Characterization of the Effects of Aryl-azido Compounds and UVA Irradiation on the Viral Proteins and Infectivity of Human Immunodeficiency Virus Type 1

Hydrophobic UV-activatable compounds have been shown to partition into the hydrophobic region of biological membranes to selectively label transmembrane proteins, and to inactivate enveloped viruses. Here, we analyze various UV-activatable azido- and iodo-based hydrophobic compounds for their ability to inactivate a model-enveloped virus, human immunodeficiency virus (HIV-1 MN). Treatment of HIV-1 with 1,5-diazidonapthalene (DAN), 1-iodo, 5-azidonaphthalene (INA), 1-azidonaphthalene (AzNAP) or 4,4′-diazidobiphenyl (DABIPH) followed by UVA irradiation for 2 min resulted in complete viral inactivation, whereas treatment using analogous non–azido-containing controls had no effect. Incorporation of an azido moiety within these hydrophobic compounds to promote photoinduced covalent reactions with proteins was found to be the primary mechanism of viral inactivation for this class of compounds. Prolonged UVA irradiation of the virus in the presence of these azido compounds resulted in further modifications of viral proteins, due to the generation of reactive oxygen species, leading to aggregation as visualized via Western blot analysis, providing additional viral modifications that may inhibit viral infectivity. Furthermore, inactivation using these compounds resulted in the preservation of surface antigenic structures (recognized by neutralizing antibodies b12, 2g12 and 4e10), which is favorable for the creation of vaccines from these inactivated virus preparations.     

A solvability criterion for the Lie algebra of derivations of a fat point

We consider the Lie algebra of derivations of a zero-dimensional local complex algebra. We describe an inequality involving the embedding dimension, the order, and the first deviation that forces this Lie algebra to be solvable. Our result was motivated by and generalizes the solvability of the Yau algebra of an isolated hypersurface singularity.     

Mechanopolymerchemie

Although many methods can be employed to transfer energy to a chemical reaction, mechanical energy has not been widely used: It is difficult to apply mechanical forces high enough to lead to breaking bonds to small molecules. Work is the product of force and displacement but when the distances are small, very high forces are needed to obtain sufficient energy to break a bond. The situation is different in polymers, where the path length can be high. Here, bond cleavage, cycloreversions and isomerisations can be observed when mechanical energy is supplied, both in solution and solid systems. Mechanical energy can lead to different mechanistic pathways than those observed under thermal conditions or irradiation. Practical applications of the mechanochemistry of polymers are only just emerging and range from a better understanding of polymer decomposition under force to the development of strain sensors using mechanochromic polymers.     

Enhancement of poly(vinyl ester) solubility in supercritical CO2 by partial fluorination: the key role of polymer-polymer interactions

An enhancement of poly(vinyl ester) solubility in supercritical carbon dioxide (sc-CO(2)) can be achieved by decreasing the strength of the polymer-polymer interactions. To demonstrate this, a library of statistical copolymers of vinyl acetate and vinyl trifluoroacetate was synthesized by RAFT/MADIX polymerization with varying compositions at a given number-average molecular weight. These copolymers exhibited unprecedentedly low cloud-point pressures in sc-CO(2) at 40 °C compared with previously reported poly(vinyl esters). Surface tension measurements combined with a computational approach evidenced the prominent role played by polymer-polymer interactions.     

Mercaptocarborane-capped gold nanoparticles: electron pools and ion traps with switchable hydrophilicity

A simple single-phase method for the preparation of ca. 2 nm gold nanoparticles capped with mercaptocarborane ligands is introduced. The resultant monolayer protected clusters (MPCs) exhibit redox-dependent solubility and readily phase transfer between water and nonpolar solvents depending on the electronic and ionic charge stored in the metal core and in the ligand shell, respectively. The particles and their properties have been characterized by high angle annular dark field imaging in a scanning transmission electron microscope, elemental analysis, centrifugal particle sizing, UV-vis and FTIR spectroscopy, and thermogravimetric analysis and by (1)H, (11)B, and (7)Li NMR spectroscopy. Cellular uptake of the MPCs by HeLa cells has been studied by TEM, and the subsequent generation of reactive oxygen species inside the cells has been evaluated by confocal fluorescence microscopy. These MPCs qualitatively showed significant toxicity and the ability to penetrate into most cell compartments with a strong tendency of finally residing inside membranes. Applications in catalysis, electrocatalysis, and biomedicine are envisaged.     

Mechanistic insights into the hydrolysis of a nucleoside triphosphate model in neutral and acidic solution

Nucleoside triphosphate hydrolysis is an essential component of all living systems. Despite extensive research, the exact modus and mechanism of this ubiquitous reaction still remain elusive. In this work, we examined the detailed hydrolysis mechanisms of a model nucleoside triphosphate in acidic and neutral solution by means of ab initio simulations. The timescale of the reaction was accessed through use of an accelerated sampling method, metadynamics. Both hydrolyses were found to proceed via different mechanisms; the acidic system reacted by means of concerted general acid catalysis (found to be a so-called D(N)A(N)A(H)D(xh) mechanism), whereas the neutral system reacted by way of a different mechanism (namely, D(N)*A(N)D(xh)A(H)). A neighboring water molecule took on the role of a general base in both systems, which has not been seen before but is a highly plausible reaction path, meaning that substrate-assisted catalysis was not observed in the bulk water environment.     

Thermally stable organically modified layered silicates based on alkyl imidazolium salts

A series of imidazolium salts having various substituents and functional groups were synthesized and characterized by FTIR and NMR spectroscopy. Organic modification of natural and synthetic layered silicates involving montmorillonite (MMT), laponite (lap), and synthetic mica (mica) was carried out by ion-exchange reaction. The obtained organo-clays were characterized by FTIR and powder X-ray diffraction techniques. Results indicate that these organically modified clays have much higher thermal stabilities compared to their corresponding imidazolium halides. It was also observed from TGA analysis that thermal stability does not depend on the functional group present at the 3-position of the imidazolium salts. These studies strongly supports premise that the removal of halide is necessary to improve the thermal stability of the organo-clay produced.     

Synthesis and Characterization of the Trisulfate Pb[S3O10] and Theoretical Analysis of H2S3O10

The reaction of (NH₄)₂PbCl₆ and fuming sulfuric acid (65 % SO₃) in a sealed glass tube at 250 °C led to colorless single crystals of Pb[S₃O₁₀] (orthorhombic, Pbcn, Z = 4, a = 10.9908(4), b = 8.5549(3), c = 8.0130(3) Å, V = 753.42(5) ų). The compound shows a three‐dimensional linkage of the tenfold oxygen coordinated Pb²⁺ ions and exhibits the unusual trisulfate anion, [S₃O₁₀]^2–, that consists of three vertex connected [SO₄] tetrahedra. The distances S–O within the S–O–S bridges of the anion are remarkable asymmetric with distances of 155 and 169 pm, respectively. This structural feature is well reproduced by calculations on a PBE0/cc‐pVTZ and a MP2/cc‐pVTZ level of theory. Similar calculations allow also for an inspection of the yet unknown corresponding acid, H₂S₃O₁₀. Also for this acid non‐symmetric S–O–S bridges are predicted. The thermal behavior of Pb[S₃O₁₀] is characterized by the loss of two equivalents of SO₃ at low temperature and the decomposition of intermediate Pb[SO₄] at higher temperature.