Influence of V5/6-His Tag on the Properties of Gap Junction Channels Composed of Connexin43, Connexin40 or Connexin45

HeLa cells expressing wild-type connexin43, connexin40 or connexin45 and connexins fused with a V5/6-His tag to the carboxyl terminus (CT) domain (Cx43-tag, Cx40-tag, Cx45-tag) were used to study connexin expression and the electrical properties of gap junction channels. Immunoblots and immunolabeling indicated that tagged connexins are synthesized and targeted to gap junctions in a similar manner to their wild-type counterparts. Voltage-clamp experiments on cell pairs revealed that tagged connexins form functional channels. Comparison of multichannel and single-channel conductances indicates that tagging reduces the number of operational channels, implying interference with hemichannel trafficking, docking and/or channel opening. Tagging provoked connexin-specific effects on multichannel and single-channel properties. The Cx43-tag was most affected and the Cx45-tag, least. The modifications included (1) V j-sensitive gating of I j (V j, gap junction voltage; I j, gap junction current), (2) contribution and (3) kinetics of I j deactivation and (4) single-channel conductance. The first three reflect alterations of fast V j gating. Hence, they may be caused by structural and/or electrical changes on the CT that interact with domains of the amino terminus and cytoplasmic loop. The fourth reflects alterations of the ion-conducting pathway. Conceivably, mutations at sites remote from the channel pore, e.g., 6-His-tagged CT, affect protein conformation and thus modify channel properties indirectly. Hence, V5/6-His tagging of connexins is a useful tool for expression studies in vivo. However, it should not be ignored that it introduces connexin-dependent changes in both expression level and electrophysiological properties.

The Fundamental Gap For Hyperbolic Triangles

In 1983, M. van den Berg made his Fundamental Gap Conjecture about the difference between the first two Dirichlet eigenvalues (the fundamental gap) of any convex domain in the Euclidean plane. Recently, progress has been made in the case where the domains are polygons and, in particular, triangles. We examine the conjecture for triangles in hyperbolic geometry, though we seek an for an upper bound for the fundamental gap rather than a lower bound.

A Historical-Institutional Study of the Welfare Systems in the United States and Sweden: Net Social Wage Approach

In this study I first look at the historical developments of the welfare systems in Sweden and the United States to understand why these countries have produced two distinct systems over the years. After understanding their historical context I turn to the question of the relationship between the welfare system and economic growth. Policy makers and the mainstream media commonly cite the critique that through government deficit and public debt, welfare systems are a drag on the economy. By calculating the net social wage, the difference in taxes paid and benefits received by workers, I test this hypothesis to see if welfare systems are self-financed by the workers. My findings demonstrate that the net social wage has been negative in the U.S. from 1962 to the early 2000s and in Sweden from 1965 to 2012. This shows that the welfare systems are entirely self-financed by the workers for the full period in Sweden and until the recent financial crisis in the U.S.