Bifunctional Bis Research Articles

Multimeric Structure of the Tumor Necrosis Factor Receptor of HeLa Cells

The tumor necrosis factor (TNF) receptor of HeLa cells was solubilized in Triton X-100 and characterized by gel filtration, affinity labeling, and ligand blotting studies. Receptors solubilized with Triton X-100 eluted in gel filtration as a major peak of Mr = 330,000 and retained high affinity binding (KD = 0.25 nM). Affinity labeling of soluble receptor/125I-TNF complexes using the reversible, bifunctional bis[2-(succinimidooxycarbonyl-oxy)ethyl] sulfone resulted in the formation of cross-linked species of Mr = 310,000, 150,000-175,000, 95,000, and 75,000. The formation of these complexes was competitively inhibited by unlabeled TNF. Partial reversal of cross-linking in these complexes and their analysis by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) resolved 125I-TNF dimers cleaved from the 95,000 band and 125I-TNF monomer cleaved from the 75,000 band, providing evidence for a Mr approximately 60,000 subunit. In addition, the 95,000 and 75,000 bands were resolved as components of larger complexes (Mr = 150,000-175,000), which presumably contain two receptor subunits. The Mr 95,000 and 75,000 bands were also released from the Mr 310,000 complex by reduction with dithiothreitol, suggesting a role for disulfide bond stabilization. To investigate the association of the putative receptor subunits, Triton X-100 extracts from HeLa membranes were fractionated by SDS-PAGE without reduction and transferred electrophoretically to nylon membranes for TNF binding assays. Only two bands of Mr = 60,000 and 70,000 specifically bound TNF, and higher Mr binding activity was not observed. These results indicate that TNF receptors in HeLa cells are high molecular weight complexes containing Mr = 60,000 and 70,000 subunits each capable of binding TNF and that the complexes are primarily stabilized by non-covalent, hydrophobic interactions.

ChemInform Abstract: Cyclic Organylarsino Sulfur Diimides.

AbstractThe reactions of the bifunctional bis(chloroarsino) compounds (I) and (III) with the salt K2SN2 lead to mono‐ and bicyclic products (II) and (IV), resp., containing arsino‐substituted sulfur diimide units.

Cyclische Organylarsino-Schwefeldiimide / Cyclic Organylarsino Sulfur Diimides

Abstract The reactions of the bifunctional bis(chloroarsino) compounds MeCH[As(But )Cl]2 and RCH[AsCl2]2 (R = H, Me) with the salt K2SN2 lead to rings and cages containing arsino-substituted sulfur diimide units.

Reactions of spin-label crosslinking reagents with red blood cell proteins

The reactions of two spin-label cross-linking reagents with components of red blood cells have been studied. A bifunctional bis(N-hydroxysuccinimide ester) reagent passes readily through the membrane of intact red cells and reacts almost exclusively with hemoglobin. The rotational motion of hemoglobin inside of red cells may be studied by electron paramagnetic resonance (EPR) by using this spin-labeling method. A second cross-linking molecule, a negatively charged, disulfide-exchange reagent, reacts both with mem- brane components and with hemoglobin when intact red cells are labeled. Upon reaction with membranes stripped of components other than band 3, this reagent readily produces dimers and higher oligomers of this protein. The EPR spec- trum of band 3 labeled in this way shows that most of the spin-label molecules are highly immobilized on the protein. When the same reagent reacts with intact red cells, the cross-linked membrane products include components identified as band 3 dimers and a high molecular weight product con- sisting primarily of bands 1 and 2 but also containing lesser amounts of most of the other red cell membrane components and a slight amount of band 3. The reagent was made ra- dioactive to demonstrate that the spin-label disulfide exchange reagent is indeed involved in formation of cross-linked products. Comparison of Coomassie Blue staining and radioactivity in the region where band 3 dimers are expected on a one-di- mensional sodium dodecyl sulfate-polyacrylamide gel shows that there is approximately 0.5 cross-linking reagent per protein Te reactions of chemical reagents with components of the red blood cell have been used in studies of the geometry of erythrocyte membrane proteins, of the mobility of the band 3 protein in membranes, and of potential antisickling agents. Questions pertaining to the geometry of erythrocyte mem- branes have been addressed by using cross-linking reagents,

Synthesis and trimerization of fluorinated tertiary cyanates

Abstract Monofunctional and bifunctional bis(α,α-trifluoromethyl) cyanates were prepared by reaction of a fluorinated alkoxide with cyanogen bromide or cyanogen chloride. In the synthesis of bifunctional cyanates, the cyanation reaction required sufficient intramolecular separation for independent functional group reactivity. Monofunctional cyanates could be rapidly and quantitatively trimerized to cyclic cyanurates by catalytic quantities of AlCl 3 . Polymerization by trimerization of bifunctional cyanates under identical conditions was not successful, apparently, due to encasement of the catalyst by the polymer network.

Synthesis of elastomers by cationic polymerization with expansion in volume

AbstractA bifunctional bis spiro ortho ester, hydroquinone bis‐(1,4,6‐trioxaspiro[4.4]non‐2‐ylmethyl) ether, was prepared in a 30% yield by treating hydroquinone diglycidyl ether with γ‐butyrolactone in the presence of boron trifluoride etherate. Copolymerization of a mixture consisting of 90% of 1,4,6‐trioxaspiro[4.4]‐nonane and 10% of the bis spiro ortho ester produced an elastomer with essentially no change in volume. Condensation of ethylene thiocarbonate with pentaerythritol in the presence of tributyltin oxide gave a 20% yield of a bis spiro ortho carbonate, 1,4,6,10,12,15,16,19‐octaoxatrispiro[4.2.2.4.2.2]nonadecane. Copolymerization of a mixture consisting of 90% of 1,5,7,11‐tetraoxaspiro[5.5]undecane and 10% of the bis spiro ortho carbonate gave an elastomer with a 3% increase in volume.