Dispersion for the Schr\"odinger Equation on Networks

In this paper we consider the Schr\"odinger equation on a network formed by a tree with the last generation of edges formed by infinite strips. We give an explicit description of the solution of the linear Schr\"odinger equation with constant coefficients. This allows us to prove dispersive estimates, which in turn are useful for solving the nonlinear Schr\"odinger equation. The proof extends also to the laminar case of positive step-function coefficients having a finite number of discontinuities.Comment: 16 pages, 2 figure

TriPer, an optical probe tuned to the endoplasmic reticulum tracks changes in luminal H2_2O2_2

$\textbf{Background:}$ The fate of hydrogen peroxide (H$_2$O$_2$) in the endoplasmic reticulum (ER) has been inferred indirectly from the activity of ER-localized thiol oxidases and peroxiredoxins, in vitro, and the consequences of their genetic manipulation, in vivo. Over the years hints have suggested that glutathione, puzzlingly abundant in the ER lumen, might have a role in reducing the heavy burden of H$_2$O$_2$ produced by the luminal enzymatic machinery for disulfide bond formation. However, limitations in existing organelle-targeted H$_2$O$_2$ probes have rendered them inert in the thiol-oxidizing ER, precluding experimental follow-up of glutathione’s role in ER H$_2$O$_2$ metabolism. $\textbf{Results:}$ Here we report on the development of TriPer, a vital optical probe sensitive to changes in the concentration of H$_2$O$_2$ in the thiol-oxidizing environment of the ER. Consistent with the hypothesized contribution of oxidative protein folding to H$_2$O$_2$ production, ER-localized TriPer detected an increase in the luminal H$_2$O$_2$ signal upon induction of pro-insulin (a disulfide-bonded protein of pancreatic β-cells), which was attenuated by the ectopic expression of catalase in the ER lumen. Interfering with glutathione production in the cytosol by buthionine sulfoximine (BSO) or enhancing its localized destruction by expression of the glutathione-degrading enzyme ChaC1 in the lumen of the ER further enhanced the luminal H$_2$O$_2$ signal and eroded β-cell viability. $\textbf{Conclusions:}$ A tri-cysteine system with a single peroxidatic thiol enables H$_2$O$_2$ detection in oxidizing milieux such as that of the ER. Tracking ER H$_2$O$_2$ in live pancreatic β-cells points to a role for glutathione in H$_2$O$_2$ turnover.This work is supported by grants from the Wellcome Trust (Wellcome 200848/Z/16/Z, WT: UNS18966), Fundação para a Ciência e Tecnologia, Portugal (PTDC/QUI/BIQ/119677/2010 and UID/BIM/04773/2013-CBMR), European Commission (EU FP7 Beta-Bat No: 277713), EPSRC (1503478), MRC (MR/K015850/1), and a Wellcome Trust Strategic Award for core facilities to the Cambridge Institute for Medical Research (Wellcome 100140). DR is a Wellcome Trust Principal Research Fellow

Retarded PDI diffusion and a reductive shift in poise of the calcium depleted endoplasmic reticulum

Background: Endoplasmic reticulum (ER) lumenal protein thiol redox balance resists dramatic variation in unfolded protein load imposed by diverse physiological challenges including compromise in the key upstream oxidases. Lumenal calcium depletion, incurred during normal cell signaling, stands out as a notable exception to this resilience, promoting a rapid and reversible shift towards a more reducing poise. Calcium depletion induced ER redox alterations are relevant to physiological conditions associated with calcium signaling, such as the response of pancreatic cells to secretagogues and neuronal activity. The core components of the ER redox machinery are well characterized; however, the molecular basis for the calcium-depletion induced shift in redox balance is presently obscure. Results: In vitro, the core machinery for generating disulfides, consisting of ERO1 and the oxidizing protein disulfide isomerase, PDI1A, was indifferent to variation in calcium concentration within the physiological range. However, ER calcium depletion in vivo led to a selective 2.5-fold decline in PDI1A mobility, whereas the mobility of the reducing PDI family member, ERdj5 was unaffected. In vivo, fluorescence resonance energy transfer measurements revealed that declining PDI1A mobility correlated with formation of a complex with the abundant ER chaperone calreticulin, whose mobility was also inhibited by calcium depletion and the calcium depletion-mediated reductive shift was attenuated in cells lacking calreticulin. Measurements with purified proteins confirmed that the PDI1A-calreticulin complex dissociated as Ca2+ concentrations approached those normally found in the ER lumen ([Ca2+] K-0.5max = 190 mu M). Conclusions: Our findings suggest that selective sequestration of PDI1A in a calcium depletion-mediated complex with the abundant chaperone calreticulin attenuates the effective concentration of this major lumenal thiol oxidant, providing a plausible and simple mechanism for the observed shift in ER lumenal redox poise upon physiological calcium depletion.Wellcome Trust [Wellcome 084812/Z/08/Z]; European Commission (EU FP7 Beta-Bat) [277713]; Fundacao para a Ciencia e Tecnologia, Portugal [PTDC/QUI-BIQ/119677/2010]info:eu-repo/semantics/publishedVersio

Official Discrepancies: Kosovo Independence and Western European Rhetoric

This article examines approaches and official discrepancies characterising Western European rhetoric with regard to the Kosovo status question. Since the early 1980s, Kosovo has been increasingly present in European debates, culminating with the 1999 international intervention in the region and subsequent talks about its final status. Although the Kosovo Albanians proclaimed independence in February 2008 and the majority of EU Member States decided to recognise Kosovo as an independent state, Western European rhetoric has been rather divided. This article shows that in addition to five EU members who have decided not to recognise Kosovo from the very beginning, and thus are powerful enough to affect its further progress, both locally and internationally, some of the recognisers, although having abandoned the policy of ‘standards before status’, have also struggled to develop full support for the province – a discrepancy that surely questions the overall Western support for Kosovo’s independence

Comparison of three methods for determination of protein concentration in lactic acid bacteria for proteomics studies

Finding the best method of cell lysis and extraction of protein from the lysed cells is the key step in detection and identification of extra- and intra-cellular proteins in all applications of proteomics. To develop an optimized protein extraction protocol, Enterococcus faecalis V583, Lactococcus lactis NIZO 0900 and Pediococcus pentosaceus OZF strains, respectively, belonging to each genus of Enterococcus, Lactococcus and Pediococcus were used as a representative cells in a study of lactic acid bacteria (LAB). This report covers the use and comparison of three different protein extraction methods including sonication, centrifugation and rupture by glass beads (FastPrep) to get a better understanding about which methods give better extract quality and higher amount of proteins when applied to one dimensional (1D) sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDSPAGE) and for subsequent analysis by two dimensional (2D)-PAGE. The results clearly showed that, all methods can be used to lyse LAB strains. However, a six fold greater amount of protein was obtained when FastPrep was applied to lyse LAB cells. Our results also indicate that, this fast and easy extraction method allows more spot-abundant polyacrylamide gels. More clear and consistent strips were detected by SDS-PAGE when proteins were extracted by FastPrep. These results testify to the suitability of FastPrep protein extraction protocols for 2D proteomic studies of representative strains of LAB.Key words: FastPrep, sonication, centrifugation, lactic acid bacteria (LAB)

Restoring the physiology of vitamin d receptor activation and the concept of selectivity

Abnormalities of bone mineral parameters (calcium, phosphate, vitamin D, and parathyroid hormone) are nearly always present in patients with chronic kidney disease (CKD). These typically consist of hypocalcemia, hyperphosphatemia, abnormalities of vitamin D metabolism, and secondary hyperparathyroidism, and are now defined as CKD mineral bone disorders (CKD-MBD). Currently, emerging evidence indicates that deficiencies in vitamin D receptor (VDR) activation play crucial roles in adversely affecting the cardiovascular health of CKD patients. VDRs are not restricted to skeletal tissue, but are instead widely expressed throughout the body at several sites, such as in cardiac tissue, vascular smooth muscle cells, endothelial cells, renal tissue, and cells of the immune system. Restoring the physiology and modulation of VDR activator levels results in correlative regulatory effects on mineral homeostasis, hypertension, cardiovascular disease, and vascular calcification, as well as a number of other endpoints in cardiac and renal pathology. Among the compounds available for treatment of CKD-MBD, paricalcitol is a selective VDR activator. The term \u2018selective\u2019 refers to paricalcitol being more selective in affecting VDR pathways in the parathyroid gland compared with bone and intestine. As such, paricalcitol\u2019s selectivity allows for a wider therapeutic window with effects beyond parathyroid hormone control and mineral management, and may explain, in part, the increased survival advantage with paricalcitol treatment