Probing metal ion binding and conformational properties of the colicin E9 endonuclease by electrospray ionization time-of-flight mass spectrometry

Nano-electrospray ionization time-of-flight mass spectrometry (ESI-MS) was used to study the conformational consequences of metal ion binding to the colicin E9 endonuclease (E9 DNase) by taking advantage of the unique capability of ESI-MS to allow simultaneous assessment of conformational heterogeneity and metal ion binding. Alterations of charge state distributions on metal ion binding/release were correlated with spectral changes observed in far- and near-UV circular dichroism (CD) and intrinsic tryptophan fluorescence. In addition, hydrogen/deuterium (H/D) exchange experiments were used to probe structural integrity. The present study shows that ESI-MS is sensitive to changes of the thermodynamic stability of E9 DNase as a result of metal ion binding/release in a manner consistent with that deduced from proteolysis and calorimetric experiments. Interestingly, acid-induced release of the metal ion from the E9 DNase causes dramatic conformational instability associated with a loss of fixed tertiary structure, but secondary structure is retained. Furthermore, ESI-MS enabled the direct observation of the noncovalent protein complex of E9 DNase bound to its cognate immunity protein Im9 in the presence and absence of Zn2+. Gas-phase dissociation experiments of the deuterium-labeled binary and ternary complexes revealed that metal ion binding, not Im9, results in a dramatic exchange protection of E9 DNase in the complex. In addition, our metal ion binding studies and gas-phase dissociation experiments of the ternary E9 DNase-Zn2+-Im9 complex have provided further evidence that electrostatic interactions govern the gas phase ion stability

Leukoencephalopathy upon disruption of the chloride channel ClC-2

ClC-2 is a broadly expressed plasma membrane chloride channel that is modulated by voltage, cell swelling, and pH. A human mutation leading to a heterozygous loss of ClC-2 has previously been reported to be associated with epilepsy, whereas the disruption of Clcn2 in mice led to testicular and retinal degeneration. We now show that the white matter of the brain and spinal cord of ClC-2 knock-out mice developed widespread vacuolation that progressed with age. Fluid-filled spaces appeared between myelin sheaths of the central but not the peripheral nervous system. Neuronal morphology, in contrast, seemed normal. Except for the previously reported blindness, neurological deficits were mild and included a decreased conduction velocity in neurons of the central auditory pathway. The heterozygous loss of ClC-2 had no detectable functional or morphological consequences. Neither heterozygous nor homozygous ClC-2 knock-out mice had lowered seizure thresholds. Sequencing of a large collection of human DNA and electrophysiological analysis showed that several ClC-2 sequence abnormalities previously found in patients with epilepsy most likely represent innocuous polymorphisms

Exploring differences between average and critical engineering changes : survey results from Denmark

Change or modification has always been a fundamental part of engineering design. Changes to a design are the rule and not the exception [Clark & Fujimoto 1991]. Engineering changes (ECs), as Jarratt et al. [2005] describe, are alterations made to parts, drawings or software that have already been released during the design process. Over the past decades, engineering change management has gained prominence in engineering design and product development literature, with a number of in-depth case studies (e.g. [Clarkson et al. 2004; Fricke et al. 2000; Giffin et al. 2009; Jarratt et al. 2010; Lindemann & Reichwald 1998; Loch & Terwiesch 1999; Vianello & Ahmed-Kristensen 2011]), industry surveys (e.g. [Deubzer et al. 2005; Huang & Mak 1999; Huang et al. 2003]), and reviews (e.g. [Ahmad et al. 2011; Jarratt et al. 2010; Wright 1997]). Researchers describe and analyse a number of aspects of changes, such as characterisations of changes, causes, initiators, objectives, effects, and potential strategies, and software support to anticipate and handle changes. Studying characterisations of changes, some investigate late engineering changes (e.g. [Coughlan 1992]), others describe strategies to detect avoidable and to cope with unavoidable changes [Fricke et al. 2000], yet others characterise initiated design changes and the associated emergent modifications according to their development over time and potential effects on implementation within the allotted amount of time forming ripple, blossom, or avalanche patterns [Eckert et al. 2004]. Whilst differing in terms of focus and research design what all studies have in common is differentiating between engineering changes for better understanding of patterns of change, ultimately better to manage engineering changes. In this paper, we aim to continue this line of investigation and - examine differences between average and critical changes according to results from a survey with industry participants, and thereby - explore as to what makes changes critical. In this paper, we focus our description on results from an industry survey. With this in mind, the remainder of the paper is structured as follows: Section 2 describes in brief what motivated criticality of engineering changes as the research focus of this paper and outlines the data acquisition and analysis procedure. We present results of this study in Section 3. Section 4 summarises contributions and concludes with suggestions for further work

Dirac-harmonic maps from degenerating spin surfaces I: the Neveu-Schwarz case

We study Dirac-harmonic maps from degenerating spin surfaces with uniformly bounded energy and show the so-called generalized energy identity in the case that the domain converges to a spin surface with only Neveu-Schwarz type nodes. We find condition that is both necessary and sufficient for the $W^{1,2} \times L^{4}$ modulo bubbles compactness of a sequence of such maps.Comment: 24 page

Surface Plasmon Polariton Graphene Photodetectors.

The combination of plasmonic nanoparticles and graphene enhances the responsivity and spectral selectivity of graphene-based photodetectors. However, the small area of the metal-graphene junction, where the induced electron-hole pairs separate, limits the photoactive region to submicron length scales. Here, we couple graphene with a plasmonic grating and exploit the resulting surface plasmon polaritons to deliver the collected photons to the junction region of a metal-graphene-metal photodetector. This gives a 400% enhancement of responsivity and a 1000% increase in photoactive length, combined with tunable spectral selectivity. The interference between surface plasmon polaritons and the incident wave introduces new functionalities, such as light flux attraction or repulsion from the contact edges, enabling the tailored design of the photodetector's spectral response. This architecture can also be used for surface plasmon biosensing with direct-electric-redout, eliminating the need of bulky optics

Analytical solutions to zeroth-order dispersion relations of a cylindrical metallic nanowire

Zeroth-order complex dispersion relations of a cylindrical metallic nanowire have been solved out analytically with approximate methods. The analytical solutions are valid for the sections of the dispersion relations whose frequencies are close to the Surface Plasmon frequency. The back bending of the Surface Plasmon-Polaritons(SPPs) can be well described by the analytical solutions, confirming that the back bending is originated from the metal Ohmic loss. The utility of the back bending point in the dispersion relation for the measurement of the metallic Ohimc loss has also been suggested.Comment: 6pages, 3figure

Search for CP violation in K0 -> 3 pi0 decays

Using data taken during the year 2000 with the NA48 detector at the CERN SPS, a search for the CP violating decay K_S -> 3 pi0 has been performed. From a fit to the lifetime distribution of about 4.9 million reconstructed K0/K0bar -> 3 pi0 decays, the CP violating amplitude eta_000 = A(K_S -> 3 pi0)/A(K_L -> 3 pi0) has been found to be Re(eta_000) = -0.002 +- 0.011 +- 0.015 and Im(eta_000) = -0.003 +- 0.013 +- 0.017. This corresponds to an upper limit on the branching fraction of Br(K_S -> 3 pi0) < 7.4 x 10^-7 at 90% confidence level. The result is used to improve knowledge of Re(epsilon) and the CPT violating quantity Im(delta) via the Bell-Steinberger relation.Comment: 18 pages, 7 figures, submitted to Phys. Lett.