Suchergebnisse

We provide fundamental guidelines in the form of a tutorial to be taken into account for the preparation and characterization of a specific class of poly(ethylene glycol) (PEG) derivatives, namely azide-terminated PEGs. Special attention is given to the effect of these chain end groups and their precursors on properties affecting the PEGylation of proteins, nanoparticles and nanostructured surfaces. Notwithstanding the presence of 13C satellite peaks, we show that 1H NMR enables not only the routine quantitative determination of chain-end substitution, but is also a unique method to calculate the absolute number average molecular weight of PEG derivatives. In the use of size exclusion chromatography to get molecular weight distributions, we highlight the importance of distinguishing between eventual secondary reactions involving molecular weight changes and the formation of PEG complexes due to residual amounts of metal cations from reactants. Finally, we show that azide end groups affect PEG melting behavior. In contrast to oxygen-containing end groups, azides do not interact with PEG segments, thus inducing defect formation in the crystal lattice and the reduction of crystal sizes. Melting temperature and degree of crystallinity decrease become especially relevant for PEGs with very low molecular weight, and its comprehension is particularly important for solid-state applications ; This research was funded by the Spanish Agencia Estatal de Investigación (PGC2018-101047). M.L. also acknowledges the Xunta de Galicia (Grupo con Potencial de Crecemento ED431B 2018/1 and Centro singular de investigación de Galicia accreditation 2019-2022, ED431G 2019/03) and the European Union (European Regional Development Fund-ERDF) ; SI

Microplastics (MPs) patterns in a weakly-stratified estuary were investigated using a combined approach of observations and modeling. The study was conducted in the Guadalquivir River Estuary, which is of high environmental value, yet significantly altered by human activities. The study aims to contribute to understanding and quantifying the land-ocean transport of MPs. Mean concentrations of MPs in the estuary were 0.041 items m(-3), with maximum values up to 0.20 items m(- 3), in agreement with the range reported in other estuaries. Polyethylene floating MPs were predominant. Relationships between increases in MP concentration and local rainfall events were identified in the middle estuary when there were no significant discharges from the head dam. Modeling results mimicked observations and revealed the effects of tidal straining, density-driven, and river flow-induced circulation on the net transport. Convergence of transports favors the MPs trapping in the vicinity of Don tilde ana National Park, overlapping the location of the Estuarine Turbidity Maximum. ; This research is funded by Spanish Ministry of Science, Innovation and Universities (AEI/FEDER/UE) through the projects CTM201677106-R and CTM2017-89531-R. Guadalquivir-LTER project was supported by IFAPA Research Projects PP.FEM.PPA201700.5 and PP.FEM. PP201900.5, 75% cofounded by European Maritime and Fisheries Fund (2014-2022), within the Spanish Operational Program "Fisheries and Maritime 2014-2020". MB and DGF acknowledge funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie, grant agreements 754446 (UGR Research and Knowledge Transfer Fund -Athenea3i) and 846843 (LitRivus), respectively. University of Granada/CBUA provided the funding for open access charges. Finally, the authors would like to thank the two anonymous reviewers and Editor for their valuable comments and suggestions.

9 pages, 5 figures.-- Under a Creative Commons license ; Small microplastics (SMPs) in the gulf of Cadiz was sampled at 5 m depth by pumping it through the ship's pipe system and filtered through a 45 μm mesh size net. Our study reveals that higher densities have been found (130 mg·m−3) compared to other regions worldwide and these densities decreased from the coastline to the outer stations, showing a general coastal gradient influenced by estuarine outflows. SMPs with a size range between 45 and 193 μm were predominant and most of them composed by polyethylene and polypropylene. The metals associated with the MPs were mainly Na (21.1%), K (11.3%), Fe (8.5%), Ca (2.1%), Cr (1.8%), Zr (13.3%) and Hf (0.7%). The high proportion of Zr compared to Fe, which is different from what can be found in the environment, suggests that this metal is intrinsic to the materials used in catalytic processes during plastic production ; Financial support to EGO and the instrument was given by CSIC through Intramural Research program 2018 under grant number 201830I081. MS is grateful to the Spanish Ministry of Science, Innovation and Universities for the Juan de la Cierva (TJFI-2017-32493) contract. DGF was funded by European Union's H2020-MSCA-IF-2018 846843—LitRivus ; Peer reviewed

Small microplastics (SMPs) in the gulf of Cadiz was sampled at 5 m depth by pumping it through the ship's pipe system and filtered through a 45 mu m mesh size net. Our study reveals that higher densities have been found (130 mg.m(-3)) compared to other regions worldwide and these densities decreased from the coastline to the outer stations, showing a general coastal gradient influenced by estuarine outflows. SMPs with a size range between 45 and 193 mu m were predominant and most of them composed by polyethylene and polypropylene. The metals associated with the MPs were mainly Na (21.1%), K (11.3%), Fe (8.5%), Ca (2.1%), Cr (1.8%), Zr (13.3%) and Hf (0.7%). The high proportion of Zr compared to Fe, which is different from what can be found in the environment, ; Financial support to EGO and the instrument was given by CSIC through Intramural Research program 2018 under grant number 201830I081. MS is grateful to the Spanish Ministry of Science, Innovation and Universities for the Juan de la Cierva (TJFI-2017-32493) contract. DGF was funded by European Union's H2020-MSCA-IF-2018 846843-LitRivus.