Palladium(II) Complexes of Bis(diphosphene) with the Different Coordination Behavior

Organophosphorus compounds possessing the P−P double-bond character are intriguing materials in coordination chemistry because it is possible to form a variety of coordination modes from the π-bond in addition to...

Cationic Peptides and their Cu(II) and Ni(II) Complexes: Coordination and Biological Characteristics

Antimicrobial peptides are a promising group of compounds used for the treatment of infections. In some cases, metal ions are essential to activate these molecules. Examples of metalloantibiotics are, for instance, bleomycin and dermcidin. This study is focused on three new pseudopeptides with potential biological activity. The coordination behavior of all ligands with Cu(II) and Ni(II) ions has been examined. Various analytical methods such as potentiometric titration, UV-Vis and CD spectroscopies, and mass spectrometry were used. All compounds are convenient chelators for metal ion-binding. Two of the ligands tested have histidine residues. Surprisingly, imidazole nitrogen is not involved in the coordination of the metal ion. The N-terminal amino group, Dab side chains, and amide nitrogen atoms of the peptide bonds coordinated Cu(II) and Ni(II) in all the complexes formed. The cytotoxicity of three pseudopeptides and their complexes was evaluated. Moreover, their other model allowed for assessing the attenuation of LPS-induced cytotoxicity and anti-inflammatory activities were also evaluated, the results of which revealed to be very promising.

Third party stabilization of unstable coordination in systems of coupled oscillators

The Haken-Kelso-Bunz (HKB) system of equations is a well-developed model for dyadic rhythmic coordination in biological systems. It captures ubiquitous empirical observations of bistability – the coexistence of in-phase and antiphase motion – in neural, behavioral, and social coordination. Recent work by Zhang and colleagues has generalized HKB to many oscillators to account for new empirical phenomena observed in multiagent interaction. Utilising this generalization, the present work examines how the coordination dynamics of a pair of oscillators can be augmented by virtue of their coupling to a third oscillator. We show that stable antiphase coordination emerges in pairs of oscillators even when their coupling parameters would have prohibited such coordination in their dyadic relation. We envision two lines of application for this theoretical work. In the social sciences, our model points toward the development of intervention strategies to support coordination behavior in heterogeneous groups (for instance in gerontology, when younger and older individuals interact). In neuroscience, our model will advance our understanding of how the direct functional connection of mesoscale or microscale neural ensembles might be switched by their changing coupling to other neural ensembles. Our findings illuminate a crucial property of complex systems: how the whole is different than the system’s parts.

A Free Aluminylene with Diverse σ-Donating and Doubly σ/π-Accepting Ligand Features for Transition Metals

We report herein the synthesis, characterization, and coordination chemistry of a free N-aluminylene, namely a carbazolylaluminylene 2b. This species is prepared via a reduction reaction of the corresponding carbazolyl aluminium diiodide. The coordination behavior of 2b towards transition metal centers (W, Cr) is shown to afford a series of novel aluminylene complexes 3-6 with diverse coordination modes. We demonstrate that the Al center in 2b can behave as: 1. a σ-donating and doubly π-accepting ligand; 2. a σ-donating, σ-accepting and π-accepting ligand; and 3. a σ-donating and doubly σ-accepting ligand. Additionally, we show ligand exchange at the aluminylene center providing access to the modulation of electronic properties of transition metals without changing the coordinated atoms. Investigations of 2b with IDippCuCl (IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) show an unprecedented aluminylene-alumanyl transformation leading to a rare terminal Cu-alumanyl complex 8. The electronic structures of such complexes and the mechanism of the aluminylene-alumanyl transformation are investigated through density functional theory (DFT) calculations.

miR-6780-5p-Enriched Exosomes Derived From Butylidenephthalide-Pre-Conditioned Human Olfactory Ensheathing Cells Via Autophagy Improve Motor Coordination and Balance in a SCA3/MJD Mouse Model

Background The development of acellular products is a new trend for regeneration medicine. To provide an acellular product exhibiting characteristics of cells and usefulness as a therapeutic agent, exosomes were employed in the current studies. Method and Result The therapeutic agent hsa-miRNA-6780-5p was enriched up to 98 folds in exosomes derived from butylidenephthalide (bdph)-pre-conditioned human olfactory ensheathing cells (hOECs) compared to naïve hOECs exosomes. The particle size of exosomes derived hOECs and exosomes derived hOECs pre-conditioned bdph were around 124.17 nm and 117.47 nm, respectively. The role of hsa-miRNA-6780-5p was first demonstrated in our studies using a liposome system, showing that it enhances autophagy and inhibits spinocerebellar ataxia type 3 (SCA3) disease proteins of polyglutamine (polyQ) tract expression. At the same time, the exosomes with enriched hsa-miRNA-6780-5p were further applied to HEK-293-84Q, thus resulting in decreased expressions of polyQ and increased autophagy in the cells. In contrast, the results were reversed when the autophagy inhibitor, 3MA, was added to the cells treated with hsa-miRNA-6780-5p enriched exosomes, indicating that the decreased polyQ expression was modulated via autophagy. The SCA3 mice showed improved motor coordination behavior when they received intracranially injected exosomes enriched with hsa-miRNA-6780-5p. The SCA3 mouse cerebellum tissue having received hsa-miRNA6780-5p enriched exosomes also showed a decreased expression of polyQ and increased expression of autophagy marker. Conclusions Together, our findings provide an alternative therapeutic strategy for SCA3 disease treatment, using miRNA enriched exosomes derived from chemically pre-conditioned cells.

α-Cationic Phosphines: from Curiosities to Powerful Ancillary Ligands

The distinguishing feature of α-cationic phosphines is the presence of at least one substituent, normally (hetero)cyclic and positively charged, which is directly attached to the phosphorus atom. As result from this unique substitution pattern, the thus designed ligands depict significantly diminished donor properties if compared with their neutral counterparts. Thus, if in a hypothetical catalytic cycle, the step that determines the rate is facilitated by an increase of the electrophilicity at the metal center; then, the use of α-cationic ancillary phosphines can be highly beneficial. This fact, combined with their easy syntheses and stability, which allows an easy handling, make α-cationic phosphines a useful tool for the synthetic practitioner. Our research on the topic demonstrates that generally a remarkable ligand acceleration effect is observed when α-cationic phosphines are employed in Au(I)- and Pt(II)-promoted cycloisomerizations; moreover, in some cases even otherwise not operative transformations can be promoted. This Account describes how we entered into the topic, our efforts, and those of others to understand the coordination behavior of α-cationic phosphines and further develop their range of applications in catalysis; but it also identifies the drawbacks associated with their use, which limit their range of application.1 Introduction2 Polycationic Phosphines: Stronger Acceptors than Phosphites3 Inconveniences Derived from the Use of (Poly)cationic phosphines4 A Second Generation of Cationic Ligands: α-Pyridiniophosphines5 Chiral α-Cationic Phosphines6 α-Radical Phosphines and (Poly)cationic Phosphine Oxides7 Conclusions and Outlook