Detection of sequential polyubiquitylation on a millisecond timescale

The pathway by which ubiquitin chains are generated on substrate through a cascade of enzymes consisting of an E1, E2 and E3 remains unclear. Multiple distinct models involving chain assembly on E2 or substrate have been proposed. However, the speed and complexity of the reaction have precluded direct experimental tests to distinguish between potential pathways. Here we introduce new theoretical and experimental methodologies to address both limitations. A quantitative framework based on product distribution predicts that the really interesting new gene (RING) E3 enzymes SCF^(Cdc4) and SCF^(β-TrCP) work with the E2 Cdc34 to build polyubiquitin chains on substrates by sequential transfers of single ubiquitins. Measurements with millisecond time resolution directly demonstrate that substrate polyubiquitylation proceeds sequentially. Our results present an unprecedented glimpse into the mechanism of RING ubiquitin ligases and illuminate the quantitative parameters that underlie the rate and pattern of ubiquitin chain assembly

Dynamics and calcium association to the N-terminal regulatory domain of human cardiac troponin C: a multiscale computational study.

Troponin C (TnC) is an important regulatory molecule in cardiomyocytes. Calcium binding to site II in TnC initiates a series of molecular events that result in muscle contraction. The most direct change upon Ca(2+) binding is an opening motion of the molecule that exposes a hydrophobic patch on the surface allowing for Troponin I to bind. Molecular dynamics simulations were used to elucidate the dynamics of this crucial protein in three different states: apo, Ca(2+)-bound, and Ca(2+)-TnI-bound. Dynamics between the states are compared, and the Ca(2+)-bound system is investigated for opening motions. On the basis of the simulations, NMR chemical shifts and order parameters are calculated and compared with experimental observables. Agreement indicates that the simulations sample the relevant dynamics of the system. Brownian dynamics simulations are used to investigate the calcium association of TnC. We find that calcium binding gives rise to correlative motions involving the EF hand and collective motions conducive of formation of the TnI-binding interface. We furthermore indicate the essential role of electrostatic steering in facilitating diffusion-limited binding of Ca(2+)

Eddy current testing of AGR fuel cladding

The scope of the presented study was to investigate feasibility of Eddy Current Testing (ECT) for detection in storage of inter-granular attack (IGA) cracking and general clad thinning of irradiated fuel cladding from Advanced Gas-cooled Reactors (AGR). The impact of the storage environment, particularly the effect of immersion in water compared to measurements in air, has also been investigated. A miniature EC probe was developed to induce eddy currents in a pin and to read out EC response. The transducer was robotically moved along the AGR pin and multi-frequency EC responses were acquired using a spectrum analyser. Main results of the experimental investigation are the following: even very small artificial defects such as short EDM notches of depth of 100μm produce distinguishable EC response; localised clad thinning of depth of 100μm and above produces considerable EC response levels; effect of water environment on the EC response is negligible; effect of anti-stacking grooves on the EC response is considerable

Controlling and characterizing microstructure in lithium-ion battery electrodes

Lithium-ion battery electrodes consist of a functional composite containing electroactive solid particles where redox reactions occur, conductive additives, a polymeric binder to provide mechanical support, and void regions filled with electrolyte during cell fabrication. While much of the focus in the battery materials field is on the chemistry of the electroactive materials that dictate the fundamental limits on the energy density of the cell, the morphology of the electroactive materials and the microstructure of the electrode also have a significant influence on the resulting electrochemical properties. An example of an electrode microstructure is shown in Figure 1. For certain operating conditions and electrode architectures the transport of ions through the electrode microstructure can limit the performance of the cell, which means that controlling and understanding the microstructure can open up battery designs that improve the performance and energy density at the cell level. This strategy should be broadly applicable to multiple battery materials. In this paper, we will describe progress in our lab in synthesizing battery electroactive particles of controllable morphology and processing these particles into composite electrodes. The size, shape, and polydispersity of the particles results in different packing in the electrode and thus different electrode microstructures, while the active material composition is kept constant. Characterization of these electrodes to elucidate microstructure effects on electrochemical performance will also be described, in particular how different transport limitations become relevant for different electrode geometries. Measurements of the tortuosity of the electrodes will be detailed, and the conditions will be determined where transport is limited either within the electroactive particles or through the electrode microstructure. The electrodes described in this paper are functional composites for energy storage applications which is of relevance to the topical theme of this conference. Please click Additional Files below to see the full abstract

Robotic ultrasonic testing of AGR fuel cladding

The purpose of the presented work was to undertake experimental trials to demonstrate the potential capabilities of an in-situ robotic ultrasonic scanning technique for measuring and monitoring loss of the cladding wall thickness in fuel pins of Advanced Gas-cooled Reactors (AGR) using inactive (i.e. non-radioactive) samples. AGR fuel pins are stainless steel cylindrical ribbed pipes of length circa of 1000 mm, inner diameter of the rod being circa 15 mm and wall thickness of circa 300µm. Spent AGR fuel pins are stored in a water pond and thus may be prone to corrosion and stresscorrosion cracking under adverse conditions. An ultrasonic immersion transducer with central frequency of 25MHz was used to measure wall thickness of the AGR fuel cladding using a frequency domain technique. Cylindrical ultrasonic scan of the samples 2 was performed using industrial robotic arm KUKA KR 5 arc HW. Also, very short (2.5mm long) and shallow (100µm in depth) crack-like defects were detected using time-domain technique

Repeated imitation makes human vocalizations more word-like

People have long pondered the evolution of language and the origin of words. Here, we investigate how conventional spoken words might emerge from imitations of environmental sounds. Does the repeated imitation of an environmental sound gradually give rise to more word-like forms? In what ways do these forms resemble the original sounds that motivated them (i.e. exhibit iconicity)? Participants played a version of the children's game ‘Telephone’. The first generation of participants imitated recognizable environmental sounds (e.g. glass breaking, water splashing). Subsequent generations imitated the previous generation of imitations for a maximum of eight generations. The results showed that the imitations became more stable and word-like, and later imitations were easier to learn as category labels. At the same time, even after eight generations, both spoken imitations and their written transcriptions could be matched above chance to the category of environmental sound that motivated them. These results show how repeated imitation can create progressively more word-like forms while continuing to retain a resemblance to the original sound that motivated them, and speak to the possible role of human vocal imitation in explaining the origins of at least some spoken words.</jats:p

Toward a model of multiple paths to language learning: response to commentaries

Language learning, while seemingly effortless for young learners, is a complex process involving many interacting pieces, both within the child and in their language-learning environments, which can result in unique language learning trajectories and outcomes. How does the brain adjust to or accommodate the myriad variations that occur during this developmental process. How does it adapt and change over time? In our review, we proposed that the timing, quantity, and quality of children's early language experiences, particularly during an early sensitive period for the acquisition of phonology, shape the establishment of neural phonological representations that are used to establish and support phonological working memory (PWM). The efficiency of the PWM system in turn, we argued, influences the acquisition and processing of more complex aspects of language. In brief, we proposed that experience modulates later language outcomes through its early effects on PWM. We supported this claim by reviewing research from several unique groups of language learners who experience delayed exposure to language (children with cochlear implants [CI] or internationally adopted [IA] children, and children with either impoverished [signing deaf children with hearing parents)] or enriched [bilingual] early language experiences). By comparing PWM and language outcomes in these groups, we sought to highlight general patterns in language development that emerge based on variation in early language exposure. Moving forward, we also proposed that the language acquisition patterns in these groups, and others, can be used to understand how variability in early language input might affect the neural systems supporting language development and how this might affect language learning itself

Abaloparatide, a PTH receptor agonist with homology to PTHrP, enhances callus bridging and biomechanical properties in rats with femoral fracture

Fractures typically heal via endochondral and intramembranous bone formation, which together form a callus that achieves union and biomechanical recovery. PTHrP, a PTH receptor agonist, plays an important physiological role in fracture healing as an endogenous stimulator of endochondral and intramembranous bone formation. Abaloparatide, a novel systemically‐administered osteoanabolic PTH receptor agonist that reduces fracture risk in women with postmenopausal osteoporosis, has 76% homology to PTHrP, suggesting it may have potential to improve fracture healing. To test this hypothesis, ninety‐six 12‐week‐old male rats underwent unilateral internally‐stabilized closed mid‐diaphyseal femoral fractures and were treated starting the next day with daily s.c. saline (Vehicle) or abaloparatide at 5 or 20 µg/kg/d for 4 or 6 weeks (16 rats/group/time point). Histomorphometry and histology analyses indicated that fracture calluses from the abaloparatide groups exhibited significantly greater total area, higher fluorescence scores indicating more newly‐formed bone, and higher fracture bridging scores versus Vehicle controls. Callus bridging score best correlated with callus cartilage score (r = 0.64) and fluorescence score (r = 0.67) at week 4, and callus area correlated with cartilage score (r = 0.60) and fluorescence score (r = 0.89) at Week 6. By micro‐CT, calluses from one or both abaloparatide groups had greater bone volume, bone volume fraction, bone mineral content, bone mineral density, and cross‐sectional area at both time points versus Vehicle controls. Destructive bending tests indicated greater callus maximum load and stiffness in one or both abaloparatide groups at both time points versus Vehicle controls. These results provide preliminary preclinical evidence for improved fracture healing with systemically‐administered abaloparatide. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop ResPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149317/1/jor24254_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149317/2/jor24254.pd