278 research outputs found
Enantioselective Transesterification by Candida antarctica Lipase B Immobilized on Fumed Silica
Enzymatic catalysis to produce molecules such as perfumes, flavors, and fragrances has the advantage of allowing the products to be labeled ânaturalâ for marketing in the U.S., in addition to the exquisite selectivity and stereoselectivity of enzymes that can be an advantage over chemical catalysis. Enzymatic catalysis in organic solvents is attractive if solubility issues of reactants or products, or thermodynamic issues (water as a product in esterification) complicate or prevent aqueous enzymatic catalysis. Immobilization of the enzyme on a solid support can address the generally poor solubility of enzymes in most solvents.
We have recently reported on a novel immobilization method for Candida antarctica Lipase B on fumed silica to improve the enzymatic activity in hexane. This research is extended here to study the enantioselective transesterification of (RS)-1-phenylethanol with vinyl acetate. The maximum catalytic activity for this preparation exceeded the activity (on an equal enzyme amount basis) of the commercial Novozyme 435Ÿ significantly. The steady-state conversion for (R)-1-phenylethanol was about 75% as confirmed via forward and reverse reaction. The catalytic activity steeply increases with increasing nominal surface coverage of the support until a maximum is reached at a nominal surface coverage of 230%. We hypothesize that the physical state of the enzyme molecules at a low surface coverage is dominated in this case by detrimental strong enzyme-substrate interactions. Enzyme-enzyme interactions may stabilize the active form of the enzyme as surface coverage increases while diffusion limitations reduce the apparent catalytic performance again at multi-layer coverage. The temperature-, solvent-, and long-term stability for CALB/fumed silica preparations showed that these preparations can tolerate temperatures up to 70°C, continuous exposure to solvents, and long term storage
Attachment, Growth, and Detachment of Human Mesenchymal Stem Cells in a Chemically Defined Medium
Citation: Denise Salzig, Jasmin Leber, Katharina Merkewitz, Michaela C. Lange, Natascha Köster, and Peter Czermak, âAttachment, Growth, and Detachment of Human Mesenchymal Stem Cells in a Chemically Defined Medium,â Stem Cells International, vol. 2016, Article ID 5246584, 10 pages, 2016. doi:10.1155/2016/5246584The manufacture of human mesenchymal stem cells (hMSCs) for clinical applications requires an appropriate growth surface and an optimized, preferably chemically defined medium (CDM) for expansion. We investigated a new protein/peptide-free CDM that supports the adhesion, growth, and detachment of an immortalized hMSC line (hMSC-TERT) as well as primary cells derived from bone marrow (bm-hMSCs) and adipose tissue (ad-hMSCs). We observed the rapid attachment and spreading of hMSC-TERT cells and ad-hMSCs in CDM concomitant with the expression of integrin and actin fibers. Cell spreading was promoted by coating the growth surface with collagen type IV and fibronectin. The growth of hMSC-TERT cells was similar in CDM and serum-containing medium whereas the lag phase of bm-hMSCs was prolonged in CDM. FGF-2 or surface coating with collagen type IV promoted the growth of bm-hMSCs, but laminin had no effect. All three cell types retained their trilineage differentiation capability in CDM and were detached by several enzymes (but not collagenase in the case of hMSC-TERT cells). The medium and coating did not affect detachment efficiency but influenced cell survival after detachment. CDM combined with cell-specific surface coatings and/or FGF-2 supplements is therefore as effective as serum-containing medium for the manufacture of different hMSC types
Regulatory effects of interleukinâ11 during acute lung inflammatory injury
The role of interleukinâ11 (ILâ11) was evaluated in the IgG immune complex model of acute lung injury in rats. ILâ11 mRNA and protein were both upâregulated during the course of this inflammatory response. Exogenously administered ILâ11 substantially reduced, in a doseâdependent manner, the intrapulmonary accumulation of neutrophils and the lung vascular leak of albumin. These in vivo antiâinflammatory effects of ILâ11 were associated with reduced NFâÎșB activation in lung, reduced levels of tumor necrosis factor α (TNFâα) in bronchoalveolar lavage (BAL) fluids, and diminished upâregulation of lung vascular ICAMâ1. It is interesting that ILâ11 did not affect BAL fluid content of the CXC chemokines, macrophage inflammatory proteinâ2 (MIPâ2) and cytokineâinducible neutrophil chemoattractant (CINC); the presence of ILâ11 did not affect these chemokines. However, BAL content of C5a was reduced by ILâ11. These data indicate that ILâ11 is a regulatory cytokine in the lung and that, like other members of this family, its antiâinflammatory properties appear to be linked to its suppression of NFâÎșB activation, diminished production of TNFâα, and reduced upâregulation of lung vascular ICAMâ1. J. Leukoc. Biol. 66: 151â157; 1999.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141937/1/jlb0151.pd
Silicon detector for a Compton Camera in Nuclear Medical Imaging
Electronically collimated gamma ca\-me\-ras based on Com\-pton scattering in silicon pad sensors may improve imaging in nuclear medicine and bio-medical research. The work described here concentrates on the silicon pad detector developed for a prototype Compton camera. The silicon pad sensors are read out using low noise VLSI CMOS chips and novel fast triggering chips. Depending on the application a light weight and dense packaging of sensors and its readout electronics on a hybrid is required. We describe the silicon pad sensor and their readout with the newly designed hybrid. %The silicon detector of a Compton camera %may contain up to ~analogue channels requiring %a fast and low cost data acquisition system. We also describe a modular and low-cost data acquisition system (CCDAQ) based on a digital signal processor which is interfaced to the EPP port of personal computers. Using the CCDAQ and the hybrids energy spectra of gamma-ray photons from technetium (Tc) and americium (Am) were acquired with an energy resolution of 2.45~keV FWHM for the 140.5~keV photo-absorption line of Tc. For all pads the discrimination threshold in the trigger chip was between (15 and 25)~keV
Conformal TiO aerogel-like films by plasma deposition: from omniphobic antireflective coatings to perovskite solar cells photoelectrodes
The ability to control porosity in oxide thin films is one of the key factors
that determine their properties. Despite the abundance of dry processes for the
synthesis of oxide porous layers, the high porosity range is typically achieved
by spin-coating-based wet chemical methods. Besides, special techniques such as
supercritical drying are required to replace the pore liquid with air while
maintaining the porous network. In this study, we propose a new method for the
fabrication of ultra-porous titanium dioxide thin films at room or mild
temperatures (T lower or equal to 120 degrees Celsius) by the sequential
process involving plasma deposition and etching. These films are conformal to
the substrate topography even for high-aspect-ratio substrates and show
percolated porosity values above 85 percent that are comparable to advanced
aerogels. The films deposited at room temperature are amorphous. However, they
become partly crystalline at slightly higher temperatures presenting a
distribution of anatase clusters embedded in the sponge-like structure.
Surprisingly, the porous structure remains after annealing the films at 450
degrees Celsius in air, which increases the fraction of the embedded anatase
nanocrystals. The films are antireflective, omniphobic, and photoactive
becoming super-hydrophilic subjected to UV light irradiation The supported
percolated nanoporous structure can be used as an electron-conducting electrode
in perovskite solar cells. The properties of the cells depend on the aerogel
film thickness reaching efficiencies close to those of commercial mesoporous
anatase electrodes. This generic solvent-free synthesis is scalable and is
applicable to ultra-high porous conformal oxides of different compositions with
potential applications in photonics, optoelectronics, energy storage, and
controlled wetting.Comment: 31 pages, 10 Figs. plus Supporting Information 7 pags, 6 figs. Full
Pape
Expansion and Harvesting of hMSC-TERT
The expansion of human mesenchymal stem cells as suspension culture by means of spinner flasks and microcarriers, compared to the cultivation in tissue culture flasks, offers the advantage of reducing the requirements of large incubator capacities as well as reducing the handling effort during cultivation and harvesting. Nonporous microcarriers are preferable when the cells need to be kept in viable condition for further applications like tissue engineering or cell therapy. In this study, the qualification of Biosilon, Cytodex 1, Cytodex 3, RapidCell and P102-L for expansion of hMSC-TERT with an associated harvesting process using either trypsin, accutase, collagenase or a trypsin-accutase mixture was investigated. A subsequent adipogenic differentiation of harvested hMSC-TERT was performed in order to observe possible negative effects on their (adipogenic) differentiation potential as a result of the cultivation and harvesting method. The cultivated cells showed an average growth rate of 0.52 d-1. The cells cultivated on Biosilon, RapidCell and P102-L were harvested succesfully achieving high cell yield and vitalities near 100%. This was not the case for cells on Cytodex 1 and Cytodex 3. The trypsin-accutase mix was most effective. After spinner expansion and harvesting the cells were successfully differentiated to adipocytes
Measurement of inclusive D*+- and associated dijet cross sections in photoproduction at HERA
Inclusive photoproduction of D*+- mesons has been measured for photon-proton
centre-of-mass energies in the range 130 < W < 280 GeV and a photon virtuality
Q^2 < 1 GeV^2. The data sample used corresponds to an integrated luminosity of
37 pb^-1. Total and differential cross sections as functions of the D*
transverse momentum and pseudorapidity are presented in restricted kinematical
regions and the data are compared with next-to-leading order (NLO) perturbative
QCD calculations using the "massive charm" and "massless charm" schemes. The
measured cross sections are generally above the NLO calculations, in particular
in the forward (proton) direction. The large data sample also allows the study
of dijet production associated with charm. A significant resolved as well as a
direct photon component contribute to the cross section. Leading order QCD
Monte Carlo calculations indicate that the resolved contribution arises from a
significant charm component in the photon. A massive charm NLO parton level
calculation yields lower cross sections compared to the measured results in a
kinematic region where the resolved photon contribution is significant.Comment: 32 pages including 6 figure
R & D for collider beauty physics at the LHC
We propose an R&D program for the development of a Beauty trigger and innovative elements of the associated spectrometer. A series of short test runs is proposed at the SPS p-pbar Collider with the minimal spectrometer which will allow a credible B signal to be obtained in an invariant mass spectrum of reconstructed B mesons. The program builds on the success of the recent collider run of the P238 Collaboration, in which clean signals from beam-beam interactions were observed in a large silicon strip microvertex detector running 1.5 mm from the circulating beams. A continuing successful R&D program of the type proposed could ultimately lead to a collider experiment at the LHC to study CP Violation and rare B decays
Targeted Deletion of HIF-1α Gene in T Cells Prevents their Inhibition in Hypoxic Inflamed Tissues and Improves Septic Mice Survival
Sepsis patients may die either from an overwhelming systemic immune response and/or from an immunoparalysis-associated lack of anti-bacterial immune defence. We hypothesized that bacterial superantigen-activated T cells may be prevented from contribution into anti-bacterial response due to the inhibition of their effector functions by the hypoxia inducible transcription factor (HIF-1alpha) in inflamed and hypoxic areas.Using the Cre-lox-P-system we generated mice with a T-cell targeted deletion of the HIF-1alpha gene and analysed them in an in vivo model of bacterial sepsis. We show that deletion of the HIF-1alpha gene leads to higher levels of pro-inflammatory cytokines, stronger anti-bacterial effects and much better survival of mice. These effects can be at least partially explained by significantly increased NF-kappaB activation in TCR activated HIF-1 alpha deficient T cells.T cells can be recruited to powerfully contribute to anti-bacterial response if they are relieved from inhibition by HIF-1alpha in inflamed and hypoxic areas. Our experiments uncovered the before unappreciated reserve of anti-bacterial capacity of T cells and suggest novel therapeutic anti-pathogen strategies based on targeted deletion or inhibition of HIF-1 alpha in T cells
Nicotinic receptors mediate stress-nicotine detrimental interplay via dopamine cellsâ activity
Epidemiological studies report strong association between mood disorders and tobacco addiction. This high comorbidity requires adequate treatment but the underlying mechanisms are unknown. We demonstrate that nicotine exposure, independent of drug withdrawal effects, increases stress sensitivity, a major risk factor in mood disorders. Nicotine and stress concur to induce long-lasting cellular adaptations within the dopamine (DA) system. This interplay is underpinned by marked remodeling of nicotinic systems, causing increased ventral tegmental area (VTA) DA neuronsâ
activity and stress-related behaviors, such as social aversion. Blocking ÎČ2 or α7 nicotinic acetylcholine receptors (nAChRs) prevents, respectively, the development and the expression of social stress-induced neuroadaptations; conversely, facilitating α7 nAChRs activation specifically in the VTA promotes stress-induced
cellular and behavioral maladaptations. Our work unravels a complex nicotine-stress bidirectional interplay and identifies α7 nAChRs as a promising therapeutic target for stress-related psychiatric disorders
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