Intramolecular stable carbon isotopic analysis of archaeal glycosyl tetraether lipids

Glycolipids are prominent constituents in the membranes of cells from all domains of life. For example, diglycosyl‐glycerol dibiphytanyl glycerol tetraethers (2Gly‐GDGTs) are associated with methanotrophic ANME‐1 archaea and heterotrophic benthic archaea, two archaeal groups of global biogeochemical importance. The hydrophobic biphytane moieties of 2Gly‐GDGTs from these two uncultivated archaeal groups exhibit distinct carbon isotopic compositions. To explore whether the isotopic compositions of the sugar headgroups provide additional information on the metabolism of their producers, we developed a procedure to analyze the δ¹³C values of glycosidic headgroups. Successful determination was achieved by (1) monitoring the contamination from free sugars during lipid extraction and preparation, (2) optimizing the hydrolytic conditions for glycolipids, and (3) derivatizing the resulting sugars into aldononitrile acetate derivatives, which are stable enough to withstand a subsequent column purification step. First results of δ¹³C values of sugars cleaved from 2Gly‐GDGTs in two marine sediment samples, one containing predominantly ANME‐1 archaea and the other benthic archaea, were obtained and compared with the δ¹³C values of the corresponding biphytanes. In both samples the dominant sugar headgroups were enriched in ¹³C relative to the corresponding major biphytane. This ¹³C enrichment was significantly larger in the putative major glycolipids from ANME‐1 archaea (～15‰) than in those from benthic archaea (<7‰). This method opens a new analytical window for the examination of carbon isotopic relationships between sugars and lipids in uncultivated organisms. Copyright © 2010 John Wiley & Sons, Ltd.     

Conformational preferences and orbital interactions for methyl haloacetates

Conformational preferences and orbital interactions of methyl chloroacetate (1), methyl bromoacetate (2) and methyl iodo-acetate (3) were analyzed using experimental infra-red data, theoretical calculations and NBO analyses. The conformational equilibria of compounds 1-3 can be represented by their cis and gauche rotamers. The gauche form of 1 is stable in the vapour phase and in a non-polar solvent, but the cis is predominant in a polar solvent. For 2 the gauche form is more stable than the cis, in both the vapour and liquid phases, but for compound 3 only the gauche form was observed both in vapour phase as in solution. These conformational preferences were attributed to the orbital interaction between two antibonding orbitals pi(C=O)(*)-->sigma(C-X)(*). This unexpected interaction was possibly due to the high (0.2) electron density on pi(C=O)(*), which results from the interaction between ether oxygen lone pair and pi(C=O)(*).     

Spontaneous formation of closed-field torus equilibrium via current jump observed in an electron-cyclotron-heated plasma

Spontaneous current jump resulting in the formation of closed field equilibrium has been observed in electron-cyclotron-heated toroidal plasmas under steady external fields composed of a toroidal field and a relatively weak vertical field in the low aspect ratio torus experiment device. This bridges the gap between the open field equilibrium maintained by a pressure-driven current in the external field and the closed field equilibrium at a larger current. Experimental results and theoretical analyses suggest a current jump model that is based on the asymmetric electron confinement along the field line appearing upon simultaneous transitions of field topology and equilibrium.     

Highly regioselective ring opening of epoxides with alcohols catalyzed by organotin phosphate condensates

Organotin phosphate condensates proved to catalyze the ring opening reaction of epoxides with alcohols in a highly regioselective manner.     

Immobilization of colloidal crystals, formed by polymer-grafted silica in organic solvent, in physical gels

Immobilization of colloidal crystals by gelation of polymer-grafted silica suspension in acetonitrile with alkyl amides derived from amino acids was investigated. Addition of N-benzyloxycarbonyl-l-isoleucylaminooctadecane (Z-Ile-C18) and 1,12-bis(N-benzyloxycarbonyl-l-valylamino)dodecane [Bis(Z-Val)-C12] to poly(maleic anhydride-co-styrene)-grafted silica suspension in acetonitrile resulted in formation of physical gels preserved colloidal crystal structure. From the reflection spectra, intersphere distance and size of crystallite in the gel formed with Bis(Z-Val)-C12 were confirmed to be mostly same as those of colloidal crystals in suspension.     

New human hair certified reference material for methylmercury and trace elements

 A new human hair certified reference material (NIES CRM No. 13) for mercury speciation and trace element analysis was prepared at the National Institute for Environmental Studies (NIES), Environmental Agency of Japan. Scalp hair from Japanese males, which is identical with the original material for the previous human hair CRM (NIES CRM No. 5), was used. Special attention was paid to reduce contamination from a grinding vessel during the preparation procedure. A newly-prepared ceramic/Teflon disc mill was used for cryogenic grinding of the hair. 1,000 bottles (3 g each) were produced after sieving and blending of the hair powder. Certified values for total mercury and methylmercury, as well as other trace elements of toxicological and nutritional significance (antimony, cadmium, copper, lead, selenium, and zinc), were determined based on analyses from extensive collaborations. Reference values for 12 elements (aluminium, arsenic, barium, calcium, cobalt, iron, magnesium, manganese, silver, sodium, sulfur and vanadium) were also given. Received: 8 February 1996/Accepted: 4 April 1996     

New human hair certified reference material for methylmercury and trace elements

A new human hair certified reference material (NIES CRM No. 13) for mercury speciation and trace element analysis was prepared at the National Institute for Environmental Studies (NIES), Environmental Agency of Japan. Scalp hair from Japanese males, which is identical with the original material for the previous human hair CRM (NIES CRM No. 5), was used. Special attention was paid to reduce contamination from a grinding vessel during the preparation procedure. A newly-prepared ceramic/Teflon disc mill was used for cryogenic grinding of the hair. 1, 000 bottles (3 g each) were produced after sieving and blending of the hair powder. Certified values for total mercury and methylmercury, as well as other trace elements of toxicological and nutritional significance (antimony, cadmium, copper, lead, selenium, and zinc), were determined based on analyses from extensive collaborations. Reference values for 12 elements (aluminium, arsenic, barium, calcium, cobalt, iron, magnesium, manganese, silver, sodium, sulfur and vanadium) were also given.     

The chamber basis of the Orlik–Solomon algebra and Aomoto complex

We introduce a basis of the Orlik–Solomon algebra labeled by chambers, the so called chamber basis. We consider structure constants of the Orlik–Solomon algebra with respect to the chamber basis and prove that these structure constants recover D. Cohen’s minimal complex from the Aomoto complex.     

Application of a quadrupole-coupling model to doublet bands in doubly-odd nuclei

A simple model is applied to the yrast and yrare states based on the νh _11/2 ⊗ πh _11/2 configuration in the doubly-odd nuclei around the mass 130. In the model, the basis state is constructed by one neutron and one proton both in the 0h _11/2 orbital, and by the collective core which couples with the two particles through a quadrupole interaction. The model reproduces quite well the overall energy levels and the electromagnetic transitions. The analysis of the yrast and yrare states reveals that the angular-momentum configuration of the neutron and the proton in the yrast states is different from that in the yrare states, when the two particles are weakly coupled with the quadrupole collective excitations of the core. The strong even-odd staggering of the ratios B(M1;I → I - 1)/B(E2;I → I - 2) for the yrast states is described by the chopsticks-like motion of two angular momenta of the neutron and the proton.     

Solvolysis of 2-m-chlorobenzoyloxy-4-isopropyl-2h-1,4-thiazin-3-one generation of a stable carbocation

The title compound $\text{2b}$ undergoes nucleophilic substition reactions with exclusive aklyl-oxygen bond fission and its rate of solvolysis is highly sensitive toward change in polarity of solvents, as is shown by its highest m-value of all reported so far in logK - logk₀ = mY.