Voltammetric Reductions of Ring-Substituted Acetophenones. 1. Determination of an Electron-Transfer Mechanism Using Cyclic Voltammetry and Computer Modeling: The Formation and Fate of a Radical Anion

In a sophomore/junior-level experiment suitable for intermediate organic or instrumental analysis, ring-substituted acetophenones were electrochemically reduced to form radical anions that then decompose in a manner determined by the ring substituent. Cyclic voltammetry was used to identify the electron-transfer (ET) mechanism, which was an electron transfer followed by a chemical reaction (EC). The product of the reaction was often electroactive (ECE) in the potential window defined by the acetonitrile/Bu₄NPF₆ solvent/supporting electrolyte. Products of the following decomposition were estimated with computer modeling (DFT) to estimate the likelihood of various decomposition pathways. Selection of the ring substituent or switching potential (E_gw) allows the instructor to ask students to assign the mechanism for a single reduction or a complete ET mechanism, matching the difficulty of this experiment to the level of audience preparation.     

Dorsal horn-enriched genes identified by DNA microarray, in situ hybridization and immunohistochemistry

Background  

Neurons in the dorsal spinal cord play important roles in nociception and pain. These neurons receive input from peripheral sensory neurons and then transmit the signals to the brain, as well as receive and integrate descending control signals from the brain. Many molecules important for pain transmission have been demonstrated to be localized to the dorsal horn of the spinal cord. Further understanding of the molecular interactions and signaling pathways in the dorsal horn neurons will require a better knowledge of the molecular neuroanatomy in the dorsal spinal cord.     

A study of high transverse momentum π0's at ISR energies

We present a study of the transverse momentum spectrum of π⁰'s produced at c.m. angles θ = 90° and 53° in pp collisions at √s = 23.6, 30.8, 45.1, 53.2, and 62.9 GeV. The experiment was performed with a lead-glass detector. The data can be described with the usual parametrization $\text{p}{}_{\mathrm{<mtext>T</mtext>}}{}^{\mathrm{?n}}\text{?;(x}{}_{\mathrm{<mtext>T</mtext>}}\text{, θ)}$, with n = 7.2 ± 0.2. Comparison between the 90° and 53° data further indicates no appreciable dependence on θ, at least for x_T < 0.3. Two-particle inclusive cross sections for π⁰'s produced alongside are also presented. They are observed to have a dependence upon the transverse momentum of the dipion similar to that of single-particle cross sections and with the same value of n. Two-photon decays of η mesons are observed between 3 and 4 GeV/c transverse momentum with a production cross section half of that of π⁰.     

Confirmation of heptachlor epoxide and octachlor epoxide in milk via fused silica gas chromatography/negative ion chemical ionization mass spectrometry

A method for the mass spectral confirmation of heptachlor epoxide and octachlor epoxide in milk is described. The method includes the use of a 30 m × 0.25 mm DB-1701 fused silica gas chromatography column combined with negative ion chemical ionization mass spectrometry. By using this technique, confirmation of these compounds in milk can be performed at a level of 0.1 parts-per-million in milk fat.     

Deciphering radical transport in the large subunit of class I ribonucleotide reductase

Incorporation of 2,3,6-trifluorotyrosine (F(3)Y) and a rhenium bipyridine ([Re]) photooxidant into a peptide corresponding to the C-terminus of the β protein (βC19) of Escherichia coli ribonucleotide reductase (RNR) allows for the temporal monitoring of radical transport into the α2 subunit of RNR. Injection of the photogenerated F(3)Y radical from the [Re]-F(3)Y-βC19 peptide into the surface accessible Y731 of the α2 subunit is only possible when the second Y730 is present. With the Y-Y established, radical transport occurs with a rate constant of 3 × 10(5) s(-1). Point mutations that disrupt the Y-Y dyad shut down radical transport. The ability to obviate radical transport by disrupting the hydrogen bonding network of the amino acids composing the colinear proton-coupled electron transfer pathway in α2 suggests a finely tuned evolutionary adaptation of RNR to control the transport of radicals in this enzyme.     

Ground-Based Gamma Ray Astronomy

This paper is the write-up of a rapporteur talk given by the author at the 33rd International Cosmic Ray Conference in Rio de Janeiro, Brazil, in 2013. It attempts to summarize results and developments in ground-based gamma-ray observations and instrumentation from among the ～300 submissions to the gamma-ray sessions of the meeting. Satellite observations and theoretical developments were covered by a companion rapporteur (Stawarz, L., 33rd ICRC, Rio de Janeiro, Brazil, Rapporteur talk: Space-based Gamma-Ray Astronomy, 2013). Any review of this nature is unavoidably subjective and incomplete. Nevertheless, the article should provide a useful status report for those seeking an overview of this exciting and fast-moving field.