Hydrothermal experiments on the thermal stability of amino substances in sediments

Aspartic acid, threonine, serine and other thermally unstable amino acids have been found in fine-grained elastic sediments of advanced geologic age. The presence of these compounds in ancient sediments conflicts with experimental data determined for their simple thermal decomposition.

Recent and Late Miocene sediments and their humic acid extracts, known to contain essentially complete suites of amino acids, were heated with H₂O in a bomb at temperatures up to 500°C in order to compare the thermal decomposition characteristics of the sedimentary amino compounds.

Most of the amino acids found in protein hydrolyzates are obtained from the Miocene rock in amounts 10 to 100 times less than from the Recent sediment. The two unheated humic acids are rather similar despite their great age difference. The Miocene rock appears uncontaminated by Recent carbon.

Yields of amino acids generally decline in the heated Recent sediment. Some amino compounds apparently increase with heating time in the Miocene rock.

Relative thermal stabilities of the amino acids in sediments are generally similar to those determined using pure aqueous solutions. The relative thermal stabilities of glutamic acid, glycine, and phenylalanine vary in the Recent sediment but are uniform in the Miocene rock.

Amino acids may occur in both proteins and humic complexes in the Recent sediment, while they are probably only present in stabilized organic substances in the Miocene rock. Thermal decomposition of protein amino acids may be affected by surface catalysis in the Recent sediment. The apparent activation energy for the decomposition of alanine in this sediment is 8400 calories per mole. Yields of amino compounds from the heated sediments are not affected by thermal decomposition only.

Amino acids in sediments may only be useful for geothermometry in a very general way.

A better picture of the amino acid content of older sedimentary rocks may be obtained if these sediments are heated in a bomb with H₂O at temperatures around 150°C prior to HCl hydrolysis.

Leucine-isoleucine ratios may prove to be useful as indicators of amino acid sources or for evaluating the fractionation of these substances during diagenesis. Leucine-isoleucine ratios of the Recent and Miocene sediments and humic acids are identical. The humic acids may have a continental source.

The carbon-nitrogen and carbon-hydrogen ratios of sediments and humic acids increase with heating time and temperature. Ratios comparable to those in some kerogens are found in the severely heated Miocene sediment and humic acid.

I. Configurational stability and redistribution equilibria in organomagnesium compounds. II. Redistribution equilibria in organocadmium compounds

I. CONFIGURATIONAL STABILITY AND REDISTRIBUTION EQUILIBRIA IN ORGANOMAGNESIUM COMPOUNDS</p>

The dependence of the rate of inversion of a dialkylmagnesium compound on the solvent has been studied.

Examination of the temperature dependence of the nuclear magnetic resonance spectrum of 1-phenyl-2-propylmagnesium bromide in diethyl ether solution indicates that inversion of configuration at the methylene group of this Grignard reagent occurs with an approximate rate of 2 sec^-1 at room temperature. This is the first example of a rapid inversion rate in a secondary Grignard reagent.

The rates of exchange of alkyl groups between dineopentylmagnesium and di-s-butylmagnesium, bis-(2-methylbutyl)-magnesium and bis-(4, 4-dimethyl-2-pentyl)-magnesium respectively in diethyl ether solution were found to be fast on the nmr time scale. However, the alkyl group exchange rate was found to be slow in a diethyl ether solution of dineopentylmagnesium and bis-(2-methylbutyl)-magnesium containing N, N, N', N'-tetramethylethylenediamine. The unsymmetrical species neopentyl-2-methylbutyl-magnesium was observed at room temperature in the nmr spectrum of the solution containing the diamine.

II. REDISTRIBUTION EQUILIBRIA IN ORGANOCADMIUM COMPOUNDS</p>

The exchange of methyl groups in dimethylcadmium has been studied by nuclear magnetic resonance spectroscopy. Activation parameters for the methyl group exchange have been measured for a neat sample and for a solution in tetrahydrofuran. The exchange is faster in the basic solvent tetrahydrofuran relative to the neat sample and in tetrahydrofuran solution is retarded by the solvating agent N, N, N’, N’-tetramethylethylenediamine and greatly increased by cadmium bromide. The addition of methanol to a solution of dimethylcadmium in tetrahydrofuran appears to have very little effect on the rate of exchange. The exchange was found to proceed with retention of configuration. The rate-limiting step for the exchange of methyl groups in a basic solvent appears to be the dissociation of coordinating solvent from dimethylcadmium.

The equilibrium between methylcadmium bromide, dimethylcadmium and cadmium bromide in tetrahydrofuran solution has also been studied. At room temperature the interconversion of the species is very fast on the nmr time scale but at -100° distinct absorptions for methylcadmium bromide and imethylcadmium are observed.

The species ethylmethylcadmium has been observed in the nmr spectrum.

The rate of exchange of vinyl groups in a solution of divinylcadmium in tetrahydrofuran has been found to be fast on the nmr time scale.

Prediction of Multi-Target Networks of Neuroprotective Compounds with Entropy Indices and Synthesis, Assay, and Theoretical Study of New Asymmetric 1,2-Rasagiline Carbamates

In a multi-target complex network, the links (L-ij) represent the interactions between the drug (d(i)) and the target (t(j)), characterized by different experimental measures (K-i, K-m, IC50, etc.) obtained in pharmacological assays under diverse boundary conditions (c(j)). In this work, we handle Shannon entropy measures for developing a model encompassing a multi-target network of neuroprotective/neurotoxic compounds reported in the CHEMBL database. The model predicts correctly >8300 experimental outcomes with Accuracy, Specificity, and Sensitivity above 80%-90% on training and external validation series. Indeed, the model can calculate different outcomes for >30 experimental measures in >400 different experimental protocolsin relation with >150 molecular and cellular targets on 11 different organisms (including human). Hereafter, we reported by the first time the synthesis, characterization, and experimental assays of a new series of chiral 1,2-rasagiline carbamate derivatives not reported in previous works. The experimental tests included: (1) assay in absence of neurotoxic agents; (2) in the presence of glutamate; and (3) in the presence of H2O2. Lastly, we used the new Assessing Links with Moving Averages (ALMA)-entropy model to predict possible outcomes for the new compounds in a high number of pharmacological tests not carried out experimentally.

Mugilid Fish Are Sentinels of Exposure to Endocrine Disrupting Compounds in Coastal and Estuarine Environments

Effects on fish reproduction can result from a variety of toxicity mechanisms first operating at the molecular level. Notably, the presence in the environment of some compounds termed endocrine disrupting chemicals (EDCs) can cause adverse effects on reproduction by interfering with the endocrine system. In some cases, exposure to EDCs leads to the animal feminization and male fish may develop oocytes in testis (intersex condition). Mugilid fish are well suited sentinel organisms to study the effects of reproductive EDCs in the monitoring of estuarine/marine environments. Up-regulation of aromatases and vitellogenins in males and juveniles and the presence of intersex individuals have been described in a wide array of mullet species worldwide. There is a need to develop new molecular markers to identify early feminization responses and intersex condition in fish populations, studying mechanisms that regulate gonad differentiation under exposure to xenoestrogens. Interestingly, an electrophoresis of gonad RNA, shows a strong expression of 5S rRNA in oocytes, indicating the potential of 5S rRNA and its regulating proteins to become useful molecular makers of oocyte presence in testis. Therefore, the use of these oocyte markers to sex and identify intersex mullets could constitute powerful molecular biomarkers to assess xenoestrogenicity in field conditions.

Revisión bibliográfica del tratamiento de biogás por biofiltración.

[ES]En el siguiente trabajo se ha realizado una revisión bibliográfica en la que se muestran los resultados obtenidos al llevar a cabo la purificación del biogás y/o la eliminación del metano, en los casos en los que su valorización no sea posible, mediante métodos biológicos (biofiltración). Se recogen asimismo las diversas fuentes desde las que se genera el biogás (generación incontrolada o producción controlada) junto con las concentraciones típicas de todos los compuestos que pueden formar su composición. En la purificación del biogás se ha estudiado la eliminación de compuestos perjudiciales para el aprovechamiento energético del biogás, como son el sulfuro de hidrógeno (H2S), los mercaptanos y los siloxanos. Para el estudio de los compuestos a eliminar se ha diferenciado entre distintas configuraciones de biorreactores (biofiltros, biofiltros percoladores y biolavadores) y para cada una de ellas se han recogido datos representativos como la temperatura óptima de operación, las diferencias entre operar a pH ácido o básico (teniendo en cuenta que el pH natural de operación es ácido pero que en estas condiciones la solubilidad del H2S es menor y el relleno se deteriora con mayor rapidez). También se ha analizado la influencia de la cantidad de oxígeno necesario para garantizar la degradación total de los contaminantes y evitar la acumulación de depósitos de azufre, llegando incluso a necesitarse proporciones de O2/H2S de 49.2 para la oxidación completa del H2S. Se ha estudiado también la cantidad necesaria de nitrógeno (nutriente) en los procesos llevados a cabo en condiciones anaerobias (cercana a 200 mgN-NO3 -/L), así como el efecto que tienen los compuestos producidos en la oxidación parcial (azufre elemental (S0), metanol, formaldehido, etc.) en el funcionamiento del sistema.

Trends in nitrate-nitrogen, nitrite-nitrogen and phosphorus concentration in Ebonyi river, Nigeria

A baseline study of the limnological integrity of Ebonyi River, a tropical lotic system in south-eastern Nigeria was conducted between September 2006 and February 2008 to assess its potential in enhancing fisheries production for the benefit of the rural poor, who depend on the resources of the river for survival. The parameters measured were nitrate-nitrogen, nitrite-nitrogen and phosphate-phosphorus. Results show that nitrate varied between 40.43mg/L in September 2006 and 1.73mg/L in December 2007, Showing significant difference (P<0.01) among months. The values recorded for nitrites varied between 0.2mg/L in September 2006 and 0.4mg/L in February 2008, showing significant (P<0.01) variation among months. Values recorded for phosphorus was highest (0.05mg/L) in the month of October 2006 while the least mean value (0.32mg/L) was recorded in the month of May 2007 and showed significant (p<0.01) variation in monthly means. It was concluded that the values of the measured parameters falls within tolerable range for enhanced fisheries development in the area. KEYWORDS: Limnology, Tropical, River, Monthly, Mean, Variation

Synthesis and stereochemical assignments of diastereomeric Ni(II) complexes of glycine Schiff base with (R)-2-(N-{2-[N-alkyl-N-(1-phenylethyl)-amino]acetyl}amino) benzophenone; a case of configurationally stable stereogenic nitrogen

A family of chiral ligands derived from alpha-phenylethylamine and 2-aminobenzophenone were prepared by alkylation of the nitrogen atom. Upon reaction with glycine and a Ni(II) salt, these ligands were transformed into diastereomeric complexes, as a result of the configurational stability of the stereogenic nitrogen atom. Different diastereomeric ratios were observed depending on the substituent R introduced in the starting ligand, and stereochemical assignments were based on X-ray analysis, along with NMR studies and optical rotation measurements.