A Simple Method for the Size Controlled Synthesis of Stable Oligomeric Clusters of Gold Nanoparticles under Ambient Conditions

Reducing dilute aqueous HAuCl4 with sodium thiocyanate (NaSCN) under alkaline conditions produces 2 to 3 nm diameter nanoparticles. Stable grape-like oligomeric clusters of these yellow nanoparticles of narrow size distribution are synthesized under ambient conditions via two methods. The delay-time method controls the number of subunits in the oligoclusters by varying the time between the addition of HAuCl4 to alkaline solution and the subsequent addition of reducing agent, NaSCN. The yellow oligoclusters produced range in size from ~3 to ~25 nm. This size range can be further extended by an add-on method utilizing hydroxylated gold chloride (Na+[Au(OH4-x)Clx]-) to auto-catalytically increase the number of subunits in the as-synthesized oligocluster nanoparticles, providing a total range of 3 nm to 70 nm. The crude oligocluster preparations display narrow size distributions and do not require further fractionation for most purposes. The oligoclusters formed can be concentrated >300 fold without aggregation and the crude reaction mixtures remain stable for weeks without further processing. Because these oligomeric clusters can be concentrated before derivatization they allow expensive derivatizing agents to be used economically. In addition, we present two models by which predictions of particle size can be made with great accuracy

A tetraethylene glycol coat gives gold nanoparticles long in vivo half-lives with minimal increase in size

In this study, we describe the experiments determining whether coating gold nanoparticles with tetraethylene glycol (TEG) provides pharmacologically relevant advantages, such as increased serum half-life and resistance to protein adsorption. Monodisperse TEG-coated, NaBH4-reduced gold nanoparticles with a hydrodynamic size comparable to albumin were synthesized by reducing gold chloride with NaBH4 under alkaline conditions in the presence of TEG-SH. The particles were characterized by gel electrophoresis, column chromatography, and transmission electron microscopy. The nanoparticles were subsequently injected intravenously into mice, and their half-lives and final destinations were determined via photometric analysis, light microscopy (LM), and transmission electron microscopy. The TEG particles had a long half-life (~400 minutes) that was not influenced by splenectomy. After 500 minutes of injection, TEG particles were found in kidney proximal tubule cell vesicles and in spleen red and white pulp. The particles induced apoptosis in the spleen red pulp but not in white pulp or the kidney. Some of the TEG particles appeared to have undergone ligand exchange reactions that increased their charge. The TEG particles were shown to be resistant to nonspecific protein adsorption, as judged by gel electrophoresis and column chromatography. These results demonstrate that naturally monodisperse, small-sized gold nanoparticles coated with TEG have long in vivo plasma half-lives, are minimally toxic, and are resistant to protein adsorption. This suggests that a TEG coating should be considered as an alternative to a polyethylene glycol coating, which is polydisperse and of much larger size

The extended loops of ribosomal proteins uL4 and uL22 of Escherichia coli contribute to ribosome assembly and protein translation

Nearly half of ribosomal proteins are composed of a domain on the ribosome surface and a loop or extension that penetrates into the organelle's RNA core. Our previous work showed that ribosomes lacking the loops of ribosomal proteins uL4 or uL22 are still capable of entering polysomes. However, in those experiments we could not address the formation of mutant ribosomes, because we used strains that also expressed wild-type uL4 and uL22. Here, we have focused on ribosome assembly and function in strains in which loop deletion mutant genes are the only sources of uL4 or uL22 protein. The uL4 and uL22 loop deletions have different effects, but both mutations result in accumulation of immature particles that do not accumulate in detectable amounts in wild-type strains. Thus, our results suggest that deleting the loops creates kinetic barriers in the normal assembly pathway, possibly resulting in assembly via alternate pathway(s). Furthermore, deletion of the uL4 loop results in cold-sensitive ribosome assembly and function. Finally, ribosomes carrying either of the loop-deleted proteins responded normally to the secM translation pausing peptide, but the uL4 mutant responded very inefficiently to the cmlAcrb pause peptide

A tetraethylene glycol coat gives gold nanoparticles long in vivo half-lives with minimal increase in size

In this study, we describe the experiments determining whether coating gold nanoparticles with tetraethylene glycol (TEG) provides pharmacologically relevant advantages, such as increased serum half-life and resistance to protein adsorption. Monodisperse TEG-coated, NaBH(4)-reduced gold nanoparticles with a hydrodynamic size comparable to albumin were synthesized by reducing gold chloride with NaBH(4) under alkaline conditions in the presence of TEG-SH. The particles were characterized by gel electrophoresis, column chromatography, and transmission electron microscopy. The nanoparticles were subsequently injected intravenously into mice, and their half-lives and final destinations were determined via photometric analysis, light microscopy (LM), and transmission electron microscopy. The TEG particles had a long half-life (~400 minutes) that was not influenced by splenectomy. After 500 minutes of injection, TEG particles were found in kidney proximal tubule cell vesicles and in spleen red and white pulp. The particles induced apoptosis in the spleen red pulp but not in white pulp or the kidney. Some of the TEG particles appeared to have undergone ligand exchange reactions that increased their charge. The TEG particles were shown to be resistant to nonspecific protein adsorption, as judged by gel electrophoresis and column chromatography. These results demonstrate that naturally monodisperse, small-sized gold nanoparticles coated with TEG have long in vivo plasma half-lives, are minimally toxic, and are resistant to protein adsorption. This suggests that a TEG coating should be considered as an alternative to a polyethylene glycol coating, which is polydisperse and of much larger size

Science Gateways: The Long Road to the Birth of an Institute

Nowadays, research in various disciplines is enhanced via computational methods, cutting-edge technologies and diverse resources including computational infrastructures and instruments. Such infrastructures are often complex and researchers need means to conduct their research in an efficient way without getting distracted with information technology nuances. Science gateways address such demands and offer user interfaces tailored to a specific community. Creators of science gateways face a breadth of topics and manifold challenges, which necessitate close collaboration with the domain specialists but also calling in experts for diverse aspects of a science gateway such as project management, licensing, team composition, sustainability, HPC, visualization, and usability specialists. The Science Gateway Community Institute tackles the challenges around science gateways to support domain specialists and developers via connecting them to diverse experts, offering consultancy as well as providing a software collaborative, which contains ready-to-use science gateway frameworks and science gateway components

Permeation of macromolecules into the renal glomerular basement membrane and capture by the tubules

Human kidneys contain ∼2 x 106 glomeruli that produce ∼180 L per day of primary filtrate. Downstream tubules reabsorb most of the water, salt, and desirable low-molecular weight substances, leaving 1 to 2 L per day of urine containing undesirable waste products. Currently, most investigators think that the primary filtrate is low in protein because fluid exiting the glomerulus passes through slits spanned by a diaphragm that acts as a low-porosity molecular sieve. Our experiments challenge this view; they show that size-dependent permeation into the glomerular basement membrane and into a gel-like coat that covers the slits, together with saturable tubular reabsorption, determines which macromolecules reach the urine. The slit diaphragm is essential for capillary structure but may not directly determine glomerular size selectivity

Toxicidade e produção de maçãs no sul do Brasil.

Explora as conexões entre uma polêmica apreensão de maçãs contaminadas no sul do Brasil, em 1989, e as reações da indústria da maçã às notícias da imprensa sobre o uso do agrotóxico nas plantações brasileiras. A problemática está inserida em análise mais ampla da ideia de toxicidade e de ‘perigo’, que começa a invadir os domínios público e privado quanto ao consumo de alimentos mais sadios e à ‘segurança alimentar’. Afirma que as respostas dos pomicultores ao problema seriam mais bem entendidas com a leitura histórica das interações entre a biologia da macieira, a agroecologia dessa monocultura e estruturas, atores e discursos que envolvem coletivos humanos e não humanos na região produtora de maçãs

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements