Das aus (t‐C4H9)2SbCl und LiAlH4 zugängliche Di‐tert.‐butylstibin reagiert mit Phenyllithium unter Bildung des Lithium‐di‐tert. butylstibids, das gegenüber anderen Alkalistibiden einen stärkeren nucleophilen Charakter besitzt und sich mit 1,4‐Dichlorbutan entweder im Sinne einer Kupplung zu (t‐C4H9)2Sb[CH2]4Sb(t‐C4H9)2 bzw. (t‐C4H9)2Sb[CH2]4Cl oder eines Metall‐Halogen‐Austausches zu (t‐C4H9)2SbSb(t‐C4H9)2 umsetzt. Letzteres entsteht auch aus (t‐C4H9)2SbCl und LiSb(t‐C4H9)2 · Dioxan und liefert mit LiC6H5 bzw. Brom unter Spaltung der SbSb‐Bindung die entsprechenden Antimonderivate. Die Bildung des Tetra‐tert. butyl‐cyclotetrastibins aus LiSb(t‐C4H9)2 und jod bzw. aus (t‐C4H9)2SbH wird beschrieben.
The understanding of biological reactions and evaluation of the significance for living cells strongly depends on the ability to visualize and quantify these processes. Digital holographic microscopy (DHM) enables quantitative phase contrast imaging for high resolution and minimal invasive live cell analysis without the need of labeling or complex sample preparation. However, due to the rather homogeneous intracellular refractive index, the phase contrast of subcellular structures is limited and often low. We analyze the impact of the specific manipulation of the intracellular refractive index by microinjection on the DHM phase contrast. Glycerol is chosen as osmolyte, which combines high solubility in aqueous solutions and biological compatibility. We show that the intracellular injection of glycerol causes a contrast enhancement that can be explained by a decrease of the cytosolic refractive index due to a water influx. The underlying principle is proven by experiments inducing cell shrinkage and with fixated cells. The integrity of the cell membrane is considered as a prerequisite and allows a reversible cell swelling and shrinking within a certain limit. The presented approach to control the intracellular phase contrast demonstrated for the example of DHM opens prospects for applications with other quantitative phase contrast imaging methods.
Here we present the structure of mouse H-chain apoferritin at 2.7 Å (FSC = 0.143) solved by single particle cryogenic electron microscopy (cryo-EM) using a 200 kV device, the Thermo Fisher Glacios ®. This is a compact, two-lens illumination system with a constant power objective lens, without any energy filters or aberration correctors, often thought of as a "screening cryo-microscope". Coulomb potential maps reveal clear densities for main chain carbonyl oxygens, residue side chains (including alternative conformations) and bound solvent molecules. We used a quasi-crystallographic reciprocal space approach to fit model coordinates to the experimental cryo-EM map. We argue that the advantages offered by (a) the high electronic and mechanical stability of the microscope, (b) the high emission stability and low beam energy spread of the high brightness Field Emission Gun (X-FEG), (c) direct electron detection technology and (d) particle-based Contrast Transfer Function (CTF) refinement have contributed to achieving high resolution. Overall, we show that basic electron optical settings for automated cryo-electron microscopy imaging can be used to determine structures approaching atomic resolution.
The high abundance of most viruses in infected host cells benefits their structural characterization; endogenous viruses are present in low copy numbers, however, and are therefore challenging to investigate. Here, we retrieve cell extracts enriched with an endogenous virus, the yeast L-A virus. The determined cryo-EM structure discloses capsid-stabilizing cation-π stacking and an interplay of non-covalent interactions from ten distinct capsomere interfaces. The capsid-embedded mRNA decapping active site trench is supported by a constricting movement of two opposite-facing loops. tRNA-loaded polysomes and other biomacromolecules, presumably mRNA, are found in virus proximity while stacked dsRNA bundles and the sub-stoichiometric polymerase localize underneath the capsid surface. Mature viruses participate in larger viral communities resembling their rare in-cell equivalents in terms of size, composition, and inter-virus distances. Our results collectively describe a 3D-architecture of a viral milieu, opening the door to cell-extract-based high-resolution structural virology.
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