Presence Of Organic Molecules Research Articles

Reactivity of hydrogen sulfide toward organic compounds with sulfur-sulfur bonds

The presence of organic molecules containing sulfur-sulfur bonds was documented in the water columns and sediments of the natural aquatic systems as well as in fossil fuels. These compounds range from small molecules of volatile organic compounds to polysulfide cross-linked macromolecules in the sediments. While processes leading to formation of these compounds were intensively studied during the last decades, kinetics and mechanisms of reactions which lead to their decomposition are poorly understood. In this work, the kinetics and products of the reactions of dimethyl disulfide, dimethyl trisulfide, and cyclic polysulfide lenthionine (1,2,3,5,6-pentathiepane) with hydrogen sulfide at the environmental pH and temperature ranges were studied. It was shown that at pH ≥ 5, the reaction of bisulfide anion (HS–) rather than that of hydrogen sulfide controls the overall reaction rates. The activation energy and the order of the reaction with respect to bisulfide anion is dimethyl disulfide– < dimethyl trisulfide < lenthionine, while the order of the reaction with respect to organosulfur compounds is lenthionine < dimethyl trisulfide < dimethyl disulfide. The obtained results suggest that bisulfide anion is responsible for fast decomposition of organosulfur compounds in aphotic natural aquatic systems. This observation leads to the conclusion that sulfurization of sedimentary organic matter during the early diagenesis is not an unidirectional but a dynamic process, and concentrations of organic compounds with sulfur-sulfur bonds are controlled by the polysulfide to sulfide sulfur concentrations ratio in the sedimentary pore waters. In addition, the cyclic polysulfides were shown to be more stable than their linear analogs that results in preferential preservation of these compounds during the maturation process.

Graphitic Carbon Nitride Meets Molecular Oxygen: New Sustainable Photocatalytic Ways for the Oxidation of Organic Molecules

In recent years, organic chemists have taken a resolute step toward green photocatalytic synthesis. In this regard, the oxidation of organic compounds with molecular oxygen is one of the most important classes of transformations, as it increases molecular complexity while avoiding the use of toxic and harmful oxidants. To this aim, the development of new and efficient photocatalysts capable of driving valuable oxidative reactions in a sustainable manner is highly desirable. These novel photocatalytic systems need to be metal-free, easy-to-prepare, and potentially recyclable. Carbon nitride (CN) fulfils all these requirements because of its outstanding physicochemical properties, thus emerging as a promising heterogeneous photocatalytic platform. The growing popularity of this material is also substantiated by its fast and facile preparation from readily available and inexpensive molecular precursors. This Review aims at highlighting the recent advances in synthesis of carbon nitride-based materials and their applications in organic photocatalysis for the oxidation of organic molecules in presence of molecular oxygen. Lastly, forward-looking opportunities within this intriguing research field are mentioned.

Comparison of clinical efficacy of three different dentin matrix biomaterials obtained from different devices

ABSTRACT Aim The aim of the present study was to propose the clinical efficacy of the different dentin matrix obtained from three devices (BonMaker, Tooth Transformer, and Smart Dentin Grinder) and to show their morphological, physical, and biochemical characteristics using scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, and Raman spectroscopy. Research design and methods The study included 70 patients who underwent bone augmentation using the BonMaker, Tooth Transformer, and Smart Dentin Grinder devices. In addition, 84 implants were placed. Furthermore, four samples, one for each device and one non-demineralized control, were analyzed with scanning electron microscopy (SEM), energy-dispersive X-ray analysis, and Raman spectroscopy. Results In all patients, augmentation of bone defects with ground dentin matrix was successful, and implants showed correct osseointegration. The morphological organization, the chemical composition, and the presence of organic molecules in the dentin samples processed by the three different devices were demonstrated using SEM, energy-dispersive X-ray analysis, and Raman spectroscopy. Conclusions Comparing BonMaker, Tooth Transformer, and Smart Dentin Grinder devices in our practice, we concluded that these systems, even with different structural and chemical differences of the dentin granules, have a comparable potential for obtaining regenerative material from the patient’s own teeth.

Evaluation of the nutrients in milk supplements suitable for children using LIBS and PAS technique

The presence of macro and micro nutrients essential for human health in four milk supplements is quickly identified using Laser-induced Breakdown Spectroscopy (LIBS) and Photoacoustic Spectroscopy (PAS). In addition to the minerals reported by the manufacturers, some additional spectral signatures of the elements like Na and K are also observed in the LIBS spectra which are not listed by some manufacturers. The ratio of various minerals like Ca/Mg, Na/Mg, etc. has been evaluated, and found a good correlation with the nutritional value listed on the product packaging. The organic elements C, H, N, and O together with the CN molecular band observed in the LIBS spectra of milk supplement indicate the presence of organic molecules. PAS is used for the identification of organic compounds such as Vitamins, Proteins, Fat, Taurine, and Sucrose in milk supplements. The results of the present study help in selecting milk supplements suitable for children suffering from chronic kidney diseases and diabetes. Based on the presence of minerals and their relative concentration, milk supplements are classified into three groups by applying Principal Component Analysis (PCA). Therefore, the results from the present work extend the application of LIBS and PAS together with PCA for the identification of the nutrients in milk supplements.

Cysteine-Mediated Green Synthesis of Copper Sulphide Nanoparticles: Biocompatibility Studies and Characterization as Counter Electrodes.

A one-pot green method for aqueous synthesis of fluorescent copper sulphide nanoparticles (NPs) was developed. The reaction was carried out in borax–citrate buffer at physiological pH, 37 °C, aerobic conditions and using Cu (II) and the biological thiol cysteine. NPs exhibit green fluorescence with a peak at 520 nm when excited at 410 nm and an absorbance peak at 410 nm. A size between 8–12 nm was determined by dynamic light scattering and transmission electron microscopy. An interplanar atomic distance of (3.5 ± 0.1) Å and a hexagonal chalcocite crystalline structure (βCh) of Cu2S NPs were also determined (HR-TEM). Furthermore, FTIR analyses revealed a Cu-S bond and the presence of organic molecules on NPs. Regarding toxicity, fluorescent Cu2S NPs display high biocompatibility when tested in cell lines and bacterial strains. Electrocatalytic activity of Cu2S NPs as counter electrodes was evaluated, and the best value of charge transfer resistance (Rct) was obtained with FTO/Cu2S (four layers). Consequently, the performance of biomimetic Cu2S NPs as counter electrodes in photovoltaic devices constructed using different sensitizers (ruthenium dye or CdTe NPs) and electrolytes (S2−/Sn2− or I−/I3−) was successfully checked. Altogether, novel characteristics of copper sulfide NPs such as green, simple, and inexpensive production, spectroscopic properties, high biocompatibility, and particularly their electrochemical performance, validate its use in different biotechnological applications.

CHEMOUT: CHEMical complexity in star-forming regions of the OUTer Galaxy

Context. The outer Galaxy is an environment with metallicity lower than the Solar one. Because of this, the formation and survival of molecules in star-forming regions located in the inner and outer Galaxy is expected to be different. Aims. To gain an understanding on how chemistry changes throughout the Milky Way, it is crucial to observe outer Galaxy star-forming regions to constrain models adapted for lower metallicity environments. Methods. In this paper, we present a new observational project: chemical complexity in star-forming regions of the outer Galaxy (CHEMOUT). The goal is to unveil the chemical composition in 35 dense molecular clouds associated with star-forming regions of the outer Galaxy through observations obtained with the Institut de RadioAstronomie Millimétrique 30 m telescope in specific 3 mm and 2 mm spectral windows. Results. In this first paper, we present the sample, and report the detection at 3 mm of simple organic species HCO+, H13CO+, HCN, c-C3H2, HCO, C4H, and HCS+, of the complex hydrocarbon CH3CCH, and of SiO, CCS, and SO. From the optically thin line JKa ,Kb = 21,2 − 10,1 of c-C3 H2 we estimate new kinematic heliocentric and Galactocentric distances based on an updated rotation curve of the Galaxy. The detection of the molecular tracers does not seem to have a clear dependence on the Galactocentric distance. Moreover, with the purpose of investigating the occurrence of outflows and investigate the association with protostellar activity, we analyse the HCO+ line profiles. We find high velocity wings in ~71% of the targets, and their occurrence does not depend on the Galactocentric distance. Conclusions. Our results, confirmed by a statistical analysis, show that the presence of organic molecules and tracers of protostellar activity is ubiquitous in the low metallicity environment of the outer Galaxy. Based on this and on the additional evidence that small, terrestrial planets are omnipresent in the Galaxy, we support previous claims that the definition of the Galactic habitable zone should be subject to further discussion in view of the ubiquitous capacity of the interstellar medium to form organic molecules.

Syzygium cumini leaf extract as an eco-friendly corrosion inhibitor for carbon steel in acidic medium

The efficiency of Syzygium cumini leaf extract (SCLE) as a corrosion inhibitor was evaluated for carbon steel in 0.5 mol L−1 H2SO4 by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) measurements. It was clearly demonstrated that the inhibition efficiency increased with increasing concentration of leaf extract, due to a decrease in the cathodic currents and blocking of the active corroding sites. The presence of organic molecules from the SCLE on the carbon steel surface was confirmed by FT-IR spectroscopy. The adsorption of species on the alloy surface was modeled using the Langmuir isotherm. A decrease in the carbon steel acid corrosion in the presence of SCLE was also confirmed through contact angle measurements and scanning electron microscopy (SEM).

Biogenic zinc-oxide nanoparticles of Moringa oleifera leaves abrogates rotenone induced neuroendocrine toxicity by regulation of oxidative stress and acetylcholinesterase activity

Zinc oxide nanoparticles (ZnONPs) from plant origin were postulated to regulate complex hormonal control through the hypothalamus– pituitary–testicular axis and somatic cells due to their unique small size and effective drug delivery to target tissues. This study therefore investigates the biogenic synthesis of zinc oxide nanoparticles (ZnO NPs) from Moringa oleifera leaves on key endocrine hormones (LH, FSH and testosterone), MDA level, antioxidant enzymes (SOD and CAT), acetylcholineesterase (AChE) activity and reactive nitrogen species (NO•) level in rotenone induced male rat. The animals were divided into six groups (n = 8). Group I was orally given olive oil as vehicle; Group II received 60 mg/kg of rotenone (RTNE) only; Group III (RTNE + ZnONPs) received 60 mg/kg RTNE + 10 mg/kg ZnONPs; Group IV (RTNE + ZnCAP) received 60 mg/kg RTNE + 50 mg/kg zinc capsule; Group V (ZnONPs only) received 10 mg/kg ZnONPs only. Group VI received 50 mg/kg ZnCAP only. The experiment lasted 10 days. TEM and XRD images revealed ZnO NPs. Moreover, the presence of organic molecules in bio-reduction reactions from the FTIR spectrum showed the stabilization of the nanoparticles. Also, animals induced with rotenone exhibited impairment in the leydig cells by depleting LH, FSH, and testosterone levels with reduced AChE activity and significant (p < 0.05) alteration in cerebral enzymatic antioxidants. There was also brain increase in NO• production: marker of pro-inflammation. Nanotherapeutically, ZnONPs regulated hypothalamus–pituitary–testicular axis via modulation of cerebral NO•, FSH, LH, testosterone and AChE activity with induction of anti-oxidative enzymes.

Presence of hydrocarbons on Mars: A possibility

There exists a fair degree of geological similarity between the internal structure of Mars, its orbital cycle, and axis tilt with that of Earth. The early plate tectonics along with subaerial volcanism have emitted oxygen as evident in the geological history of Earth during the Archaean–Proterozoic transition. The ancient Valles Marineris equatorial rift basin of Mars could have resulted because of lithospheric dynamics. The associated large-scale transtensional strike-slip during the Late Amazonian Period further implies manifestation of possible plate tectonics on Mars. The presence of the earliest organic species, 3.7 billion years ago, had been established on Earth. The presence of lake and ocean and evidence of glaciation infer probable evolution of life in early Mars. The depositional morphology like alluvial fans, debris flow fans, deltas, and lacustrine fans implies possible sedimentation processes active on early Mars. Organic matters on Mars could be in situ or could have been delivered by meteorites. The presence of organic molecules of benzene and propane in 3-billion-year-old rock samples has been evidenced in Gale crater. Deposition of source rock and subsequent decomposition of organic matter could have generated hydrocarbons in early Mars. A comparative geological phenomenon between Meso-Neoproterozoic petroleum geology of Earth and the equivalent Amazonian and older periods has been analyzed in the light of the envisaged hydrocarbon generation and entrapment on early Mars. Possible martian petroleum systems of the ancient Valles Marineris rift basin and crater-induced basins including prevalence of gas hydrate and abiotic origin of methane have been studied.

Systematic laboratory approach to produce Mg-rich carbonates at low temperature.

Dolomite is a common Mg-rich carbonate in the geological record, but the mechanism of its formation remains unclear. At low temperature, the incorporation of magnesium ions into the carbonate minerals necessary to form dolomite is kinetically inhibited. Over the decades, several factors that possibly allow for overcoming this kinetic barrier have been proposed, and their effectiveness debated. Here, we present the results of a large number of laboratory precipitation experiments that have been designed to identify and compare the factors that promote the formation of Mg-rich carbonates. Under the tested conditions, the most interesting observations include: (1) from solutions that mimic evaporitic seawater, the maximum mol% of Mg incorporated in high Mg calcite is 35, (2) carbonates with a mol% of Mg above 40 were obtained exclusively in the presence of organic molecules, (3) no correlation was observed between the charge of the organic molecules and the incorporation of Mg, (4) the mode (i.e., slow vs. fast mixing) used to add carbonate to the solution obtaining supersaturation has a significant impact on the forming mineral phase (aragonite vs. nesquehonite vs. high Mg calcite) and its Mg content. These findings allow for a more informed evaluation of the existing models for dolomite formation, which are based on the study of natural environments and ancient sedimentary sequences.

The distinct binding modes of pesticides affect the phase transitions of lysozyme

Studying the aggregation and nucleation of proteins in the presence of organic molecules is helpful for disclosing the mechanisms of protein crystallization.

Quantum Chemical Study of the Formation of Urea in Interstellar Medium

Background: Many observational studies have found the presence of organic molecules in interstellar medium (ISM) via spectroscopy. NH2CONH2 (urea) was first detected in ISM in 2014. Containing two NH2 groups, urea is an important biological molecule in metabolism as a carrier for waste nitrogen. The discovery of urea in ISM suggests the possibility of the formation of other biomolecules which contain peptide bonds, such as proteins. This supports the origin of life theory proposing that these biomolecules were initially formed in space and later arrived to Earth.&#x0D; Methods: This study investigates two possible reaction pathways for the formation of protonated urea (ureaH+) in dense molecular clouds via molecules previously observed in the ISM, formamide (HCONH2) and protonated hydroxylamine (NH2OH2+). The thermodynamics and optimized geometries were calculated for the final steps of the formation of ureaH+ using Gaussian16 at the APFD/6-31G(d,p) level of theory and a transition state was confirmed.&#x0D; Results: The overall mechanism, as well as the studied proton rearrangement of an intermediate to ureaH+, were found to be exothermic and exergonic processes.&#x0D; Conclusion: From the calculations, the conditions of ISM provide an adequate environment for the formation of ureaH+ and urea.

Green synthesis of iron oxide nanoparticles using Cymbopogon citratus extract and sodium carbonate salt: Nanotoxicological considerations for potential environmental applications

Synthesis of functional and biocompatible nanomaterials, based on the green chemistry paradigm, aims to innovate by using environmentally friendly techniques. Green synthesis using natural extracts instead of chemicals is proving to be an efficient route to prepare metal and metal oxide nanoparticles. In this study, the green synthesis of iron oxide nanoparticles (FeO-NPs) is reported, using a Cymbopogon citratus (C. citratus) extract and sodium carbonate as the reducing and pH stabilizer agents, respectively. FeO-NPs are extensively studied and applied due to the exceptional physicochemical properties, outstanding the superparamagnetism, and the large surface area. These properties are corroborated using different characterization techniques, in which a regular crystal structure and the magnetic response are similar compared with FeO-NPs synthesized via the traditional methods. The presence of magnetite and maghemite (Fe3O4 and γ-Fe2O3) phases are evidenced. A major composition of Fe3O4 allows predominant superparamagnetism. However, surface functionalization reduces the spin coordination avoiding a high saturation magnetization. The presence of phytochemical content in the C. citratus allows the reduction of iron(III) to iron(II) using H+ radicals produced from hydroxyl and carbonyl groups, and the in-situ functionalization using these groups. Additionally, the biocompatibility of the FeO-NPs is evaluated performing a nanotoxicological assessment, in which Caenorhabditis elegans nematodes are used as the biological model. The presence of organic molecules on FeO-NPs promotes no toxicity and low effects on the locomotion, growth, and reproduction, suggesting a low risk using these functional nanoparticles for environmental applications, and outstanding the synthesis route with a green approach.

Organic molecule enhanced 1O2 electrochemiluminescence from the phase transformation of amorphous calcium phosphate

Organic molecule enhanced the singlet oxygen (1O2) electrochemiluminescence (ECL) generated during the phase transition of calcium phosphates (CaPs) is presented. As a classic precursor of hydroxyapatite (HAP, Ca10(PO4)6(OH)2), amorphous calcium phosphate (ACP) was in-situ assembled on Nafion film (denoted as ACP/Nafion). The electrochemical oxidation peak and ECL phenomenon were observed when the ACP/Nafion electrode was subjected to cyclic voltammetry (CV) scanning in phosphate buffer solution. The characteristic spectrum of 1O2 dimol emission was observed at 634 nm. And the ECL intensity could be markedly increased and stabilized in the presence of organic molecules, e.g., isopropanol (IPA), oxalate (C2O42−) and L-Lysine. The electron spin resonance (ESR) measurement confirmed that a large number of relevant radicals were produced during the electrochemical oxidation, and these radicals are believed to have played the essential role for the 1O2 generation. Based on the enhancement effect, we exploited the feasibility of direct ECL detection of IPA and L-Lysine by using the ACP/Nafion electrode. And the results show that IPA and L-Lysine can be detected in the range 1.0 μM to 1.0 mM and 0.1 μM to 0.1 mM, with a limit of detection (LOD) 0.15 and 0.03 μM respectively for IPA and L-Lysine. Thus present work not only provides insight for the organic molecule enhanced 1O2 ECL, but also shows the potential for the development of widely applicable ECL detection platform based on abundantly available materials.

Degradation study of arsenic oxides under XPS measurements

XPS is extensively used for the characterization of arsenic-containing compounds like As(V) oxides, which can be found on the surface of minerals and important functional materials such as semiconductors and catalysts. However, potential sample degradation could alter the results. In this study, we explore the nature and extent of As2O5.5/3H2O phase degradation under XPS measurements in order to assess the intrinsic impact of this spectroscopic technique on the collected data. A series of experiments were designed for unravelling the effect of several factors like X-ray.irradiation time and intensity, vacuum time and charge compensation system. The influence of the structure and composition of the oxide was tested by taking the As2O5 phase as reference. Analyses were based on curve fitting of As3d, C1s and O1s high-resolution spectra, including survey quantification. Results show that degradation involves reduction of As(V) to As(III) species along with oxygen lost from the oxide lattice. As(V) photoreduction becomes extensive by repeating doses of X-ray irradiation; the photon beam intensity plays a major role in degradation, especially combined with the use of a dual flood gun as charge compensation system, while longer vacuum times also favor reduction. The dehydrated phase is more resistant to degradation likely due to a broader valence-band width. The presence of organic molecules from carbon contamination seems to play an important role in degradation. The possible underlying mechanism based on Auger decay of the initial core hole is considered. Minimal sample damage can be obtained by fixing the operating power and the vacuum and irradiation times at the least affordable values.

Selective Conversion of Glucose to 5-Hydroxymethylfurfural by Using L-Type Zeolites with Different Morphologies

In the present work, the morphology of L-type zeolite (LTL topology) has been modified in order to evaluate the influence of several protonated-form LTL-zeolites with different morphologies on their stability and catalytic performance in the conversion of glucose into 5-hydroxymethylfurfural (5-HMF). Physico-chemical characterization of the LTL-based catalysts has revealed that the three types of morphologies (needle, short rod and cylinder) are active, providing complete glucose conversion and high 5-HMF yield values. The addition of CaCl2 had a positive influence on the catalytic performance. It was found that morphology influences the textural and acid properties of LTL-zeolites, and hence their catalytic performance. The best catalytic results have been obtained with the NEEDLE-LTL, showing nanoparticles with a length of 4.46 μm and a width of 0.63 μm, which attains a 5-HMF yield of 63%, at 175 °C after 90 min of reaction, and a glucose conversion of 88%. The reusability study has revealed a progressive decrease in 5-HMF yield after each catalytic cycle. Different regeneration methods have been essayed without recovering the initial catalytic activity. The presence of organic molecules in micropores has been demonstrated by TG analysis, which are difficult to remove even after a regeneration process at 550 °C.

Evidence of noncovalent complexes in some natural extracts: Ceylon tea and mate extracts.

Considering the high complexity of natural extracts, because of the presence of organic molecules of different chemical nature, the possibility of formation of noncovalent complexes should be taken into account. In a previous investigation, the formation of bimolecular complexes between caffeine and catechins in green tea extracts (GTE) has been experimentally proven by means of mass spectrometric and 1 H nuclear magnetic resonance experiments. The same approaches have been employed in the present study to evaluate the presence of bimolecular complexes in Ceylon tea and mate extracts. The obtained results show that in the case of Ceylon tea extracts, protonated theaflavin is detectable, together with theaflavin/caffein complexes, while caffeine/catechin complexes, already detected in green tea, are still present but at lower concentration. This aspect is evidenced by the comparison of precursor ion scans performed on protonated caffeine for the two extracts. The spectra obtained in these conditions for GTE and Ceylon tea show that the complexes of caffeine with epigallocatechin (EGC), epicatechin gallate (ECG), and epigallocatechin gallate (EGCG), highy abundant in the case of GTE (signal-to-chemical noise ratio in the range 50-100), are negligible (signal-to-chemical noise ratio in the range 2-3) in the case of Ceylon tea. Mate extracts show the formation of bimolecular complexes involving caffeine but not catechins, and chlorogenic acid becomes responsible for other complex formation. Under positive ion and negative ion conditions, accurate mass measurements allow the identification of malealdehyde, chlorogenic acid, caffeine, two isomers of dicaffeoylquinic acid, rutin, and kaempferol-3-O-rutinoside. These data indicate that the formation of complexes in natural extracts is a common behavior, and their presence must be considered in the description of natural extracts and, consequently, in their biological activity.

Coral calcification, mucus, and the origin of skeletal organic molecules

Biocalcification encompasses the kinetic and structural, abiotic and biologically mediated processes involved in the formation of calcium carbonate skeletons by marine organisms and represents a key process in the global carbon cycle. Throughout the geological record, this process has evolved repetitively and has altered global biogeochemical cycles. Besides the structural variability of calcium carbonate polymorphs laid down by different organisms, biogenic carbonate skeletons are characterized by the presence of organic molecules that are incorporated into the growing skeleton. Major advances have identified the macromolecules associated to the organic matrix within marine calcifiers, however, it has yet to be established the actual role these organic molecules play in the calcification process. In this study, we isolated the effect of skeletal organic molecules (SOM) on the precipitation of calcium carbonate on coral skeleton fragments by adding extracted SOM or coral mucus (CM) to oversaturated calcium carbonate solutions. We found that the precipitation rate did not change regardless if organic molecules were present or not. However, the primary polymorph did change between the treatments, suggesting that organic molecules influence the surface processes that lead to the formation of the crystal lattice but not the kinetic processes that transport ions to the crystal surface. Since SOM and CM both altered the crystal polymorph but not the crystallization rate, we argue that SOM may not represent a specialized biomineralization toolkit, but that SOM originate from CM and the requirement of the polyp to adhere to the substratum.

Calcium Carbonate Formation in the Presence of Biopolymeric Additives.

Biomineralization is the formation of minerals in the presence of organic molecules, often related with functional and/or structural roles in living organisms. It is a complex process and therefore a simple, in vitro, system is required to understand the effect of isolated molecules on the biomineralization process. In many cases, biomineralization is directed by biopolymers in the extracellular matrix. In order to evaluate the effect of isolated biopolymers on the morphology and structure of calcite in vitro, we have used the vapor diffusion method for the precipitation of calcium carbonate, scanning electron microscopy and micro Raman for the characterization, and ultraviolet-visible (UV/Vis) absorbance for measuring the quantity of a biopolymer in the crystals. In this method, we expose the isolated biopolymers, dissolved in a calcium chloride solution, to gaseous ammonia and carbon dioxide that originate from the decomposition of solid ammonium carbonate. Under the conditions where the solubility product of calcium carbonate is reached, calcium carbonate precipitates and crystals are formed. Calcium carbonate has different polymorphs that differ in their thermodynamic stability: amorphous calcium carbonate, vaterite, aragonite, and calcite. In the absence of biopolymers, under clean conditions, calcium carbonate is mostly present in the calcite form, which is the most thermodynamically stable polymorph of calcium carbonate. This method examines the effect of the biopolymeric additives on the morphology and structure of calcium carbonate crystals. Here, we demonstrate the protocol through the study of an extracellular bacterial protein, TapA, on the formation of calcium carbonate crystals. Specifically, we focus on the experimental set up, and characterization methods, such as optical and electron microscopy as well as Raman spectroscopy.

Towards a Miniaturized Device to Evaluate the BOD Parameter of Wastwater

The concentration of organic pollutants present in wastewater is classically evaluated by measuring the quantity of dissolved oxygen during five days; it is quantified by the so called BOD5 parameter (Biological Oxygen Demand). This work constitutes the first step of an overall strategy targeting to improve the monitoring of this indicator of the water quality. We focus on the development of a microsystem approach allowing monitoring the O 2 consumption induced by the biodegradation process of organic matter. To evaluate the organic pollutants concentration, we use Escherichia coli as bacterial indicator, confined in a PDMS-glass chip. Their metabolic activity in presence of organic molecules is deduced from their oxygen consumption. These measurements are ensured by optical sensors present in each of the five instrumented chambers of the chip. The results show that the microsystem approach is suitable to measure simultaneously different concentrations of organic load, and that it is possible to reduce the analysis time. By examining the O 2 diffusion towards the walls of the device, we analyze the different part of the experimental results; it allows, on the basis of a theoretical model, to predict a precise evaluation of the BOD value within few hours.