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Lohrmann, R.

Publications and source records attributed to Lohrmann, R..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Oligonucleotide formation catalyzed by mononucleotide matrices

Pb(2+)-containing precipitates of mononucleotides form matrices which catalyze the self-condensation of nucleotide 5-prime-phosphorimidazolides and their condensation with nucleosides. The reactions exhibit base-pairing specificity between matrix nucleotide and substrate, and usually follow the Watson-Crick pairing rules. Although purine polynucleotides do not facilitate the oligomerization of pyrimidine nucleotide monomers in solution, it is interesting that purine-containing matrices do catalyze such a reaction. The significance of the results in the context of the prebiotic evolution of polynucleotides is discussed.

Lohrmann, R.↗
NASA NTRS1981

Condensation of activated diguanylates on a Poly/C/ template

The metal-ion catalysis of the oligomerization of activated diguanylate isomers on a polycytidylic acid template is studied in an investigation of possible early prebiotic polynucleotide replication mechanisms. The 5'-imidazolides of diguanylates linked 2' to 5' or 3' to 5' were reacted with polyC in a 1-methylimidazole or a 2,6-lutidine buffer in the presence of a Zn(+2) or a Pb(+2) catalyst, and reaction products were determined by paper chromatography, paper electrophoresis and liquid chromatography. In the lutidine buffer, the presence of both the Zn(+2) catalyst and the polyC template is found to result in the production of 3'-5' linked oligomers with up to 10 diguanylate units, and from diguanylates in the presence of the monomer. In the reactions conducted in the 1-methylimidazole buffer, the addition of Pb(+2) is found to lead to less marked increases in oligomerization in the presence of template, with approximately equal proportions of 2'-5' and 3'-5' oligomers formed from the 2'-5' substrate and mainly 3'-5' bonds from the 3'-5' linked dimer.

Lohrmann, R.↗
NASA NTRS1981

Template-directed synthesis of oligoguanylic acids - Metal ion catalysis

The effects of Zn(2+), Pb(2+) and other metal ions on the efficiency and stereo-selectivity of the template-directed oligomerization of guanosine 5'-phosphorimidazolide are investigated. Reactions were run in the presence of a polyC template in a 2,6-lutidine buffer, and products analyzed by high-performance liquid chromatography on an RPC-5 column. The presence of the Pb(2+) ion is found to lead to the formation of 2'-5' linked oligomers up to the 40-mer, while Zn(2+) favors the formation of predominantly 3'-5' linked oligomers up to the 35-mer. When amounts of uracil, cytidine or adenosine 5'-phosphorimidazole equal to those of the guanosine derivative are included in the reaction mixture, the incorrect base is incorporated into the oligomer about 10% of the time with a Pb(2+) catalyst, but less than 0.5% of the time with Zn(2+). The Sn(2+), Sb(3+) and Bi(3+) ions are also found to promote the formation of 2'-5' oligomers, although not as effectively as Pb(2+), while no metal ions other than Zn(2+) promote the formation of the 3'-5' oligomers. The results may be important for the understanding of the evolution of nucleic acid replication in the absence of enzymes.

Bridson, P. K.↗
NASA NTRS1980

Template-directed synthesis and selective adsorption of oligoadenylates in hydroxyapatite

Polyuridylic acid is adsorbed completely from aqueous solution by hydroxyapatite under conditions that permit template-directed synthesis of oligoadenylates in free solution. The yield of oligoadenylates is enhanced to almost the same extent by poly(U) in the presence or the absence of hydroxyapatite. Under very similar conditions small quantities of hydroxyapatite adsorb higher-molecular-weight oligoadenylates selectively from a mixture of oligomers. On the basis of these results a mechanism for prebiotic oligonucleotide formation is proposed in which selective adsorption on hydroxyapatite or some other immobilized anion-exchanging material plays a major role. Monomers are released from the surface for reactivation, while oligomers are retained in a protected environment by adsorption to the apatite surface.

Gibbs, D.↗
NASA NTRS1979

Self-condensation of activated dinucleotides on polynucleotide templates with alternating sequences

Substantial quantities of the alternating polymers poly(U-G) and poly(C-A) have been prepared and used as templates for the self-condensation of ImpApC, ImpCpA, ImpGpU and ImpUpG. It is found that the condensation of ImpGpu and ImpUpG on poly(C-A) is efficient, the condensation of ImpCpA on poly(U-G) is moderately efficient, while the condensation of ImpApC on poly(U-C) proceeds poorly. In many cases, the product is predominantly 3'-5'-linked. These reactions demonstrate unequivocally, for the first time, that template-directed reactions occur in double-helical structures. Furthermore, they describe for the first time a pair of reactions in which each of two complementary polymers facilitates the synthesis of the other. The prebiotic significance of these findings is discussed.

Lohrmann, R.↗
NASA NTRS1979

Template-directed synthesis of oligoadenylates catalyzed by Pb/2+/ ions

The Pb(2+) ion is an effective catalyst for the template-directed condensation of ImpA on poly(U). This reaction generates up to 35% of oligomers 5 or more units long. Furthermore, the product is predominantly 3'-5'-linked (75%) unlike that from the uncatalyzed reaction which is more than 90% 2'-5'-linked. The significance of metal-ion catalysis for prebiotic polynucleotide formation is discussed.

Sleeper, H. L.↗
NASA NTRS1978

Formation of the imidazolides of dinucleotides under potentially prebiotic conditions

Imidazolides of dinucleotides such as ImpApA can be formed from the corresponding dinucleotides in a two-stage process, which gives up to 15% yields under potentially prebiotic conditions. First a solution of the dinucleotide and sodium trimetaphosphate is dried out at constant temperature and humidity. This produces polyphosphates such as p(n)ApA in excellent yield (greater than or equal to 80%). The products are dissolved in water, imidazole is added, and the solution is dried out again. This yields the 5'-phosphorimidazolides.

Sleeper, H. L.↗
NASA NTRS1976

Formation of nucleoside 5'-polyphosphates under potentially prebiological conditions

The characteristics and efficiencies of biochemical reactions involving nucleoside 5'-diphosphates and -triphosphates (important substrates of RNA and DNA synthesis) under conditions corresponding to the primitive prebiotic earth are investigated. Urea catalysis of the formation of linear inorganic polyphosphates and metal ions promoting the reactions are discussed. Linear polyphosphate was incubated with Mg(++) in the presence of a nucleoside 5'-phosphate, to yield nucleoside 5'-polyphosphates when products are dried, while Mg(++) prompts depolymerization to trimetaphosphate in aqueous solutions. Plausible biogenetic pathways are examined.

Lohrmann, R.↗
NASA NTRS1975

Formation of nucleoside 5'-polyphosphates from nucleotides and trimetaphosphate

Nucleoside 5'-polyphosphates (N5PP) formed when solutions of nucleoside 5'-phosphates (N5P) and trimetaphosphate (TMP) are dessicated at room temperature are studied by paper chromatography, electrophoresis, and metal catalytic reactions. Divalent Mg ion exhibited superior catalytic function to other divalent metal ions in the reaction. Major reaction products are indicated. The importance of the N5PP series, TMP, and N5-triphosphate as substrates of RNA and DNA synthesis, and under postulated prebiotic conditions likely to obtain during prebiological ages of the earth, is emphasized and discussed. Alternate drying and wetting, evaporation from a prebiotic puddle, concentration of solubles in the remaining liquid phase, metal catalysis, and the role of these substances in the formation of amino acids and long-chain polyphosphates are considered.

Lohrmann, R.↗
NASA NTRS1974

Prebiotic chemistry and nucleic acid replication

Recent work is reviewed on some reactions that could have occurred on the primitive earth and that could have played a part in the evolution of a self-replicating system. The transition from the primitive atmosphere to the simplest replicating molecules is considered in four stages: (1) the formation of a 'prebiotic soup' of organic precursors, including the purine and pyrimidine bases and the pentose sugars; (2) the condensation of these precursors and inorganic phosphate to form monomeric nucleotides and activated nucleotide derivatives; (3) the polymerization of nucleotide derivatives to oligonucleotides; and (4) the complementary replication of oligonucleotides in a template-directed process that depends on Watson-Crick base pairing.

Orgel, L. E.↗
NASA NTRS1973

The effect of Mg/2+/ and Ca/2+/ on urea-catalyzed phosphorylation reactions

The effect of Mg(2+) and Ca(2+) on phosphorylation reactions catalyzed by urea is investigated, showing that Mg(2+) improves markedly the yield of products containing pyrophosphate bonds. Yields of up to 25% of uridine diphosphate can be obtained with struvite at temperatures as low as 65 C.

Handschuk, G. J.↗
NASA NTRS1973

Prebiotic activation processes.

Questions regarding the combination of amino acids and ribonucleotides to polypeptides and polynucleotides are investigated. Each of the reactions considered occurs in the solid state in plausible prebiotic conditions. Together they provide the basis for a unified scheme of amino acid and nucleotide activation. Urea, imidazole and Mg(++) are essential catalytic components of the reaction mixtures. However, these compounds could probably be replaced by other organic molecules.

Lohrmann, R.↗
NASA NTRS1972

Prebiotic phosphorylation of thymidine at 65 C in simulated desert conditions.

The phosphorylation of thymidine is described for a variety of conditions at 65 C to demonstrate that the reaction could readily take place in deserts at the present time. This might be used as an indication that urea-phosphate mixtures could have been important as phosphorylating agents on the primitive earth. Reaction products were identified by comparing their chromatographic and electrophoretic mobilities with those of authentic materials and by enzymatic degradation. The results show that good yields of nucleotides are obtained when nucleosides are heated with urea-phospate mixtures at 65 C. Reactions proceed more rapidly at moderate humidities than in a stream of dry nitrogen. Occasional wetting results in even faster and more extensive reactions. There was no reaction for a mixture of urea and trimetaphosphate.

Bishop, M. J.↗