Synthesis, Characterization of Green Tea Stabilized Iron Nanoparticles and their Synergistic Effect on Polyaniline

This work reports the synthesis of polydisperse iron nanoparticles (FeNPs) stabilized on green tea polyphenol stabilizing and capping agents

Structural resolution of switchable states of a de novo peptide assembly

De novo protein design is advancing rapidly. However, most designs are for single states. Here we report a de novo designed peptide that forms multiple α-helical-bundle states that are accessible and interconvertible under the same conditions. Usually in such designs amphipathic α helices associate to form compact structures with consolidated hydrophobic cores. However, recent rational and computational designs have delivered open α-helical barrels with functionalisable cavities. By placing glycine judiciously in the helical interfaces of an α-helical barrel, we obtain both open and compact states in a single protein crystal. Molecular dynamics simulations indicate a free-energy landscape with multiple and interconverting states. Together, these findings suggest a frustrated system in which steric interactions that maintain the open barrel and the hydrophobic effect that drives complete collapse are traded-off. Indeed, addition of a hydrophobic co-solvent that can bind within the barrel affects the switch between the states both in silico and experimentally

Tillage and vegetative barrier effects on soil conservation and short-term economic benefits in the Central Kenya highlands

Minimum tillage and vegetative barriers can conserve soil and water resources in the steep-sloping highlands of East Africa but there has been little adoption by smallholder farmers. Soil conservation efficiency and short-term economic benefits provided by tillage and vegetative barriers were assessed over four cropping seasons to understand performance under local farming conditions. Minimum tillage was compared with regular tillage and vegetative barriers (leucaena and Napier) with no barriers. Maize and soybean yields were greater with than without vegetative barriers, except with Napier barriers when minimum tillage was practiced where strong root competition occured. Cumulatively for the four cropping seasons, Napier barriers with regular tillage conserved most soil (72%) followed by Napier with minimum tillage (53%). The least soil (1%) was conserved for minimum tillage without barriers and leucaena barriers were intermediate in decreasing soil erosion. The highest positive marginal rate of returns (MRRs) were realized under leucaena barriers with regular tillage (2.09) followed by Napier with regular tillage (1.32). Minimum tillage without barriers had the lowest positive MRRs (0.08). Future increase in the price of key inputs would have greater depressive effect on the MRRs of Napier barriers with regular tillage than leucaena barriers with regular tillage. Minimum tillage without barriers was inefficient in soil conservation particularly when rainfall was intense and had poor MRRs. Leucaena barriers conserved less soil than Napier barriers but were more economically attractive, demonstrating a clear trade-off between soil erosion that is likely to impact crop yields in the long-term and short-term economic benefits. Napier barriers with regular tillage present a win–win scenario due to efficient soil conservation and attractive economic returns provided future prices of labour and Napier cuttings remain stable

Minimum tillage and vegetative barrier effects on crop yields in relation to soil water content in the Central Kenya highlands

The sub-humid zone of Central Kenya is water deficient due to regular intra-seasonal dry spells that constrain rain-fed crop production. A study was initiated to investigate the effects of minimum tillage and vegetative barriers on soil and water conservation and crop yield. There were two tillage practices; minimum and regular tillage and two vegetative barriers; 'leucaena' consisting of leguminous trees (Leucaena trichandra). and 'Napier' consisting of Napier grass (Pennisetum purpureum) in addition to a control without barriers. Maize and soybean crops were planted in rotation in the terraces between the barriers. Soil moisture content was measured near the barriers and at the centre of the terraces. Vegetative barriers impeded run-off and controlled soil loss. There was a positive linear relationship between soil loss and rainfall for Napier grass barriers. For leucaena barriers, soil loss increased quadratically with rainfall. At the onset of rainfall, soil water content increased for all tillage and barrier practices. With more rainfall, soil water content increased marginally without barriers while with barriers there was continued soil water build-up. At the end of the wet period and across tillage practice, the soil contained 43% more water near leucaena barriers compared with no barriers and 20% more at the centre of the terrace. For Napier barriers, the soil water content was 60% more near barriers and 30% more at the centre of the terrace. Without barriers, the soil water content was 10% more with regular rather than minimum tillage. At the cessation of rainfall, soil water declined in all tillage and barrier treatments. At the centre of the terraces and across barriers, soil water reduction compared with no barriers was 10% less for minimum tillage and 24% more for regular tillage. Nearer barriers, the soil water reduction (relative to regular tillage without barriers) for leucaena barriers was 56% less with minimum tillage and 77% less with regular tillage. Conversely with Napier barriers, there was stronger water reduction with minimum (116%) than regular tillage (102%). At the centre of the terraces and across vegetative barriers, the upper soil layers (60 cm) independent of tillage practice. In contrast, Napier barriers extracted more water from the upper end of the profile, especially with minimum tillage. Napier barriers with minimum tillage suppressed maize row-grain yields (relative to regular tillage without barriers) by 26% over a distance of 311 along the barrier crop interface. Maize yield suppression for Napier barriers with regular tillage was less pronounced (occurring over a distance of 1.5 m) and improved maize crop performance at the centre of the terraces increased overall row grain yields by 14% relative to regular tillage without barriers. Soybean yields with Napier barriers were suppressed over a distance of 0.5 m in the barrier crop interface. Maize and soybean yield suppression with leucaena barriers for the different tillage practices was less pronounced, and improved crop performance at the centre of terraces consistently compensated for any yield reductions at the barrier crop interface. Between tillage and barriers treatments, the degree of yield suppression was related to the water use pattern of the vegetative barriers, and more severe with Napier than with leucaena barriers, particularly with minimum tillage. A possible strategy for successful introduction of a combination of minimum tillage and the vegetative barriers into water deficient highland regions would include leucaena barriers with minimum tillage due to less competition for water between barriers and companion crops. Napier barriers with minimum tillage do not combine well due to strong competition for available water between the barriers and crops, even when intensely harvested

Socio-ecological Niches for Minimum Tillage and Crop-residue Retention in Continuous Maize Cropping Systems in Smallholder Farms of Central Kenya

Soil fertility gradients develop on smallholder farms due to preferential allocation of inputs. A multi-location on-farm trial was conducted in Meru South, Central Kenya whose overall aim was to test minimum tillage and crop-residue retention practices in socio-ecological niches across heterogeneous smallholder farms. We identified three soil fertility classes together with the farmers, namely: good, medium, and poor. In each soil fertility class, two tillage (minimum or regular) and two crop residue (removed or retained) practices were tested for four consecutive seasons. Maize (Zea mays L.) grain yields in the good fields were above 2.5 Mg ha-1 across cropping seasons and cumulated yields were not influenced by tillage or crop residue management. The grain yields in the medium fields ranged between 1.3 and 5.4 Mg ha-1 and were greater with crop residue retention. In the poor fields, grain yield wa

De novo designed peptides for cellular delivery and subcellular localisation

Increasingly, it is possible to design peptide and protein assemblies de novo from first principles or computationally. This approach provides new routes to functional synthetic polypeptides, including designs to target and bind proteins of interest. Much of this work has been developed in vitro. Therefore, a challenge is to deliver de novo polypeptides efficiently to sites of action within cells. Here we describe the design, characterisation, intracellular delivery, and subcellular localisation of a de novo synthetic peptide system. This system comprises a dual-function basic peptide, programmed both for cell penetration and target binding, and a complementary acidic peptide that can be fused to proteins of interest and introduced into cells using synthetic DNA. The designs are characterised in vitro using biophysical methods and X-ray crystallography. The utility of the system for delivery into mammalian cells and subcellular targeting is demonstrated by marking organelles and actively engaging functional protein complexes