Single active-site mutants are sufficient to enhance serine:pyruvate α-transaminase activity in an ω-transaminase

We have analysed the natural evolution of transaminase structure and sequence between an α-transaminase serine-pyruvate aminotransferase, and an ω-transaminase from Chromobacterium violaceum with <20% sequence identity, and identified the active-site regions which are least conserved structurally. We also show that these structural changes correlate strongly with transaminase substrate specificity during evolution and therefore might normally be presumed to be essential determinants of substrate specificity. However, key residues are often conserved spatially during evolution and yet come from within a different region of the sequence via structural reorganisations. Here we also show that α-transaminase-type serine-pyruvate aminotransferase activity, can be engineered into the CV2025 ω-transaminase scaffold with any one of many possible single point mutations at three key positions, without the requirement for significant backbone remodeling, or repositioning of the residue from a different region of sequence. This finding has significant implications for enzyme redesign in which solutions to substrate specificity changes may be found that are significantly more efficient than by engineering in all sequence and structure determinants identified by correlation to substrate specificity. This article is protected by copyright. All rights reserved

Airborne electromagnetic imaging of discontinuous permafrost

The evolution of permafrost in cold regions is inextricably connected to hydrogeologic processes, climate, and ecosystems. Permafrost thawing has been linked to changes in wetland and lake areas, alteration of the groundwater contribution to stream flow, carbon release, and increased fire frequency. But detailed knowledge about the dynamic state of permafrost in relation to surface and groundwater systems remains an enigma. Here, we present the results of a pioneering ~1,800 line-kilometer airborne electromagnetic survey that shows sediments deposited over the past ~4 million years and the configuration of permafrost to depths of ~100 meters in the Yukon Flats area near Fort Yukon, Alaska. The Yukon Flats is near the boundary between continuous permafrost to the north and discontinuous permafrost to the south, making it an important location for examining permafrost dynamics. Our results not only provide a detailed snapshot of the present-day configuration of permafrost, but they also expose previously unseen details about potential surface – groundwater connections and the thermal legacy of surface water features that has been recorded in the permafrost over the past 1,000 years. This work will be a critical baseline for future permafrost studies aimed at exploring the connections between hydrogeologic, climatic, and ecological processes, and has significant implications for the stewardship of Arctic environments

Induction of autophagy by spermidine promotes longevity.

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Admixtures effectiveness in mortars in the presence of calcareous fly ash

This paper presents a study on the influence of various admixtures (SP, PL, AE, R, ACC) on rheological properties, air content, setting time and heat of hydration of mortars with the addition of calcareous fly ash. Rheological parameters of mortars were determined using a rheometer Viskomat NT. The content of air in the mortar was determined using pressure method according to PN-EN 413-2 and initial setting time was specified according to PN-EN 196-3. The study on the heat of hydration was based on an isothermal microcalorimeter TamAir. The calcareous fly ash presence usually exerts negative influence on additives effectiveness. Activating the ash by grinding improves the additives efficiency (e.g. plasticizers, superplasticizers). The influence of calcareous fly ash on effectiveness of the additives is dependent not only on its type, but also on the type of admixture. The choice of compatible admixture should be made experimentally, taking into account the presence of calcareous fly ash

Study of Gold, Copper and Nickel Adsorption, from their Acidic Chloride Solutions, Onto Activated Carbon

In this paper, a simple and effective method for gold recovery is described. The paper describes a way to recover gold onto activated carbon from a synthetic solution of gold(III) chloride. The method can also be used on nickel(II) as well as copper(II) chloride of where the metal ion ratios are comparable to the metal ratios found in some electronic waste. With the use of activated carbon in the process of electrolyte purification it is possible to selectively remove gold in metallic form from the solution. XPS studies have confirmed that metallic gold is present on the carbon surface. A spectrophotometric method was used to determine the concentration of Au(III) in the solution. Different concentration of nickel(II) as well as copper(II) were investigated. In all cases, adsorption and reduction of Au(III) to the metallic form was observed

Electrochemical Method of Copper Powder Synthesis on Rotating Electrode in the Presence of Surfactants

This paper presents a method of synthesizing copper powders by electrochemical method with the use of a rotating working electrode. The influence of the rotation speed of the working electrode, the current density, the concentration of copper ions, and the addition of ethylene glycol on the shape, size, and size distribution of the obtained powders were investigated. Properties of the synthesized powders were characterized by scanning electron microscopy (SEM) and X-ray powder diffractometry (XRD). It has been shown that it is possible to obtain copper powders with a size of 1 µm by an electrochemical method using the rotary cathode, in sulphate bath with addition of ethylene glycol as a surfactant. Increasing current density causes a decrease in the average size of the obtained powder particles. The addition of 2.5% of ethylene glycol prevents the formation of dendritic powders. The change in the concentration of copper ions in the range from 0.01 to 0.15 mol/dm3 in the electrolyte did not show any significant effect on the size of obtained particles. However, higher concentrations of copper limiting the presence of dendritic-shape particles. Changing the speed of rotation of the electrode affects both the size and the shape of synthesized copper powder. For the rotational speed of the electrode of 115 rpm, the obtained powders have a size distribution in the range of 0-3 µm and an average particle size of 1 µm. The particles had a polygonal shape with an agglomeration tendency