Isolation of a Kluyveromyces lactis Mutant Enriched in S-Adenosyl-L-Methionine and Growing in Whey Medium

The ability of six lactose-digesting yeast strains to accumulate S-adenosyl-L-methionine (AdoMet) when grown on whey medium was studied.Kluyveromyces lactis ATCC 8585 accumulated the greatest amount of AdoMet (15.2 mg per gram biomass) and was chosen for the development of an Ado-Met-enriched mutant. The Ado-Met-enriched mutant AM-65 was selected from mutants induced with N-methyl-N-nitro-N"-nitrosoguanidine. The strain accumulated 61.6 mg AdoMet per gram biomass. The effect of concentrations of medium components on AdoMet biosynthesis was studied. The ability of the mutant to accumulate AdoMet remained stable after multiple reinoculations.     

Graph-theoretic methods for the analysis of chemical and biochemical networks. I. Multistability and oscillations in ordinary differential equation models

A chemical mechanism is a model of a chemical reaction network consisting of a set of elementary reactions that express how molecules react with each other. In classical mass-action kinetics, a mechanism implies a set of ordinary differential equations (ODEs) which govern the time evolution of the concentrations. In this article, ODE models of chemical kinetics that have the potential for multiple positive equilibria or oscillations are studied. We begin by considering some methods of stability analysis based on the digraph of the Jacobian matrix. We then prove two theorems originally given by A. N. Ivanova which correlate the bifurcation structure of a mass-action model to the properties of a bipartite graph with nodes representing chemical species and reactions. We provide several examples of the application of these theorems.     

Legionella pneumophila-induced PKCalpha-, MAPK-, and NF-kappaB-dependent COX-2 expression in human lung epithelium

Legionella pneumophila causes community- and hospital-acquired pneumonia. Lung airway and alveolar epithelial cells comprise an important barrier against airborne pathogens. Cyclooxygenase (COX) and microsomal PGE(2) synthase-1 (mPGES-1)-derived prostaglandins like prostaglandin E(2) (PGE(2)) are considered as important regulators of lung function. Herein we tested the hypothesis that L. pneumophila induced COX-2 and mPGES-1-dependent PGE(2) production in pulmonary epithelial cells. Legionella induced the release of PGE(2) in primary human small airway epithelial cells and A549 cells. This was accompanied by an increased expression of COX-2 and mPGES-1 as well as an increased PLA(2) activity in infected cells. Deletion of the type IV secretion system Dot/Icm did not impair Legionella-related COX-2 expression or PGE(2) release in A549 cells. L. pneumophila induced the degradation of IkappaBalpha and activated NF-kappaB. Inhibition of IKK blocked L. pneumophila-induced PGE(2) release and COX-2 expression. We noted activation of p38 and p42/44 MAP kinase in Legionella-infected A549 cells. Moreover, membrane translocation and activation of PKCalpha was observed in infected cells. PKCalpha and p38 and p42/44 MAP kinase inhibitors reduced PGE(2) release and COX-2 expression. In summary, PKCalpha and p38 and p42/44 MAP kinase controlled COX-2 expression and subsequent PGE(2) release by Legionella-infected lung epithelial cells. These pathways may significantly contribute to the host response in Legionnaires' disease.     

High Molecular Weight Poly(butylene succinate-co-butylene furandicarboxylate) Copolyesters: From Catalyzed Polycondensation Reaction to Thermomechanical Properties

Novel potentially biobased aliphatic-aromatic copolyesters poly(butylene succinate-co-butylene furandicarboxylate) (PBSFs) in full composition range were successfully synthesized from 2,5-furandicarboxylic acid (FA), succinic acid (SA), and 1,4-butanediol (BDO) via an esterification and polycondensation process using tetrabutyl titanate (TBT) or TBT/La(acac)(3) as catalyst. The copolyesters were characterized by size exclusion chromatography (SEC), Fourier transform infrared (FTIR), (1)H NMR, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), and their tensile properties were also evaluated. The weight average molecular weight (M(w)) ranges from 39?000 to 89?000 g/mol. The copolyesters are random copolymers whose composition is well controlled by the feed ratio of the diacid monomers. PBSFs have excellent thermal stability. The glass transition temperature (T(g)) increases continuously with ?(BF) and agrees well with the Fox equation. The crystallizability and T(m) decrease with increasing butylene furandicarboxylate (BF) unit content (?(BF)) from 0 to 40 mol %, but rise again at ?(BF) of 50-100 mol %. Consequently, the tensile modulus and strength decrease, and the elongation at break increases with ?(BF) in the range of 0-40 mol %. At higher ?(BF), the modulus and strength increase and the ultimate elongation decreases. Thus, depending on ?(BF), the structure and properties of PBSFs can be tuned ranging from crystalline polymers possessing good tensile modulus (360-1800 MPa) and strength (20-35 MPa) to nearly amorphous polymer of low T(g) and high elongation (～600%), and therefore they may find applications in thermoplastics as well as elastomers or impact modifiers.     

Human homeodomain-interacting protein kinase-2 (HIPK2) is a member of the DYRK family of protein kinases and maps to chromosome 7q32-q34

Here we identified the human serine/threonine kinase HIPK2 as a novel member of the DYRK kinase subfamily. Alignment of several DYRK family proteins including the kinases minibrain, MJAK, PKY, the Dictyostelium kinase YakA and Saccharomyces YAK1 allowed the identification of several evolutionary conserved DYRK consensus motifs within the kinase domain. A lysine residue conserved between all DYRK kinase family members was found to be essential for the kinase function of HIPK2. Human HIPK2 was mapped to chromosome 7q32-q34 and murine HIPK2 to chromosome 6B, the homologue to human chromosome 7.     

Isolation of S-adenosyl-L-methionine from an enriched Kluyveromyces lactis mutant,grown in whey media

The ability of six lactose-digesting yeast strains to accumulate S-adenosyl-L-methionine (AdoMet) when grown on whey medium was studied. Kluyveromyces lactis ATCC 8585 accumulated the greatest amount of AdoMet (15.2 mg per gram biomass) and was chosen for the development of an Ado-Met-enriched mutant. The Ado-Met-enriched mutant AM-65 was selected from mutants induced with N-methyl-N-nitro-N'-nitrosoguanidine. The strain accumulated 61.6 mg AdoMet per gram biomass. The effect of concentrations of medium components on AdoMet biosynthesis was studied. The ability of the mutant to accumulate AdoMet remained stable after multiple reinoculations.