Transmethylation of metals in aquatic systems

Transmethylation reactions between organometals and metal ions in aqueous solutions in biotic and abiotic systems, with and without the presence of sediment, were investigated. It was found that alkyllead compounds can transfer their alkyl groups to Sn(II) and Sn(IV) ions to form various methyltin compounds in biotic and abiotic systems. The presence of sediment enhanced the transmethylation reactions. Methyltin compounds do not transfer their methyl groups of Pb(II). Methylarsenic acids transfer their methyl groups to Sn(II) and Sn(IV) in an abiotic system, but not in a biotic system containing sediment. The strong adsorption of tin onto sediment was the reason for the non-availability of tin ions for methylation. Methylarsenic acids do not transmethylate Pb(II). Other alkyllead compounds, such as ethyllead and butyllead species were also able to transfer their alkyl groups to tin. When both trimethyllead and triethyllead species are present in the same system, only the individual monoalkyl tin species were formed in both the Sn(II) and Sn(IV) solutions. No mixed alkyltin was produced. The findings of this study suggest that alkyllead compounds, if present in the environment, could be potential methylating agents for the formation of other methylmetals, such as methyltins. Methyltin compounds have already been documented to methylate mercuric ions in aqueous solution. Thus the study of transmethylation reactions opens up a new area of research that is essential in predicting the fate of organometals in the environment.     

Characterization of chronic vocal fold scarring in a rabbit model

The purpose of the current study was to assess the histologic and rheologic properties of the scarred vocal fold lamina propria during a chronic phase of wound repair in a rabbit model. Eighteen rabbit larynges were scarred using a procedure that involved stripping the vocal fold lamina propria down to the thyroarytenoid muscle, using 3-mm microforceps. The approximate dimension of injury to the vocal fold was 3 x 1.5 x 0.5 mm [length x width x depth]. At 6 months postoperatively, histologic analysis of the scarred and control lamina propria in eight of these rabbits was completed for collagen, procollagen, elastin, and hyaluronic acid. Compared with control samples, scarred tissue samples revealed fragmented and disorganized elastin fibers. Additionally, collagen was significantly increased, organized, and formed thick bundles in the scarred vocal fold lamina propria. Measurements of the viscoelastic shear properties of the scarred and control lamina propria in the remaining 10 rabbits revealed increased elastic shear modulus (G') in 8 of 10 scarred samples and increased dynamic viscosity (eta') in 9 of 10 scarred samples. Although rheologic differences were not statistically significant, they revealed that on average, scarred samples were stiffer and more viscous than the normal controls. Histologic data are interpreted as indicating that by 6 months postinjury, the scarred rabbit vocal fold has reached a mature phase of wound repair, characterized by an increased, organized, and thick bundle collagen matrix. Rheologic data are interpreted as providing support for the potential role of increased, thick bundle collagen, and a disorganized elastin network on shear stiffness and dynamic viscosity in the chronic vocal fold scar. Based on these results, a 6-month postoperative time frame is proposed for future studies of chronic vocal fold scarring using the rabbit animal model.     

Precision measurement of neutrino oscillation parameters at INO-ICAL detector

A magnetized Iron CALorimeter (ICAL) detector at the India-based neutrino observatory (INO) is used to study neutrino oscillation sensitivity using atmospheric muon neutrino source. The ICAL detector will be able to detect muon tracks and hadron showers produced by neutrino interactions with the iron target. We have performed precision measurement analysis for the atmospheric neutrino oscillation parameters with the muon neutrino events, generated by Monte Carlo NUANCE event generator. A marginalized χ² analysis based on reconstructed neutrino energy and muon zenith angle binning scheme has been performed to determine the sensitivity for the atmospheric neutrino mixing parameters, \(\sin ^{2}\theta _{23}\) and \(| {\Delta } m^{2}_{23}|\).     

A thermally stable and sterically unprotected terminal electrophilic phosphinidene complex of cobalt and its conversion to an eta(1)-phosphirene

The terminal chloroaminophosphido complex [Co(CO)3(PPh3){P(Cl)NiPr2}] is formed via reaction of K[Co(CO)4] with iPr2NPCl2 in the presence of triphenylphosphine. Chloride abstraction by aluminum trichloride leads to the first terminal phosphinidene complex of cobalt, [Co(CO)3(PPh3)(PNiPr2)][AlCl4]. The electrophilicity of the phosphinidene was demonstrated by its reaction with diphenylacetylene to form the phosphirene complex [Co(CO)3(PPh3){P(NiPr2)C(Ph)C(Ph)}][AlCl4].     

Iron(II) complexes of imidazoline-2-thiones: the crystal structure of dichlorobis(1-methylimidazoline-2-thione)iron(II)

Summary Imidazoline-2-thione (imtH ₂) and 1-methylimidazoline-2-thione (mimtH) react with FeCl₂·4H₂O in rigorously anhydrous media producing complexes of general formula Fe(LH)₂Cl₂.Infrared and electronic spectra as well as room temperature magnetic moments are consistent with mononuelear, pseudotetrahedral species. The crystal structure of [Fe(mimHH)₂Cl₂] confirms this arrangement. The complex crystallises in a triclinic unit cell (a=7.376(2),b=7.595(2),c=15.043(4) Å. =76.80(1)°, =79.60(1)°, =61.90(1)°; V=721.13 ų; space group=P1, Z=2). Final conventional R from 2267 observed data (F >4(F)) is 0.0271. Average bond lengths are 2.353 Å (Fe–S) and 2.265 Å (Fe–Cl). Angles at the metal range from 91.5(1)° to 114.5(1)°.Thermal degradation of the complexes in flowing air involves sequential loss of halogen and ligand with -Fe₂O₃ as the final product. The decomposition is exothermic in flowing dinitrogen.     

Synthesis of 62-electron square planar clusters with group 15 and 16 main group atoms: Structural characterization of Ru4(CO)11(μ4-PPh)(μ4-S) and Ru4(CO)10(μ4-PPh)(μ4-Se)(PEt3): Bonding preferences in cappingNido Ru4(CO)13(μ3-PPh)

Thecloso octahedral cluster Ru₄(CO)₁₁(μ₄-PPh)(μ₄-S)1 and selenium and tellurium analogues, the first examples of unsaturated ruthenium clusters with a planar metal core and different main group 15 and 16 atoms have been synthesized fromnido Ru₄(CO)₁₃(μ₃-PPh). An X-ray analysis of1 and Ru₄(CO)₁₀(μ₄-PPh)(μ₄-Se)(PEt₃)2a has confirmed thetrans disposition of phosphorus and group 16 main group fragments.     

Purification of human glutamate dehydrogenase (GDH) and an adsorptive voltammetric investigation of the interaction of GDH with rabbit anti-human GDH antibody

A procedure for the isolation of glutamate dehydrogenase (GDH) from human liver, which involves the use of ion-exchange chromatography on diethylaminoethyl cellulose and affinity chromatography on guanosine triphosphate conjugated to Sepharose 4B, is described. The adsorptive voltammetric behaviour of human GDH, bovine GDH and rabbit anti-human GDH antibody was optimised with respect to accumulation potential, accumulation time and scan rate. The lower limits of detection were 0.2 and 1.2 mg l-1 for human and bovine GDH, respectively, and the lower limit of detection for rabbit anti-GDH antibody was 0.04 mg l-1. The interaction of human GDH with rabbit anti-human GDH antibody was also examined using this method.     

Reactions of the (2-pyridyl) pyrrolide platinum(II) complex driven by sterically encumbered chelation: a model for the reversible attack of alcohol at the coordinated carbon monoxide

Treatment of 3,5-bis(trifluoromethyl)-2-(2'-pyridyl)pyrrole (fpyroH) with Pt(DMSO)2Cl2 and Na2CO3 in THF solution gave a light-yellow complex denoted as [Pt(fpyro)2] (1). A single-crystal X-ray diffraction study on 1 revealed a large conformational distortion around the platinum(II) center, which is attributed to interligand repulsion between the pyridyl groups and the CF3 substituents of the nearby pyrrolides. Reaction of 1 with N- and C-donor ligands such as acetonitrile, pyridine, isocyanide, and CO affords the adducts [Pt(fpyro)2(L)], L = NCMe (2), pyridine (3), CNBut (4), and CO (5), showing formation of one monodentate fpyro ligand by release of the strain energy. The variable-temperature 1H NMR studies showed a static structure for the N-substituted adducts 2 and 3, whereas the C-adducts 4 and 5 are shown to be more labile, displaying a pairwise exchange of bidentate and monodentate fpyro ligands in solution. Addition of ethanol to the coordinated CO in 5 during recrystallization is also established, affording an ethoxycarbonyl complex [Pt(fpyro)(fpyroH)(CO2Et)] (6), which was isolated as a crystalline solid and can be readily converted back to 5 and free ethanol upon dissolution at room temperature.