Complejación de metales por sustancias húmicas acuáticas como proceso natural, tomando como caso de estudio el Lago de Xochimilco

AbstractThe aim of this study was to compare the quality of clutches and reproduction results of two groups of Roman snails (Helix pomatia) from the same local population, laying eggs simultaneously in semi-natural farm conditions and in a natural habitat. The study material were Roman snails aged 2 or more years which had entered the third phenological season of their life and thus the first season of sexual maturity. Observations were conducted at an earthen enclosure in a greenhouse belonging to the experimental farm for edible snails at the National Research Institute of Animal Reproduction in Balice near Kraków (Poland) as well as at a site where a local population naturally occurs in the uncultivated park surrounding the Radziwiłł Palace. In the June-July season, differences among such parameters as weight of clutch, number of eggs in clutch, mean egg weight, and hatchling percentage when compared to the total number of eggs in the clutch were compared. It was determined that clutches of eggs from the natural population laid in the greenhouse were of lesser weight (P<0.01), contained fewer eggs (P<0.05), and the mean weight of individual eggs was less (P<0.05) than in clutches laid simultaneously in a natural habitat. Both in the greenhouse and the natural habitat, in the first phase of laying eggs (June) the weight of the clutch and number of eggs its contained were greater than in the second phase (July). However, only for snails laying eggs in the greenhouse were these differences statistically significant (P<0.05) and highly significant (P<0.01), respectively. Statistically significant differences were not observed in hatchling percentage between eggs laid in the greenhouse and the natural habitat. The lower number of eggs laid in the farmed conditions of the greenhouse was successfully compensated for by the absence of mass destruction by rodents which occurred in the natural habitat.

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Lanthanoid Complexes Supported by Retro-Claisen Condensation Products of β-Triketonates

10.26434/chemrxiv.6448253.v3 ◽

2018 ◽

Author(s):

Laura Abad Galán ◽

Alexandre N. Sobolev ◽

Eli Zysman-Colman ◽

Mark Ogden ◽

Massimiliano Massi

Keyword(s):

Chelating Ligands ◽

X Ray Diffraction ◽

Reaction Conditions ◽

Claisen Condensation ◽

X Ray ◽

Condensation Products ◽

Complexation Reactions ◽

The Impact ◽

Low Solubility

β-Triketonates have been recently used as chelating ligands for lanthanoid ions, presenting unique structures varying from polynuclear assemblies to polymers. In an effort to overcome low solubility of the complexes of tribenzoylmethane, four β-triketones with higher lipophilicity were synthesised. Complexation reactions were performed for each of these molecules using different alkaline bases in alcoholic media. X-ray diffraction studies suggested that the ligands were undergoing decomposition under the reaction conditions. This is proposed to be caused by in situretro-Claisen condensation reactions, consistent with two examples that have been reported previously. The lability of the lanthanoid cations in the presence of a varying set of potential ligands gave rise to structures where one, two, or three of the molecules involved in the retro-Claisen condensationreaction were linked to the lanthanoid centres. These results, along with measurements of ligand decomposition in the presence of base alone, suggest that using solvents of lower polarity will mimimise the impact of the retro-Claisen condensation in these complexes.

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Site-Selective C-C Modification of Proteins at Neutral pH Using Organocatalyst-Mediated Cross Aldol Ligations

10.26434/chemrxiv.5872461.v1 ◽

2018 ◽

Author(s):

Martin A. Fascione ◽

Richard J. Spears ◽

Robin L. Brabham ◽

Darshita Budhadev ◽

Tessa Keenan ◽

...

Keyword(s):

Small Molecules ◽

Stable Carbon ◽

Biological Mechanisms ◽

Large Excess ◽

Reaction Conditions ◽

Chemical Methods ◽

Neutral Ph ◽

Chemical Modification Of Proteins ◽

A Site ◽

Site Selective

The bioconjugation of proteins with small molecules has proved an invaluable strategy for probing and perturbing dynamic biological mechanisms. The general use of chemical methods for the functionalisation of proteins remains limited however by the frequent requirement for complicated reaction partners to be present in large excess, and harsh reaction conditions which are incompatible with many protein scaffolds. Herein we describe a site-selective organocatalyst-mediated protein aldol ligation (OPAL) that affords stable carbon-carbon linked bioconjugates at neutral pH under biocompatible conditions. OPAL enables rapid chemical modification of proteins within an hour using simple aldehyde probes in minimal excess, and is utilised here in the selective affinity tagging of proteins in cell lysate. Furthermore we demonstrate that the b-hydroxy aldehyde product of the OPAL can be functionalised a second time at neutral pH in a subsequent organocatalyst-mediated oxime ligation. This tandem strategy is showcased in the ‘chemical mimicry’ of a previously inaccessible natural dual post-translationally modified protein integral to the pathogenesis of the neglected tropical disease Leishmaniasis.

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Temperature tunability in Sr1−xCaxFeO3−δ for reversible oxygen storage: a computational and experimental study

Journal of Materials Chemistry A ◽

10.1039/c9ta09307a ◽

2020 ◽

Vol 8 (5) ◽

pp. 2602-2612 ◽

Cited By ~ 3

Author(s):

Eric J. Popczun ◽

De Nyago Tafen ◽

Sittichai Natesakhawat ◽

Chris M. Marin ◽

Thuy-Duong Nguyen-Phan ◽

...

Keyword(s):

Experimental Study ◽

Oxygen Storage ◽

Oxygen Carriers ◽

Reaction Conditions ◽

Specific Reaction ◽

A Site

Sr1−xCaxFeO3−δ oxygen carriers can be designed for specific reaction conditions through selective Ca2+ inclusion at the A-site.

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Silver(I) and Copper(I) Complexation with Decachloro-Closo-Decaborate Anion

Crystals ◽

10.3390/cryst10050389 ◽

2020 ◽

Vol 10 (5) ◽

pp. 389

Author(s):

Varvara V. Avdeeva ◽

Grigoriy A. Buzanov ◽

Elena A. Malinina ◽

Nikolay T. Kuznetsov ◽

Anna V. Vologzhanina

Keyword(s):

Complexation Reaction ◽

Similar Reaction ◽

Cluster Anions ◽

X Ray Diffraction ◽

Reaction Conditions ◽

Boron Cluster ◽

Composition And Structure ◽

Coinage Metals ◽

Closo Decaborate Anion ◽

Complexation Reactions

A series of complexation reactions of silver(I) and copper(I) in the presence of a polyhedral weakly coordinating [B10Cl10]2− anion has been carried out. The effect of the solvent and the presence of Ph3P on the composition and structure of the reaction product were studied. Eight novel complexes were obtained and characterized by 11B Nuclear magnetic resonance, Infra-Red, and Raman spectroscopies as well as powder and single-crystal X-ray diffraction techniques. The [B10Cl10]2− anion demonstrated weaker coordinating ability towards coinage metals than [B10H10]2− at similar reaction conditions. The [B10Cl10]2− anion remains unreacted in the copper(I) complexation reaction, while in the absence of competing ligands, we obtained the first complexes containing decachloro-closo-decaborate anion directly coordinated by the metal atom. The bonding between metal atoms and the boron cluster anions was studied using the atomic Hirshfeld surfaces. Besides edge and face coordination of the polyhedral anion, this method allowed us to reveal the Ag–Ag bond in crystal of {Ag2(DMF)2[B10Cl10]}n, the presence of which was additionally supported by the Raman spectroscopy data.

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Concerning the location of the GTP hydrolysis site on microtubules

Canadian Journal of Biochemistry and Cell Biology ◽

10.1139/o85-061 ◽

1985 ◽

Vol 63 (6) ◽

pp. 422-429 ◽

Cited By ~ 11

Author(s):

Michael Caplow ◽

John Shanks ◽

Bruna Pegoraro Brylawski

Keyword(s):

Steady State ◽

Reaction Scheme ◽

Product Inhibition ◽

Microtubule Assembly ◽

Assembly Process ◽

Progressive Decrease ◽

Reaction Conditions ◽

Gtp Hydrolysis ◽

Tubulin Subunit ◽

A Site

The kinetics for GTP hydrolysis associated with microtubule assembly with microtubular protein has been analyzed under reaction conditions where tubulin–GDP does not readily assemble into microtubules. The GTPase rate is only slightly faster during the time when net microtubule assembly occurs, as compared with steady state. The slightly slower steady-state GTPase rate apparently results from GDP product inhibition, since the progressive decrease in the rate can be quantitatively accounted for using the previously determined GTP dissociation constant and the Ki value for GDP. Since the GTPase rate is not a function of the rate for net microtubule assembly, it is concluded that GTP hydrolysis is not required for tubulin subunit incorporation into microtubules. The constancy of the rate indicates that the GTPase reaction occurs at a site, the concentration of which does not change during the assembly process. This result is consistent with a reaction scheme in which GTP hydrolysis occurs primarily at microtubule ends. We propose that hydrolysis occurs at microtubule ends, at the interface between a long core of tubulin–GDP subunits and a short cap of tubulin–GTP subunits.

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A general framework to model the fate of trace elements in anaerobic digestion environments

Scientific Reports ◽

10.1038/s41598-021-85403-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Bikash Chandra Maharaj ◽

Maria Rosaria Mattei ◽

Luigi Frunzo ◽

Eric D. van Hullebusch ◽

Giovanni Esposito

Keyword(s):

Trace Elements ◽

Anaerobic Digestion ◽

Analytical Techniques ◽

Modeling Framework ◽

Organic Matter Concentration ◽

Modelling Framework ◽

Site Density ◽

Dosing Strategy ◽

Complexation Reactions ◽

Adsorption Desorption

AbstractDue to the multiplicity of biogeochemical processes taking place in anaerobic digestion (AD) systems and limitations of the available analytical techniques, assessing the bioavailability of trace elements (TEs) is challenging. Determination of TE speciation can be facilitated by developing a mathematical model able to consider the physicochemical processes affecting TEs dynamics. A modeling framework based on anaerobic digestion model no 1 (ADM1) has been proposed to predict the biogeochemical fate TEs in AD environments. In particular, the model considers the TE adsorption–desorption reactions with biomass, inerts and mineral precipitates, as well as TE precipitation/dissolution, complexation reactions and biodegradation processes. The developed model was integrated numerically, and numerical simulations have been run to investigate the model behavior. The simulation scenarios predicted the effect of (i) organic matter concentration, (ii) initial TEs concentrations, (iii) initial Ca–Mg concentrations, (iv) initial EDTA concentration, and (v) change in TE binding site density, on cumulative methane production and TE speciation. Finally, experimental data from a real case continuous AD system have been compared to the model predictions. The results prove that this modelling framework can be applied to various AD operations and may also serve as a basis to develop a model-predictive TE dosing strategy.

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A Review on the Catalytic Decomposition of NO by Perovskite-Type Oxides

Catalysts ◽

10.3390/catal11050622 ◽

2021 ◽

Vol 11 (5) ◽

pp. 622

Author(s):

Qiuwan Shen ◽

Shuangshuang Dong ◽

Shian Li ◽

Guogang Yang ◽

Xinxiang Pan

Keyword(s):

Mixed Oxides ◽

Low Cost ◽

Influence Factors ◽

Catalytic Decomposition ◽

Catalytic Performance ◽

No Decomposition ◽

Reaction Conditions ◽

A Site ◽

Perovskite Type ◽

Decomposition Of No

Direct catalytic decomposition of NO has the advantages of being a simple process, producing no secondary pollution, and being good for the economy, which has attracted extensive research in recent years. Perovskite-type mixed oxides, with an ABO3 or A2BO4 structure, are promising materials as catalysts for NO decomposition due to their low cost, high thermal stability, and, of course, their good catalytic performances. In this review, the influence factors, such as A-site substitution, B-site substitution and reaction conditions on the catalytic performance of catalysts have been expounded. The reaction mechanisms of direct NO decomposition are also discussed. Finally, major conclusions are drawn and some research challenges are highlighted.

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COMBUSTION AND LEACHING BEHAVIOR OF TRACE ELEMENTS IN LIGNITE AND COMBUSTION BY-PRODUCTS FROM THE MUĞLA BASIN, SW TURKEY

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.11421 ◽

2017 ◽

Vol 43 (5) ◽

pp. 2218 ◽

Cited By ~ 1

Author(s):

M. Fotopoulou ◽

G. Siavalas ◽

H. İnaner ◽

K. Katsanou ◽

N. Lambrakis ◽

...

Keyword(s):

Trace Elements ◽

Environmental Impacts ◽

Bottom Ash ◽

Lignite Fly Ash ◽

Sw Turkey ◽

Hazardous Trace Elements ◽

Mode Of Occurrence ◽

Leaching Behaviour ◽

Ph Conditions ◽

Ash Disposal

The Muğla Basin is one of the most well-documented coal basins of Anatolia, SW Turkey. Previous studies mainly focused on coal geology, as well as on the environmental impacts from trace elements emitted into the atmosphere during coal combustion. However, the environmental impacts from coal utilization also include groundwater contamination from hazardous trace elements leached from exposed lignite stockpiles or ash disposal dumps. In the present study a comparative assessment of the combustion, as well as the leaching behaviour of trace elements from sixteen lignite, fly ash and bottom ash samples under various pH conditions is attempted. The samples were picked up from three regions in the Muğla Basin, namely, these of Yeniköy, Kemerköy and Yatağan. Proximate and ultimate analyses were performed on all samples. Quantitative mineralogical analysis was carried out using a Rietveld-based full pattern fitting technique. The elements Ag, As, B, Ba, Be, Co, Cr, Cu, Fe, Ga, Hf, Li, Mn, Mo, Ni, Pb, Sr, U, V and Zn were grouped according to their volatility during combustion and their leachability in the various types of samples. The pH of the leaching agent little affected the leaching trends of most elements and the mode of occurrence proved to be the major factor controlling primarily combustion and to a lesser extent leaching. The elements were classified into 7 classes with increasing environmental significance with Mo, Sr and V being the most potentially hazardous trace elements in the Muğla region.

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Lanthanoid Complexes Supported by Retro-Claisen Condensation Products of β-Triketonates

10.26434/chemrxiv.6448253 ◽

2018 ◽

Author(s):

Laura Abad Galán ◽

Alexandre N. Sobolev ◽

Eli Zysman-Colman ◽

Mark Ogden ◽

Massimiliano Massi

Keyword(s):

Chelating Ligands ◽

X Ray Diffraction ◽

Reaction Conditions ◽

Claisen Condensation ◽

X Ray ◽

Condensation Products ◽

Complexation Reactions ◽

The Impact ◽

Low Solubility

β-Triketonates have been recently used as chelating ligands for lanthanoid ions, presenting unique structures varying from polynuclear assemblies to polymers. In an effort to overcome low solubility of the complexes of tribenzoylmethane, four β-triketones with higher lipophilicity were synthesised. Complexation reactions were performed for each of these molecules using different alkaline bases in alcoholic media. X-ray diffraction studies suggested that the ligands were undergoing decomposition under the reaction conditions. This is proposed to be caused by in situretro-Claisen condensation reactions, consistent with two examples that have been reported previously. The lability of the lanthanoid cations in the presence of a varying set of potential ligands gave rise to structures where one, two, or three of the molecules involved in the retro-Claisen condensationreaction were linked to the lanthanoid centres. These results, along with measurements of ligand decomposition in the presence of base alone, suggest that using solvents of lower polarity will mimimise the impact of the retro-Claisen condensation in these complexes.

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