The use of polyurethane foams for the extraction of platinum (II) from hydrochloric acid solutions in the presence of tin (II) chloride

A preliminary investigation prior to the study of the extraction of platinum, was conducted on the Co(NCS)₄²⁻ /foam system to, (a) develop a suitable experimental apparatus in order to study the loading of platinum foams and (b) obtain fundamental kinetic and thermodynamic data concerning the sorption process. The sorption of platinum(II) as complexes of [Pt(SnCl₃)nCl₄-n]²⁻ and [Pt(SnCl₃)₅]³⁻ from hydrochloric acid solutions by polyurethane foams was examined in detail. Our studies show that the capacity of the foam to extract platinum depends on the following solution conditions of, temperature, initial platinum concentration, hydrochloric acid and hydrogen ion concentrations, the Sn:Pt ratio and the presence of interfering cations and anions. The rate of platinum sorption is shown to be dependent on temperature, initial platinum concentration, the Sn:Pt ratio and the mass of the foam. The foam's ability to selectively extract platinum from solutions containing platinum and certain base metals is examined. Results obtained show that in all cases almost complete extraction of platinum was achieved. Of all the base metals investigated only Cu(II) co-extracts to a small extent with the noble metal. In this work a procedure has been developed in which we are able to quantitatively recover both platinum and tin from loaded foams, by dissolving the polyurethane in warm nitric acid. A simple distillation allows for the satisfactory separation of platinum from tin

Rapid and sensitive large-scale screening of low affinity extracellular receptor protein interactions by using reaction induced inhibition of Gaussia luciferase.

Extracellular protein interactions mediated by cell surface receptors are essential for intercellular communication in multicellular organisms. Assays to detect extracellular interactions must account for their often weak binding affinities and also the biochemical challenges in solubilising membrane-embedded receptors in an active form. Methods based on detecting direct binding of soluble recombinant receptor ectodomains have been successful, but genome-scale screening is limited by the usual requirement of producing sufficient amounts of each protein in two different forms, usually a "bait" and "prey". Here, we show that oligomeric receptor ectodomains coupled to concatenated units of the light-generating Gaussia luciferase enzyme robustly detected low affinity interactions and reduced the amount of protein required by several orders of magnitude compared to other reporter enzymes. Importantly, we discovered that this flash-type luciferase exhibited a reaction-induced inhibition that permitted the use of a single protein preparation as both bait and prey thereby halving the number of expression plasmids and recombinant proteins required for screening. This approach was tested against a benchmarked set of quantified extracellular interactions and shown to detect extremely weak interactions (KDs ≥ μM). This method will facilitate large-scale receptor interaction screening and contribute to the goal of mapping networks of cellular communication

Growth of market-size abalone (Haliotis midae) fed kelp (Ecklonia maxima) versus a low-protein commercial feed

The growth of grow-out abalone fed on kelp, with ca. 10 % dry weight protein content, was compared with that of those fed a new ,ca. 26 % protein, commercial feed in a flow-through system on a South African west coast commercial abalone farm. While both feeds produced similar gains in shell length (45.220 μm.day-1 for kelp, 46.839 μm.day-1 for commercial feed), the latter significantly outperformed kelp in terms of weight gain (0.266 % body weight.day-1 for commercial feed; 0.257 % body weight.day-1 for kelp). This low-protein commercial feed may prove to be of considerable benefit as substitute for the kelp plus high-protein feed sometimes used for abalone, because it has most of the benefits of the two feeds, but none of their apparent disadvantages.Web of Scienc

Determining the most appropriate feeding regime for the South African abalone Haliotis midae Linnaeus grown on kelp

Beach-cast kelp (the most widely used feed for commercially grown South African abalone) is plentiful during winter months when periodic storms cause kelp to wash ashore. During summer, however, this resource is not always readily available and farmed abalone are often starved for short periods. The aim of this research was to assess how periodic kelp starvation influences growth of the commercially grown abalone, Haliotis midae Linnaeus. Growth of grow-out abalone was monitored on a commercial abalone farm over a period of six months and consisted of 3 treatments with 2 replicates (n = ±250 abalone per replicate). The treatments were: Control (abalone always given more kelp than what they typically needed); Treatment 1 (abalone fed their weekly ration only once a week); Treatment 2 (abalone fed half their weekly ration every 3 and then 4 days respectively). While the data at first suggest that the control animals outperform the treatment animals, after undergoing an initial adjustment period to the new feeding regime, the treatment animals perform better. Weight gain and feed conversion efficiencies show that the treatment animals perform better overall. The control animals generally required much more feed to produce comparable increases in both length and weight compared to the treatment animals. This study has shown that periodic bouts of starvation is beneficial to Haliotis midae, allowing variable growth spurts when returned to full feed rations.Web of Scienc

Resurrection of the ancestral RH5 invasion ligand provides a molecular explanation for the origin of P. falciparum malaria in humans.

Many important infectious diseases are the result of zoonoses, in which pathogens that normally infect animals acquire mutations that enable the breaching of species barriers to permit the infection of humans. Our understanding of the molecular events that enable host switching are often limited, and yet this is a fundamentally important question. Plasmodium falciparum, the etiological agent of severe human malaria, evolved following a zoonotic transfer of parasites from gorillas. One gene-rh5-which encodes an essential ligand for the invasion of host erythrocytes, is suspected to have played a critical role in this host switch. Genome comparisons revealed an introgressed sequence in the ancestor of P. falciparum containing rh5, which likely allowed the ancestral parasites to infect both gorilla and human erythrocytes. To test this hypothesis, we resurrected the ancestral introgressed reticulocyte-binding protein homologue 5 (RH5) sequence and used quantitative protein interaction assays to demonstrate that this ancestral protein could bind the basigin receptor from both humans and gorillas. We also showed that this promiscuous receptor binding phenotype of RH5 was shared with the parasite clade that transferred its genome segment to the ancestor of P. falciparum, while the other lineages exhibit host-specific receptor binding, confirming the central importance of this introgression event for Plasmodium host switching. Finally, since its transfer to humans, P. falciparum, and also the RH5 ligand, have evolved a strong human specificity. We show that this subsequent restriction to humans can be attributed to a single amino acid mutation in the RH5 sequence. Our findings reveal a molecular pathway for the origin and evolution of human P. falciparum malaria and may inform molecular surveillance to predict future zoonoses