Orthogonal Ubiquitin Transfer through Engineered E1-E2 Cascades for Protein Ubiquitination

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Highlights? Orthogonal ubiquitin (UB) transfer pathway to synthesize specific UB-E2 conjugates ? Phage display to engineer UB-E1 and UB-E2 interactions ? Engineered xUB-xE1 and xE1-xE2 pairs with no cross-reactivities with native enzymes     

The Vlasov–Poisson–Landau System in {\mathbb{R}^{3}_{x}}

For the Landau–Poisson system with Coulomb interaction in ${\mathbb{R}^{3}_{x}}$ R x 3 , we prove the global existence, uniqueness, and large time convergence rates to the Maxwellian equilibrium for solutions which start out sufficiently close.     

Structure of 4-amino-3-butyl-1,2,4-triazole-5-thione: Relation to derivatives with H, Me, Et, and Pr in the 3-position

The compound 4-amino-3-butyl-1,2,4-triazole-5-thione [crystal data: C₆H₁₂N₄S, triclinic, P , Z = 2, a = 7.546(2), b = 11.217(3), c = 5.681(1) ?, α = 103.12(2), β = 91.33(2), γ = 72.41(2)°, V = 445.9(2) ?³] contains an essentially planar triazole ring with the butyl group rotated out of the plane by approximately 104°. The molecules form hydrogen-bonded dimers through intermolecular N–HS interactions involving the thione sulfur atom and the protonated nitrogen atom on the ring. These units are then linked into columns through N–HN hydrogen bonds between the amine group and the unsubstituted ring N atom of adjacent molecules. The structural features of this compound are compared with those of the corresponding triazoles with H, methyl, ethyl and propyl groups on the 3-carbon.     

Density functional studies of LiN and LiN+ (N = 2–30) clusters: Structure,binding and charge distribution

Density functional calculations using B3LYP/6‐311G method have been carried out for small to medium‐sized lithium clusters (Li_N, N = 2–30). The optimized geometries of neutral and singly charged clusters, their binding energies, ionization potential, electron affinity, chemical potential, softness, hardness, highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO–LUMO) gap, and static dipole polarizability have been investigated systematically. In addition, we study the distribution of partial charges in detail using natural population analysis (NPA) in small‐sized clusters (Li_N, N = 2–10), both neutral and cationic, and demonstrate the correlation between symmetry and charge. Uniform distribution of charges in cationic clusters confirms them to be energetically more favorable than the neutral counterparts. Whenever possible, results have been compared with available data. An excellent agreement in every case supports new results as reliable predictions. A careful study of optimized geometries shows that Li₉ is derivable from bulk Li structure, i.e., body centered cubic cell, and higher clusters have optimized shapes derived from this. Further, the turnover form two to three dimensional structure occurs at cluster size N = 6. The quantity α^1/3 (α = polarizability) per atom is found to be broadly proportional to softness (per atom) as well as inverse ionization potential (per atom). The present work forms a sound basis for further study of large‐sized clusters as well as other atomic clusters. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Controlling the density and site of attachment of gold nanoparticles onto the surface of carbon nanotubes

A facile method for controlling the density and site of attachment of gold nanoparticles onto the surface of carbon nanotubes is demonstrated. Nitric acid based oxidation was carried out to create carboxylic groups exclusively at the ends of carbon nanotubes, whereas oxidation using a mixture of nitric and sulfuric acid with varied reaction time was carried out to control the population of carboxylic groups on the side walls of nanotubes. In turn, 4-aminothiophenol modified gold nanoparticles were covalently interfaced to these carboxylated multi-walled carbon nanotubes in the presence of a zero length cross-linker, 1-ethylene-3-(3-dimethylaminopropyl) carbodiimide. Raman spectroscopic results showed increase in height of disorder band with each of these successive steps, indicating the increase in degree of functionalization of the carbon nanotubes. Fourier transformed infrared spectroscopic analysis affirmed the functionalization of nanostructures and the formation of nanohybrid. Transmission electron and field emission scanning electron microscopic analysis ascertained the attachment of gold nanoparticles to the ends and side walls of the multi-walled carbon nanotubes. The new hybrid nanostructures may find applications in electronic, optoelectronic, and sensing devices.     

A first principle study of adsorption of two proximate nitrogen atoms on graphene

Different possible configurations of two nitrogen‐adatoms on graphene are studied using density functional theory. Adsorption of single nitrogen atom on the bridge site of graphene is accompanied by distortion of the sheet. Electronically, this case amounts to p‐type doping. Two N atoms adsorbed on the graphene sheet can share a bond in two ways. They acquire positions either just above two adjacent carbon atoms or they form a bridge across opposite bonds of a hexagon in the sheet. Both these configurations also induce structural distortion of the sheet. Another stable configuration consists of two N atoms bonded as an N₂ molecule physisorbed on the graphene sheet. It is also possible to adsorb two N atoms on opposite sides of the graphene sheet, bonded to the same two C atoms. Moreover, two N atoms can be individually adsorbed on alternate bridge sites of neighboring hexagons experiencing a repulsion, the energy for which arises from the additional distortion of the graphene sheet. The densities of states near the Fermi level are found to be dependent on the adsorption configurations of two nitrogen atoms on graphene. Thus the electronic properties of graphene can be controlled by the selective adsorption of two nitrogen atoms. © 2014 Wiley Periodicals, Inc.     

The Rearrangement of 3, 4-Dihydro-2, 2-Dimethy-2H, 5H-Pyrano [2, 3-b][1] Benzopyran-5-Ones With DDQ

A novel rearrangement of 3, 4-dihydro-2, 2-dimethyl-2H, 5H-pyrano [2, 3-b] [1] benzopyran-5-ones (dihydropyranochromones) has been observed during the dehydrogenation with DDQ. The products obtained are found to be 2, 2-dimethyl-2H, 5H-pyrano [3, 2-c] [1] benzopyran-5-ones (pyranocoumarins).     

Charge Carrier Transport in Phenazine

The mode of charge carrier transport in Phenazine has been investigated in the light of existing theorise. The effect of heteroatoms (nitrogen atoms) and the sensitivity of energy bands to crystal structrue has been discussed. The mobilities of electrons and holes have been calculated under an anisotropic but constant relaxation time approximation. The anisotropic relaxation time reduces the anisotropy of the mobility tensor.     

Molecular dynamics simulation of AFM studies of a single polymer chain

Single polymer chain force-extension behavior measured by Atomic Force Microscopy (AFM) was interpreted by molecular dynamics (MD) simulation performed by applying a bead-spring (coarse-graining) model in which the bond potential function between adjacent beads is described by a worm-like chain (WLC) model. Simulation results indicate that caution should be applied when interpreting experimental AFM data, because the data vary depending on the point of AFM tip-polymer chain attachment. This approach offers an effective way for eventual analysis of the mechanical behavior of complex polymer networks.     

Stationary coupled cluster response: Role of cubic terms in molecular properties

We have demonstrated an application of a stationary coupled cluster response approach for molecular properties using an Euler functional. This involves terms which are of cubic power in cluster amplitudes. We have shown that these are important terms and have also discussed the convergence properties of the functional for higher order properties.