An efficient synthesis of sialic‐acid‐terminated glycerol dendron to chemically functionalize 2 nm and 14 nm gold nanoparticles (AuNPs) is described. These nanoparticles are highly stable and show ...high activity towards the inhibition of influenza virus infection. As the binding of the viral fusion protein hemagglutinin to the host cell surface is mediated by sialic acid receptors, a multivalent interaction with sialic‐acid‐functionalized AuNPs is expected to competitively inhibit viral infection. Electron microscopy techniques and biochemical analysis show a high binding affinity of the 14 nm AuNPs to hemagglutinin on the virus surface and, less efficiently, to isolated hemagglutinin. The functionalized AuNPs are nontoxic to the cells under the conditions studied. This approach allows a new type of molecular‐imaging activity‐correlation and is of particular relevance for further application in alternative antiviral therapy.
Densely sugar‐coated gold nanoparticles are prepared by covalently attaching sialic‐acid‐modified dendrons to the nanoparticle surface. Such multivalent constructs are designed to bind hemagglutinin envelope‐protein arrays on the influenza surface, thus inhibiting viral invasion of host cells. Various chemical and biological assays, as well as electron microscopy, are presented to validate this approach and visualize for the first time the multiple binding of AuNP inhibitors to the virus surface.
Steric effects in chemistry are a consequence of the space required to accommodate the atoms and groups within a molecule, and are often thought to be dominated by repulsive forces arising from ...overlapping electron densities (Pauli repulsion). An appreciation of attractive interactions such as van der Waals forces (which include London dispersion forces) is necessary to understand chemical bonding and reactivity fully. This is evident from, for example, the strongly debated origin of the higher stability of branched alkanes relative to linear alkanes and the possibility of constructing hydrocarbons with extraordinarily long C-C single bonds through steric crowding. Although empirical bond distance/bond strength relationships have been established for C-C bonds (longer C-C bonds have smaller bond dissociation energies), these have no present theoretical basis. Nevertheless, these empirical considerations are fundamental to structural and energetic evaluations in chemistry, as summarized by Pauling as early as 1960 and confirmed more recently. Here we report the preparation of hydrocarbons with extremely long C-C bonds (up to 1.704 Å), the longest such bonds observed so far in alkanes. The prepared compounds are unexpectedly stable--noticeable decomposition occurs only above 200 °C. We prepared the alkanes by coupling nanometre-sized, diamond-like, highly rigid structures known as diamondoids. The extraordinary stability of the coupling products is due to overall attractive dispersion interactions between the intramolecular H•••H contact surfaces, as is evident from density functional theory computations with and without inclusion of dispersion corrections.
The formation of a single product from terminal functionalization of linear alkanes from a transition metal-catalyzed reaction is reported. The rhodium complex Cp*Rh(η4-C6Me6) (Cp*, C5Me5; Me, ...methyl) catalyzes the high-yield formation of linear alkylboranes from commercially available borane reagents under thermal conditions. These reactions now allow catalytic, regiospecific functionalization of alkanes under thermal conditions. The organoborane products are among the most versatile synthetic intermediates in chemistry and serve as convenient precursors to alcohols, amines, and other common classes of functionalized molecules.
We demonstrate a phase transfer method to create stable colloidal solutions of Au nanoparticles with 4-methoxypyridine ligands. We then investigate the adsorption behavior of 4-methoxypyridine onto ...gold surfaces by Raman spectroscopy, DFT calculations, and 1H NMR. In contrast to unsubstituted pyridine and the frequently used (N,N-dimethylamino)pyridine (DMAP), a flat adsorption of 4-methoxypyridine on gold was found.
A series of mononuclear trimethylplatinum( iv ) complexes of bipyridine ligands, PtMe 3 (L–L)I (L–L = bipy, 4-Mebipy, 4-MeObipy and 4-Me 2 Nbipy) has been synthesized by the reaction of ...trimethylplatinum( iv ) iodide with bipyridine ligands L–L in an equimolar ratio. Also, treatment of mononuclear trimethylplatinum( iv ) iodide complexes of pyridine ligands, PtMe 3 L 2 I (L = py, 4-Mepy, 4-MeOpy and 4-Me 2 Npy) with the corresponding bipyridine ligands leads to the exchange of the pyridines by the bipyridine ligands, thereby resulting in the formation of the more stable chelate bipyridine complexes. The ligand-exchange reactions have been studied by 1 H NMR spectroscopy. The 1 H NMR spectra of a 1 : 1 mixture of mononuclear pyridine complexes PtMe 3 L 2 I and corresponding bipyridine ligands L–L reveal the formation of two chelate bipyridine complexes, PtMe 3 (L–L)I and PtMe 3 (L–L)LI, in solution. Speciation of the pyridine and bipyridine complexes in solution was found to be dependent on the substituent as well as on the nature of the solvent. Furthermore, crystal structures of three bipyridine complexes PtMe 3 (L–L)I (L–L = 4-Mebipy, 4-MeObipy and 4-Me 2 Nbipy) have also been investigated here.
We have computed the lattice structure, bulk modulus, electronic structure, and cohesive energies for the CoSb3 skutterudite by performing plane wave and atomic basis set DFT, as well as HF atomic ...basis set calculations. We find that plane wave and atomic basis set DFT calculations compare almost perfectly well. Band gaps vary significantly, depending on the applied functional and subtle changes of the lattice structure of CoSb3. Where LDA strongly overestimates the binding, cohesive energies are reasonably well described by GGA and hybrid DFT functionals within 2 eV in comparison to experiment. HF results are unreasonably far off compared to DFT and experimental values for all calculated properties, which indicates that correlation effects play an important role in the characterization of skutterudites.
The mucin MUC1 is a glycoprotein involved in fundamental biological processes, which can be found over-expressed and with a distinctly altered glycan pattern on epithelial tumor cells; thus it is a ...promising target structure in the quest for effective carbohydrate-based cancer vaccines and immunotherapeutics. Natural glycopeptide antigens indicate only a low immunogenicity and a T-cell independent immune response; however, this major drawback can be overcome by coupling of glycopeptide antigens multivalently to immunostimulating carrier platforms. In particular, gold nanoparticles are well suited as templates for the multivalent presentation of glycopeptide antigens, due to their remarkably high surface-to-volume ratio in combination with their high biostability. In this work the synthesis of novel MUC1-glycopeptide antigens and their coupling to gold nanoparticles of different sizes are presented. In addition, the development of a new dot-blot immunoassay to test the potential antigen-antibody binding is introduced.
We have synthesized undoped, Co-doped (up to 5%), and Se-doped (up to 4%) FeS
2
materials by mechanical alloying in a planetary ball mill and investigated their thermoelectric properties from room ...temperature (RT) to 600 K. With decreasing particle size, the undoped FeS
2
samples showed higher electrical conductivity, from 0.02 S cm
−1
for particles with 70 nm grain size up to 3.1 S cm
−1
for the sample with grain size of 16 nm. The Seebeck coefficient of the undoped samples showed a decrease with further grinding, from 128
μ
V K
−1
at RT for the sample with 70-nm grains down to 101
μ
V K
−1
for the sample with grain size of 16 nm. The thermal conductivity of the 16-nm undoped sample lay within the range from 1.3 W m
−1
K
−1
at RT to a minimal value of 1.2 W m
−1
K
−1
at 600 K. All doped samples showed improved thermoelectric behavior at 600 K compared with the undoped sample with 16 nm particle size. Cobalt doping modified the
p
-type semiconducting behavior to
n
-type and increased the thermal conductivity (2.1 W m
−1
K
−1
) but improved the electrical conductivity (41 S cm
−1
) and Seebeck coefficient (-129
μ
V K
−1
). Isovalent selenium doping led to a slightly higher thermal conductivity (1.7 W m
−1
K
−1
) as well as to an improved electrical conductivity (26 S cm
−1
) and Seebeck coefficient (110
μ
V K
−1
). The
ZT
value of FeS
2
was increased by a factor of five by Co doping and by a factor of three by Se doping.
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