Search results for "metals"
showing 10 items of 2013 documents
Lead(II) ions adsorption onto amyloid particulates: An in depth study
2022
The production of new cost-effective biocompatible sorbent sustainable materials, with natural origins, able to remove heavy metals from water resources is nowadays highly desirable in order to reduce pollution and increase clean water availability. In this context, self-assembled protein materials with amyloid structures seem to have a great potential as natural platform for a broader development of highly-tunable structures. In this work we show how protein particulates, a generic form of protein aggregates, with spherical micro sized shape can be used as adsorbents of Pb2+ ions from aqueous solution. The effect of pH, ionic medium, ionic strength and temperature of the metal ion solution…
Do zwitterionic species exist in the non-enzymatic peptide bond formation?
2012
The use of proper computational methods and models has allowed answering the controversial question of whether zwitterionic species exist in the mechanism of peptide bond synthesis in aqueous solution. In fact, the different conformations of zwitterionic species open the door to different mechanistic paths.
Bridging rigidity and flexibility : modulation of supramolecular hydrogels by metal complexation
2021
The combination of complementary, noncovalent interactions is a key principle for the design of multistimuli responsive hydrogels. In this work, an amphiphilic peptide, supramacromolecular hydrogelator which combines metal-ligand coordination induced gelation and thermoresponsive toughening is reported. Following a modular approach, the incorporation of the triphenylalanine sequence FFF into a structural (C3EG ) and a terpyridine-functionalized (C3Tpy ) C3 -symmetric monomer enables their statistical copolymerization into self-assembled, 1D nanorods in water, as investigated by circular dichroism (CD) spectroscopy and transmission electron microscopy (TEM). In the presence of a terpyridine …
History of bioavailable lead and iron in the Greater North Sea and Iceland during the last millennium – A bivalve sclerochronological reconstruction
2014
We present the first annually resolved record of biologically available Pb and Fe in the Greater North Sea and Iceland during 1040-2004 AD based on shells of the long-lived marine bivalve Arctica islandica. The iron content in pre-industrial shells from the North Sea largely remained below the detection limit. Only since 1830, shell Fe levels rose gradually reflecting the combined effect of increased terrestrial runoff of iron-bearing sediments and eutrophication. Although the lead gasoline peak of the 20th century was well recorded by the shells, bivalves that lived during the medieval heyday of metallurgy showed four-fold higher shell Pb levels than modern specimens. Presumably, pre-indus…
Calcium, magnesium, sodium, potassium and iron content of infant formulas and estimated daily intakes
1996
The calcium, magnesium, sodium, potassium and iron content of a total of 22 different infant formulas marketed in Spain were measured by atomic spectrometry, and the mineral intake of infants fed exclusively with these formulas was estimated. The contents (mg/100kJ) are in the following ranges: Ca, 14-24; Mg, 1.1-2.8; Na, 5.6-9.8; K, 19-35; Fe, 0.02-0.50. These values coincide with those recommended by the Codex and European Society for Paediatric Gastroenterology and Nutrition (ESPGAN), and do not exceed the limits established by the European Union (EU). The mean values and ranges of estimated intakes for each formula type and period of infancy (0-1, 1-2, 2-3, 3-4 and 4-5 months) expressed…
Intramolecular electron transfer between molybdenum and iron mimicking bacterial sulphite dehydrogenase
2014
Diferrocenyl/diferrocenium substituted dioxido molybdenum(VI) complexes [Fe2MoO2] 2(Fc)/[2(FC)]²⁺ mimic the catalytic active site including the redox subunits as well as the catalytic function of bacterial sulphite oxidases.
The elemental role of iron in DNA synthesis and repair
2017
Iron is an essential redox element that functions as a cofactor in many metabolic pathways. Critical enzymes in DNA metabolism, including multiple DNA repair enzymes (helicases, nucleases, glycosylases, demethylases) and ribonucleotide reductase, use iron as an indispensable cofactor to function. Recent striking results have revealed that the catalytic subunit of DNA polymerases also contains conserved cysteine-rich motifs that bind iron–sulfur (Fe/S) clusters that are essential for the formation of stable and active complexes. In line with this, mitochondrial and cytoplasmic defects in Fe/S cluster biogenesis and insertion into the nuclear iron-requiring enzymes involved in DNA synthesis a…
Laser spectroscopy of radioactive Ti, Zr and Hf isotopes and isomers at the JYFL laser-IGISOL facility
2003
Abstract The recent progress at the laser-ion guide isotope separator on-line facility, JYFL, is presented. At the facility new techniques for studying short-lived radioisotopes by laser spectroscopy have been developed and applied to the study of isotopes in refractory metal elements. In particular, recent results on the spectroscopy of cooled ion beams of radioactive Ti, Zr and Hf isotopes are discussed.
A theoretical model for laser and powder particles interaction during laser cladding
2002
Abstract Interactions between the laser and the powder particles lead to attenuation of the laser and make the powder particles temperatures raise. According to given stream spread and speed of the powder particles, their temperature distribution at the surface of the workpiece is calculated. The attenuation of the laser induced by the cloud is also computed. These results are plotted for the case of a Gaussian distribution. Results show that with the increasing of the powder jet incidence angle, both temperature distribution of powder particles and attenuation of the laser have very different profiles. Their effects on the clad should be considered for modelling of laser cladding.
Stereodifferentiation in the formation and decay of the encounter complex in bimolecular electron transfer with photoactivated acceptors.
2005
Experimental evidence has been obtained for the involvement of encounter complexes between both enantiomers of a π,π* triplet excited ketone and a chiral phenol or indole. Determination of the pre-equilibrium constants (KEC) and the intrinsic decay rate constants (kd) indicates a significant stereodifferentiation in both steps of the quenching process. Perez Prieto, Julia, Julia.Perez@uv.es ; Galian, Raquel Eugenia, Raquel.Galian@uv.es ; Morant Miñana, Maria Carmen, Maica.Morant@uv.es