Sequence-Dependent Guest Release Triggered by Orthogonal Chemical Signals.

Three Zn(II)4L4 coordination cages, assembled from trisiminopyridine ligands, exhibit differences in their guest-binding selectivities and reactivity with tris(2-aminoethyl)amine (tren), which enabled the design of a molecular network that responded in distinct ways to different chemical signals. When two of these cages were present in solution together, one of them was observed to selectively encapsulate chloroform, and the other was observed to selectively encapsulate cyclohexane. The two guests could be released sequentially, in a specified order defined by the input of two separate chemical signals: tren and perrhenate. Furthermore, the observed reactivity of tren with the initial cage mixture provided control over the uptake and release of perrhenate within the third cage formed in situ. One of these tetrahedral cages has been identified as a tight (K(a) > 10(7) M(-1)) and selective host for perrhenate, an anion of great physicochemical similarity to pertechnetate, both having uses in nuclear medicine.This work was supported by the European Research Council. We thank Diamond Light Source (UK) for synchrotron beamtime on I19 (MT8464) and Dr. Rana A. Bilbeisi for a preliminary screening of guests for cage 1.This is the author accepted manuscript. The final version is available from the American Chemical Society via http://dx.doi.org/10.1021/jacs.5b1301

Carbon Sequestration in Managed Temperate Coniferous Forests Under Climate Change

Management of temperate forests has the potential to increase carbon sinks and mitigate climate change. However, those opportunities may be confounded by negative climate change impacts. We therefore need a better understanding of climate change alterations to temperate forest carbon dynamics before developing mitigation strategies. The purpose of this project was to investigate the interactions of species composition, fire, management, and climate change in the Copper–Pine Creek valley, a temperate coniferous forest with a wide range of growing conditions. To do so, we used the LANDIS-II modelling framework including the new Forest Carbon Succession extension to simulate forest ecosystems under four different productivity scenarios, with and without climate change effects, until 2050. Significantly, the new extension allowed us to calculate the net sector productivity, a carbon accounting metric that integrates aboveground and belowground carbon dynamics, disturbances, and the eventual fate of forest products. The model output was validated against literature values. The results implied that the species optimum growing conditions relative to current and future conditions strongly influenced future carbon dynamics. Warmer growing conditions led to increased carbon sinks and storage in the colder and wetter ecoregions but not necessarily in the others. Climate change impacts varied among species and site conditions, and this indicates that both of these components need to be taken into account when considering climate change mitigation activities and adaptive management. The introduction of a new carbon indicator, net sector productivity, promises to be useful in assessing management effectiveness and mitigation activities

Sialic acids on B cells are crucial for their survival and provide protection against apoptosis.

Sialic acids (Sias) on the B cell membrane are involved in cell migration, in the control of the complement system and, as sialic acid-binding immunoglobulin-like lectin (Siglec) ligands, in the regulation of cellular signaling. We studied the role of sialoglycans on B cells in a mouse model with B cell-specific deletion of cytidine monophosphate sialic acid synthase (CMAS), the enzyme essential for the synthesis of sialoglycans. Surprisingly, these mice showed a severe B cell deficiency in secondary lymphoid organs. Additional depletion of the complement factor C3 rescued the phenotype only marginally, demonstrating a complement-independent mechanism. The B cell survival receptor BAFF receptor was not up-regulated, and levels of activated caspase 3 and processed caspase 8 were high in B cells of Cmas-deficient mice, indicating ongoing apoptosis. Overexpressed Bcl-2 could not rescue this phenotype, pointing to extrinsic apoptosis. These results show that sialoglycans on the B cell surface are crucial for B cell survival by counteracting several death-inducing pathways

Thixotropy in macroscopic suspensions of spheres

An experimental study of the viscosity of a macroscopic suspension, i.e. a suspension for which Brownian motion can be neglected, under steady shear is presented. The suspension is prepared with a high packing fraction and is density-matched in a Newtonian carrier fluid. The viscosity of the suspension depends on the shear rate and the time of shearing. It is shown for the first time that a macroscopic suspension shows thixotropic viscosity, i.e. shear-thinning with a long relaxation time as a unique function of shear. The relaxation times show a systematic decrease with increasing shear rate. These relaxation times are larger when decreasing the shear rates, compared to those observed after increasing the shear. The time scales involved are about 10000 times larger than the viscous time scale and about 1000 times smaller than the thermodynamic time scale. The structure of the suspension at the outer cylinder of a viscometer is monitored with a camera, showing the formation of a hexagonal structure. The temporal decrease of the viscosity under shear coincides with the formation of this hexagonal pattern

Tuning the Redox Properties of Fullerene Clusters within a Metal-Organic Capsule.

A porphyrin-edged metal-organic tetrahedron forms host-guest complexes containing 1-4 equiv of fullerene C60, depending on the solvent employed. The molecules of C60 were bound anticooperatively within well-defined pockets; an X-ray crystal structure of three fullerenes inside the tetrahedron was obtained. Electrochemical measurements revealed that the electron-accepting properties of the fullerenes inside the capsules were altered depending on the mode of encapsulation. The binding of multiple fullerenes was observed to increase the electron affinity of the overall cluster, providing a noncovalent method of tuning fullerene electronics.This work was supported by the UK Engineering and Physical Sciences Research Council (EPSRC EP/M01083X/1). F.J.R. acknowledges Cambridge Australia Scholarships for Ph.D. funding. We thank Diamond Light Source (UK) for synchrotron beam time on I19 (MT8464 and MT11397)

Anion Recognition as a Supramolecular Switch of Cell Internalization.

The cell internalization of designed oligoarginine peptides equipped with six glutamic acid residues and an anionic pyranine at the N-terminus is triggered upon addition of a supramolecular host. This host binds specifically to the pyranine moiety, enabling the complex to traverse the cell membrane. Interestingly, none of the components, neither the host nor the guest, are able to cross the cell membrane on their own

Revival of Philozoon Geddes for host-specialized dinoflagellates, ‘zooxanthellae’, in animals from coastal temperate zones of northern and southern hemispheres

The dinoflagellate family Symbiodiniaceae comprises numerous genera and species with large differences in diversity, ecology and geographic distribution. An evolutionarily divergent lineage common in temperate symbiotic cnidarians and designated in the literature by several informal names including ‘temperate–A’, AI, Phylotype A´ (A-prime) and ‘Mediterranean A’, is here assigned to the genus Philozoon. This genus was proposed by Geddes (1882) in one of the earliest papers that recognized ‘yellow cells’ as distinct biological entities separate from their animal and protist hosts. Using phylogenetic data from nuclear (rDNA), chloroplast (cp23S) and mitochondrial genes (cob and cox1), as well as morphology (cell size), ecological traits (host affinity) and geographic distributions, we emend the genus Philozoon Geddes and two of its species, P. medusarum and P. actiniarum, and describe six new species. Each symbiont species exhibits high host fidelity for particular species of sea anemone, soft coral, stony coral and a rhizostome jellyfish. Philozoon is most closely related to Symbiodinium (formerly Clade A), but, unlike its tropical counterpart, occurs in hosts in shallow temperate marine habitats in northern and southern hemispheres including the Mediterranean Sea, north-eastern Atlantic Ocean, eastern Australia, New Zealand and Chile. The existence of a species-diverse lineage adapted to cnidarian hosts living in high latitude habitats with inherently wide fluctuations in temperature calls further attention to the ecological and biogeographic reach of the Symbiodiniaceae