The need for magnetic resonance imaging (MRI) contrast agents with improved relaxivity maintains the development of new GdIII chelates as an intensive and demanding field of research. In this work, we introduce the new dimeric chelators bis{1,4,7,10‐tetraazacyclododecane‐1‐[(6‐amino)hexanoic]‐4,7,10‐triacetic acid}adipate [L2, bis(DOTA‐AHA)adipate] and bis{1,4,7,10‐tetraazacyclododecane‐1‐[(6‐amino)hexanoic]‐4,7,10‐triacetic acid}1,3‐phenyldiacetate [L3, bis(DOTA‐AHA)1,3‐phenyldiacetate], which are based on the bifunctional ligand 1,4,7,10‐tetraazacyclododecane‐1‐[(6‐amino)hexanoic]‐4,7,10‐triacetic acid (L1, DOTA‐AHA). Their GdIII chelates were studied by variable‐temperature 1H nuclear magnetic relaxation dispersion (NMRD) and 17O NMR spectroscopy to measure their relaxivities and the parameters that govern them. The rates of exchange of inner‐sphere water from the monomer GdL1 and from the two dinuclear chelates Gd2L2 and Gd2L3 are very similar (298kex ≈ 6.5 × 106 s–1) and slightly faster than that for [Gd(DOTA)H2O]– (298kex = 4.1 × 106 s–1). All three compounds form weakly bound aggregates with equilibrium constants 298K of 2.9, 15.6, and 14.6 for GdL1, Gd2L2, and Gd2L3, respectively. Even though the aggregates contain only 10 to 15 % of the total amount of GdIII ions, a marked increase in relaxivity between 30 and 100 MHz is observed. Furthermore, the distance between the two GdIII centers in the dinuclear compounds has been determined by double electron–electron resonance (DEER) spectroscopy experiments and by molecular modeling studies, which afforded comparable distances. The linkers between the chelating moieties allow GdIII–GdIII distances of ca. 3.0 nm for the completely stretched linker conformation and less than 1.9 nm for the conformation with the metal centers at a closer distance. These metal‐to‐metal distances by themselves cannot explain the considerably long tumbling times of the chelates in solution. Only a model consistent with some level of aggregation for the dinuclear chelates in aqueous solution could satisfactorily explain our results.

In this work, we report on a synthetic strategy using amphiphilic DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid)-based chelators bearing a variable-sized α-alkyl chain at one of the pendant acetate arms (from 6 to 14 carbon atoms), compatible with their covalent coupling to amine-bearing biomolecules. The amphiphilic behavior of the micelles-forming Ga(III) chelates (critical micellar concentration), their stability in blood serum and their lipophilicity (logP) were investigated. Biodistribution studies with the (67)Ga-labeled chelates were performed in Wistar rats, which showed a predominant liver uptake with almost no traces of the radiochelates in the body after 24 h.

Das Zusammenspiel zwischen biologischen Systemen hängt entscheidend von der Bidirektionalität des chemischen Informationsaustauschs ab. Die Implementierung eines derartigen Kommunikationsprotokolls für abiologische Systeme gelingt unter Nutzung von zwei Nanoschaltern, die beide unter Übertragung von Kupferionen in den Oxidationsstufen +I und +II jeweils als Empfänger und Sender eingesetzt werden können. Selbst bei mikromolaren Konzentrationen verläuft die Kommunikation in beide Richtungen mit t1/2=2–3 min beachtlich schnell. Die Metallionenübertragung löst einen Schwenk des Dreharms um 20 Å an beiden Schaltern und damit beachtliche geometrische und elektronische Veränderungen aus.

Invited for the cover of this issue are Dr. João Paulo André, Dr. Paula Margarida Ferreira, and Dr. André Fontes at the University of Minho, Braga, Portugal, and Prof. Lothar Helm at the EPFL, Lausanne, Switzerland. The cover image shows the general structure of PEGylated DOTA‐based GdIII chelates developed as potential contrast agents for magnetic resonance imaging. The rotating arrow illustrates the importance of the tumbling behavior of the chelates for their relaxivity.

The authors summarize the origin and evolution of the urban “island” of BelaVista in Porto, Portugal, since the 19th century. Despite local residents mobilizing in the wake of the revolution of April 25th 1974 in the context of the urban housing and design initiative (Local Ambulatory Support Service — Serviço de Apoio Ambulatório Local, SAAL), they were unable to renovate the crumbling neighbourhood. The Residents’ Association, resisting the onslaught of demolition strategies that were driven by real estate interests, eventually managed, with the support from a technical team of architects, social scientists and activists, to mobilize residents and ensure the political commitment of an independent parliamentary candidate in order to rehabilitate the “island” of Bela Vista. The project was also subsequently supported by the Councillors of Culture and Urbanism. Though various quantitative (survey) and qualitative (interviews, life stories) methods were applied in the study, the article highlights and expands on the action-research method opposite to positivist assumptions.