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  • Carbohydrates  (3)
  • Occupational Health and Environmental Toxicology  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Glycosyl Phosphatidylinositol (GPI) Anchor Synthesis Based on Versatile Building Blocks - Total Synthesis of a GPI Anchor of Yeast (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1153-1165 
    Details
    ISSN: 1434-193X
    Keywords: Carbohydrates ; Phospholipids ; Glycolipids ; Sphingosines ; Ceramides ; Ceramides-1-phosphates ; Glycosylation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -For the design of a synthesis of target molecule 1 the retrosynthetic analysis yielded building blocks 2-5, of which ceramide 2-phosphite derivative 2 and aminoethyl phosphite derivative 5 are known. The generation of α-glucosaminyl (1→6)inositol building block 3 was based on pseudodisaccharide 6 which was selectively benzoylated at 6b-O and then selectively benzylated at 3b-O to give 3. The synthesis of tetramannosyl building block 4 started from known ortho ester derivative 8 which was transformed into versatile mannosyl donors 13 and 18 and into acceptor 22. Reaction of 13 with 22 gave α-disaccharide 23, deacetylation and then mannosylation with 18 gave trisaccharide 25; ensuing deacetylation and mannosylation with 13 gave tetrasaccharide 27; deallylation, acetylation, regioselective removal of the anomeric O-acetyl group and treatment with CCl3CN/DBU afforded 4. Glycosylation of 3 with donor 4 led to pseudohexasaccharide 31 in high yield. Replacement of the O-acyl groups by O-benzyl groups and then exchange of the menthyloxycarbonyl group by an O-acetyl group gave 36 which enabled regioselective attachment of 2 and 5. To this end, the 6e-O-silyl group was removed and then the aminoethyl phosphate residue was attached with reagent 5 to give 38 in high yield. 1a-O-Deacetylation and then reaction with 2 afforded 40 as fully protected 1 which was liberated in two steps; treatment with acid removed all acid labile protective groups and finally catalytic hydrogenation afforded the desired GPI anchor 1 which could be fully structurally assigned.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis of D-erythro-Ceramide-1-phosphoinositol and Its Aminoglucosylated Derivative - Intermediates in GPI-Anchor Biosynthesis (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 291-298 
    Details
    ISSN: 1434-193X
    Keywords: Carbohydrates ; Phospholipids ; Glycolipids ; Sphingosines ; Ceramides ; Ceramide-1-phosphates ; Inositols ; Glycophosphosphingolipids, synthesis ; Glycophosphoinositol anchors ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The readily available 2,3:4,5-di-O-cyclohexylidene-D-myo-inositol derivative 3 was converted into the 1-O-unprotected D-myo-inositol derivative 6. Reaction with the phosphite derivative 7 of 3-O-tert-butyldimethylsilyl-protected ceramide furnished the target molecule D-erythro-ceramide-1-phosphoinositol (1). Reaction of O-(3,4,6-tri-O-acetyl-2-azido-β-D-glucopyranosyl)trichloroacetimidate (20) with 3 gave exclusively α(1→6)-connected glycoside 21 which was converted into the 1α-O-unprotected derivative 24. Reaction with the D-erythro-azidophytosphingosine-derived ceramide-1-phosphite derivative 17 led, after oxidation and removal of the cyanoethyl group, to protected 2-azido-D-glucopyranosyl-α(1→6)-D-myo-inositol-1-phospho-ceramide (25) which could be fully deprotected in two steps to afford the target molecule, the ceramide derivative of 2-amino-2-deoxy-D-glucopyranosyl-α(1→6)-D-myo-inositol-1-phosphate (2).
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis Of Labeled Glycosyl Phosphatidyl Inositol (GPI) Anchors (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2563-2571 
    Details
    ISSN: 1434-193X
    Keywords: Carbohydrates ; Phospholipids ; Glycolipids ; Diacylglycerolphosphates ; Glycophosphoinositol anchors ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The exploration of the molecular and structural basis for the sorting of GPI-anchored proteins is based on labeled partial structures of GPI′s which can be incorporated into the GPI anchor biosynthesis and cellular transport systems. To this end, from mannosyl donor 6 and the D-glucosaminyl-(1→6)-D-myo-inositol derivative 7 as acceptor, the pseudotrisaccharide 8 was prepared. Compound 8 was transformed into the GPI partial structures 5a,b which contain the pseudotrisaccharide ligated to two different phosphatidyl residues. Compounds 5a,b have Boc protection at the 2-amino group of the glucosamine residue (2b-position) and a free amino group at the 6b-position. The 6b-amino group was used for the ligation of the 3-(7-nitrobenzofurazan-4-yl)-aminopropanoyl group as a fluorescent label, the 5-azido-2-nitrobenzoyl and 4-azidophenylaminothiocarbonyl groups as photolabels, and the 4-azido-2-hydroxybenzoyl group as a radiolabel after the introduction of radioactive iodine by an electrophilic aromatic substitution. Thus, after acid-catalyzed removal of the protective groups, the unprotected target molecules 1-4 were obtained.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Electromagnetic pulsed-wave radiation in spherical models of dispersive biological substances (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 12 (1991), S. 319-333 
    Details
    ISSN: 0197-8462
    Keywords: pulse-train ; dispersive dielectrics ; Fourier transform ; focusing ; hot-spot ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: In analytical studies, we investigated induced-field patterns and SAR distributions in a lossy, dispersive, homogeneous, dielectric sphere typical of muscle tissue as irradiated by a plane-wave pulse train consisting of a pulse-modulated sinusoidal carrier wave. Calculations were made for carrier frequencies of 1, 3, and 15 GHz, pulse widths of 0.333, 2.0 and 4 ns, and pulse repetition rates of 1.11 × 106, 100 × 106, and 181.18 × 106 pps. The classical Mie solution was modified for a train of incident pulses that was represented by a Fourier series, and the fast-Fourier transform was used to sum the series. Computationally, the technique proved to be feasible and less expensive than we expected. The calculated field patterns show that the sphere's physical dimensions and the internal wavelength of the carrier greatly influence the nature of pulse-train propagation in the sphere. Harmonics having internal wavelengths nearly equal to the radius of the sphere produce most of the absorption; other harmonics produce little absorption. An intense hot spot is observed in spheres with radii that match the carriers' wavelengths.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250120602
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  • 5
    Electronic Resource
    Electronic Resource
    Temporal bisection in rats: The effects of high-peak-power pulsed microwave irradiation (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 14 (1993), S. 459-478 
    Details
    ISSN: 0197-8462
    Keywords: high-peak-power pulsed microwaves ; time perception ; time discrimination ; decision-making ; rats ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The effects of high-peak-power, pulsed microwaves on a time perception and discrimination task were studied in rats. Exposures were performed with the TEMPO exposure system, which produces an 80 nanosecond pulse with peak-power levels in excess of 700 megawatts. The ability to expose animals to such fields within a controlled environment is unique. As determined by calorimetry, a maximal, whole-body-averaged, specificabsorption rate of 0.072 W/kg was produced. Thus exposures were well below a recommended SAR limit of 0.4 W/kg. Power levels of transmitted microwaves were varied over a 50 dB range to obtain ascending and descending dose-response functions for each of the behavioral measures. Measures of time perception, response bias, and total trials did not change with power level. Dose-response effects were observed for discriminability (ability to distinguish between durations), session time, and trial completions (null responses, failures to respond on a trial). Covarying sound and X-ray exposures produced by TEMPO did not reliably correlate with the observed microwave effects. The observation of repeatable dose-response effects on discriminability and null responses indicates that the microwave exposures were affecting cognitive function in the rats, particularly the decision-making process. © 1993 wiley-Liss, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250140507
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  • 6
    Electronic Resource
    Electronic Resource
    Electromagnetic pulse propagation in dispersive planar dielectrics (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 10 (1989), S. 35-49 
    Details
    ISSN: 0197-8462
    Keywords: pulse train ; dispersive dielectrics ; fast Fourier transform ; specific absorption rate ; biological effects ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The responses of a plane-wave pulse train irradiating a lossy dispersive dielectric half-space are investigated. The incident pulse train is expressed as a Fourier series with summing done by the inverse fast Fourier transform. The Fourier series technique is adopted to avoid the many difficulties often encountered in finding the inverse Fourier transform when transform analyses are used. Calculations are made for propagation in pure water, and typical waveforms inside the dielectric half-space are presented. Higher harmonics are strongly attenuated, resulting in a single continuous sinusoidal waveform at the frequency of the fundamental depth in the material. The time-averaged specific absorption rate (SAR) for pulse-train propagation is shown to be the sum of the time-averaged SARs of the individual harmonic components of the pulse train. For the same average power, calculated SARs reveal that pulse trains generally penetrate deeper than carrier-frequency continuous waves but not deeper than continuous waves at frequencies approaching the fundamental of the pulse train. The effects of rise time on the propagating pulse train in the dielectrics are shown and explained. Since most practical pulsed systems are very limited in bandwidth, no pronounced differences between their response and continuous wave (CW) response would be expected. Typical results for pulse-train propagation in arrays of dispersive planar dielectric slabs are presented. Expressing the pulse train as a Fourier series provides a practical way of interpreting the dispersion characteristics from the spectral point of view.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250100105
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