Carbonyl complexes of rhodium(I) and rhodium(III) with 2,2′-biquinoline

Novel carbonyl complexes of rhodium(I) and rhodium(III) containing the bidenate nitrogen donor ligand 2,2′-biquinoline (biq) have been prepared; they are of the types RhX(CO)2 biq and RhX(CO)biq (X = Cl, Br, I). Cationic carbonyl and substituted carbonyl complexes of the types [Rh(CO)2biq]ClO4 and [Rh(CO)biqL2]ClO4, where L is tertiary phosphine or arsine have also been isolated. In spite of considerable steric crowding around the nitrogen atoms, 2,2′-biquinoline behaves much like 2,2′-bipyridine in forming carbonyl complexes of rhodium. © 1979

Cationic carbonyl complexes of rhodium(I)

A number of cationic Rh(I) complexes of the type [Rh(CO)​2Q]​ClO4, [Rh(CO)​2L3]​ClO4, and [Rh(CO)​QL2]​ClO4, where Q = 2,​2'-​bipyridine or 1,​10-​phenanthroline and L is a tertiary phosphine or arsine, were isolated and their structures assigned. The configuration of the complex ion [Rh(CO)​2L3]​+ appears to depend critically on the size of the ligand L

Causes, effects, and implications of the relationships amongst fluids, serpentinisation, and alloys

Diverse assemblages of metal alloys occur within ultramafic rocks from a wide range of tectonic settings and geological environments. Alloys are typically small and can be difficult to find and identify, but they can host Re and Os, which are significant for geochronology, as well as other elements of economic interest, and can act as catalysts that help to form organic compounds. The alloys typically form from elements that show chalcophile and siderophile characteristics, indicating that alloys generally form under reducing, S-poor conditions. These conditions can be generated by a range of mechanisms that differ amongst alloy-forming environments, but include desulfidation during melting, exsolution from magmatic S-bearing phases during melt crystallisation, auto-hydrothermal, and sub-solidus processes involving a reduction in fS2, and electron transfer processes related to serpentinisation. Alloy formation during serpentinisation is typically associated with the formation of a companion phase that hosts Fe3+, such as Fe3+-bearing serpentine, magnetite, ferrit-chromite, or andradite, recording disproportionation of Fe2+ released by olivine alteration to form Fe0 and Fe3+. An additional source of electrons for alloy formation is provided by the reduction of H+ in water to H2, and the reduction of water activity couples with a reduction in fS2, driving desulfidation reactions and facilitating alloy formation. Other electron donors, such as methane, may also contribute to alloy formation. Alloy-forming serpentinites are strongly internally-buffered, but can follow a range of trajectories through compositional space. Serpentinite-hosted alloys offer opportunities to better understand a range of geological processes with applications within earth and material sciences. However, these advances require new thermodynamic data and activity composition models for all but the most common alloys, and better characterisation of alloy compositions

Selection of elite seedling clones of mango (Mangifera indica L.) exposed by phylogenetic relationship and morpho-taxonomic traits

Almost all the current commercial mango cultivars in India are the result of selection from the natural seedling population and majority of them have been selected by the farmers.The conventional breeding system with traditional knowledge is evolving more and more towards preservation of genetic diversity. In Pusa site of the UNEP/GEF sponsored project in the Bihar state of India, many mango seedlings are found growing in the orchards as well as in the backyards. Mango being a highly cross-pollinated fruit crop exhibits a lot of variability in morpho-physico-chemical traits of fruits in these seedling plants. For selection of the elite seedling genotypes, farmers play an important role and with the help of the breeder they can pave the way for maintaining the local germplasm. Hence, in order to study the genetic variability among mango seedlings and to select elite mango genotypes and to conserve them, a survey was conducted in the four project communities and the surrounding villages. A total of 74 seedling types of mango were characterized using morpho-taxonomic parameters. Physico-chemical characterization of fruit samples revealed the existence of a great variability in the seedling mango plants, which not only contributes to biological diversity, but can also be used for crop improvement or for varietal selection. Based on this physico-chemical characterization, principal component and cluster analysis and grouping of seedling clones on the basis of possession of desirable characters by them, six seedling clones, having the majority of desirable fruit characteristics were selected. These selected clones will definitely broaden the genetic base of mango in the Pusa site as well offer the scope for choice of selection of varieties by the farmers and ultimately the conservation of the valuable germplasm

Fibroblastic niches prime T cell alloimmunity through Delta-like Notch ligands.

Alloimmune T cell responses induce graft-versus-host disease (GVHD), a serious complication of allogeneic bone marrow transplantation (allo-BMT). Although Notch signaling mediated by Delta-like 1/4 (DLL1/4) Notch ligands has emerged as a major regulator of GVHD pathogenesis, little is known about the timing of essential Notch signals and the cellular source of Notch ligands after allo-BMT. Here, we have shown that critical DLL1/4-mediated Notch signals are delivered to donor T cells during a short 48-hour window after transplantation in a mouse allo-BMT model. Stromal, but not hematopoietic, cells were the essential source of Notch ligands during in vivo priming of alloreactive T cells. GVHD could be prevented by selective inactivation of Dll1 and Dll4 in subsets of fibroblastic stromal cells that were derived from chemokine Ccl19-expressing host cells, including fibroblastic reticular cells and follicular dendritic cells. However, neither T cell recruitment into secondary lymphoid organs nor initial T cell activation was affected by Dll1/4 loss. Thus, we have uncovered a pathogenic function for fibroblastic stromal cells in alloimmune reactivity that can be dissociated from their homeostatic functions. Our results reveal what we believe to be a previously unrecognized Notch-mediated immunopathogenic role for stromal cell niches in secondary lymphoid organs after allo-BMT and define a framework of early cellular and molecular interactions that regulate T cell alloimmunity

A Model for the Development of the Rhizobial and Arbuscular Mycorrhizal Symbioses in Legumes and Its Use to Understand the Roles of Ethylene in the Establishment of these two Symbioses

We propose a model depicting the development of nodulation and arbuscular mycorrhizae. Both processes are dissected into many steps, using Pisum sativum L. nodulation mutants as a guideline. For nodulation, we distinguish two main developmental programs, one epidermal and one cortical. Whereas Nod factors alone affect the cortical program, bacteria are required to trigger the epidermal events. We propose that the two programs of the rhizobial symbiosis evolved separately and that, over time, they came to function together. The distinction between these two programs does not exist for arbuscular mycorrhizae development despite events occurring in both root tissues. Mutations that affect both symbioses are restricted to the epidermal program. We propose here sites of action and potential roles for ethylene during the formation of the two symbioses with a specific hypothesis for nodule organogenesis. Assuming the epidermis does not make ethylene, the microsymbionts probably first encounter a regulatory level of ethylene at the epidermis–outermost cortical cell layer interface. Depending on the hormone concentrations there, infection will either progress or be blocked. In the former case, ethylene affects the cortex cytoskeleton, allowing reorganization that facilitates infection; in the latter case, ethylene acts on several enzymes that interfere with infection thread growth, causing it to abort. Throughout this review, the difficulty of generalizing the roles of ethylene is emphasized and numerous examples are given to demonstrate the diversity that exists in plants