SEARCH · Engineering Papers

Results for “oligomerization”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4

All sources NASA NTRS DOE OSTI

NASA NTRS1999

Nonenzymatic synthesis of RNA and DNA oligomers on hexitol nucleic acid templates: the importance of the A structure

Hexitol nucleic acid (HNA) is an analogue of DNA containing the standard nucleoside bases, but with a phosphorylated 1,5-anhydrohexitol backbone. HNA oligomers form duplexes having the nucleic acid A structure with complementary DNA or RNA oligomers. The HNA decacytidylate oligomer is an efficient template for the oligomerization of the 5'-phosphoroimidazolides of guanosine or deoxyguanosine. Comparison of the oligomerization efficiencies on HNA, RNA, and DNA decacytidylate templates under various conditions suggests strongly that only nucleic acid double helices with the A structure support efficient template-directed synthesis when 5'-phosphoroimidazolides of nucleosides are used as substrates.

Non-NASA Center↗

NASA NTRS1994

Oligonucleotides as probes for studying polymerization reactions in dilute aqueous solution

We have prepared a [32P]-labled oligonucleotide probe carrying a free primary amine at its 3'-terminus. This probe is used to initiate polymerization of aziridine (ethyleneimine) in aqueous solution. The nature of the oligomeric products and the kinetics of their formation are then monitored by gel electrophoresis. Our results are generally consistent with those obtained using conventional techniques. We have also investigated the effect of polyanionic templates on the rate of oligomerization of aziridine. We find that water-soluble polyanions generally accelerate the polymerization. The sodium salt of polymethacrylic acid is the most effective of the templates that we studied. The methods introduced in this paper should be applicable to a variety of polymerization reactions in aqueous solution. They should greatly simplify the screening of potentially prebiotic polymerization reactions.

NASA Discipline Exobiology↗

NASA NTRS1998

Polymerization on the rocks: beta-amino acids and arginine

We have studied the accumulation of long oligomers of beta-amino acids on the surface of minerals using the 'polymerization on the rocks' protocol. We find that long oligopeptides of beta-glutamic acid which cannot be formed in homogeneous aqueous solution are accumulated efficiently on the surface of hydroxylapatite using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC) as condensing agent. The EDAC-induced oligomerization of aspartic acid on hydroxylapatite proceeds even more efficiently. Hydroxylapatite can also facilitate the ligation of the tripeptide (glu)3. The 'polymerization on the rocks' scenario is not restricted to negatively-charged amino acids. Oligoarginines are accumulated on the surface of illite using carbonyldiimidizole (CDI) as condensing agent. We find that FeS2 catalyzes the CDI-induced oligomerization of arginine, although it does not adsorb oligoarginines. These results are relevant to the formation of polypeptides on the primitive earth.

NASA Discipline Exobiology↗

NASA NTRS2005

Pre-biotic stage of life origin under non-photosynthetic conditions

Spontaneous assembling of a simplest bacterial cell even if all necessary molecules are present in a solution seems to be extremely rare event and from the scientific standpoint has to be considered as impossible. Therefore, a predecessor of a living cell has to be very simple for providing its self-assembling and at the same time it should be able of progressive increase in complexity. Now phase-separated particles, first of all micelles, are put forward as possible predecessors of living cell. According to the offered working concept only phase-separated particles possessing autocatalytic properties can be considered as predecessors of living cells. The first stage of evolution of these phase-separated autocatalytic systems is the appearance of pre-biotic metabolism providing synthesis of amphiphiles for formation of capsules of these systems. This synthesis is maintained by the energy of a base reaction being a component of a planet-chemical cycle. Catalytic system providing functioning of pre-biotic metabolism is based on multivariate oligomeric autocatalyst, which reproduces itself from monomers, penetrating the particles from the outside. Since the autocatalyst realizes random polymerization then a collection of other oligomers possessing different catalytic functions is produced. In the paper the functioning of multivariate oligomeric autocatalyst in flow reactor is analyzed. c2005 Published by Elsevier Ltd on behalf of COSPAR.

Biogenesis↗

NASA NTRS2010

Microwave Plasma Hydrogen Recovery System

A microwave plasma reactor was developed for the recovery of hydrogen contained within waste methane produced by Carbon Dioxide Reduction Assembly (CRA), which reclaims oxygen from CO2. Since half of the H2 reductant used by the CRA is lost as CH4, the ability to reclaim this valuable resource will simplify supply logistics for longterm manned missions. Microwave plasmas provide an extreme thermal environment within a very small and precisely controlled region of space, resulting in very high energy densities at low overall power, and thus can drive high-temperature reactions using equipment that is smaller, lighter, and less power-consuming than traditional fixed-bed and fluidized-bed catalytic reactors. The high energy density provides an economical means to conduct endothermic reactions that become thermodynamically favorable only at very high temperatures. Microwave plasma methods were developed for the effective recovery of H2 using two primary reaction schemes: (1) methane pyrolysis to H2 and solid-phase carbon, and (2) methane oligomerization to H2 and acetylene. While the carbon problem is substantially reduced using plasma methods, it is not completely eliminated. For this reason, advanced methods were developed to promote CH4 oligomerization, which recovers a maximum of 75 percent of the H2 content of methane in a single reactor pass, and virtually eliminates the carbon problem. These methods were embodied in a prototype H2 recovery system capable of sustained high-efficiency operation. NASA can incorporate the innovation into flight hardware systems for deployment in support of future long-duration exploration objectives such as a Space Station retrofit, Lunar outpost, Mars transit, or Mars base. The primary application will be for the recovery of hydrogen lost in the Sabatier process for CO2 reduction to produce water in Exploration Life Support systems. Secondarily, this process may also be used in conjunction with a Sabatier reactor employed to stockpile life-support oxygen as well as propellant and fuel production from Martian atmospheric CO2

Atwater, James↗

NASA NTRS2020

A Sensitive Quantitative Analysis of Abiotically Synthesized Short Homopeptides using Ultraperformance Liquid Chromatography and Time-of-Flight Mass Spectrometry

In the origins of life field understanding the abiotic polymerization of simple organic monomers (e.g., amino acids) into larger biomolecules (e.g., oligopeptides), remains a seminal challenge. Recently, preliminary observations showed a limited set of peptides formed in the presence of the plausible prebiotic phosphorylating agent, diamidophosphate (DAP), highlighting the need for an analytical tool to critically evaluate the ability of DAP to induce oligomerization of simple organics under aqueous conditions. However, performing accurate and precise, targeted analyses of short oligopeptides remains a distinct challenge in the analytical chemistry field. Here, we developed a new technique to detect and quantitate amino acids and their homopeptides in a single run using ultraperformance liquid chromatography-fluorescence detection/time of flight mass spectrometry. Over an 8-minute retention time window, 18 target analytes were identified and quantitated, 16 of which were chromatographically separated at, or near baseline resolution. Compound identity was confirmed by accurate mass analysis using a 10 ppm mass tolerance window. This method featured limits of detection < 5 nM (< 1 fmol on column) and limits of quantitation (LOQs) <15 nM (< 3 fmol on column). The LODs and LOQs were upwards of ∼28x and ∼788x lower, respectively, than previous methods for the same analytes, highlighting the quantifiable advantages of this new method. Both detectors provided good quantitative linearity (R(exp 2) > 0.985) for all analytes spanning concentration ranges ∼3 - 4 orders of magnitude. We performed a series of laboratory experiments to investigate DAP-mediated oligomerization of amino acids and peptides and analyzed experimental products with the new method. DAP readily polymerized amino acids and peptides under a range of simulated environmental conditions. This research underscores the potential of DAP to have generated oligopeptides on the primordial Earth, enhancing prebiotic chemical diversity and complexity at or near the origin of life.

Prebiotic Chemistry and Analytical Chemistry↗

NASA NTRS2020

Metal-Templated Design of Chemically Switchable Protein Assemblies with High-Affinity Coordination Sites

To mimic a hypothetical pathway for protein evolution, we previously tailored a monomeric protein (cyt cb562) for metal-mediated self-assembly, followed by re-design of the resulting oligomers for enhanced stability and metal-based functions. We show that a single hydrophobic mutation on the cyt cb562 surface drastically alters the outcome of metal-directed oligomerization to yield a new trimeric architecture, (TriCyt1)3. This nascent trimer was redesigned into second and third-generation variants (TriCyt2)3 and (TriCyt3)3 with increased structural stability and preorganization for metal coordination. The three TriCyt variants combined furnish a unique platform to 1) provide tunable coupling between protein quaternary structure and metal coordination, 2) enable the construction of metal/pH-switchable protein oligomerization motifs, and 3) generate a robust metal coordination site that can coordinate all mid-to-late first-row transition-metal ions with high affinity.

Albert Kakkis↗

NASA NTRS1979

Association of nucleotides with homoionic clays

The binding of nucleotides to homoionic clays is studied as a possible mechanism for the concentration and catalysis of biological or prebiotic materials on the prebiotic earth. Samples of radioactively labeled adenosine and thymidine nucleotides were mixed in solutions with bentonite, kaolinite or Dowex-50 particles in which all exchangeable sites were occupied by Na, Mg, Ca, Mn, Fe, Cu or Zn ions. The binding of nucleotides to homoionic clays is observed, with adenosine nucleotides favored over thymidine, bentonite as the best absorber, and greater binding to clays homoionic in transition metal ions. Results indicate that the oligomerization of nucleotides may be possible by this mechanism, however difficulties in nucleotide variability and base pairing may arise due to the observed preference for purines at the adsorption sites.

Odom, D. G.↗

NASA NTRS1979

LARC-13 polyimide adhesive bonding

The development of an addition-curing polyimide adhesive suitable for low pressure bonding without the generation of volatiles during cure is reported. LARC-13 is designed for bonding of polyimide matrix composites and of titanium to be used above 500 F, and is based on an oligomeric bis-nadimide which allows its processing at 50 psi or less, making it suitable for the bonding of fragile honeycomb sandwich structures. Few volatiles are evolved during its cure allowing large enclosed structures to be bonded, and it has high room and elevated temperature strengths and good strength retention after short terms up to 1100 F. LARC-13 was successfully used to bond the outer and inner skins of a polyimide/graphite wing shear panel for 500 F use, and for a short-term exposure up to 1100 F. Preparation of the adhesive, bonding, aging, and testing of lap shear and honeycomb samples are discussed.

Saint Clair, T. L.↗

NASA NTRS1980

Clays in prebiological chemistry

The ways in which clays have been utilized in studies of prebiological chemistry are reviewed, and an assessment is given of the possible role of clays in prebiological systems. The adsorption of organic molecules on clays has been demonstrated, as has the synthesis of bioorganic monomers in the presence of clays. For instance, amino acids, purines and pyrimidines have been obtained from carbon monoxide and nitric acid in the presence of clays at relatively high temperatures (250-325 C). The oligomerization of biochemical monomers, mediated by clays, has also been shown to result in the formation of polymer molecules basic to life. Clays have also been found to affect the condensation of mononucleotides to oligonucleotides.

Rao, M.↗

NASA NTRS1982

Preparation of Perfluorinated Imidoylamidoxime Polymers

Perfluorinated imidoylamidoxime polymers with excellent resistance to heat, chemicals and solvents are prepared by condensing a perfluorinated nitrile with a perfluorinated amidoxime in vacuum or inert atmosphere from 20 degrees to 70 degrees C. When both reactants are difunctional, oligomeric or polymeric products are obtained. After cyclization of imidoylamidoxime groups to 1,2,4-oxadiazole linkages, process yields highly resistant elastomers. Competing side reactions are inhibited by low processing temperature.

Rosser, R. W.↗

NASA NTRS1980

A theory for the origin of a self-replicating chemical system. I - Natural selection of the autogen from short, random oligomers

A general theory is presented for the origin of a self-replicating chemical system, termed an autogen, which is capable of both crude replication and translation (protein synthesis). The theory requires the availability of free energy and monomers to the system, a significant background low-yield synthesis of kinetically stable oligopeptides and oligonucleotides, the localization of the oligomers, crude oligonucleotide selectivity of amino acids during oligopeptide synthesis, crude oligonucleotide replication, and two short peptide families which catalyze replication and translation, to produce a localized group of at least one copy each of two protogenes and two protoenzymes. The model posits a process of random oligomerization, followed by the random nucleation of functional components and the rapid autocatalytic growth of the functioning autogen to macroscopic amounts, to account for the origin of the first self-replicating system. Such a process contains steps of such high probability and short time periods that it is suggested that the emergence of an autogen in a laboratory experiment of reasonable time scale may be possible.

White, D. H.↗

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 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 NTRS1982

Chemical evolution. XL - Clay-mediated oxidation of diaminomaleonitrile

The inhibition of the oligomerization of HCN by montmorillonite clays is shown to be caused by oxidation of diaminomaleonitrile (DAMN) by ferric ion in the clay lattice, with ferrous ion and oxalic acid the reaction products. It is demonstrated that diiminosuccinonitrile is the initial reaction product and is rapidly hydrolized to oxalic acid and HCN. The same oxidative transformations are effected by ferric ion bound to Dowex 50, ferric ion in solution, and Ni(NH3)6(2+). The rate of reaction of DAMN indicates no catalytic role for the clay in the oxidation of DAMN, and little reaction of the latter was observed with montmorillonite in which the bulk of the iron was in the divalent state. The possible significance of these redox reactions to chemical evolution is discussed.

Ferris, J. P.↗

NASA NTRS1982

Template directed reactions of 2-aminoadenylic acid derivatives

The template-directed oligomerization of activated derivatives of 2-aminoadenylic acid (paA) on polyuridylic acid (poly(U)) in aqueous buffers was studied. The reaction differs from that of adenylic acid (pA) under identical conditions, in that only di- and tri-nucleotides are observed as substantial products rather than a longer sequence of oligomers. The reaction of paA also differs from that of pA in that it does not require Mg (2+), and is less susceptible to increased temperature. The relevance of these observations to the chemical evolution of polynucleotide replication is discussed. Improved syntheses of paA and its diphosphate are reported.

Webb, T. R.↗

NASA NTRS1982

Criteria for the emergence and evolution of life in the solar system

It is proposed that there are at least 25 specific conditions or requirements which have to be fulfilled in order for life to appear and evolve in a planetary system such as ours. The criteria are grouped into five major general areas: (1) Planetary criteria relate to the physical properties of the planet as it is formed and as it becomes a cosmic body with the potential to provide an abode for life. (2) Chemical criteria concern the composition, availability of effective energy sources, and chemical constraints of the environment where reactions take place for the prebiological formation of biochemical compounds. (3) Protobiological criteria relate to the prebiologically synthesized oligomeric and polymeric biomolecules, how they interact cooperatively to form protobiological structures and functions, and self-assemble to give rise to a living system. (4) Evolutionary criteria are concerned with the processes responsible for the increase in complexity of organisms by genomic multiplication, symbiotic integration, and cellular differentiation, as well as with the negentropic ability of organisms to continuously recycle all the volatile biogenic elements. (5) Stellar criteria relate to the elemental composition mass, lifetime, and other features of Main Sequence stars which may be surrounded by planetary systems similar to our own.

Oro, J.↗

NASA NTRS1982

Bisimide amine cured epoxy /IME/ resins and composites. II - Ten-degree off-axis tensile and shear properties of Celion 6000/IME composites

Bisimide amines (BIAs), which are presently used as curing agents in a state-of-the-art epoxy resin, are oligomeric and polymeric mixtures. A series of composites consisting of the novel BIA-cured epoxy resin reinforced with Celion 6000 graphite fibers were fabricated and evaluated, and the ten-degree, off-axis uniaxial tensile and shear properties of these composites were determined. The use of the intralaminar shear strain-to-failure was used in the calculation of resin shear strain-to-failure. Study results indicate that several of these novel composite systems exhibit shear strain properties that are superior to those of the control composite system of the present experiments, which employed a sulfone curing agent.

Scola, D. A.↗