Integrated membrane systems for gas separation in biotechnology: potential and prospects

Integrated non-porous membrane systems were applied for microbial combustible gas separation processes. Methane/CO₂ mixtures of various concentrations from methane fermentation processes (biogas) were separated using a membrane-separation complex of permabsorber type into individual components of technical grade (more than 95% purity). In experiments with three-component mixtures, using a selective membrane valve with various liquid carriers, all the gases of interest (H₂, CH₄ and CO₂) were obtained at greater than 90% purity in one separation step. The perspectives for the further application of non-porous membrane separating devices for various gaseous mixtures from different microbial processes are discussed.V. Teplyakov and E. Sostina are with the A.V. Topchiev institute of Petrochemical Synthesis, Russian Academy of Sciences, Membrane Research Center, Moscow 117912, Russia. E. Sostina is also, and A. Netrusov is with the Microbiology Department, Moscow University, Moscow 119899, Russia. I. Beckman is with the Chemistry Department, Moscow University, Moscow 119899, Russia.     

Peroxynitrite-Induced Cytotoxicity in PC12 Cells: Evidence for an Apoptotic Mechanism Differentially Modulated by Neurotrophic Factors

Abstract: Peroxynitrite is a powerful oxidant formed by the near-diffusion-limited reaction of nitric oxide with superoxide. Large doses of peroxynitrite (>2 m M ) resulted in rapid cell swelling and necrosis of undifferentiated PC12 cells. However, brief exposure to lower concentrations of peroxynitrite (EC₅₀ = 850 µ M ) initially (3–4 h) caused minimal damage to low-density cultures. By 8 h, cytoplasmic shrinkage with nuclear condensation and fragmentation became increasingly evident. After 24 h, 36% of peroxynitrite-treated cells demonstrated these features associated with apoptosis. In addition, 46% of peroxynitrite-treated cells demonstrated DNA fragmentation (by terminal-deoxynucleotide transferase-mediated dUTP-digoxigenin nick end-labeling) after 7 h, which was inhibited by posttreatment with the endonuclease inhibitor aurintricarboxylic acid. Serum starvation also resulted in apoptosis in control cells (23%), the percentage of which was not altered significantly by peroxynitrite treatment. Although peroxynitrite is known to be toxic to cells, the present study provides a first indication that peroxynitrite induces apoptosis. Furthermore, pretreatment of cells with nerve growth factor or insulin, but not epidermal growth factor, was protective against peroxynitrite-induced apoptosis. However, both acidic and basic fibroblast growth factors greatly increased peroxynitrite-initiated apoptosis, to 63 and 70%, respectively. Thus, specific trophic factors demonstrate differential regulation of peroxynitrite-induced apoptosis in vitro.     

Chilling-sensitive mutants of arabidopsis

Twenty-one mutants ofArabidopsis thaliana were isolated that developed chlorosis or necrosis upon incubation at low temperature (10°C to 15°C). Crosses among mutants in different phenotypic classes showed that mutants in three of four classes were found in a small number of loci. This article is reproduced fromWeeds World, vol. 1. For electronic access toWeeds World, see PMBR 12(4):302–303.     

Protein extraction and activity in reverse micelles of a nonionic detergent

We describe, for the first time, the ability of a polyoxyethylene sorbitan trioleate-isopropanol microemulsion in hexane to solubilize pure proteins. The dependences of cytochrome c extraction and buffer solubilization by the reverse micellar system on ionic strength of the aqueous phase, detergent concentration, and cosurfactant concentration result in increased extraction. In addition, subtilisin (a serine protease) is shown to be active in this microemulsion. Further the activity of the enzyme can be regulated by the water content of the micelles, enabling control of enzyme activity by "solvent engineering."     

A general synthesis of long chain ω- and (ω-1)-hydroxy fatty acids

A method for the synthesis of long chain fatty acids substituted at the ω and ω-1 positions has been developed. The key step is the isomerization of the triple bond of an alkyn-1-ol from an internal position in the chain to the free terminus with a new, convenient reagent, sodium aminopropylamide (NaAPA). Standard functional group manipulations i.e., Jones oxidation, esterification and hydroboration of the triple bond are used to prepare ω-hydroxy fatty esters. The generality of the method is illustrated with syntheses of ω-hydroxy fatty esters with 24, 26, 28 and 30 carbon chains.In the 24 carbon series, hydration of the terminal triple bond of alkynoic ester 4a followed by reduction gave the (ω-1)-hydroxy ester.     

The PRiMA-linked Cholinesterase Tetramers Are Assembled from Homodimers: HYBRID MOLECULES COMPOSED OF ACETYLCHOLINESTERASE AND BUTYRYLCHOLINESTERASE DIMERS ARE UP-REGULATED DURING DEVELOPMENT OF CHICKEN BRAIN*

Acetylcholinesterase (AChE) is anchored onto cell membranes by the transmembrane protein PRiMA (proline-rich membrane anchor) as a tetrameric globular form that is prominently expressed in vertebrate brain. In parallel, the PRiMA-linked tetrameric butyrylcholinesterase (BChE) is also found in the brain. A single type of AChE-BChE hybrid tetramer was formed in cell cultures by co-transfection of cDNAs encoding AChE_T and BChE_T with proline-rich attachment domain-containing proteins, PRiMA I, PRiMA II, or a fragment of ColQ having a C-terminal GPI addition signal (Q_N-GPI). Using AChE and BChE mutants, we showed that AChE-BChE hybrids linked with PRiMA or Q_N-GPI always consist of AChE_T and BChE_T homodimers. The dimer formation of AChE_T and BChE_T depends on the catalytic domains, and the assembly of tetramers with a proline-rich attachment domain-containing protein requires the presence of C-terminal “t-peptides” in cholinesterase subunits. Our results indicate that PRiMA- or ColQ-linked cholinesterase tetramers are assembled from AChE_T or BChE_T homodimers. Moreover, the PRiMA-linked AChE-BChE hybrids occur naturally in chicken brain, and their expression increases during development, suggesting that they might play a role in cholinergic neurotransmission.     

Pectate distribution and esterification in Dubautia leaves and soybean nodules,studied with a fluorescent hybridization probe

Carbohydrate-hybridization probes (Vreeland and Laetsch, 1989, Planta (177, 423–434) were used to localize the homogalacturonan (pectate) component of pectins in the cell walls of leaves and soybean root nodules. Leaves of two species of the dicotyledon Dubautia were compared; these species contain much pectin but differ in their tissue water relations with respect to their cell-wall properties. Maturation of the primary cell walls in nodules was studied in the Bradyrhizobium japonicum-Glycine max symbiosis. Probe labelling was based on the divalent-cation-mediated association between pectate in tissue sections and fluorescein-conjugated pectate fragments. Pectate was also labelled by mixed-dimer formation with fluorescent polyguluronate derived from alginate. The specificity of the probe for unesterified polygalacturonate was indicated by increased cell-wall labelling after chemical or enzymatic deesterification of tissue sections, in contrast to elimination of labelling by chemical esterification. Postfixation of tissue sections improved retention of soluble pectate. Pectate differences were found in the leaves among cell types, in degree of esterification, and between plant species. The cell walls of soybean nodules were strongly labelled by the pectate probe in nodules one week and three weeks after infection. Pectate was more highly esterified in the central infected zone than in the surrouding cortex. Within the infected zone, walls of uninfected cells and infected cells were similarly labelled by the pectate probe. The results indicate that the pectate molecular probe provides detailed information on pectate distribution at the cellular level for investigations of cell-wall structure, development and physiology.Abbreviations EDTA ethylenedinitrilotetraacetic acid (ethylenediaminetetraacetic acid) - NMR nuclear magnetic resonance spectroscopy - TTB 1,3,5-triazido-2,4,6-trinitrobenene     

Characterization of an antigenically related family of cell-type specific proteins implicated in slug migration in Dictyostelium discoideum

The monoclonal antibody MUD50 recognizes a group of developmentally regulated proteins, which are almost exclusively expressed by prespore cells in developing aggregates of Dictyostelium discoideum. Some of these antigens are integrally associated with the cell membrane, as assessed by physical and detergent-fractionation procedures. The MUD50-reactive proteins are glycosylated and some are phosphorylated. Post-translational modification is the common antigenic feature that is recognized by the MUD50 antibody in these cell-type-specific proteins. A glycosylation-defective mutant, DL118, (modB) does not express the MUD50 epitope, but does express the MUD52 epitope, which is found on a different group of glycoproteins. Therefore, we conclude that MUD50 recognizes a particular carbohydrate epitope on a restricted group of proteins. These proteins are structurally diverse, but are apparently involved in the maintenance of structure and movement of the multicellular D. discoideum slug.