Interpenetrated Cage Structures Frank, Marina; Johnstone, Mark D.; Clever, Guido H.
Chemistry : a European journal,
September 26, 2016, Letnik:
22, Številka:
40
Journal Article
Recenzirano
This Review covers design strategies, synthetic challenges, host–guest chemistry, and functional properties of interlocked supramolecular cages. Some dynamic covalent organic structures are ...discussed, as are selected examples of interpenetration in metal–organic frameworks, but the main focus is on discrete coordination architectures, that is, metal‐mediated dimers. Factors leading to interpenetration, such as geometry, flexibility and chemical makeup of the ligands, coordination environment, solvent effects, and selection of suitable counter anions and guest molecules, are discussed. In particular, banana‐shaped bis‐pyridyl ligands together with square‐planar metal cations have proven to be suitable building blocks for the construction of interpenetrated double‐cages obeying the formula M4L8. The peculiar topology of these double‐cages results in a linear arrangement of three mechanically coupled pockets. This allows for the implementation of interesting guest encapsulation effects such as allosteric binding and template‐controlled selectivity. In stimuli‐responsive systems, anionic triggers can toggle the binding of neutral guests or even induce complete structural conversions. The increasing structural and functional complexity in this class of self‐assembled hosts promises the construction of intelligent receptors, novel catalytic systems, and functional materials.
Entangling alliances: Interlocked supramolecular cages represent a rapidly growing compound class whose preparation has evolved from serendipitous findings to the application of rational design strategies. Owing to their topological peculiarities, such self‐assemblies show interesting properties as receptors (tunable selectivity, allosteric regulation and switching) and structural motifs for adaptive materials.
A strategy to implement four members of the classic coal‐tar dye family, Michler's ketone, methylene blue, rhodamine B, and crystal violet, into Pd2L4 self‐assemblies is introduced. Chromophores were ...incorporated into bis‐monodentate ligands using piperazine linkers that allow to retain the auxochromic dialkyl amine functionalities required for intense colors deep in the visible spectrum. Upon palladium coordination, ligands with pyridine donors form lantern‐shaped dinuclear cages while quinoline donors lead to strongly twisted Pd2L4 helicates in solution. In one case, single crystal X‐ray diffraction revealed rearrangement to a Pd3L6 ring structure in the solid state. For nine examined derivatives, showing colors from yellow to deep violet, CD spectroscopy discloses different degrees of chiral induction by an enantiomerically pure guest. Ion mobility mass spectrometry allows to distinguish two binding modes. Self‐assemblies based on this new ligand class promise application in chiroptical recognition, photo‐redox catalysis and optical materials.
A family of classic organic dyes, known since the advent of modern chemistry, was integrated into 3‐dimensional, self‐assembled nano‐objects via a novel piperazine‐based linker strategy that conserves the auxochromic substituents. The dynamic nature of the lantern‐shaped cages and helicates allows to recognize enantiopure guests via chirality transfer to the host, detected by circular dichroism response far in the visible region.
Photon-powered charge separation is achieved in a supramolecular architecture based on the dense packing of functional building blocks. Therefore, self-assembled dimers of interpenetrated ...coordination cages consisting of redoxactive chromophors were synthesized in a single assembly step starting from easily accessible ligands and Pd(II) cations. Two backbones consisting of electron rich phenothiazine (PTZ) and electron deficient anthraquinone (ANQ) were used to assemble either homo-octameric or mixed-ligand double cages. The electrochemical and spectroscopic properties of the pure cages, mixtures of donor and acceptor cages and the mixed-ligand cages were compared by steady-state UV–vis and transient absorption spectroscopy, supported by cyclic voltammetry and spectroelectrochemistry. Only the mixed-ligand cages, allowing close intra-assembly communication between the donors and acceptors, showed the evolution of characteristic PTZ radical cation and ANQ radical anion features upon excitation in the transient spectra. In contrast, excitation of the mixtures of the homo-octameric donor and acceptor cages in solution did not lead to any signs of electron transfer. Densely packed photo- and redox-functional self-assemblies promise molecular-level control over the morphology of the charge separation layer in future photovoltaic applications.
A person's first language (L1) affects the way they acquire speech in a second language (L2). However, we know relatively little about the role different varieties of the L1 play in the acquisition ...of L2 speech. This study focuses on German (L1) learners of English (L2) and asks whether the degree to which German speakers distinguish between the two vowels /eː/ and /ɛː/ in their L1 has an impact on how well these individuals identify /æ/ and discriminate between the two English vowels /ɛ/ and /æ/. These two English vowels differ in both vowel quality and duration (/æ/ is longer than /ɛ/). We report on an identification and a discrimination experiment. In the first study, participants heard a sound file and were asked to indicate whether they heard "pen" or "pan" (or "pedal" or "paddle"). The stimuli differed from each other in terms of both vowel quality (11 steps on a spectral continuum from an extreme /æ/ to an extreme /ɛ/) and duration (short, middle, long). In the second study, participants had to signal whether two sound files they were exposed to differed from each other. We modeled the percentage of /æ/ ("pan," "paddle") selection (identification task only, binomial logistic regression), accuracy (discrimination task only, binomial logistic regression), and reaction time (identification and discrimination tasks, linear mixed effects models) by implementing the German Pillai score as a measure of vowel overlap in our analysis. Each participant has an individual Pillai score, which ranges from 0 (= merger of L1 German /eː/ and /ɛː/) to 1 (=maintenance of the contrast between L1 German /eː/ and /ɛː/) and had been established, prior to the perception experiments reported here, in a production study. Although the findings from the discrimination study remain inconclusive, the results from the identification test support the hypothesis that maintaining the vowel contrast in the L1 German leads to a more native-like identification of /æ/ in L2 English. We conclude that sociolinguistic variation in someone's L1 can affect L2 acquisition.
Denervation of skeletal muscles induces atrophy, preceded by changes in sarcolemma permeability of causes not yet completely understood. Here, we show that denervation-induced Evans blue dye uptake ...in vivo of fast, but not slow, myofibers was acutely inhibited by connexin (Cx) hemichannel/pannexin1 (Panx1) channel and purinergic ionotropic P2X7 receptor (P2X7R) blockers. Denervated myofibers showed up-regulation of Panx1 and de novo expression of Cx39, Cx43, and Cx45 hemichannels as well as P2X7Rs and transient receptor potential subfamily V, member 2, channels, all of which are permeable to small molecules. The sarcolemma of freshly isolated WT myofibers from denervated muscles also showed high hemichannel-mediated permeability that was slightly reduced by blockade of Panx1 channels or the lack of Panx1 expression, but was completely inhibited by Cx hemichannel or P2X7R blockers, as well as by degradation of extracellular ATP. However, inhibition of transient receptor potential subfamily V, member 2, channels had no significant effect on membrane permeability. Moreover, activation of the transcription factor NFκB and higher mRNA levels of proinflammatory cytokines (TNF-α and IL-1β) were found in denervated WT but not Cx43/Cx45-deficient muscles. The atrophy observed after 7 d of denervation was drastically reduced in Cx43/Cx45-deficient but not Panx1-deficient muscles. Therefore, expression of Cx hemichannels and P2X7R promotes a feed-forward mechanism activated by extracellular ATP, most likely released through hemichannels, that activates the inflammasome. Consequently, Cx hemichannels are potential targets for new therapeutic agents to prevent or reduce muscle atrophy induced by denervation of diverse etiologies.
A breath of fresh air is sufficient for the eightfold S‐monooxygenation of an interpenetrated double cage based on eight phenothiazine ligands and four square‐planar‐coordinated PdII cations. Besides ...these two cages, which were both characterized by X‐ray crystallography, an eightfold S‐dioxygenated double‐cage was obtained under harsher oxidation conditions.
Connexins have been implicated in the regulation of precursor cell migration and proliferation during embryonic development of the mammalian brain. However, their function in postnatal neurogenesis ...is unclear. Here we demonstrate that connexin (Cx) 45 is expressed in transit-amplifying cells and neuroblasts in the postnatal subventricular zone (SVZ) and modulated the proliferation of SVZ-derived precursor cells in vivo. Thus, overexpression of Cx45 by retroviral injections increased the proliferation of Mash-1–positive transit-amplifying precursor cells in the SVZ. Conversely, conditional deletion of Cx45 in precursor cells decreased proliferation. Finally, we established that Cx45 positively influences cell cycle reentry via ATP signaling that involves intracellular calcium stores and ERK1/2 signaling.
A solvent‐free multicomponent protocol for the rapid (< 30 min) synthesis of pyridyl‐functionalised 5polynorbornane ligands is described in which both 1,3‐dipolar cycloaddition and imide formation ...occur. The ligands produced by this approach have been incorporated into new Pd and Pt M1L2 chelate complexes as well as an M2L4 cage as elucidated from NMR spectroscopy, ESI‐MS and computational data.
Eight new bonds are formed in this new multicomponent method for the rapid synthesis of pyridine‐functionalised 5polynorbornane ligands. The new bis(pyridyl) ligands have been used to construct a new M2L4 cage and M1L2 chelate complexes with Pt and Pd.
The gap junctional protein connexin (Cx) 45 is strongly expressed in the early embryonic myocardium. In the adult hearts of mice and humans, the expression mainly is restricted to the cardiac ...conduction system. Cx45 plays an essential role for development and function of the embryonic heart because general and cardiomyocyte-directed deficiencies of Cx45 in mice lead to embryonic lethality attributable to morphological and functional cardiovascular defects. The function of Cx45 in the adult mouse has not yet been cleared.
To clarify the function of Cx45 in the adult mouse heart.
To circumvent the embryonic lethality resulting from Cx45 deficiency, mice were generated in which deletion of Cx45 specifically was induced in cardiomyocytes of adult mice. These Cx45-deficient mice were viable but showed a decrease in atrioventricular nodal conductivity. In addition, the Cx30.2 protein that is coexpressed with Cx45 in the cardiac conduction system was posttranscriptionally reduced by 70% in mutant hearts. Furthermore, deletion of both Cx45 and Cx30.2 resulted in viable mice that, however, showed stronger impairment of atrioventricular nodal conduction than the single Cx45-deficient mice.
Cx45 is required for optimal impulse propagation in the atrioventricular node and stabilizes the level of the coexpressed Cx30.2 protein in the adult mouse heart. In contrast to the embryo, Cx45 is not essential for the viability of adult mice.
This study deals with the diminutive suffixes -chen and -elchen in the Moselfranconian base dialects on both sides of the Luxo-German state border. It covers the entirety of the state of Luxembourg ...as well as the Moselfranconian dialects of German within the area of investigation of the Linguistic Atlas of the Central Rhine (MRhSA). The study examines the Wenker questionnaires from the end of the 19th century that were collected by Georg Wenker and John Meier as well as a second and third series of data in the form of Wenker questionnaires that were collected in the 1920s by Richard Huss and data from the MRhSA collected in the 1980s. Building on Edelhoff (2016), who analyses the development of diminutive plurals and plural diminutives in German and Luxemburgish dialects, and Edelhoff (2017a, 2017b) this study provides a closer look on the forms of the diminutive suffix in the singular, particularly of the two lexemes Augenblickchen ,moment.dim’ and Stückchen ,piece.dim’. It is not only a matter of general concern to show the spatial distribution of the suffix forms ‑chen and ‑elchen in the base dialects, but it attempts to shed some light on language-dynamic processes taking place. Specifically, this involves taking a closer look at the following questions: 1) Can language change in the direction of the prestige variety of Central Luxemburgish on the Luxemburgish and in the direction of Standard German on the German side of the state border be shown, in the sense of the Language Dynamics Approach (Schmidt/Herrgen 2011)? 2) Can Edelhoff’s (2016) constatation that the state border has become a dialect border with regard to the use of the diminutive plural suffix also be demonstrated for the diminutive singular suffix variants ‑chen and ‑elchen? 3) Is there geolinguistic evidence for the thesis that the morphological variant ‑elchen is a fusion of the suffixes -lein and -chen? This article provides a preliminary answer to these questions and sketches some lines of inquiry for future research.
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