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  • 1
    Electronic Resource
    Electronic Resource
    Poly(U)-directed peptide-bond formation from the 2′(3′)-glycyl esters of adenosine derivatives (1980)
    Springer
    Journal of molecular evolution 16 (1980), S. 1-10 
    Details
    ISSN: 1432-1432
    Keywords: Aminoacyl ester ; Template ; Polynucleotide ; Molecular evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The self-condensation of 2′(3′)-O-glycyl esters of adenosine, adenosine-5′-(O-methylphosphate) and P1, P2-diadenosine-5′-pyrophosphate in 6.2 mM solutions at pH 8.0 and -5°C in the presence of 12.5 mM poly(U) yields approximately 3 times as much diketopiperazine as reactions without poly(U). As the concentration of 2′(3′)-O-(glycyl)-P1, P2-diadenosine-5′-pyrophosphate is decreased from 6.2 mM to 1.5 mM the yield of diketopiperazine in the presence of poly(U) decreases slightly from 6.6% to 5.2%, whereas, in the absence of poly(U) the yield of diketopiperazine decreases substantially from 2.4% to 0.75%. The enhanced yield of diketopiperazine that is attributed to the template action of poly(U) is temperature dependent and is observed only at temperatures below 10°C (5°C to -5°C) for 6.2 mM 2′(3′)-O-(glycyl)-adenosine-5′-(O-methylphosphate) and below 23°C (15°C to -5°C) for 6.2 mM 2′(3′)-O-(glycyl)-P1, P2-diadenosine-5′-pyrophosphate. The absence of a template effect at high temperatures is attributed to the melting of the organized helices. The hydrolysis half-lives at pH 8.0 and -5°C of 2′(3′)-O-(glycyl)-adenosine, 2′(3′)-O-(glycyl)-adenosine-5′-(O-methylphosphate), 2′(3′)-O-(glycyl)-P1, P2-diadenosine-5′-pyrophosphate, and 5′-O-(glycyl)-adenosine in the presence of poly(U) are substantially larger than their half-lives in the absence of poly(U). The condensation of 2′(3′)-O-(glycyl)-adenosine yields 5% of 5′-O-(glycyl)-adenosine in the presence of poly(U) compared to 0.7% in the absence of poly(U).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01732065
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  • 2
    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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  • 3
    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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  • 4
    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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