1. The missing organic molecules on Mars - Benner, Steven A.; Devine, Kevin G.; Matveeva, Lidia N.; Powell, David H.
GC-MS on the Viking 1976 Mars missions did not detect organic molecules on the Martian surface, even those expected from meteorite bombardment. This result suggested that the Martian regolith might hold a potent oxidant that converts all organic molecules to carbon dioxide rapidly relative to the rate at which they arrive. This conclusion is influencing the design of Mars missions. We reexamine this conclusion in light of what is known about the oxidation of organic compounds generally and the nature of organics likely to come to Mars via meteorite. We conclude that nonvolatile salts of benzenecarboxylic acids, and perhaps oxalic...

2. Disruption of matrix metalloproteinase 2 binding to integrin ?v?3 by an organic molecule inhibits angiogenesis and tumor growth in vivo - Silletti, Steve; Kessler, Torsten; Goldberg, Joel; Boger, Dale L.; Cheresh, David A.
Matrix metalloproteinase 2 (MMP2) can associate with integrin ?v?3 on the surface of endothelial cells, thereby promoting vascular invasion. Here, we describe an organic molecule (TSRI265) selected for its ability to bind to integrin ?v?3 and block ?v?3 interaction with MMP2. Although disrupting ?v?3/MMP2 complex formation, TSRI265 has no effect on ?v?3 binding to its extracellular matrix ligand vitronectin and does not influence MMP2 activation or catalytic activity directly. However, TSRI265 acts as a potent antiangiogenic agent and thereby blocks tumor growth in vivo. These findings suggest that activated MMP2 does not facilitate vascular invasion during angiogenesis unless it forms...

3. Differential adsorption of nucleic acid bases: Relevance to the origin of life - Sowerby, Stephen J.; Cohn, Corey A.; Heckl, Wolfgang M.; Holm, Nils G.
The adsorption of organic molecules onto the surfaces of inorganic solids has long been considered a process relevant to the origin of life. We have determined the equilibrium adsorption isotherms for the nucleic acid purine and pyrimidine bases dissolved in water on the surface of crystalline graphite. The markedly different adsorption behavior of the bases describes an elutropic series: guanine > adenine > hypoxanthine > thymine > cytosine > uracil. We propose that such differential properties were relevant to the prebiotic chemistry of the bases and may have influenced the composition of the primordial genetic architecture.

4. Species-specific polyamines from diatoms control silica morphology - Kröger, Nils; Deutzmann, Rainer; Bergsdorf, Christian; Sumper, Manfred
Biomineralizing organisms use organic molecules to generate species-specific mineral patterns. Here, we describe the chemical structure of long-chain polyamines (up to 20 repeated units), which represent the main organic constituent of diatom biosilica. These substances are the longest polyamine chains found in nature and induce rapid silica precipitation from a silicic acid solution. Each diatom is equipped with a species-specific set of polyamines and silica-precipitating proteins, which are termed silaffins. Different morphologies of precipitating silica can be generated by polyamines of different chain lengths as well as by a synergistic action of long-chain polyamines and silaffins.

5. Oceanic protection of prebiotic organic compounds from UV radiation - Cleaves, H. James; Miller, Stanley L.
It is frequently stated that UV light would cause massive destruction of prebiotic organic compounds because of the absence of an ozone layer. The elevated UV flux of the early sun compounds this problem. This applies to organic compounds of both terrestrial and extraterrestrial origin. Attempts to deal with this problem generally involve atmospheric absorbers. We show here that prebiotic organic polymers as well as several inorganic compounds are sufficient to protect oceanic organic molecules from UV degradation. This aqueous protection is in addition to any atmospheric UV absorbers and should be a ubiquitous planetary phenomenon serving to increase the...

6. Desarrollo de un modelo de simulación para evaluar el horizonte de contaminación con cobre de bosques esclerófilos - Ruz Frías, Ana María
En Chile Central, las emisiones de las fundiciones de cobre han sido fuente importante de contaminación en las áreas donde se instalaron. Uno de los contaminantes ha sido el cobre, el cual forma parte del material particulado que se deposita y se incorpora en los ciclos de los ecosistemas. La Refinería y Fundición de Ventanas comenzó a operar hace más de tres décadas, consecuencia de lo cual los ecosistemas han sido impactados por la depositación de cobre, entre otros metales pesados, y por lluvia ácida. Los metales pesados tienen la particularidad de no poder ser degradados, a diferencia de las...

7. The origin of intermediary metabolism - Morowitz, Harold J.; Kostelnik, Jennifer D.; Yang, Jeremy; Cody, George D.
The core of intermediary metabolism in autotrophs is the citric acid cycle. In a certain group of chemoautotrophs, the reductive citric acid cycle is an engine of synthesis, taking in CO2 and synthesizing the molecules of the cycle. We have examined the chemistry of a model system of C, H, and O that starts with carbon dioxide and reductants and uses redox couples as the energy source. To inquire into the reaction networks that might emerge, we start with the largest available database of organic molecules, Beilstein on-line, and prune by a set of physical and chemical constraints applicable to...

8. A role for coenzyme M (2-mercaptoethanesulfonic acid) in a bacterial pathway of aliphatic epoxide carboxylation - Allen, Jeffrey R.; Clark, Daniel D.; Krum, Jonathan G.; Ensign, Scott A.
The bacterial metabolism of short-chain aliphatic alkenes occurs via oxidation to epoxyalkanes followed by carboxylation to ?-ketoacids. Epoxyalkane carboxylation requires four enzymes (components I–IV), NADPH, NAD+, and a previously unidentified nucleophilic thiol. In the present work, coenzyme M (2-mercaptoethanesulfonic acid), a compound previously found only in the methanogenic Archaea where it serves as a methyl group carrier and activator, has been identified as the thiol and central cofactor of aliphatic epoxide carboxylation in the Gram-negative bacterium Xanthobacter strain Py2. Component I catalyzed the addition of coenzyme M to epoxypropane to form a ?-hydroxythioether, 2-(2-hydroxypropylthio)ethanesulfonate. Components III and IV catalyzed the...

9. Compositional genomes: Prebiotic information transfer in mutually catalytic noncovalent assemblies - Segré, Daniel; Ben-Eli, Dafna; Lancet, Doron
Mutually catalytic sets of simple organic molecules have been suggested to be capable of self-replication and rudimentary chemical evolution. Previous models for the behavior of such sets have analyzed the global properties of short biopolymer ensembles by using graph theory and a mean field approach. In parallel, experimental studies with the autocatalytic formation of amphiphilic assemblies (e.g., lipid vesicles or micelles) demonstrated self-replication properties resembling those of living cells. Combining these approaches, we analyze here the kinetic behavior of small heterogeneous assemblies of spontaneously aggregating molecules, of the type that could form readily under prebiotic conditions. A statistical formalism for...

10. Biochemical evolution. I. Polymerization on internal, organophilic silica surfaces of dealuminated zeolites and feldspars - Smith, Joseph V.
Catalysis at mineral surfaces might generate replicating biopolymers from simple chemicals supplied by meteorites, volcanic gases, and photochemical gas reactions. Many ideas are implausible in detail because the proposed mineral surfaces strongly prefer water and other ionic species to organic ones. The molecular sieve silicalite (Union Carbide; = Al-free Mobil ZSM-5 zeolite) has a three-dimensional, 10-ring channel system whose electrically neutral Si-O surface strongly adsorbs organic species over water. Three -O-Si tetrahedral bonds lie in the surface, and the fourth Si-O points inwards. In contrast, the outward Si-OH of simple quartz and feldspar crystals generates their ionic organophobicity. The ZSM-5-type...

11. Quorum sensing in Escherichia coli and Salmonella typhimurium - Surette, Michael G.; Bassler, Bonnie L.
Escherichia coli and Salmonella typhimurium strains grown in Luria–Bertani medium containing glucose secrete a small soluble heat labile organic molecule that is involved in intercellular communication. The factor is not produced when the strains are grown in Luria–Bertani medium in the absence of glucose. Maximal secretion of the substance occurs in midexponential phase, and the extracellular activity is degraded as the glucose is depleted from the medium or by the onset of stationary phase. Destruction of the signaling molecule in stationary phase indicates that, in contrast to other quorum-sensing systems, quorum sensing in E. coli and S. typhimurium is critical...

12. Calcimimetics with potent and selective activity on the parathyroid calcium receptor - Nemeth, Edward F.; Steffey, Michael E.; Hammerland, Lance G.; Hung, Benjamin C. P.; Van Wagenen, Bradford C.; DelMar, Eric G.; Balandrin, Manuel F.
Parathyroid hormone (PTH) secretion is regulated by a cell surface Ca2+ receptor that detects small changes in the level of plasma Ca2+. Because this G protein-coupled receptor conceivably provides a distinct molecular target for drugs useful in treating bone and mineral-related disorders, we sought to design small organic molecules that act on the Ca2+ receptor. We discovered that certain phenylalkylamine compounds, typified by NPS R-568 and its deschloro derivative NPS R-467, increased the concentration of cytoplasmic Ca2+ ([Ca2+]i) in bovine parathyroid cells and inhibited PTH secretion at nanomolar concentrations. These effects were stereoselective and the R enantiomers were 10- to...

13. Etude par modélisation moléculaire de dimères de cyclodextrines et de leurs complexes dinclusion - Bonnet, Pascal
Las ciclodextrinas (CDS) son oligómeros cíclicos de varias unidades de a-D-glucopiranosa. Las más frecuentes se denominan a-, b- y g-CD dependiendo de cuantas unidades de glucosa (6, 7 o 8 respectivamente forman la pared del macrociclo toroidal. Esta poca común forma define dos zonas especiales bien definidas: una pared externa hidrófila y una cavidad interna hidrófoba que puede incluir substratos orgánicos en medio aucoso. Los complejos de inclusión son asociaciones moleculares en las que un componente (el host) incluye a una molécula (el guest) generalmente con una estequiometría 1:1. Sin embargo, si el guest es más grande, la estequiometría puede...

14. Separació de compostos aniònics i neutres amb membranes de transport facilitat. Millores en la selectivitat - Calzado Cuevas, Joan Antoni
Les membranes han estat àmpliament emprades en molts processos, p.e. les membranes sintètiques dultrafiltració, macrofiltració o les de diàlisi. Al mateix temps, les membranes líquides (LM) han rebut un gran desenvolupament per crear-ne noves, de més selectives i estables per millorar el seu funcionament en els processos de separació en que intervenen reaccions químiques específiques. En aquest sentit, nhi moltes aplicacions per a la separació de metalls i alguna per a espècies no metàl·liques. Lús de ML comporta majors fluxos que a les membranes sòlides de filtració i la inclusió de transportadors també produeix una millor selectivitat. La interacció entre...