A Nanoscale Molecular Switch Triggered by Thermal,Light, and Guest Perturbation

Bottoms up! A discrete metallo‐supramolecular nanoball (see picture), synthesized by using “bottom‐up” methodologies, uniquely undergoes a solvent‐sensitive, physically addressable electronic spin switching. The switching occurs by thermal, light, or solvent perturbation, where importantly it can be switched “on” or “off” by green or red laser irradiation, respectively.

     

Inside Cover: A Nanoscale Molecular Switch Triggered by Thermal,Light, and Guest Perturbation (Angew. Chem. Int. Ed. 14/2009)

Continuous switching between high‐spin and low‐spin magnetic states can be accomplished by irradiation with red and green laser light, respectively. In their Communication on page 2549 ff., S. R. Batten and co‐workers report a metallo‐supramolecule that undergoes spin crossover (SCO) switching induced by temperature change or light irradiation. The SCO behavior is also dependent on the presence and nature of intercalated solvent molecules within the porous crystal structure.

     

Systems-based decomposition schemes for the approximate solution of multi-term fractional differential equations

We give a comparison of the efficiency of three alternative decomposition schemes for the approximate solution of multi-term fractional differential equations using the Caputo form of the fractional derivative. The schemes we compare are based on conversion of the original problem into a system of equations. We review alternative approaches and consider how the most appropriate numerical scheme may be chosen to solve a particular equation.     

Illuminating the BOLD signal: combined fMRI-fNIRS studies

Functional magnetic resonance imaging (fMRI) is currently combined with electrophysiological methods to identify the relationship between neuronal activity and the blood oxygenation level-dependent (BOLD) signal. Several processes like neuronal activity, synaptic activity, vascular dilation, blood volume and oxygenation changes underlie both response modalities, that is, the electrophysiological signal and the vascular response. However, accessing single process relationships is absolutely mandatory when aiming at a deeper understanding of neurovascular coupling and necessitates studies on the individual building blocks of the vascular response. Combined fMRI and functional near-infrared spectroscopy studies have been performed to validate the correlation of the BOLD signal to the hemodynamic changes in the brain. Here we review the current status of the integration of both technologies and judge these studies in the light of recent findings on neurovascular coupling.     

End effects influence short model peptide conformation

Previously, we derived a P(II) propensity scale using N- and C-terminally blocked host-guest peptide model AcGGXGGNH(2) (X ≠ Gly) and concluded that P(II) represents a dominant conformation in the majority of this series of 19 peptides (Shi et al. Proc. Natl. Acad. Sci. U.S.A. 2005, 102, 17964-17968). Recently, Schweitzer-Stenner and co-workers examined a series of eight short host-guest tripeptides with the sequence GXG (X = A, V, F, S, E, L, M, and K) in which both N- and C-ends were unblocked and reported major differences in P(II) content for F, V, and S compared to our scale (Hagarman et al. J. Am. Chem. Soc. 2010, 132, 540-551). We have investigated four representative amino acids (X = A, V, F, and S) in three series of peptides (GXG, AcGXGNH(2), and AcGGXGGNH(2)) as a function of pH in this study. Our data show that P(II) content in the GXG series (X = A, V, F, and S) is pH-dependent and that the conformations of each amino acid differ markedly between the GXG and AcGXGNH(2)/AcGGXGGNH(2) series. Our results indicate that P(II) scales are sequence and context dependent and the presence of proximal charged end groups exerts a strong effect on P(II) population in short model peptides.     

Influence of Mg^2＋ on Initial Stages of CaCO3 Scale Formed on Metal Surface

Magnesium ions, which exist in formation water and injection water under downhole conditions in the oil and gas production industry, are a key determinant in the CaCO3 scale formation. Many studies have focused their attention on the effect of magnesium on the kinetics, the morphology and the content of Mg in the Ca-CO3 scale. Little attention has been paid to the effect of Mg^2 on the initial stages of CaCO3 formation on a metal surface. In this study, an electrochemical technique was used to study the influence of Mg^2 on the ini-tial stages of CaCO3 scale formed on a metal surface. With this electrochemical technique, the reduction of the dissolved oxygen in an analysis solution is considered on the surface of a rotating disk electrode (RDE) un-der potentiostatic control. The rate of oxygen reduction on the surface of the RDE enables the extent of sur-face coverage of scale to be assessed. With this electrochemical technique, a new insight into the effect of Mg^2 on CaCO3 scale formed on a metal surface is given.