Modification of the conductance of single fullerene molecules by endohedral doping

We use scanning tunneling microscopy to establish controlled contacts to single molecules of endohedrally doped Ce(2)@C(80) fullerenes with C(60) as a reference. The stability of the experimental setup allows for the determination of the conductance of Ce(2)@C(80) relative to the conductance of C(60). The endohedral doping reduces the conductance of Ce(2)@C(80) by a factor of about five with respect to C(60). Ab initio calculations show that the reason for this reduced conductance is the absence of electron orbitals delocalized over the cage of Ce(2)@C(80) in the energy window of the conductance measurement. (C) 2009 American Institute of Physics. (doi:10.1063/1.3236529

Heart Rate Variability Characteristics in Sedentary Postmenopausal Women Following Six Months of Exercise Training: The DREW Study

Article on heart rate variability characteristics in sedentary postmenopausal women following six months of exercise training

Engineering the Melanocortin-4 Receptor to Control Constitutive and Ligand-Mediated Gs Signaling In Vivo

The molecular and functional diversity of G protein–coupled receptors is essential to many physiological processes. However, this diversity presents a significant challenge to understanding the G protein–mediated signaling events that underlie a specific physiological response. To increase our understanding of these processes, we sought to gain control of the timing and specificity of Gs signaling in vivo. We used naturally occurring human mutations to develop two Gs-coupled engineered receptors that respond solely to a synthetic ligand (RASSLs). Our Gs-coupled RASSLs are based on the melanocortin-4 receptor, a centrally expressed receptor that plays an important role in the regulation of body weight. These RASSLs are not activated by the endogenous hormone α-melanocyte-stimulating hormone but respond potently to a selective synthetic ligand, tetrahydroisoquinoline. The RASSL variants reported here differ in their intrinsic basal activities, allowing the separation of the effects of basal signaling from ligand-mediated activation of the Gs pathway in vivo. These RASSLs can be used to activate Gs signaling in any tissue, but would be particularly useful for analyzing downstream events that mediate body weight regulation in mice. Our study also demonstrates the use of human genetic variation for protein engineering

Scanning tunneling microscopy contrast in lateral Ge-Si nanostructures on Si(111)-3x3-Bi

We investigate the origin of scanning tunneling microscope (STM) contrast in lateral Ge-Si nanostructures prepared on the Si(111)-root 3x root 3-Bi surface [M. Kawamura, N. Paul, V. Cherepanov, and B. Voigtlander, Phys. Rev. Lett. 91, 096102 (2003)]. At low sample bias, the voltage-dependent apparent height difference between Si-and Ge-terminated areas in STM images corresponds exceptionally well to the difference in voltage-integrated scanning tunneling spectroscopy (STS) curves measured in Si-and Ge-terminated areas. The STS curves and the STM contrast reflect both differences in local density of states and in tip-induced effects in Si- and Ge-terminated areas. At higher bias voltage, the tunneling into unoccupied states on Ge-terminated areas is strongly influenced by lowering of the local height of the tunneling barrier with respect to Si. The lowering of the local tunneling barrier height vanishes for the occupied states and can be traced back to different tip-induced band bending on Si-and Ge-terminated areas