Structure of very early protein folding intermediates: new insights through a variant of hydrogen exchange labelling

BACKGROUND: Hydrogen exchange labelling has been a key method in characterizing the structure of transient folding intermediates. In studies of several proteins, however, there has been clear spectroscopic evidence for partial folding of some kind at very early times, before any protection from exchange was measurable. These results, presumably a consequence of limited stability of specific backbone interactions, have made it difficult to assess the extent of native-like folding in the very early intermediates. We have used a variant of the labelling method to investigate marginally stable structures formed within the first few milliseconds of refolding of two such proteins, hen lysozyme and ubiquitin. RESULTS: In lysozyme, population of a subset of native-like secondary structures on this timescale is revealed, thus reconciling the exchange behaviour with circular dichroism measurements and confirming the significance of the rapidly formed embryonic structure as a foundation for the subsequent folding pathway. In the case of ubiquitin, by contrast, no significantly protective structure was detectable, suggesting that here secondary structural elements can be populated only marginally ahead of the major cooperative folding event; this was also supported by stopped-flow circular dichroism measurements. CONCLUSIONS: The hydrogen exchange approach can be extended to probe the formation of native-like structure formed in very early folding intermediates, even when the stability of specific interactions is marginal. In the case of lysozyme, this has provided a new window on an early stage of organization of the alpha-helical domain.     

Ethanol and Ambrosia Beetles in Douglas Fir Logs Exposed or Protected from Rain

Logs from the base of Douglas fir (Pseudotsuga menziesii) trees cut in October 1993 were randomly assigned to one of three treatment groups: (1) wet logs—cut from the fallen tree and left exposed to rain, (2) dry logs—cut from the fallen tree, placed on blocks, and protected from rain under a plastic tent, and (3) crown logs—left attached to the fallen tree with its branches intact and exposed to rain. The following May, ethanol concentrations were highest in the phloem and sapwood of wet logs (0.24 and 0.35 mol/g fresh wt, respectively). Ethanol concentrations in tissues from dry and crown logs were similar to each other (ranging from 0.002 to 0.03 mol/g fresh wt), but were significantly lower than in wet logs. It appears that rain absorbed by the outer bark of wet logs creates a barrier to gas exchange between living tissues and the atmosphere, which facilitates the development of hypoxic conditions necessary for ethanol synthesis and accumulation. Branches on crown logs exposed to rain help maintain low ethanol concentrations in the log tissues; we discuss several potential mechanisms to explain this response. By early September, the densities of Gnathothrichus spp. gallery entrance holes were high on wet logs (21.5/m²) and low on dry (2.5/m²) and crown logs (5.8/m²), indicating their preference for logs with higher ethanol concentrations. Protecting logs from rain will significantly reduce ethanol concentrations and the density of ambrosia beetle galleries. Leaving branches attached to logs will produce similar results, but its effectiveness may vary depending on the environmental conditions. Host selection by secondary scolytid beetles that use ethanol as a kairomone can be manipulated and possibly managed by controlling the production of ethanol in the host resource.     

Captured Kriegsmarine Enigma Documents at Bletchley Park

Abstract

The discovery of intercepts in the Japanese “Orange Translations” regarding the sinking of merchant ships (marus) bearing allied POWs led to the conclusion that the Joint Intelligence Center Pacific Ocean Area (JICPOA) gave latitudes and longitudes of these vessels to the Commander, Submarine Force, Pacific (ComSubPac) knowing that POWs would be killed. An examination of the “Orange Translations” reveals that most of the intercepts are from the Japanese Water Transport Code (2468) system, not the “Maru Code” (JN-11). The author concludes that while JICPOA provided ComSubPac with convoy coordinates, they were unaware of the presence of POWs on the marus.     

Creep crack growth behaviour of Type 316H steels and proposed modifications to standard testing and analysis methods

Tests have been performed on Type 316H stainless-steel compact tension specimens from four ex-service components and creep crack growth rates from these tests have been characterised using C^*$C^{*}$. Several modifications to standard creep crack growth testing and analysis methods have been proposed, including an improved approach for determining whether widespread creep conditions have been developed in the specimens. The observed behaviour has then been compared with existing creep crack growth rate data for this material. A change in cracking mode from ductile to brittle intergranular fracture was observed with increasing test duration. In addition, creep crack growth rates for several of the longest-term tests lie above an extrapolation of existing data from shorter-term tests. Models based on ductility exhaustion have been used to derive new equations for predicting creep crack growth rates in Type 316H steel at temperatures of 525 and 550 °C.     

Shaping futures: A dialogue on chemical engineering education

Engineering as a discipline, profession, practice, and area of study continues to add substantial value in an increasingly complex world. With continually evolving complexity around the planet, such as the need for massive energy transition, global health technologies, or sustainable food systems, how might engineering education practices and theory be considered within these rapid and necessary changes? This paper presents an experiment of co-creation through experiential reflection about the state of chemical engineering education. Four chemical engineering professors engaged in a dialogue, facilitated by a researcher in education, through collaborative and actionable research. This dialogue uncovered innovative possibilities, educational themes, experiences, and opportunities for others in the profession to consider. The process of dialogue also encouraged the development of an imaginative future sense-making, known as futuring, through a collective experience. The findings reveal instructive perspectives on the shape of chemical engineering education that should be of value not only to engineers, but also other professionals, practitioners, or those in various science, technology, and math fields.     

Ethanol and Water in Pseudotsuga menziesii and Pinus ponderosa Stumps

Douglas fir (Pseudotsuga menziesii), west of the Oregon Cascades, and ponderosa pine (Pinus ponderosa), east of the Cascades, were cut during the fall in conjunction with various forest management practices. Trees cut varied in size and age, and the stumps were exposed to disparate winter temperatures and precipitation patterns. Nevertheless, the stumps showed similar responses in their synthesis and accumulation of ethanol. The following spring, ethanol concentrations in above-ground tissues of both species ranged from 3 to 116 times higher than in their corresponding root tissues. We suggest that this difference results from the above-ground tissues being more hypoxic than roots because they were exposed to more water from precipitation and warmer temperatures. Ethanol concentrations in the above-ground tissues of ponderosa pine stumps were about two to six times higher than in Douglas fir, and root tissues from pine stumps usually contained more ethanol after anaerobic incubation than roots from Douglas fir. Ethanol and volatile terpenes released from stumps can attract various beetle species that not only vector root diseases, but can also damage or kill seedlings and saplings. Understanding the dynamics of ethanol synthesis and accumulation in stumps and slash might contribute to new alternatives for managing these insects.     

Ambrosia Beetle Host Selection Among Logs of Douglas Fir, Western Hemlock, and Western Red Cedar with Different Ethanol and α-Pinene Concentrations

Logs from Douglas fir, Pseudotsuga menziesii; western hemlock, Tsuga heterophylla; and western red cedar, Thuja plicata, were left in the forest through winter. In April, segments from these logs were removed and randomly positioned adjacent to one another allowing ambrosia beetles to select their preferred host. In early June the tissues of Douglas fir and western hemlock logs contained significantly higher ethanol concentrations and ambrosia beetle (Trypodendron lineatum and Gnathotrichus spp.) densities than logs of western red cedar. Low beetle attack densities in western red cedar were probably a consequence of low ethanol concentrations. Although Douglas fir tissues produced significantly higher ethanol concentrations than western hemlock, the beetles did not effectively discriminate between these two conifer species. Ethanol and α-pinene were significant covariates for the ambrosia beetle densities. α-Pinene concentrations were highest in the phloem of western red cedar, intermediate in Douglas fir, and nearly absent in western hemlock. α-Pinene did not synergize the beetle's response to ethanol or to ethanol + pheromone during host selection, and it may have functioned as a deterrent.     

The use of a low-viscosity epoxy resin in the preparation of undecalcified bone sections for light microscopy

A method using the Spurr low-viscosity epoxy resin medium for the preparation of Von Kossa impregnated undecalcified bone sections for light microscopy is described. The method gives high quality thin sections (0·6–1·0 μm) of cancellous bone and overcomes some of the difficulties experienced with other plastics. The procedure is relatively simple and is well suited for use in a routine diagnostic laboratory.     

CRACK GROWTH RATES DURING CREEP, FATIGUE AND CREEP-FATIGUE IN AN AUSTENITIC FEATURE WELD SPECIMEN

Abstract— Static creep crack growth tests and displacement controlled fatigue and creep-fatigue crack growth tests have been performed on austenitic feature weld specimens at 650°C. The creep-fatigue tests incorporated hold times of up to 96 h. During these tests, crack growth appeared to comprise cyclic and dwell components. Cyclic crack growth components were characterised by the fracture mechanics parameter K whilst creep crack growth contributions were correlated with C *. In order to determine K and C * for the non-standard feature weld specimen, elastic and elastic-plastic creep finite element analyses were conducted. Good correspondence is shown between the feature weld data and comparable data from compact tension specimen tests on similar materials. Equations obtained from the compact tension specimen results, which describe total crack growth rates as the sum of the cyclic and dwell contributions, are shown to adequately describe the features test results also. Furthermore, it is demonstrated that a reference stress approach can be used to estimate C * for the features specimens.