Building block libraries and structural considerations in the self-assembly of polyoxometalate and polyoxothiometalate systems

Inorganic metal-oxide clusters form a class of compounds that are unique in their topological and electronic versatility and are becoming increasingly more important in a variety of applications. Namely, Polyoxometalates (POMs) have shown an unmatched range of physical properties and the ability to form structures that can bridge several length scales. The formation of these molecular clusters is often ambiguous and is governed by self-assembly processes that limit our ability to rationally design such molecules. However, recent years have shown that by considering new building block principles the design and discovery of novel complex clusters is aiding our understanding of this process. Now with current progress in thiometalate chemistry, specifically polyoxothiometalates (POTM), the field of inorganic molecular clusters has further diversified allowing for the targeted development of molecules with specific functionality. This chapter discusses the main differences between POM and POTM systems and how this affects synthetic methodologies and reactivities. We will illustrate how careful structural considerations can lead to the generation of novel building blocks and further deepen our understanding of complex systems

Molecular evolution of Adh and LEAFY and the phylogenetic utility of their introns in Pyrus (Rosaceae)

<p>Abstract</p> <p>Background</p> <p>The genus <it>Pyrus </it>belongs to the tribe Pyreae (the former subfamily Maloideae) of the family Rosaceae, and includes one of the most important commercial fruit crops, pear. The phylogeny of <it>Pyrus </it>has not been definitively reconstructed. In our previous efforts, the internal transcribed spacer region (ITS) revealed a poorly resolved phylogeny due to non-concerted evolution of nrDNA arrays. Therefore, introns of low copy nuclear genes (LCNG) are explored here for improved resolution. However, paralogs and lineage sorting are still two challenges for applying LCNGs in phylogenetic studies, and at least two independent nuclear loci should be compared. In this work the second intron of <it>LEAFY </it>and the alcohol dehydrogenase gene (<it>Adh</it>) were selected to investigate their molecular evolution and phylogenetic utility.</p> <p>Results</p> <p>DNA sequence analyses revealed a complex ortholog and paralog structure of <it>Adh </it>genes in <it>Pyrus </it>and <it>Malus</it>, the pears and apples. Comparisons between sequences from RT-PCR and genomic PCR indicate that some <it>Adh </it>homologs are putatively nonfunctional. A partial region of <it>Adh1 </it>was sequenced for 18 <it>Pyrus </it>species and three subparalogs representing <it>Adh1-1 </it>were identified. These led to poorly resolved phylogenies due to low sequence divergence and the inclusion of putative recombinants. For the second intron of <it>LEAFY</it>, multiple inparalogs were discovered for both <it>LFY1int2 </it>and <it>LFY2int2</it>. <it>LFY1int2 </it>is inadequate for phylogenetic analysis due to lineage sorting of two inparalogs. <it>LFY2int2-N</it>, however, showed a relatively high sequence divergence and led to the best-resolved phylogeny. This study documents the coexistence of outparalogs and inparalogs, and lineage sorting of these paralogs and orthologous copies. It reveals putative recombinants that can lead to incorrect phylogenetic inferences, and presents an improved phylogenetic resolution of <it>Pyrus </it>using <it>LFY2int2-N</it>.</p> <p>Conclusions</p> <p>Our study represents the first phylogenetic analyses based on LCNGs in <it>Pyrus</it>. Ancient and recent duplications lead to a complex structure of <it>Adh </it>outparalogs and inparalogs in <it>Pyrus </it>and <it>Malus</it>, resulting in neofunctionalization, nonfunctionalization and possible subfunctionalization. Among all investigated orthologs, <it>LFY2int2-N </it>is the best nuclear marker for phylogenetic reconstruction of <it>Pyrus </it>due to suitable sequence divergence and the absence of lineage sorting.</p

Iron-Substituted Polyoxotungstates as Inorganic Synzymes: Evidence for a Biomimetic Pathway in the Catalytic Oxygenation of Catechols

Convergent structural, spectroscopic, and mechanistic evidence is presented on the bio-inspired catalysis by FeIII-substituted polyoxotungstates [Fe4(H2O)10(\u3b2-XW9O33)2]n 12 (X=AsIII, SbIII, SeIV, TeIV) in promoting the aerobic cleavage of catechols (see figure). These polyanions display two of the four iron sites with three external and substitution-labile coordination positions typical of non-heme dioxygenase enzymes

15-Copper(ii)-containing 36-tungsto-4-silicates(iv) [Cu15O2(OH)(10)X(A--SiW9O34)(4)](25-) (X = Cl, Br): synthesis, structure, magnetic properties, and electrocatalytic CO2 reduction

The 15-copper(ii)-containing 36-tungsto-4-silicates [Cu15O2(OH)(10)X(A--SiW9O34)(4)](25-) (X = Cl, 1; Br, 2) have been prepared in 70% yield by reaction of the trilacunary 9-tungstosilicate precursor [A--SiW9O34](10-) with Cu2+ ions in aqueous pH 8 medium. Both polyanions 1 and 2 were isolated as hydrated mixed potassium/sodium salts and characterized in the solid state by FT-IR, TGA, single-crystal XRD, and elemental analysis. DC magnetic susceptibility measurements from 1.8-300 K established the ground state to be paramagnetic with a magnetic moment corresponding to 15 uncoupled Cu2+ (S = 1/2) ions. EPR measurements and simulations were consistent with this analysis. Electrochemical studies were performed for polyanions 1 and 2 dissolved in solution to elucidate the electroactivity of both copper and tungstate sites. Using 2 as a representative example, the electrocatalytic activity towards CO2 reduction upon deposition on a glassy carbon electrode surface, while retaining selectivity relative to hydrogen evolution, was demonstrated.</p

Molecular and morphological diversity of on-farm hazelnut (Corylus avellana L.) landraces from southern Europe and their role in the origin and diffusion of cultivated germplasm

Hazelnut (Corylus avellana L.) is a traditional nut crop in southern Europe. Germplasm exploration conducted on-farm in five countries (Portugal, Spain, Italy, Slovenia, and Greece) identified 77 landraces. The present work describes phenotypic variation in nut and husk traits and investigates genetic relationships using ten simple sequence repeat (SSR) markers among these landraces, 57 well-known references cultivars, and 19 wild accessions. Among the 77 landraces, 42 had unique fingerprints while 35 showed a SSR profile identical to a known cultivar. Among the 42 unique landraces, morphological observations revealed high phenotypic diversity, and some had characteristics appreciated by the market such as nut round and caliber. Analysis of genetic relationships and population structure allowed investigation of the origin and spread of the cultivated germplasm in southern Europe. Our results indicate the existence of three primary centers of diversity in the Mediterranean basin: northwestern Spain (Tarragona) and southern Italy (Campania) in the West and Black Sea (Turkey) in the East. Moreover, the data suggest the existence of secondary gene pools in the Iberian (Asturias) and Italian (Liguria and Latium) Peninsulas, where local varieties were recently domesticated from wild forms and/or from introduced ancient domesticated varieties