No abstract

The first metal-xenon compound with direct gold-xenon bonds is achieved by reduction of AuF(3) with elemental xenon. The square planar AuXe(4)2+ cation is established by a single-crystal structure determination, with a gold-xenon bond length of approximately 274 picometers. The bonding between gold and xenon is of the final sigma donor type, resulting in a charge of approximately 0.4 per xenon atom.

He received a master's degree in business administration from the University of Bayreuth, Germany. His research interests comprise big data analytics and information privacy. His work has been published in Electronic Markets.

The serotonin transporter (SERT) terminates neurotransmission by removing serotonin from the synaptic cleft. In addition, it is the site of action of antidepressants (which block the transporter) and of amphetamines (which induce substrate efflux). We explored the functional importance of the N terminus in mediating the action of amphetamines by focusing initially on the highly conserved threonine residue at position 81, a candidate site for phosphorylation by protein kinase C. Molecular dynamics simulations of the wild type SERT, compared with its mutations SERTT81A and SERTT81D, suggested structural changes in the inner vestibule indicative of an opening of the inner vestibule. Predictions from this model (e.g. the preferential accumulation of SERTT81A in the inward conformation, its reduced turnover number, and a larger distance between its N and C termini) were verified. Most importantly, SERTT81A (and the homologous mutations in noradrenaline and dopamine) failed to support amphetamine-induced efflux, and this was not remedied by aspartate at this position. Amphetamine-induced currents through SERTT81A were comparable with those through the wild type transporter. Both abundant Na+ entry and accumulation of SERTT81A in the inward facing conformation ought to favor amphetamine-induced efflux. Thus, we surmised that the N terminus must play a direct role in driving the transporter into a state that supports amphetamine-induced efflux. This hypothesis was verified by truncating the first 64 amino acids and by tethering the N terminus to an additional transmembrane helix. Either modification abolished amphetamine-induced efflux. We therefore conclude that the N terminus of monoamine transporters acts as a lever that sustains reverse transport.

This essay derives a schema for specifying design principles for information technology-based artifacts in sociotechnical systems. Design principles are used to specify design knowledge in an accessible form, but there is wide variation and lack of precision across views regarding their formulation. This variation is a sign of important issues that should be addressed, including a lack of attention to human actors and levels of complexity as well as differing views on causality, on the nature of the mechanisms used to achieve goals, and on the need for justificatory knowledge. The new schema includes the well-recognized elements of design principles, including goals in a specific context and the mechanisms to achieve the goal. In addition, the schema allows: (1) consideration of the varying roles of the human actors involved and the utility of design principles, (2) attending to the complexity of IT-based artifacts through decomposition, (3) distinction of the types of causation (i.e., deterministic versus probabilistic), (4) a variety of mechanisms in achieving aims, and (5) the optional definition of justificatory knowledge underlying the design principles. We illustrate the utility of the proposed schema by applying it to examples of published research.