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Fox, S. W.

Publications and source records attributed to Fox, S. W..

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Polycondensation of alpha-amino acids by pyrosulfuric acid

The thermal polycondensation of amino acids common to protein is promoted at 80 deg C by pyrosulfuric acid. This is in contrast to the noncondensation at 100 deg C in the presence of concentrated sulfuric acid. These results are in accord with an anhydride mechanism, as proposed earlier for copolycondensation promoted by polyphosphoric acid. The amino acid composition, molecular weight, near-homogeneity, and infrared absorption of the polymer formed are described. The potential significance of planetary pyrosulfuric acid is discussed.

Denes, F.↗
NASA NTRS1976

Linkages in thermal copolymers of lysine

The thermal copolymerization of lysine with other alpha-amino acids has been studied further. The identity of the second amino acid influences various properties of the polymer obtained, including the proportion of alpha and epsilon linkages of lysine. A review of linkages in proteinoids indicates alpha and beta linkages for aspartic acid, alpha and gamma linkages for glutamic acid, alpha and epsilon linkages for lysine, and alpha linkages for other amino acids. Thermal proteinoids are thus more complex in types of linkage than are proteins

Fox, S. W.↗
NASA NTRS1976

Contributions of experimental protobiogenesis to the theory of evolution

Inferences from experiments in protobiogenesis are examined as a forward extension of the theory of evolutionary biology. A nondiscontinuous, intraconsistent theory of general evolution embracing both protobiology and biology is outlined. This overview emphasizes Darwinian selection in the later stages of evolution, and stereochemical molecular selection in some of its earlier stages. It incorporates the concept of limitation of the scope of evolution by internal constraints on variation, based on the argument that internally limiting constraints observed in experiments with molecules are operative in organisms, if chemical processes occur within biological processes and biological processes are assumed to be exponentializations of chemical processes. Major evolutionary events might have occurred by rapid self-assembly processes analogous to those observed in the formation of phase-separated microspheres from amorphous powder or supersaturated solutions.

Fox, S. W.↗
NASA NTRS1975

Linkages in thermal copolymers of lysine

The thermal copolymerization of lysine with other alpha-amino acids was studied. The identity of the second amino acid influences various properties of the polymer obtained, including the proportion of alpha and epsilon linkages of lysine. A review of linkages in proteinoids indicates alpha and beta linkages for aspartic acid, alpha and gamma linkages for glutamic acid, alpha and epsilon linkages for lysine, and alpha linkages for other amino acids. Thermal proteinoids are thus more complex in types of linkage than are proteins.

Fox, S. W.↗
NASA NTRS1975

Looking forward to the present

The present understanding of the origin of life based on Oparin's (1924) conception of life as a manifestation of matter in a special stage of its development is outlined. The results of chemical analyses of lunar samples are discussed, and their implications regarding chemical reactions beginning with carbonaceous dust are considered. Amino acids isolated from lunar samples taken from different sites show a high degree of similarity, in agreement with the hypothesis that carbon compounds, including amino acid precursors, were implanted on the lunar surface by components of the solar wind. The amino acid precursors are most likely a cyanide compound. Overlapping amino acid/carbon ratios from lunar samples and samples of meteorites suggest a common cosmochemical state of carbon in the solar system.

Fox, S. W.↗
NASA NTRS1975

Stereomolecular interactions and microsystems in experimental protobiogenesis

A theory on the origin of the first reproducing (in the sense of Fox, 1973) cells on earth is presented. A degree of self-ordering has been observed in the selective thermal reactions of certain ones of the amino acids which have been found in samples of meteorites, lunar samples, and terrestrial lava, and which have been synthesized from formaldehyde and ammonia under conditions modeling those assumed to have been present in the primitive earth. The genetic code is supposed to have arisen from a nonrandom matrix of preproteins. The ordering of preproteins specified limitations in the identity of the pre-enzymes and primordial microsystems which gave rise to contemporary living systems. The evolution of progresively more complex system was largely determined by stereochemical forces involving the shapes of the molecules themselves and the regulatory effects of the confines of the microsystems.

Fox, S. W.↗
NASA NTRS1974

Origins of biological information and the genetic code

Information, defined as the capacity of a molecule or system for selective interactions with other molecules or systems, is followed through its evolution from prebiological information to protoribosomes. Emphasis is on proteins and protein-like polymers, and later on ATP. The research will contribute more to the understanding of the essence of the genetic mechanism.

Fox, S. W.↗
NASA NTRS1974

Coacervate droplets, proteinoid microspheres, and the genetic apparatus

Differences between typical coacervate droplets and typical proteinoid microspheres are examined. It is pointed out that coacervate droplets are produced from polymers obtained from contemporary organisms. The microspheres considered are aggregates of proteinoid formed from monomeric amino acids under geologically relevant conditions. Aspects regarding the primordial sequence are discussed along with the origin of the genetic apparatus and the genetic code.

Fox, S. W.↗
NASA NTRS1974

Thermodynamic perspectives and the origin of life

A qualitative appraisal of a recently enlarged laboratory model for macromolecular and cellular origins is given. The experiments were performed under geologically relevant conditions, i.e., with irreversible thermodynamics, emphasizing open systems and changes in phase. It was found that heating appropriate nonneutral alpha-amino acids with other alpha-amino acids yields partly branched, mainly linear, copolymeric peptides incorporating some of the alpha-amino acids that would of themselves decompose. The resultant copolyamino acids display a high degree of internal order, enzymelike activities, enzymelike characteristics, and a tendency to form a kind of cell having many of the properties of contemporary cells.

Fox, S. W.↗
NASA NTRS1973

The Apollo program and amino acids

Apollo lunar sample analyses designed to detect the presence of organic compounds are reviewed, and the results are discussed from the viewpoint of relevance to laboratory experiments on the synthesis of amino acids and to theoretical models of cosmochemical processes resulting in the formation of organic compounds. Glycine, alanine, glutamic acid, aspartic acid, serine, and threonine have been found repeatedly in the hydrolyzates of hot aqueous extracts of lunar dust. These compounds represent an early step in the sequence of events leading to the rise of living material and were probably deposited by the solar wind. The results of the Apollo program so far suggest that the pathway from cosmic organic matter to life as it evolved on earth could have been pursued on the moon to the stage of amino acid precursors and then may have been terminated for lack of sufficient water.

Fox, S. W.↗
NASA NTRS1973

Origin of the cell - Experiments and premises

Theories and component concepts of the origin of life, i.e., primordial life, have emerged from (1) constructionistic studies on model materials and systems, and (2) reductionistic studies of contemporary cells. The resultant views conflict in a number of aspects; many of the differences are analyzed in this article. Constructionistic experiments are appropriate to asking questions about origins since they are in the same direction as evolution itself. These experiments have revealed self-ordering properties and associated emergent functions, which were not predictable.

Fox, S. W.↗
NASA NTRS1973

The hydrolysis of polyimides

Thermal polymerization of aspartic acid produces a polysuccinimide (I), a chain of aspartoyl residues. An investigation was made of the alkaline hydrolysis of the imide rings of (I) which converts the polyimide to a polypeptide. The alkaline hydrolysis of polyimides can be expected to be kinetically complex due to increasing negative charge generated by carboxylate groups. For this reason, a diimide, phthaloyl-DL-aspartoyl-beta-alanine (IIA) was synthesized for a progressive study of the hydrolysis of polyimides. In addition, this diimide (IIA) can be related to thalidomide and might be expected to exhibit similar reactivity during hydrolysis of the phthalimide ring.

Hoagland, P. D.↗
NASA NTRS1973

Accumulated analyses of amino acid precursors in returned lunar samples

Six amino acids (glycine, alanine, aspartic acid, glutamic acid, serine, and threonine) obtained by hydrolysis of extracts have been quantitatively determined in ten collections of fines from five Apollo missions. Although the amounts found, 7-45 ng/g, are small, the lunar amino acid/carbon ratios are comparable to those of the carbonaceous chondrites, Murchison and Murray, as analyzed by the same procedures. Since both the ratios of amino acid to carbon, and the four or five most common types of proteinous amino acid found, are comparable for the two extraterrestrial sources despite different cosmophysical histories of the moon and meteorites, common cosmochemical processes are suggested.

Fox, S. W.↗
NASA NTRS1972

Amino acid precursors in lunar samples.

The use of hot water to extract lunar samples, followed by the hydrolysis of the aqueous extract, appears to be the method of choice for identification and quantitation of amino acid precursors in extraterrestrial sources. The net inferences from the analyses to date are (1) that amino acid precursors are verifiably present in lunar dust, and (2) that they are quite certainly not the consequence of contamination by terrestrial organisms, including man. It is suggested that prebiotic evolutionary pathways such as have been traversed on the earth were terminated on the moon for lack of sufficient water. Although some or all of the amino acid precursors may be indigenous, the low level observed suggests that they may also result from onfall of organic compounds from interstellar matter, comets, tails, solar wind, or meteorites.

Fox, S. W.↗
NASA NTRS1972

Evolution from amino acids - Lunar occurrence of their precursors.

Review of the present state of experimentally based concepts of organic evolution from amino acids. Earlier studies of the synthesis of amino acid precursors from meteoritic material, lunar dust, and terrestrial lava are briefly summarized, and laboratory experiments in which polymers of amino acids were obtained either by direct heating of dry amino acids or by heating aqueous solutions of mixtures of amino acids are described. In particular, a process is described by which alpha-amino acids were made to react to form linear chains of proteinoids. It is concluded that a proteinoid microsystem was a common ancestor of all life on earth.

Fox, S. W.↗
NASA NTRS1972

Selective condensation of aminoacyl adenylates by nucleoproteinoid microparticles.

Microparticles composed of each of four enzymically synthesized homopolynucleotides and the same lysine-rich proteinoid have been found to influence the condensation of the AMP-anhydrides of each of four amino acids. The conditions of preparation of the particles and other variables of the experiments control the types of reaction. When a period set of conditions was identified empirically, the incorporation favored the amino acids whose present-day codons are related to the homopolynucleotide in the particle.

Nakashima, T.↗