ChemBioCenter

Slow oxidation of cobalt(II) ions by aerial oxygen in the presence of S-prolinate led to isolation of a new m-OH bridged binuclear chiral complex of cobalt(III): Co 2 (m-OH) 2 (S-Pro) 4 . The X-ray structure of this compound was studied. Co III ions are located in N 2 O 4 donor sets containing N and O atoms of S-prolinates at trans(N), cis(O)-or cis(N), trans(O)-positions. Optical properties of Co 2 (m-OH) 2 (S-Pro) 4 were investigated by means of electronic and circular dichroism spectroscopy providing data for comparison with the corresponding mononuclear complex of S-prolinate, cis-(À)-Co(S-Pro) 3 , as well as with other previously reported m-OH bridged cobalt(III) complexes. CD spectra also confirmed that no racemization of S-prolinate occurred during synthesis. The solution behaviour of Co 2 (m-OH) 2 (S-Pro) 4 in the presence of various organic acids was studied by 1 H and 13 C NMR techniques evidencing specific interactions between carboxylic groups of the substrate and hydrogen-bonding groups of the Co 2 (m-OH) 2 (S-Pro) 4 molecule. Relying on the NMR spectroscopy results, the most probable models of binding between Co 2 (m-OH) 2 (S-Pro) 4 and S-proline as well as N-benzoylated a-amino acids were discussed.

There are more than 50 families of dendrimers, and some of which, such as polyamidoamine PAMAM, are well studied, and some are just starting to attract the attention of researchers. One promising type of dendrimers is sulfonimide-based dendrimers (SBDs). To date, SBDs are used in organic synthesis as starting reagents for the convergent synthesis of higher generations dendrimers, in materials science as alternative electrolyte solutions for fuel cells, and in medicinal chemistry as potential substances for drug transfer procedures. Despite the fact that most dendrimers are amorphous substances among the SBDs, several structures are distinguished that are prone to the formation of crystalline solids with melting points in the range of 120–250 °C. Similar to those of other dendrimers, the chemical and physical properties of SBDs depend on their outer shell, which is formed by functional groups. To date, SBDs decorated with end groups such as naphthyl, nitro, methyl, and methoxy have b...

A study towards a convergent synthesis of sulfonimide-type dendrons and dendrimers was undertaken. Dendrons up to the third-generation bearing chlorosulfo-groups at their focal points were synthesized using both convergent and divergent routes. The convergent synthesis of dendrons reached its practical limit in the third-generation that makes the divergent route more practical. The synthetic utility of the dendritic sulfonyl chlorides was exemplified by a fourfold regioselective sulfonylation of a calix[4]resorcinarene octaol with a first-generation dendron.

The synthesis of dendrimers and a chlorosulfo-dendron possessing a unique combination of 1 ? 2 and 1 ? 4 branching types is described. The procedure consists of a two-step preparation of 3,5-dinitrobenzene-1-sulfonyl chloride, which was used for the persulfonylation of p-toluidine and 4-(benzylthio)aniline. The obtained tetranitro compounds were reduced to the corresponding tetraamines. The latter were decorated with eight 4-toluene sulfonyl groups each to furnish the corresponding dendrimers. Oxidation of the dendrimer possessing a 4-(benzylthio)phenylene core with N-chlorosuccinimide resulted in the formation of a dendron with a sulfonyl chloride functionality at the focal point.

Two-dimensional (2D) polymers attract considerable attention in different fields of basic and applied science. In this work, the synthesizability and properties of the 2D covalently stabilized monolayers built up of different monomeric subunits bearing 3, 4, and 6 photoreactive chalcone functionalities have been investigated. The self-assembled monolayers of the monomers have been polymerized under the UVirradiation conditions on a LangmuireBlodgett trough at the air/water interface. A trifunctional phloroglucinol-cored monomer formed mechanically poorly stable 2D covalent monolayers. On the contrary, the covalent monolayer films of calix[4]-and calix[6]arene based monomers bearing 4 chalcone groups each were mechanically stable enough to be span over 19 Â 19 mm-sized holes of copper grids. Hexafunctionalized calix[6]arene failed to form stable monolayers at the air/water interface. The films have been transferred on different substrates and investigated by ellipsometry, optical microscopy, TEM, and AFM revealing details of their thickness, stability, and morphology.

Key indicators: single-crystal X-ray study; T = 100 K; mean (C-C) = 0.009 Å; disorder in main residue; R factor = 0.067; wR factor = 0.172; data-to-parameter ratio = 19.6. Refinement R[F 2 > 2(F 2 )] = 0.067 wR(F 2 ) = 0.172 S = 1.08 7345 reflections 375 parameters 63 restraints H-atom parameters constrained Á max = 1.54 e Å À3 Á min = À1.51 e Å À3

In the title compound, C(9)H(10)N(4)O(2), the pyridine ring is twisted by 16.5 (1)° from the mean plane defined by the remaining non-H atoms. An intra-molecular N-H⋯N inter-action is present. In the crystal, inter-molecular O-H⋯N and N-H⋯O hydrogen bonds link mol-ecules into layers parallel to the bc plane. The crystal packing exhibits π-π inter-actions indicated by the short distance of 3.649 (1) Å between the centroids of the pyridine rings of neighbouring mol-ecules.

Enzymes fold into unique three-dimensional structures, which underlie their remarkable catalytic properties. The requirement to adopt a stable, folded conformation is likely to contribute to their relatively large size (> 10,000 Dalton). However, much shorter peptides can achieve well-defined conformations through the formation of amyloid fibrils. To test whether short amyloid-forming peptides might in fact be capable of enzyme-like catalysis, we designed a series of 7-residue peptides that act as Zn 2+ -dependent esterases. Zn 2+ helps stabilize the fibril formation, while also acting as a cofactor to catalyze acyl ester hydrolysis. These results indicate that prion-like fibrils are able to not only catalyze their own formation -they also can catalyze chemical reactions. Thus, they might have served as intermediates in the evolution of modern-day enzymes. These results also have implications for the design of self-assembling nanostructured catalysts including ones containing a variety of biological and nonbiological metal ions.

Toll-like receptors (TLRs) act as the first line of defense against bacterial and viral pathogens by initiating critical defense signals upon dimer activation. The contribution of the transmembrane domain in the dimerization and signaling process has heretofore been overlooked in favor of the extracellular and intracellular domains. As mounting evidence suggests that the transmembrane domain is a critical region in several protein families, we hypothesized that this was also the case for Toll-like receptors. Using a combined biochemical and biophysical approach, we investigated the ability of isolated Toll-like receptor transmembrane domains to interact independently of extracellular domain dimerization. Our results showed that the transmembrane domains had a preference for the native dimer partners in bacterial membranes for the entire receptor family. All TLR transmembrane domains showed strong homotypic interaction potential. The TLR2 transmembrane domain demonstrated strong heterotypic interactions in bacterial membranes with its known interaction partners, TLR1 and TLR6, as well as with a proposed interaction partner, TLR10, but not with TLR4, TLR5, or unrelated transmembrane receptors providing evidence for the specificity of TLR2 transmembrane domain interactions. Peptides for the transmembrane domains of TLR1, TLR2, and TLR6 were synthesized to further study this subfamily of receptors. These peptides validated the heterotypic interactions seen in bacterial membranes and demonstrated that the TLR2 transmembrane domain had moderately strong interactions with both TLR1 and TLR6. Combined, these results suggest a role for the transmembrane domain in Toll-like receptor oligomerization and as such, may be a novel target for further investigation of new therapeutic treatments of Toll-like receptor mediated diseases. Citation: Godfroy JI III, Roostan M, Moroz YS, Korendovych IV, Yin H (2012) Isolated Toll-like Receptor Transmembrane Domains Are Capable of Oligomerization. PLoS ONE 7(11): e48875.