לוח שנה משולב

The detection of biological analytes or of biochemical processes by electrochemical methods requires in many cases the presence of a redox-active probe as part of the detection system. Here we report some recent results on the use of ferrocene as a redox label to study protein binding and enzymatic transformations. The focus of the lecture will be on the use of ferrocene-peptide conjugates and on a ferrocene-ATP conjugate. Applications presented here will demonstrate the versatility of these conjugates to study protein binding and enzymatic transformations.

Some people adapt well in the aftermath of traumatic events and are quickly able to inhibit their fear responses to trauma-associated stimuli. Fear responses, however, persist for longer periods of time for others to the point where they reach a pathological state. Why are some people more resilient to trauma while others are not? What are the neural substrates that underlie fear inhibition and extinction? Are these circuits deficient in patients with anxiety disorders? In my talk, I will focus on presenting translational data from the rat and human brains with the objective of trying to provide some preliminary answers to the above stated questions. Specifically, I will review human studies indicating that prefrontal areas homologous to those critical for extinction in rats. Furthermore, I will present some data to show that those brain regions in the rat brain appear to be structurally and functionally homologous to specific brain regions in the human brain. I will also show some data suggesting that these brain regions, the ventromedial prefrontal cortex (vmPFC) and the dorsal anterior cingulate cortex (dACC), appear to be deficient in patients with posttraumatic stress disorder (PTSD). I will present some structural and functional neuroimaging and psychophysiological studies done in our lab that focused on the neural mechanisms of fear extinction, particularly extinction recall and the contextual modulation of extinction recall. These recent studies suggest that: 1) human vmPFC is involved in the recall of extinction memory; 2) the size of the vmPFC might explain individual differences in the ability to modulate fear among humans; 3) hippocampal activation is observed during the recall of extinction memory in a context where extinction training took place but not in the initial conditioning context; 4) and the dACC may be involved in the expression of fear responses. I will also present recent neuroimaging and psychophysiological data from PTSD patients suggesting that 1) the retention of extinction memory is impaired in PTSD, and 2) the function of the vmPFC and dACC (measured by fMRI) appears to be impaired in PTSD in the context of fear extinction. Implications of these findings to the pathophysiology of anxiety disorders such as PTSD and current extinction-based behavioral therapies for anxiety disorders will be discussed.

In future microelectronic circuits a partial replacement of certain electronic functions by organic molecule junctions may become very likely. The realization of such concepts will benefit from a “monolithic” fabrication of nanoscale contacts on the same semiconductor wafer using current microelectronic process technology. We have investigated the fabrication of such nanogap electrode devices based on different layered semiconductor materials including Silicon-on-Insulator [1] and GaAs/AlGaAs heterostructures [2, 3].
In my presentation, I will focus on vertical nanogap electrode devices that comprise smooth metallic contact pairs situated at the sidewalls of pillar-like structures, with separations down to few nanometers. We have used these devices to study the electronic transport properties of 9-12 nm long, dithiolated oligo-phenylene-vinylene (OPV) “molecular wires” assembled onto the electrode gap from solution. A pronounced, non-linear current-voltage characteristic with a conductance gap of up to approx. ±1.5 V at low temperatures is observed. The magnitude of this gap can be correlated with the molecular structure at the termini of the molecules, in good agreement to model calculations [4].

References:
[1] S. Strobel, R. M. Hernández, A. G. Hansen, M. Tornow, J. Phys. Cond. Matt. (JPCM) 20, 374126 (2008)
[2] S. M. Luber, F. Zhang, S. Lingitz, A. G. Hansen, F. Scheliga, E. Thorn-Csányi, M. Bichler, M.Tornow, Small 3, 285 (2007)
[3] S. Strobel, S. Harrer, G. Penso Blanco, G. Scarpa, G. Abstreiter, P. Lugli, M. Tornow, Small 5, 579 (2009)
[4] R. Søndergaard, S. Strobel, E. Bundgaard, K. Norrman, A. G. Hansen, E. Albert, G. Csaba, P. Lugli, M. Tornow, F. C. Krebs, J. Mater. Chem. 19, 3899 (2009)