avoid fragmentation of desorbed ions. At low mass, 200-500 u, spectra from the pyrolysis tars and liquefaction extracts showed common features: intense peaks originating from the sinapinic acid matrix, m/z 205, 224 and 246, and, a range of peaks in the mass range from about 250 u to 400 u, which probably corresponds to overlapping homologous series of apparently polar material. A peak of ion intensity between 1000 and 5000 u was systematically observed, which was sample dependent and not always similar for the tar and extract prepared from the same coal. At high masses, separate trends were observed for coal pyrolysis tars and liquefaction extracts: molar mass ranges of pyrolysis tars were smaller, and showed no particular trend with carbon content of the original coal; these findings are consistent with size-exclusion chromatography derived findings. Spectra of liquefaction extracts extended over wider ranges of molar masses and increased with increasing coal rank; the highest masses extended to 50 000u. Overall, pyrolysis tars appeared structurally different from liquefaction extracts and more difficult to desorb. The effect of changes in laser fluence and ion extraction voltage on mass spectra have been investigated: high-mass regions of the spectra were found to be very sensitive to the magnitude of the ion extraction voltage. No carbon clusters or fullerene structures were detected.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290081005
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  • 4
    Electronic Resource
    Electronic Resource
    Charting cation migration in a nickel exchanged zeolitic catalyst: An in situ rietveld X-ray studyWe thank the Science and Engineering Research Council for general support and the Laura Ashley Foundation for a Teenager Fellowship (to B.J.S.). (1990)
    Weinheim : Wiley-Blackwell
    Advanced Materials 2 (1990), S. 181-183 
    Details
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19900020405
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  • 5
    Electronic Resource
    Electronic Resource
    Study on separation of conalbumin and lysozyme from high concentration fresh egg white at high flow rates by a novel ion-exchanger (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1086-1090 
    Details
    ISSN: 0006-3592
    Keywords: ion-exchanger ; conalbumin ; lysozyme ; egg-white ; separation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this report, we show that it is possible to separate valuable proteins from egg-white using a ProductivTM CM ion-exchanger column operated at flow rates significantly higher than those than can be achieved using traditional particulate adsorbents. In the approach taken, sample pretreatment is restricted to a simple dilution of the egg-white, which can then be applied to the column at superficial velocities (Vs) of up to 13.8 m/h. Under a loading of 220 mg total protein per milliliter of ion-exchanger, the resolution (Rs) between the eluted conalbumin and lysozyme fractions was found to be almost constant during nine consecutive adsorption/desorption cycles. For all nine consecutive batches, the column average adsorption capacity was greater than 30 mg/mL, with 90% recovery of adsorbed protein being achieved in each run. The overall productivity achieved was 12.6 kg/m3 h for lysozyme and 31.2 kg/m3 h for conalbumin. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260420910
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  • 6
    Electronic Resource
    Electronic Resource
    Blueprint for a lipase support: Use of hydrophobic controlled-pore glasses as model systems (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 934-938 
    Details
    ISSN: 0006-3592
    Keywords: immobilization ; nonaqueous enzymology ; esterification ; Rhizomucor miehei lipase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: For the commercial exploitation of lipase biocatalysis to be successful, it is essential that effective supports are selected for lipase immobilization. In this study hydrophobic controlled-pore glasses have been used as model systems for the immobilization of Rhizomucor miehei lipase. The effect of pore diameter and surface chemistry on enzyme efficiency in a typical esterification reaction under essentially nonaqueous conditions has been examined. It has been found that pore diameters of at least 35 nm are needed for the lipase to be able to utilize the internal volume of the support particles in the immobilization process. Despite the small size of the substrates in the esterification reaction, even larger pores (〉100 nm) are required for the lipase efficiency to become independent of pore diameter; below 100 nm lipase activity and efficiency are markedly reduced. It has also been shown that the chemical nature of the hydrophobic surface plays an important part in catalyst design. Although lipase will adsorb readily to a wide range of hydrophobic groups, the highest catalyst activities are obtained when the glass surface is derivatized to give long alkyl chains; the presence of unsaturated derivatives gonerally leads to a reduction in activity. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260431006
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  • 7
    Electronic Resource
    Electronic Resource
    The geometry of multivariate object preprocessing (1993)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 7 (1993), S. 393-425 
    Details
    ISSN: 0886-9383
    Keywords: Preprocessing ; Closure ; Normalization ; Ratioing ; Constant sum transformation ; Constant length transformation ; Maximum value transformation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The geometric properties of three common object-preprocessing transformations (constant sum, or closure; constant length, or normalization; and maximum value, or ratioing) are investigated. An argument is made for using absolute values in the constant sum and maximum value transformations. In general, each transformation distorts the shape and dimensionality of patterns in the data: transformed data lie on (C-1)-dimensional surfaces in the original C-dimensional space. A data set that has been closed by one of these transformations can be reopened if a vector containing the constant sums, constant lengths or maximum values of the original objects was retained. Transformed data sets may be freely interconverted among these three transformations without the loss of information.
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180070506
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  • 8
    Electronic Resource
    Electronic Resource
    The methyleneketene radical anion (1994)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 533-534 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The methyleneketene radical anion is formed from Me3SiCOCH=CH2. Deprotonation of this neutral by NH2- yields Me3SiCOC̄=CH2 which then decomposes by loss of Me3Si· to yield CH2=C=C=O-·. The identity of the product radical anion is determined by its charge-reversal (positive ion) mass spectrum.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290080708
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  • 9
    Electronic Resource
    Electronic Resource
    Evidence for a lysine-specific fragmentation in fast-atom bombardment mass spectra of peptides (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 257-264 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A fragmentation proccess observed for peptides that contain lysine, or other amino acids which possess a free amino group on their sidechain, is reported. The ions generated by this process are found 16 Da below the acylium-type B ions that result from fragmentation at the C-terminal side of lysine or other amine-containing residues in fast-atom bombardment (FAB) mass spectra. These ions, which are referred to as (B - 16) ions, permit differentiation between the isobaric amino acids lysine and glutamine in peptide mass spectra. High resolution measurements indicate that (B - 16) ions differ in composition from the corresponding B ions by the removal of one oxygen atom. Formation is believed to occur through a cyclization process initiated by nucleophilic attack by the free amino group of the lysine sidechain at the carbon of the acylium ion (B ion). A similar process initiated derectly from the protonated peptide may also occur. Analogous cyclization processes are restricted for glutamine because this residue is comparatively less nucleophilic than lysine (i.e., amide vs amine). Although (B - 16) ions have been detected under high energy collisionally induced dissociation, they are formed less readily than by FAB mass spectrometry. A mechanism consistent jwith this observation as well as other experimental evidence is presented to account for the formation of (B - 16) ions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290060407
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  • 10
    Electronic Resource
    Electronic Resource
    Improved resolution of (±)-trans-2'-hydroxy-5,9-dimethyl-6,7-benzomorphans (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 439-442 
    Details
    ISSN: 0899-0042
    Keywords: trans-nor-pentazocine ; Sigma ; PCP ; NMR analysis ; GC analysis ; chiral derivatizing reagents ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An efficient resolution of (±)-trans-2'-hydroxy-5,9-dimethyl-6,7-benzomorphan has been developed employing ( - )-(R)- and (+)-(S)-O-acetylmandelic acids. Measurement of optical rotations on the resolved bases, NMR analyses of diastereomeric urea derivatives, as well as gas chromatographic analyses of diastereomeric amide derivatives indicate a net improvement over previous resolution methodology and an enantiomeric excess ≥ 99%. © 1992 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040707
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