Reactivities of the coordinated organonitriles in molybdenum(0) and tungsten(0) phosphine complexes: protonation of the nitrile carbon and cleavage of the CN triple bond

The molybdenum and tungsten dinitrogen-organonitrile complexes trans-[M(N₂)(NCR)(dppe)₂] (2, M=Mo; 4, M=W; R=Ph, C₆H₄Me-p, C₆H₄OMe-p, Me; dppe=Ph₂PCH₂CH₂PPh₂) underwent double protonation at the nitrile carbon atom with loss of N₂ and a change in oxidation state to +4 on treatment with hydrochloric acid to afford the cationic imido complexes trans-[MCl(NCH₂R)(dppe)₂]⁺. The solid-state structure of trans-[WCl(NCH₂CH₃)(dppe)₂][PF₆]·CH₂Cl₂ was determined by single-crystal X-ray analysis. Protonation of complexes 2 by fluoroboric acid or hydrobromic acid also formed the similar imido complexes trans-[MoX(NCH₂R)(dppe)₂]⁺ (X=F, Br). In contrast, the dinitrogen complex trans-[Mo(N₂)₂(dppe)₂] reacted with two equiv. of benzoylacetonitrile, a nitrile with acidic CH hydrogen atoms, to give the nitrido complex trans-[Mo(N)(NKCCHCOPh)(dppe)₂] (12), which was accompanied by evolution of dinitrogen and the formation of 1-phenyl-2-propen-1-one in high yields. For complex 12, the zwitterionic structure, where the anionic enolate ligand PhC(O⁺)=CHCN coordinates to the cationic Mo(IV) center through its nitrogen atom, was confirmed by spectroscopic measurements and single-crystal X-ray analysis. A unique intermolecular aromatic C---HO hydrogen bonding was observed in that crystal structure. Complex 12 is considered to be formed via the cleavage of the CN triple bond of benzoylacetonitrile on the metal. A reaction mechanism is proposed, which includes the double protonation of the nitrile carbon atom of the ligating benzoylacetonitrile on a low-valent molybdenum center.     

A study of the occurrence of regulator secondary structures in globular proteins

The distribution of regular secondary structures, viz. α-helices and β-strands, along the length of over 70 properties whose secondary structural details have been reported, has been analysed. The occurrence of these regular structures tends to be a maximum at the N- and C-termini. Our analysis suggests that both these free ends could possibly serve as nucleating centers for secondary structures and could play an important role in the folding of proteins.     

Plant action: Multiple levels of regulation

This lecture is devoted to the relative contribution of various levels of regulation of the actin cytoskeleton functioning in the cell. Regulation at the levels of gene expression, mRNA and protein synthesis and stability, processes of actin polymerization/depolymerization and actin structures reorganization is briefly considered. Novel information about the pathways of signal transduction to the actin cytoskeleton with the involvement of Arp2/3 complex and RIC proteins is highlighted.     

A Search for Discrete Cholinergic Nuclei in the Human Ventral Forebrain

Abstract: Slices cut from five frozen human brains were dissected into 2-mm cubes and assayed for choline acetyltransferase (ChAT) activity and protein content. A pattern of enrichment of ChAT activity was found ventral to the anterior commissure; this finding is consistent with the location of the enzyme in the cells of the nucleus basalis of Meynert. The region beneath the anterior commissure was the only place a discrete enrichment of activity could be found, and the precise topography of the enrichment was somewhat variable from brain to brain. The results are discussed in the light of recent knowledge concerning the source of the cortical cholinergic innervation.     

Specific paracrystalline structures of rough endoplasmic reticulum in the follicular (stellate) cells of the dog adenohypophysis

Summary The fine structure of follicular cells of the adenohypophysis was examined in fetal, neonatal, and adult beagle dogs. Prior to birth, undifferentiated follicular cells are common. At birth mature cells that form follicles are routinely encountered. The fine structural appearance of follicular cells is unchanged between birth and adulthood. Follicular cells of puppies and adults are, however, distinguished by the presence of unusual complexes within distended cisternae of the rough endoplasmic reticulum. These complexes vary greatly in morphology, some appear as a maze of interconnecting tubules while others show a highly organized paracrystalline configuration. The presence of these paracrystalloid structures in follicular cells supports the view that they represent a distinct pituitary cell type.Supported by NIH Grants AM19743 and NS12969The authors wish to thank John Patrikes and Helen Mantulin for their expert technical assistance     

An application of the theoretical group methods to modeling of complex systems

The applicability of theoretical group methods to studying complex physical and biological systems with the potential of self-organization was demonstrated. The problem of calculating climate sensitivity parameters taking into account the cyclone-anticyclone structure of the atmosphere optically dense in the infrared region is considered as an example.     

Process of Making Three-dimensional Microstructures using Vaporization of a Sacrificial Component

Vascular structures in natural systems are able to provide high mass transport through high surface areas and optimized structure. Few synthetic material fabrication techniques are able to mimic the complexity of these structures while maintaining scalability. The Vaporization of a Sacrificial Component (VaSC) process is able to do so. This process uses sacrificial fibers as a template to form hollow, cylindrical microchannels embedded within a matrix. Tin (II) oxalate (SnOx) is embedded within poly(lactic) acid (PLA) fibers which facilitates the use of this process. The SnOx catalyzes the depolymerization of the PLA fibers at lower temperatures. The lactic acid monomers are gaseous at these temperatures and can be removed from the embedded matrix at temperatures that do not damage the matrix. Here we show a method for aligning these fibers using micromachined plates and a tensioning device to create complex patterns of three-dimensionally arrayed microchannels. The process allows the exploration of virtually any arrangement of fiber topologies and structures.     

Genome‐wide association study identifies loci associated with liability to alcohol and drug dependence that is associated with variability in reward‐related ventral striatum activity in African‐ and European‐Americans

Genetic influences on alcohol and drug dependence partially overlap, however, specific loci underlying this overlap remain unclear. We conducted a genome‐wide association study (GWAS) of a phenotype representing alcohol or illicit drug dependence (ANYDEP) among 7291 European‐Americans (EA; 2927 cases) and 3132 African‐Americans (AA: 1315 cases) participating in the family‐based Collaborative Study on the Genetics of Alcoholism. ANYDEP was heritable (h ² in EA = 0.60, AA = 0.37). The AA GWAS identified three regions with genome‐wide significant (GWS; P < 5E‐08) single nucleotide polymorphisms (SNPs) on chromosomes 3 (rs34066662, rs58801820) and 13 (rs75168521, rs78886294), and an insertion‐deletion on chromosome 5 (chr5:141988181). No polymorphisms reached GWS in the EA. One GWS region (chromosome 1: rs1890881) emerged from a trans‐ancestral meta‐analysis (EA + AA) of ANYDEP, and was attributable to alcohol dependence in both samples. Four genes (AA: CRKL, DZIP3, SBK3; EA: P2RX6) and four sets of genes were significantly enriched within biological pathways for hemostasis and signal transduction. GWS signals did not replicate in two independent samples but there was weak evidence for association between rs1890881 and alcohol intake in the UK Biobank. Among 118 AA and 481 EA individuals from the Duke Neurogenetics Study, rs75168521 and rs1890881 genotypes were associated with variability in reward‐related ventral striatum activation. This study identified novel loci for substance dependence and provides preliminary evidence that these variants are also associated with individual differences in neural reward reactivity. Gene discovery efforts in non‐European samples with distinct patterns of substance use may lead to the identification of novel ancestry‐specific genetic markers of risk.