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  • 1
    Electronic Resource
    Electronic Resource
    A Conformation- and Phosphorylation-Dependent Antibody Recognizing the Paired Helical Filaments of Alzheimer's Disease (1997)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 69 (1997), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Hyperphosphorylated tau (PHF-tau) is the major constituent of paired helical filaments (PHFs) from Alzheimer's disease (AD) brains. This conclusion has been based largely on the creation and characterization of monoclonal antibodies raised against PHFs, which can be classified in three categories: (a) those recognizing unmodified primary sequences of tau, (b) those recognizing phosphorylation-dependent epitopes on tau, and (c) those recognizing conformation-dependent epitopes on tau. Recent studies have suggested that the antibodies recognizing primary sequence and phosphorylation-dependent epitopes on tau are unable to distinguish between normal adult biopsy tau and PHF-tau. We now present evidence for a new fourth class of monoclonal antibodies recognizing conformation-dependent phosphoepitopes on tau, typified by TG-3, a monoclonal antibody raised to PHFs from AD brain homogenates. Studies using a series of deletional tau mutants, site-directed tau mutants, and synthetic peptides enable the precise epitope mapping of TG-3. Additional studies demonstrate that TG-3 reacts with neonatal mouse tau and PHF-tau but does not recognize adult mouse tau or tau derived from normal human autopsy or biopsy tissue. Further investigation reveals that TG-3 recognizes a unique conformation of tau found almost exclusively in PHFs from AD brains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1997.69052087.x
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  • 2
    Electronic Resource
    Electronic Resource
    Selective dimerization of cysteines in glycopeptides and phosphopeptides (1997)
    Springer
    International journal of peptide research and therapeutics 3 (1997), S. 371-377 
    Details
    ISSN: 1573-3904
    Keywords: Alzheimer's disease ; Disulfide bond formation ; Peptide ; Repeat domains ; Tau protein ; Thiopyridyl activation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary To study the influence of phosphorylation and oxidation on the repeat domains of human Tau protein, we faced the challenge to selectively dimerize two cysteine-containing peptides in the presence of a nearby phosphate group. To this end, we were able to demonstrate the utility of a selective dimerization approach by forming disulfide bonds in unprotected phosphopeptides and extended the methodology to unprotected glycopeptides. Activation of one cysteine of a peptide chain with 2,2′-dithiodipyridine and coupling this thiopyridyl-peptide to another peptide chain, containing an unprotected cysteine residue, yielded the mixed dimers in high purities and reasonable yields. Phosphate or sugar side chains on either peptide component remained unaffected during the activation and dimerization processes. While for mixed dimers the activated peptides were isolated by chromatography, homodimers were obtained by a simple one-pot reaction after 1 h. We demonstrate that cysteines can be dimerized in unprotected phosphopeptides and glycopeptides, without any side reactions affecting these posttranslational modifications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00127968
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  • 3
    Electronic Resource
    Electronic Resource
    2,3-Donor-Acceptor-Substituted 1,3-Butadienes. Synthesis by SO2-extrusion from 3-sulfolenes and diels-alder reactions (1994)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 336 (1994), S. 343-349 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal extrusion of SO2 from disubstituted 3-sulfolenes 3 leads to 2,3-donor-acceptor-substituted 1,3-butadienes 4. These dienes react with acrylic acid ester and ethyl vinyl ether to the corresponding Diels-Alder adducts 5 and 6 and with themselves to the cyclic dimerization products 7 and 8. The regiochemistry of the cycloadducts has been determined by chemical- and NMR-methods.The pyrolysis of 3-sulfolene 11 afforded the thiolactone 13 whose structure has been verified by X-ray diffraction analysis. In addition, the influence of Lewis acid catalysts on the Diels-Alder reaction and an approach to transition state calculation by means of the semiempirical AM 1 method has also been investigated.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19943360413
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  • 4
    Electronic Resource
    Electronic Resource
    Cycloadditions, 53. New spirocyclic chiral dienes  -  synthesis and diastereoselective Diels-Alder reactions with N-phenylmaleimide (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1455-1461 
    Details
    ISSN: 0947-3440
    Keywords: Dienes, chiral ; 1,3-Dioxin-4-ones ; (-)-Menthone ; Diels-Alder reactions, diastereoselective ; Cycloadditions, high-pressure ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and diastereoselective Diels-Alder reactions of new spirocyclic chiral dienes are reported. Starting with diketene and (-)-menthone (1), we prepared the diastereomeric diketene-menthone adducts 2 and 3. Further derivatization and olefination afforded four chiral dienes 12-15. Diastereoselective Diels-Alder reactions of these dienes with N-phenylmaleimide (NPM) under high-pressure conditions yielded the corresponding cycloadducts 16-19. Olefination of 6-diethylphosphonomethyl-2,2-dimethyl-1,3-dioxin-4-one 8 with formaldehyde led to unexpected compounds 9-11 resulting from the originally formed olefination product.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199508198
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  • 5
    Electronic Resource
    Electronic Resource
    Natural infection with microsporidian organisms (KW19) in Vannella spp. (Gymnamoebia) isolated from a domestic tap-water supply (1997)
    Springer
    Parasitology research 84 (1997), S. 164-166 
    Details
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004360050377
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  • 6
    Electronic Resource
    Electronic Resource
    Vannella sp. harboring Microsporidia-like organisms isolated from the contact lens and inflamed eye of a female keratitis patient (2000)
    Springer
    Parasitology research 86 (2000), S. 514-520 
    Details
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Viable Hartmannella sp. and two strains of Vannella sp. – but no Acanthamoebae– multiplied on NN-agar inoculated with pieces of the contact lens from a female keratitis patient. Within the cytoplasm of one Vannella isolate, intracellular parasites could be observed whose earliest stages were developing within the nucleus, resembling those Microsporidia-like parasites seen within Vannella isolated recently from a warm tapwater system. This assumption was also confirmed by electron microscopy. In swabs taken directly from the cornea, Pseudomonas aeruginosa were identified, but they did not yield any growth of amebas in culture. However, cocultivation of parasite-free Vannella strains with the above-mentioned swab matter resulted in infected amebas harboring the same intracellular parasites seen before. This infection could be established only if the corresponding spores were present as infective agents in the swab matter. The successful treatment of the patient with antibiotics supports the assumption that P. aeruginosa was the main cause of the corneal ulceration. The extent to which the Microsporidia-like organisms may have been involved in the development of keratitis remains a matter of discussion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004360050704
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  • 7
    Electronic Resource
    Electronic Resource
    Solid-phase synthesis of tyrosyl H-phosphonopeptides and methylphosphonopeptides (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 3 (1997), S. 186-192 
    Details
    ISSN: 1075-2617
    Keywords: H-phosphonopeptides ; mass spectrometry ; methylphosphonopeptides ; peptide synthesis ; phosphopeptides ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Phosphopeptides are a useful tool for the investigation of phosphorylation as a reversible post-translational modification. There is a growing interest in using mimics of phosphoamino acids involved in phosphorylation in order to study the enzymes concerned in these processes. These mimics should contain a non-hydrolysable or isoelectrically modified phosphate moiety to be used as a specific inhibitor of phosphatases and kinases. We introduce solid-phase synthesis of H- and methylphosphonopeptides as a new class of mimics of phosphotyrosyl peptides. The peptides were synthesized on solid phase using the standard fluorenyl-methyloxycarbonyl (Fmoc) strategy. Tyrosine residues were incorporated as allyl-protected derivatives, which were selectively deprotected on the resin by treatment with Pd(PPh3)4. The peptide resin carrying the side-chain unprotected tyrosine of the model peptide Gly-Gly-Tyr-Ala was phosphonylated with di-tert-butyl-N,N-diethyl-phosphoramidite in the presence of 1H-tetrazole, yielding H-phosphonopeptides after trifluoroacetic acid (TFA) cleavage. Alternatively, phosphonylation of the unprotected tyrosine with O-tert-butyl-N,N-diethyl-P-methylphosphonamidite catalysed by 1H-tetrazole and followed by oxidation led to the methylphosphonopeptides after TFA cleavage. We obtained both the H-phosphonopeptides and the methylphosphonopeptides of the tetrapeptide in high yields and purities above 90%, according to reversed-phase high-performance liquid chromatography (RP-HPLC). To investigate the general applicability of our new methodology, we synthesized phosphonopeptides up to 13 amino acids long, corresponding to recognition sequences of tyrosine kinases. After cleavage and deprotection, all phosphonopeptides were obtained in high yields and purities of about 90%, as shown by mass spectrometry. The only by-product found was the unmodified peptide. © 1997 European Peptide Society and John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    The Saccharomyces cerevisiae gene PPH3 encodes a protein phosphatase with properties different from ppx, PP1 and PP2A (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 10 (1994), S. 567-578 
    Details
    ISSN: 0749-503X
    Keywords: Protein phosphatase ; PPX ; PPH3 kinetics ; bacterial expression ; expression strain ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: A clone encoding the catalytic subunit of a protein phosphatase from Saccharomyces cerevisiae was isolated. Except for replacement of IIe-245 by Met the structure of the phosphatase was identical to that encoded by PPH3 (Ronne, H., Carlberg, M., Hu, G. Z. and Nehlin, J. O. (1991). Mol. Cell. Biochem. 11, 4876-4884) and exhibited 63% sequence identity to PPX cloned from a rabbit liver cDNA library (Brewis, N. D., Street, A. J., Prescott, A. R. and Cohen, P. T. W. (1993). EMBO J. 12, 987-996). Expression of active enzyme was achieved in Escherichia coli mutants which were generated by a genetic selection based on functional complementation of bacterial phosphoserine phosphatase. Though some of the properties of PPH3 resembled those of protein phosphatase 2A and PPX, others were different. PPH3 exhibited lower sensitivity against inhibition by okadaic acid, showed different substrate specificity and required a divalent cation (Mn2+ was preferred before Mg2+ and Ca2+) for activity when assayed with phospho-histone as a substrate. However, 25% of maximum activity was observed in the absence of divalent cations when the peptide LRRAS(P)LG was used as substrate. The PPH3-protein was also identified by chromatography of extracts from S. cerevisiae on DEAE-cellulose. Protein immunoreactive with an antiserum raised against the non-conserved N-terminal 53 amino acids of PPH3 was coeluted with a single peak of LRRAS(P)LG dephosphorylating activity.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320100502
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