Biomedical subjects

Klaus Ensslin

Publications and source records attributed to Klaus Ensslin.

3 recordsLinked to original sources

PubMed2006

Phase coherence in the inelastic cotunneling regime.

Two quantum dots with tunable mutual tunnel coupling have been embedded in a two-terminal Aharonov-Bohm geometry. Aharonov-Bohm oscillations investigated in the cotunneling regime demonstrate coherent tunneling through nonresonant states. Visibilities of more than 0.8 are measured indicating that phase-coherent processes are involved in the elastic and inelastic cotunneling. An oscillation-phase change of pi is detected as a function of bias voltage at the inelastic cotunneling onset.

Journal Article↗

PubMed2003

Quantitative topographical analysis of nuclear pore complex function using scanning force microscopy.

The only avenue for macromolecular communication between nucleoplasmic and cytoplasmic compartments of the cell is through the nuclear pore complexes (NPCs), which are thus situated at a key location for the control of downstream transcriptional processes. The translocation of cargo through the NPC is mediated by transport receptors, which have the difficult task of making specific, yet transitory, interactions with the NPC in order to support efficient transport. In this report we have examined two stages in the translocation process using scanning force microscopy. We show that the initial docking of importin beta 45-462 is rapid and occurs at nanomolar concentrations. Later stages of transport involve translocation through the central lumen of the NPC and are thought to involve hydrophobic interactions between transport receptors and the NPC. Using calcium-depleted nuclear envelopes we argue that luminal regions of the NPC exhibit hydrophobic characteristics that are not observed for other regions of the NPC.

Animals↗

PubMed2003

Modulation of nuclear pore topology by transport modifiers.

The nuclear pore complex (NPC) represents the only pathway for macromolecular communication between the nuclear and cytoplasmic compartments of the cell. Nucleocytoplasmic transport requires the interaction of transport receptors with phenylalanine-glycine (FG)-repeats that line the transport pathway through the NPC. Here we examine the effects of transport receptors and amphipathic alcohols on NPC topology using scanning force microscopy. We show that transport receptors that irreversibly bind FG-repeats increase NPC vertical aspect, whereas transport receptors that weakly interact with FG-repeats increase NPC diameter. Interestingly, small polar alcohols likewise increase NPC diameter. These opposing effects agree with the inhibition or enhancement of nuclear transport, respectively, previously ascribed to these agents.

Active Transport, Cell Nucleus↗