Optimization and simulation of continuous affinity-recycle extraction (care).

Simulation and optimization of continuous affinity recycle extraction (CARE), a protein purification unit operation based on protein adsorption to solid phase adsorbents, is described in this paper. Rather than packing conventional adsorbent particles in a fixed bed (column), solid/liquid contact is carried out in well-mixed reactors. Continuous operation is achieved by recirculation of the adsorbent particles between two or more contactors. The feasibility of this purification scheme was established with the recovery and isolation of the enzyme beta-galactosidase from E.coli, using the affinity support PABTG/Agarose. A mathematical model describing system performance was developed. The mathematical model was used to optimize several facets of the system design and operation. The base two-stage contractor design was modified by the addition of an intermediate wash stage as well as the incorporation of multiple adsorption stages. These design modifications serve to increase purification, concentration and recovery while utilizing the same amount of adsorbent. The methodology for defining and optimizing objective functions was developed and experimentally validated. Finally, optimum system start-up protocols, minimizing the time required to reach steady-state operation, were developed and experimentally validated. The impact of early introduction of adsorptive purification in a downstream processing sequence, with CARE, was evaluated and is described. Through the early introduction of a highly specific adsorptive step, significant purification is achieved simultaneously with clarification and concentration. In addition, purification performance in CARE was contrasted with that achievable in conventional column chromatography.     

Enhancement of oxygen transfer in highly viscous non-newtonian fermentation broths

The influence of short draft tubes covered by perforated plates on gas-liquid mass transfer was examined in external-loop airlift bioreactors. The volumetric mass transfer coefficients in a model external-loop airlift bioreactor were measured with water and non-Newtonian media. It was found that introduction of draft tubes covered with perforated plates in the riser significantly improved the mass transfer rate, particularly in higher viscous non-Newtonian fermentation media. The enhancement of mass transfer rate might be due mainly to an increase in bubble coalescence and redispersion. (c) 1994 John Wiley & Sons, Inc.     

A Similar Expression Pattern of Adhesion Molecules between Intermediate TCR Cells in the Liver and Intraepithelial Lymphocytes in the Intestine

Two major populations of extrathymically differentiated T cells exist in the liver and intestine. Such T cells in the liver have TCR of intermediate intensity (i.e., intermediate TCR cells) and constitutively express IL-2 receptor β-chain (IL-2Rβ), whereas those in the intestine, especially intraepithelial lymphocytes, have TCR of bright intensity, consisting of a mixture of IL-2Rβ⁺ and IL-2Rβ^–. All mature thymocytes and thymus-derived T cells seen in the peripheral immune organs are TCR-bright⁺IL-2Rβ^– under resting conditions. When the expression pattern of adhesion molecules, including CD44, L-selectin, LFA-1 and ICAM-1, was compared among these T-cell populations, they displayed quite unique patterns of expression. All extrathymic T cells in the liver, intestine, and even other organs were CD44⁺L-selectin^– LFA-1⁺⁺ICAM-1⁺, whereas thymocytes and thymus-derived T cells were CD44^– L-selectin⁺LFA-1⁺ICAM-1^–. This inverted expression of adhesion molecules between extrathymic T cells and thymus-derived T cells might be associated with their unique tissue-localization.     

Respiratory inhibitors of a magnetic bacterium Magnetospirillum sp. AMB-1 capable of growing aerobically

Respiratory inhibitors of a magnetic bacterium Magnetospirillum sp. AMB-1, which is able to grow aerobically, were investigated using a microbial electrode system. The respiration of strain AMB-1 was inhibited by 2-heptyl-4-hydroxyquinoline N-oxide (HQNO), KCN and dicumarol. Strain AMB-1 cannot grow in the presence of these inhibitors under aerobic conditions. On the other hand, strain AMB-1 can grow and form magnetite (Fe₃O₄) particles with HQNO and KCN under anaerobic conditions. Growth and magnetite formation of strain AMB-1 were reduced by dicumarol, which also inhibited iron reduction under anaerobic conditions, whereas iron reduction was not inhibited by HQNO and KCN.     

Reproductive biology of the slender smoothhound,Gollum attenuatus,collected from New Zealand waters

Synopsis The reproductive biology of 385 male and 373 female slender smoothhounds,Gollum attenuatus, collected from New Zealand waters was examined. Size at maturity for both sexes was about 700 mm TL. Litter size was usually two. The sex ratio of embryos was 1:1. The right ovary ovulated 50–100 ova, 4–8 mm in diameter, and 30–80 ova were enclosed in each egg capsule. Only one embryo developed from the many ova in each egg capsule, the other undeveloped ova were ingested and passed to an external yolk sac which formed the yolk supply for the developing embryo.     

Purification and properties of thiamine-binding proteins from sesame seed

Three thiamine-binding proteins of 17-19 kDa (STBP-I, II, and III) were purified from sesame seed (Sesamum indicum L.). Each of the proteins was composed of two subunits of equal molecular mass and each subunit consisted of a large polypeptide and a small polypeptide linked by a disulfide bond(s). They were rich in glutamic acid (or glutamine) and arginine. Their binding activities were optimal at neutral pH. They bound specifically free thiamine but not thiamine phosphates. STBP-I had higher affinity for thiamine than STBP-II or STBP-III. STBP-II and STBP-III bound one molecule of thiamine per molecule, and STBP-I bound 0.5 molecule. The amino acid composition and structure of the STPBs were similar to those of 2S storage proteins.     

A sulfotransferase model: Covalent participation of a macrocyclic oxime in the hydrolysis of 2,4-dinitrophenyl sulfate

The liberation of 2,4-dinitrophenolate ion from 2,4-dinitrophenyl sulfate (DNPS) in aqueous organic solvent with 0.1 N sodium hydroxide was accelerated upon addition of an equimolar amount of Oxime-I (10-hydroxy-11-hydroxyimino[20]-paracyclophane) to the sulfate ester. Oxime-I was found to undergo covalent participation at the oxime group to afford oxime O-sulfonate. The rate acceleration with Oxime-I was larger than that with β-CD (cycloheptaamylose). The catalytic efficiency of Oxime-I has been ascribed primarily to the tighter inclusion of the substrate ester into the more hydrophobic Oxime-I cavity provided by the effective apolar paracyclophane skeleton, as well as to the greater nucleophilicity of the oxime group than of the hydroxyl group in β-CD. Consequently, Oxime-I may be considered as a conventional model for arylsulfatases and sulfotransferases, providing the effective binding process for the substrate.     

Observations on the effect of visual and olfactory ablation on the swimming behavior of migrating adult chum salmon,Oncorhynchus keta

The behavior of chum slamon,Oncorhynchus keta, was studied using ultrasonic telemetry in the waters off the Okhotsk coast of Hokkaido from 1979 to 1981. Thirty-six adult fish were outfitted with a 50 KHz ultrasonic transmitter provided with either a depth sensor, depth/illumination sensors, or depth/ temperature sensors. Twenty-one of the experimental fish were used as controls and left intact. Of the remaining fish, six had their sight destroyed, seven had their olfactory nerves severed or their nares filled with wax, one had both senses destroyed, and one had a sham operation, but had only a shallow transverse cut made in the skin over the olfactory nerves. Control fish and the fish with the sham operation initially swam in a horizontal zigzag pattern while fish with an obliterated sense swam in a similar pattern but to a reduced extent. The horizontal and vertical speeds of the intact fish were faster than those of the fish with a destroyed sense. Amplitude of vertical movements of the intact fish stretched from surface to bottom, while fish with destroyed vision tended towards midwater. Fish without an olfactory sense tended to be at the surface or near the bottom. Regular vertical movement would be effective in refreshing olfactory epithelia which might become acclimated when exposed to one odor. The vertical movements can be found in the horizontal zigzag movements in coastal and near shore migrations, as well as in the stream phase of homing. The zigzag movements, both horizontal and vertical, allow the fish to sense the water masses and locate the correct tributary.     

Direct Visualization of the Interfacial Degradation of Cathode Coatings in Solid State Batteries: A Combined Experimental and Computational Study

The interfacial instability between a thiophosphate solid electrolyte and oxide cathodes results in rapid capacity fade and has driven the need for cathode coatings. In this work, the stability, evolution, and performance of uncoated, Li₂ZrO₃‐coated, and Li₃B₁₁O₁₈‐coated LiNi_0.5Co_0.2Mn_0.3O₂ cathodes are compared using first‐principles computations and electron microscopy characterization. Li₃B₁₁O₁₈ is identified as a superior coating that exhibits excellent oxidation/chemical stability, leading to substantially improved performance over cells with Li₂ZrO₃‐coated or uncoated cathodes. The chemical and structural origin of the different performance is interpreted using different microscopy techniques which enable the direct observation of the phase decomposition of the Li₂ZrO₃ coating. It is observed that Li is already extracted from the Li₂ZrO₃ in the first charge, leading to the formation of ZrO₂ nanocrystallites with loss of protection of the cathode. After 50 cycles separated (Co, Ni)‐sulfides and Mn‐sulfides can be observed within the Li₂ZrO₃‐coated material. This work illustrates the severity of the interfacial reactions between a thiophosphate electrolyte and oxide cathode and shows the importance of using coating materials that are absolutely stable at high voltage.     

Binding of HIV-1 gp120 to DC-SIGN Promotes ASK-1-Dependent Activation-Induced Apoptosis of Human Dendritic Cells

During disease progression to AIDS, HIV-1 infected individuals become increasingly immunosuppressed and susceptible to opportunistic infections. It has also been demonstrated that multiple subsets of dendritic cells (DC), including DC-SIGN(+) cells, become significantly depleted in the blood and lymphoid tissues of AIDS patients, which may contribute to the failure in initiating effective host immune responses. The mechanism for DC depletion, however, is unclear. It is also known that vast quantities of viral envelope protein gp120 are shed from maturing HIV-1 virions and form circulating immune complexes in the serum of HIV-1-infected individuals, but the pathological role of gp120 in HIV-1 pathogenesis remains elusive. Here we describe a previously unrecognized mechanism of DC death in chronic HIV-1 infection, in which ligation of DC-SIGN by gp120 sensitizes DC to undergo accelerated apoptosis in response to a variety of activation stimuli. The cultured monocyte-derived DC and also freshly-isolated DC-SIGN(+) blood DC that were exposed to either cross-linked recombinant gp120 or immune-complex gp120 in HIV(+) serum underwent considerable apoptosis after CD40 ligation or exposure to bacterial lipopolysaccharide (LPS) or pro-inflammatory cytokines such as TNFα and IL-1β. Furthermore, circulating DC-SIGN(+) DC that were isolated directly from HIV-1(+) individuals had actually been pre-sensitized by serum gp120 for activation-induced exorbitant apoptosis. In all cases the DC apoptosis was substantially inhibited by DC-SIGN blockade. Finally, we showed that accelerated DC apoptosis was a direct consequence of excessive activation of the pro-apoptotic molecule ASK-1 and transfection of siRNA against ASK-1 significantly prevented the activation-induced excessive DC death. Our study discloses a previously unknown mechanism of immune modulation by envelope protein gp120, provides new insights into HIV immunopathogenesis, and suggests potential therapeutic approaches to prevent DC depletion in chronic HIV infection.