Asymmetric transfer hydrogenation using amino acid derivatives; further studies and a mechanistic proposal

A series of investigations into the use of amino acid derivatives for the asymmetric catalysis of the transfer hydrogenation of ketones are presented. Based on the results observed, a mechanistic suggestion for the origin of the enantioselective induction is proposed.     

Identification of archaeal proteins that affect the exosome function in vitro

Background  

The archaeal exosome is formed by a hexameric RNase PH ring and three RNA binding subunits and has been shown to bind and degrade RNA in vitro. Despite extensive studies on the eukaryotic exosome and on the proteins interacting with this complex, little information is yet available on the identification and function of archaeal exosome regulatory factors.     

Mathematical programming approach to the Petri nets reachability problem

This paper focuses on the resolution of the reachability problem in Petri nets, using the mathematical programming paradigm. The proposed approach is based on an implicit traversal of the Petri net reachability graph. This is done by constructing a unique sequence of Steps that represents exactly the total behaviour of the net. We propose several formulations based on integer and/or binary linear programming, and the corresponding sets of adjustments to the particular class of problem considered. Our models are validated on a set of benchmarks and compared with standard approaches from IA and Petri nets community.     

Asymptotic behavior of manifolds without conjugate points

This research was partially supported by GARC-KOSEF.     

Common variants at the promoter region of the APOM confer a risk of rheumatoid arthritis

Although the genetic component in the etiology of rheumatoid arthritis (RA) has been consistently suggested, many novel genetic loci remain to uncover. To identify RA risk loci, we performed a genome-wide association study (GWAS) with 100 RA cases and 600 controls using Affymetrix SNP array 5.0. The candidate risk locus (APOM gene) was re-sequenced to discover novel promoter and coding variants in a group of the subjects. Replication was performed with the independent case-control set comprising of 578 RAs and 711 controls. Through GWAS, we identified a novel SNP associated with RA at the APOM gene in the MHC class III region on 6p21.33 (rs805297, odds ratio (OR) = 2.28, P = 5.20 × 10-7). Three more polymorphisms were identified at the promoter region of the APOM by the re-sequencing. For the replication, we genotyped the four SNP loci in the independent case-control set. The association of rs805297 identified by GWAS was successfully replicated (OR = 1.40, P = 6.65 × 10-5). The association became more significant in the combined analysis of discovery and replication sets (OR = 1.56, P = 2.73 × 10-10). The individuals with the rs805297 risk allele (A) at the promoter region showed a significantly lower level of APOM expression compared with those with the protective allele (C) homozygote. In the logistic regressions by the phenotype status, the homozygote risk genotype (A/A) consistently showed higher ORs than the heterozygote one (A/C) for the phenotype-positive RAs. These results indicate that APOM promoter polymorphisms are significantly associated with the susceptibility to RA.     

Geodesic connectedness of the causal completion in the Lorentzian geometry

We consider the topology of the BS causal completion, and show that it is not distorted in the causal direction. Using this result, we show that the causal completion with spacelike causal boundary in the sense of the BS construction satisfies the formal definition of the global hyperbolicity. We also show that any two causally related points in the causal completion can be connected by a causal geodesic.     

Pteridines. Part CVI. Isolation and characterization of limipterin (1-O-(L-erythro-biopterin-2′-yl)-β-N-acetylglucosamine) and its 5,6,7,8-tetrahydro derivative from green sulfur bacterium Chlorobium limicola f. thiosulfatophilum NCIB 8327

A new pteridine compound was isolated from green sulfur photosynthetic bacteria, Chlorobium limicola f. thiosulfatophilum NCIB 8327. The structure of this pterin derivative was established to be 1-O-(L -erythro-5,6,7,8- tetrahydropterin-2′-yl)-β-N-acetylglucosamine ( 1 ) from ¹H-NMR and CD spectra as well as from various mass spectrometric techniques and chemical-cleavage techniques. Upon acid hydrolysis of 1 , equimolar amounts of biopterin ( 2 ) and N-acetylglucosamine were produced. The structure of the hydrolysis product 2 was confirmed by comparing its NMR, UV, CD, and MS and its chromatographical behavior with those of an authentic specimen. N-Acetylglucosamine was identified by an enzymatic hydrolysis experiment as well as by NMR and thin layer chromatography. Electrospray (ES), fast-atom-bombardment (FAB), and thermospray (TS) mass spectrometry of 1 yielded an MH⁺ at m/z 441. Periodate-oxidation experiments of the intact molecule 1 and of its hydrolysis product 2 are consistent with the proposed structure. Differential I₂ oxidation experiments with the native compound showed that the in vivo oxidation state of this pterin is its tetrahydro form. We propose the trivial name ‘limipterin’ for this new compound.