Development of a frugal, in-situ sensor implementing a ratiometric method for continuous monitoring of turbidity in natural waters

International audienceTurbidity is a commonly used indicator of water quality in continental and marine waters, mostly caused by suspended and colloidal particles such as organic and inorganic particles. Many methods are available for the measurement of turbidity, ranging from the Secchi disk to infrared light-based benchtop or in-situ turbidimeters as well as acoustic methods. The operational methodologies of the large majority of turbidity instruments involve the physics of light scattering and absorption by suspended particles when light is passed through a sample. As such, in the case of in-situ monitoring in water bodies, the measurement of turbidity is highly influenced by external light and biofouling. Our motivation for this project is to propose an open-source, low-cost in-situ turbidity sensor with a suitable sensitivity and operating range to operate in low to medium turbid natural waters. This prototype device combines two angular photodetectors and two infrared light sources with different positions, resulting in two different types of light detection: nephelometric (i.e. scattering) and attenuation light, according to the ISO 7027 method. The mechanical design involves 3D-printed parts by stereolithography which are compatible with commercially available waterproof enclosures, thus ensuring easy integration for future users. An effort has been made to rely on mostly off-the-shelf electronic components to encourage replication of the system, with the use of a highly integrated photometric front-end commonly used in portable photoplethysmography systems. The sensor was tested in laboratory conditions against a commercial benchtop turbidimeter with Formazin standards. The monitoring results were analysed getting a linear trendline from 0 to 50 Nephelometric Turbidity Unit (NTU), and an accuracy of +/-0.4 NTU in the 0 to 10 NTU range with a response time of less than 100 ms

Impact of environmental factors on in situ determination of iron in seawater by flow injection analysis

International audienceA sensitive method for iron determination in seawater has been adapted on a submersible chemical analyser for in situ measurements. The technique is based on flow injection analysis (FIA) coupled with spectrophotometric detection. When direct injection of seawater was used, the detection limit was 1.6 nM, and the precision 7%, for a triplicate injection of a 4 nM standard. At low iron concentrations, on line preconcentration using a column filled with 8-hydroxyquinoline (8HQ) resin was used. The detection limit was 0.15 nM (time of preconcentration = 240 s), and the precision 6%, for a triplicate determination of a 1 nM standard, allowing the determination of Fe in most of the oceanic regimes, except the most depleted surface waters. The effect of temperature, pressure, salinity, copper, manganese, and iron speciation on the response of the analyser was investigated. The slope of the calibration curves followed a linear relation as a function of pressure (C p = 2.8 Â 10 À 5 P + 3.4 Â 10 À 2 s nmol À 1 , R 2 = 0.997, for H = 13 8C) and an exponential relation as a function of temperature (C H = 0.009e 0.103H , R 2 = 0.832, for P = 3 bar). No statistical difference at 95% confidence level was observed for samples of different salinities (S = 0, 20, 35). Only very high concentration of copper (1000 Â [Fe]) produced a detectable interference. The chemical analyser was deployed in the coastal environment of the Bay of Brest to investigate the effect of iron speciation on the response of the analyser. Direct injection was used and seawater samples were acidified on line for 80 s. Dissolved iron (DFe, filtered seawater (0.4 Am), acidified and stored at pH 1.8) corresponded to 29 F 4% of Fe a (unfiltered seawater, acidified in line at pH 1.8 for 80 s). Most of Fe a (71 F 4%) was probably a fraction of total dissolvable iron (TDFe, unfiltered seawater, acidified and stored at pH 1.8)

Large scale functional exploration of the GH5 family

The large and functionally diverse GH5 family is one of the very first Carbohydrate-Active enZYme families classified back in 1991 [3], [4]. The number of confirmed members in CAZy has grown to a staggering 27,000 where only approximately 600 (2%) have been assigned a function experimentally. In spite of early large-scale efforts [1], [2], the eye-watering paucity of characterized GH5 enzymes constitutes a general problem observed in most CAZy families, worsened by an unequal distribution of the characterized GH5 across the sequence space. This project attempts to address this problem by implementing large scale functional screening of approximately 200 carefully chosen GH5 candidates that systematically targets low or unexplored subfamilies in the known sequence space, thereby creating an excellent and large training set for use in developing progressive machine-learning algorithms that potentially can provide reliable and stable functional predictions of enzymes based on sequence information

An autonomous nutrient analyzer for oceanic long-term in situ biogeochemical monitoring

An autonomous nutrient analyzer in situ (ANAIS) has been developed to monitor nitrate, silicate, and phosphate concentrations while deployed at sea at pressure (down to 1000 m). Detection is made by spectrophotometry. The instrument uses solenoid-driven diaphragm pumps to propel the sample, the standards, and the reagents through a microconduit, flow injection-style thermostated manifold. The analyzers are placed in an equipressure container filled with oil. The analyzers operate until a pressure of 100 bar and show a linear response up to 40 μM nitrate,150 μM silicate, and 5 μM phosphate with a detection limit less than 0.1, 0.5, and 0.1 μM and an accuracy of 1, 1, and 3% for nitrate, silicate, and phosphate, respectively. The measurement protocol includes three steps over 13 min:  rinsing with the sample stream, reagents introduction, and absorbance detection. Field tests comprise ANAIS nitrate, silicate, and phosphate testing alone in the surface ocean. Phosphate results are not yet fully satisfactory. The instrument implemented on top of a YOYO vertical eulerian profiler was then deployed successfully in the northwestern Mediterranean Sea acquiring 30 nitrate profiles between 200 and 1100 m over a 15-day period. This chemical analyzer can be a valuable observing asset adapted on any type of oceanographic platform.Peer reviewe

Florilège des actualités oncologiques internationales en 2019

International audienceComme chacune de ces dernières années, le monde de l’oncologie bouge et avance. Les résultats de grands essais changent nos pratiques, voire les révolutionnent ! Dans ce manuscrit, humblement, le comité éditorial du Bulletin du Cancer fait le focus sur certains d’entre eux qui lui ont semblé importants de connaître peut-être même au-delà de nos spécialités

Characterization and structural study of a novel β‐ N ‐acetylgalactosaminidase from Niabella aurantiaca

International audienceWe report here the identification, characterization and three‐dimensional (3D) structure determination of Na Nga, a newly identified β‐ N ‐acetylgalactosaminidase from the Gram‐negative soil bacterium Niabella aurantiaca DSM 17617. When recombinantly expressed in Escherichia coli , the enzyme selectively cleaved 4‐nitrophenyl‐ N ‐acetyl‐β‐ d ‐galactosamine ( p NP‐β‐ d ‐Gal p NAc). The X‐ray crystal structure of the protein was refined to 2.5 Å and consists of an N‐terminal β‐sandwich domain and a (β/α) 8 barrel catalytic domain. Despite a mere 22% sequence identity, the 3D structure of Na Nga is similar to those previously determined for family GH123 members, suggesting it also employs the same substrate‐assisted catalytic mechanism. Inhibition by N ‐acetyl‐galactosamine thiazoline (GalNAc‐thiazoline) supports the suggested mechanism. A phylogenetic analysis of its proximal sequence space shows significant clustering of unknown sequences around Na Nga with sufficient divergence with previously identified GH123 members to subdivide this family into distinct subfamilies. Although the actual biological substrate of our enzyme remains unknown, examination of the active site pocket suggests that it may be a β‐ N ‐acetylgalactosaminide substituted by a monosaccharide at O‐3. Analysis of the genomic context suggests, in turn, that this substituted β‐ N ‐acetylgalactosaminide may be appended to a d ‐arabinan from an environmental Actinomycete

L’année 2021 dans tous ses états : une synthèse digérée

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