59 research outputs found
Unified Strategy Enables the Collective Syntheses of Structurally Diverse Indole Alkaloids
Natural
products and their analogues are significant sources of
therapeutic lead compounds. However, synthetic strategies for generating
large collections of these molecules remain a significant challenge.
The most difficult step in their synthesis is the design of a common
intermediate that can be easily transformed into natural products
belonging to different families. This study demonstrates the evolution
of synthetic tactics designed to assemble the functionalized piperidines
present in indole alkaloids from a common intermediate. More importantly,
we also report a previously unknown Ir- and Er-catalyzed dehydrogenative
spirocyclization reaction that enables direct access to spirocyclic
oxindole alkaloids. As a practical application, the asymmetric total
syntheses of 29 natural alkaloids belonging to different families
were accomplished by following a uniform synthetic route. The proposed
methodology extends the capability of the iridium-catalyzed dehydrogenative
coupling reaction to the realm of indole–alkaloid synthesis
and provides new opportunities for the efficient preparation of natural
product-like molecules
The cell membrane permeability coefficients of Sf21 for 1.0 M glycerol.
<p>The cell membrane permeability coefficients of Sf21 for 1.0 M glycerol.</p
Dual Dependence of Cryobiogical Properties of Sf21 Cell Membrane on the Temperature and the Concentration of the Cryoprotectant
<div><p>The Sf21 cell line is extensively used for virus research and producing heterologous recombinant proteins. To develop optimal strategies for minimizing cell injury due to intracellular ice formation and excessive volume shrinkage during cryopreservation, the fundamental transport properties including the osmotic inactive volume (<i>V<sub>b</sub></i>), the hydraulic conductivity (<i>L<sub>p</sub></i>), and the glycerol permeability (<i>P<sub>s</sub></i>) of Sf21 cell membrane at 25, 15, 5 and −2°C were characterized using a micro-perfusion chamber. The effects of temperature on the hydraulic conductivity and the glycerol permeability of Sf21 cell membrane, reflected by the activation energies, were quantitatively investigated. It was found that the hydraulic conductivity decreases along with the increase of the final CPA concentration at a given temperature, and quantitative analysis indicates that the hydraulic conductivity has a significant linear attenuation along with the increase of the concentration of glycerol. Therefore, we incorporate the concentration dependence of the hydraulic conductivity into the classic Arrhenius relationship by replacing the constant reference value of the hydraulic conductivity at the reference temperature with a function that is linearly dependent on the CPA concentration. Consequently, the prediction of the Arrhenius relationship is improved, and the novel Arrhenius relationship could be very important to the development of optimal strategies for cell cryopreservation.</p></div
Arrhenius plot of the hydraulic conductivity for solution in the presence of 1.0, 1.5, 2.0 M glycerol.
<p>The natural logarithms of the glycerol permeability coefficient (10<sup>−8 </sup>m/s) are linearly dependent to the 1000 fold of the reciprocal of the absolute temperature.</p
Arrhenius plot of the hydraulic conductivity for solution in the presence of 0, 1.0, 1.5, 2.0 M glycerol.
<p>The natural logarithms of the hydraulic conductivity (10<sup>−14</sup>m/Pa/s) are linearly dependent to the 1000 fold of the reciprocal of the absolute temperature.</p
The cell membrane permeability coefficients of Sf21 for 2.0 M glycerol.
<p>The cell membrane permeability coefficients of Sf21 for 2.0 M glycerol.</p
Dependence of the hydraulic conductivity of Sf21 cell membrane on the final glycerol concentration at 25, 15, 5 and −2°C, respectively.
<p>Dependence of the hydraulic conductivity of Sf21 cell membrane on the final glycerol concentration at 25, 15, 5 and −2°C, respectively.</p
The <i>E<sub>Lp</sub></i>, <i>L<sub>pg</sub></i>, <i>E<sub>Ps</sub> and P<sub>sg</sub></i> of the Sf21 for different osmotic shifts.
<p>The <i>E<sub>Lp</sub></i>, <i>L<sub>pg</sub></i>, <i>E<sub>Ps</sub> and P<sub>sg</sub></i> of the Sf21 for different osmotic shifts.</p
The cell membrane permeability coefficients of Sf21 for 1.5 M glycerol.
<p>The cell membrane permeability coefficients of Sf21 for 1.5 M glycerol.</p
The morphology and volume changes of representative cell.
<p>A The Sf21 cells were immobilized on the micro-channel. B The volume changes of a typical cell during the osmotic shift from PBS to 3×PBS solution at −2°C.</p
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