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  • Organic Chemistry  (5)
  • Molecular evolution  (3)
  • Cell & Developmental Biology  (2)
  • Polymer and Materials Science  (2)
  • (PAP, LAP, SDH, plasmin)  (1)
  • 1980-1984  (13)
  • 1955-1959
  • 1981  (13)
Document type
Keywords
Publisher
Years
  • 1980-1984  (13)
  • 1955-1959
Year
  • 1
    Electronic Resource
    Electronic Resource
    Reasons for the occurrence of the twenty coded protein amino acids (1981)
    Springer
    Journal of molecular evolution 17 (1981), S. 273-284 
    Details
    ISSN: 1432-1432
    Keywords: Amino acids ; Molecular evolution ; Genetic Code ; Protein synthesis ; Prebiotic synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Factors involved in the selection of the 20 protein L-α-amino acids during chemical evolution and the early stages of Darwinian evolution are discussed. The selection is considered on the basis of the availability in the primitive ocean, function in proteins, the stability of the amino acid and its peptides, stability to racemization, and stability on the transfer RNA. We conclude that aspartic acid, glutamic acid, arginine, lysine, serine and possibly threonine are the best choices for acidic, basic and hydroxy amino acids. The hydrophobic amino acids are reasonable choices, except for the puzzling absences ofα-amino-n-butyric acid, norvaline and norleucine. The choices of the sulfur and aromatic amino acids seem reasonable, but are not compelling. Asparagine and glutamine are apparently not primitive. If life were to arise on another planet, we would expect that the catalysts would be poly-α-amino acids and that about 75% of the amino acids would be the same as on the earth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01795749
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  • 2
    Electronic Resource
    Electronic Resource
    Formation of pyrophosphate, tripolyphosphate, and phosphorylimidazole with the thioester, N, S-diacetylcysteamine, as the condensing agent (1981)
    Springer
    Journal of molecular evolution 18 (1981), S. 24-29 
    Details
    ISSN: 1432-1432
    Keywords: Thioester ; Pyrophosphate ; Tripolyphosphate ; Phosphorylimidazole ; Molecular evolution ; Prebiotic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Reaction of 0.20M orthophosphate with 0.20M N,S-diacetylcysteamine in 0.40M imidazole at pH 7.0 or 8.0 under drying conditions at 50°C for 6 days yields pyrophosphate and tripolyphosphate in the presence and absence of 0.10M divalent metal ion. The efficiency of utilization of N,S-diacetylcysteamine in the formation of pyrophosphate linkages ranges from 3 – 8% under the above conditions. The thioester, N,S-diacetylcysteamine, and imidazole are required for phosphoanhydride formation. Reaction of 0.40M orthophosphate with 0.20M N, S-diacetylcysteamine in 0.40M imidazole at ambient temperature for 6 days yields phosphorylimidazole in the absence or presence of 0.05M MgCl2. Phosphorylimidazole and pyrophosphate are formed in the presence of 0.05M CaCl2; pyrophosphate and tripolyphosphate are formed with 0.15M CaCl2. The efficiency of utilization of N,S-diacetylcysteamine in the formation of pyrophosphate linkages is roughly 7% at 6 days of reaction with 0.15M CaCl2. The thioester, N,S-diacetylcysteamine and imidazole are required for the formation of phosphoanhydrides. The significance of these reactions to molecular evolution is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01733208
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  • 3
    Electronic Resource
    Electronic Resource
    Formation of the thioester, N,S-diacetylcysteine, from acetaldehyde and N,N′diacetylcystine in aqueous solution with ultraviolet light (1981)
    Springer
    Journal of molecular evolution 17 (1981), S. 103-107 
    Details
    ISSN: 1432-1432
    Keywords: Thioester ; Disulfide ; Acetaldehyde ; Ultraviolet light ; Molecular evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The thioester, N,S-diacetylcysteine, is formed during the illumination of phosphate buffered (pH 7.0) aqueous solutions of acetaldehyde and N,N′-diacetylcystine with ultraviolet light. The yield of N,S-diacetylcysteine relative to N-acetylcysteine and unidentified products progressively increases as ultraviolet light below 239 nm, 253 nm and 281 nm is cut off with optical filters. When ultraviolet light below 320 nm is removed with an optical filter, there is no detectable reaction. Illumination of 0.025 M N,N′-diacetylcystine with 0.5 M and 1.0 M acetaldehyde with filtered ultraviolet light gives, respectively, 20% and 80% yields of N,S-diacetylcysteine. In the reaction with 1.0 M acetaldehyde, N-acetylcysteine forms early in the reaction and later decreases with its conversion to N,S-diacetylcysteine. The prebiotic significance of these reactions is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01732680
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  • 4
    Electronic Resource
    Electronic Resource
    Polyamines, hydrolases (PAP, LAP, SDH, plasmin) TSH, T3, T4 and C-peptide in benign hyperplasia of the prostate (1981)
    Springer
    Urological research 9 (1981), S. 137-142 
    Details
    ISSN: 1434-0879
    Keywords: BPH ; Polyamines ; Hydrolases ; (PAP, LAP, SDH, plasmin) ; TSH ; T3 ; T4 ; C-peptide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary High concentrations of polyamines have been found in the normal human prostate. The profile of these amines appeared significantly changes in benign hypertrophy of the prostate. An increase of spermine and a fall of putrescine were always found in patients with a hypertrophied prostate weighing more than 30 g. Alterations of plasmin in these tissues seemed to reflect changes in the matrix; abnormalities of thyroid and pancreatic function documented by changes in the serum levels of TSH and c-peptide which are thought to be further evidence of a mesenchymal-epithelial interaction in the pathogenesis of benign prostate hypertrophy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00254408
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  • 5
    Electronic Resource
    Electronic Resource
    Total Synthesis of All Eight Stereoisomers of α-Tocopheryl Acetate. Determination of their diastereoisomeric and enantiomeric purity by gas chromatographyDedicated to Professor G. Büchi on the occasion of his 60th birthday (1981)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 1158-1173 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: All eight stereoisomers of α-tocopheryl acetate have been synthesized in a state of high chemical and stereoisomeric purity. Key chiral side-chain intermediates were prepared from (+)-(S)-3-hydroxy-2-methylpropanoic acid. New routes to (2R, 4′ RS, 8′ RS)-α-tocopheryl acetate, a mixture of four diastereoisomers, were also developed. A sensitive gas chromatographic method was developed to determine the diastereoisomeric and enantiomeric purity of α-tocopherol samples as the methyl ethers. It was established for the first time that naturally occurring α-tocopherol is essentially a single enantiomer (2 R, 4′ R, 8′ R), synthetic all-rac-α-tocopherol an equimolar mixture of four racemates, and that natural (E)-(7 R, 11 R)-phytol is diastereoisomerically and enantiomerically homogeneous.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19810640422
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  • 6
    Electronic Resource
    Electronic Resource
    Nucleophilic Aromatic Substitutions. Part XIV.Part XIII, see [1].. Investigation of the mechanism of hydroxy-denitration of 4,2-and 2,4-chloronitrobenzenediazonium ions as a function of pH (1981)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 1777-1789 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 4,2-Chloronitrobenzenediazonium ions in aqueous buffer solutions between pH 2.9 and 7.9 do not hydrolyze by dediazoniation as previous authors have assumed, but by denitration. The isomeric 2,4-compound reacts by denitration (ca. 70%) and dechlorination (ca. 30%). The reactions are general base catalyzed. The products and kinetics are consistent with an SNAr-mechanism in which the general base-catalyzed addition of a hydroxyl group at the reacting C-atom is rate-limiting. The rate maxima at or near the pH-values corresponding to (pK1 + pK2)/2 of the diazonium ⇄ cis-diazotate equilibria can be rationalized on the assumption that the diazonium ion is the only equilibrium form of the diazo compound which enters the substitution proper, and the superposition of the rate term B∑kB[B] of all nucleophiles involved (H2O, OH- and buffer bases).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19810640607
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  • 7
    Electronic Resource
    Electronic Resource
    Herstellen von Hochmodulfäden aus PolyethylenVorgetragen auf dem Hamburger Makromolekularen Symposium 16. - 18. September 1980. (1981)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 637-642 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1981.021820232
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  • 8
    Electronic Resource
    Electronic Resource
    Zur Reaktion von Cyanodithioformiaten mit primären Aminen (1981)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 323 (1981), S. 41-48 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of Cyanodithioformates with Primary AminesN-Alkyldithiooxamides 3 and N,N -dialkyldithiooxamides 4 were synthesized in good yields by reaction of cyanodithioformates 1 with primary aliphatic amines. N-Alkylcyanothioformamides 2, intermediates in these reactions were obtained in very low yields only. The reaction of 1 and diaminoethane or 1.3-diaminopropane afforded imidazolidine-2-thione 5a respectively perhydropyrimidine-2-thione 5b. The reaction of 1 with 1-chloro-2-aminoethane did gave 2-thiocarbamoylthiazoline 7.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19813230107
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  • 9
    Electronic Resource
    Electronic Resource
    Mikrobielle Reduktion 2,2-disubstituierter Cyclopentan-1,3-dione. Darstellung chiraler Cyclopentanderivate für die Synthese von 8-Methyl-prostaglandinen (1981)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 323 (1981), S. 729-736 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Microbial Reduction of 2,2-Disubstituted Cyclopentan-1,3-diones. Synthesis of Chiral Cyclopentane Derivatives Useful as Intermediates for 8-Methyl ProstaglandinsThe microbial reduction of the 2,2-disubstituted cyclopentan-1,3-diones 3a—c giving rise to the chiral compounds 2, 4b and 4c is described.The incubation products can be used as intermediates for 8-methyl prostaglandins.The structures of the fermentatively formed compounds, including their chirality and optical purity have been established by comparison with authentic specimen (cp. 2) or by chemical and spectroscopic methods (cp. 4b, 4c) respectively.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19813230505
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  • 10
    Electronic Resource
    Electronic Resource
    Structure, histochemistry, ontogenetic development, and regeneration of the ocellus of Cladonema radiatum dujardin (cnidaria, hydrozoa, anthomedusae) (1981)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 167 (1981), S. 313-331 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The ectodermal eyes, 45-55 μm in diameter, of the cnidarian hydrozoan Cladonema radiatum Dujardin possess a lens approximately 15 μm in diameter enveloped by an eyecup (retina). An overlying layer of intensely vacuolated distal process of the adjoining epithelial cells forms a transparent cornea. The eyecup is composed of three cell types: basal cells, melanin-containing pigment cells, and photoreceptor cells. The last two cell types occur in the ratio of approximately 2:1. Histogenesis of the eye both during ontogeny and regeneration is described from light and electron microscopic investigations. During ontogeny the cell types forming the retina are derived from a compact group of morphologically undifferentiated cells, but during regeneration a primordium is formed by regeneration cells. In both cases the lens is built from distal nonnucleated cytoplasmic portions pinched off from the pigment cells. The cornea is formed by distal lamellar processes of the ocellus adjoining the epithelial cells. Through EM-histochemical methods (silver impregnation and DOPA-oxidase reaction) the pigment of the chromatophores of the retina was identified as melanin.
    Additional Material: 25 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051670306
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