Regulation of Orai1/STIM1 mediated ICRAC by intracellular pH

Ca²⁺ release activated Ca²⁺-(CRAC) channels composed of two cellular proteins, Ca²⁺-sensing stromal interaction molecule 1 (STIM1) and pore-forming Orai1, are the main mediators of the Ca²⁺ entry pathway activated in response to depletion of intracellular Ca²⁺ stores. Previously it has been shown that the amplitude of CRAC current (ICRAC) strongly depends on extracellular and intracellular pH. Here we investigate the intracellular pH (pHi) dependence of ICRAC mediated by Orai1 and STIM1ectopically expressed in HEK293 cells. The results indicate that pHi affects not only the amplitude of the current, but also Ca²⁺ dependent gating of CRAC channels. Intracellular acidification changes the kinetics of ICRAC, introducing prominent re-activation component in the currents recorded in response to voltage steps to strongly negative potentials. ICRAC with similar kinetics can be observed at normal pHi if the expression levels of Orai1 are increased, relative to the expression levels of STIM1. Mutations in the STIM1 inactivation domain significantly diminish the dependence of ICRAC kinetics on pHi, but have no effect on pHi dependence of ICRAC amplitude, implying that more than one mechanism is involved in CRAC channel regulation by intracellular pH.D. Gavriliouk, N.R. Scrimgeour, S. Grigoryev, L. Ma, F.H. Zhou, G.J. Barritt, G.Y. Rychko

Integrable Circular Brane Model and Coulomb Charging at Large Conduction

We study a model of 2D QFT with boundary interaction, in which two-component massless Bose field is constrained to a circle at the boundary. We argue that this model is integrable at two values of the topological angle, $\theta =0$ and $\theta=\pi$. For $\theta=0$ we propose exact partition function in terms of solutions of ordinary linear differential equation. The circular brane model is equivalent to the model of quantum Brownian dynamics commonly used in describing the Coulomb charging in quantum dots, in the limit of small dimensionless resistance $g_0$ of the tunneling contact. Our proposal translates to partition function of this model at integer charge.Comment: 20 pages, minor change

Mitochondrial DNA signals of late glacial recolonization of Europe from near Eastern refugia

Human populations, along with those of many other species, are thought to have contracted into a number of refuge areas at the height of the last Ice Age. European populations are believed to be, to a large extent, the descendants of the inhabitants of these refugia, and some extant mtDNA lineages can be traced to refugia in Franco-Cantabria (haplogroups H1, H3, V, and U5b1), the Italian Peninsula (U5b3), and the East European Plain (U4 and U5a). Parts of the Near East, such as the Levant, were also continuously inhabited throughout the Last Glacial Maximum, but unlike western and eastern Europe, no archaeological or genetic evidence for Late Glacial expansions into Europe from the Near East has hitherto been discovered. Here we report, on the basis of an enlarged whole-genome mitochondrial database, that a substantial, perhaps predominant, signal from mitochondrial haplogroups J and T, previously thought to have spread primarily from the Near East into Europe with the Neolithic population, may in fact reflect dispersals during the Late Glacial period, ?19–12 thousand years (ka) ago.<br/

Notes on parafermionic QFT's with boundary interaction

The main result of these notes is an analytical expression for the partition function of the circular brane model for arbitrary values of the topological angle. The model has important applications in condensed matter physics. It is related to the dissipative rotator (Ambegaokar-Eckern-Schon) model and describes a ``weakly blocked'' quantum dot with an infinite number of tunneling channels under a finite gate voltage bias. A numerical check of the analytical solution by means of Monte Carlo simulations has been performed recently. To derive the main result we study the so-called boundary parafermionic sine-Gordon model. The latter is of certain interest to condensed matter applications, namely as a toy model for a point junction in the multichannel quantum wire.Comment: 55 pages, 6 figure