Mapping the binding site of thiopeptide antibiotics by proximity-induced covalent capture

Proximity-induced covalent capture (PICC) has been established for the investigation of ligand binding to composite protein/oligonucleotide target complexes. The RNA-induced attachment of the thiopeptides Thiostrepton and Nosiheptide to engineered Cys mutants of the ribosomal protein L11 was highly position selective and allowed mapping of their binding site at amino acid resolution.     

Structural Relations in the Family of Nonmetallic Filled β-Manganese Phases: The new members AGa6Te10 (A: Sn,Pb) and PbIn6Te10

Nonmetallic filled β-manganese phases form a new class of solids with a wide spaced (“eutactical”) partial structure of nonmetal atoms (Te, I), which is topologically equivalent to the arrangement of manganese atoms in cubic β-Mn (a = 6.315 Å, P4₁32, Z = 20), a manganese polymorph crystallizing in a tetrahedrally close packed structure. Different fractions of the 100 tetrahedral and 4 metaprismatic holes per unit cell of the β-Mn like arrangement of nonmetal atoms are occupied by metal atoms or pairs of covalently bonded metal atoms, leading to the different chemical compositions M₇Te₁₀, AM₆Te₁₀, Ag₂Ga₆Te₁₀, RbX₄I₅ (M: Al, Ga, In; A: Ca, Pb, Sn; X: Ag, Cu;). Basic structural properties and structural relations between the members of this new family of solids are discussed. In addition we present structural data for three new members of the family of filled β-Mn phases: SnGa₆Te₁₀ (single crystal data: a = 10.203 Å, α = 89.94°, space group R32, Z = 2) PbIn₆Te₁₀ (single crystal data: a = 10.619 Å, R32, Z = 2) and PbGa₆Te₁₀ (powder data: a = 10.237 Å, α = 89.93°, R32, Z = 2).     

Few-boson dynamics in double wells: from single-atom to correlated pair tunneling

We investigate few-boson tunneling in a one-dimensional double well, covering the full crossover from weak interactions to the fermionization limit of strong correlations. Based on exact quantum-dynamical calculations, it is found that the tunneling dynamics of two atoms evolves from Rabi oscillations to correlated pair tunneling as we increase the interaction strength. Near the fermionization limit, fragmented-pair tunneling is observed and analyzed in terms of the population imbalance and two-body correlations. For more atoms, the tunneling dynamics near fermionization is shown to be sensitive to both atom number and initial configuration.     

Liquid chromatography/electrospray time-of-flight mass spectrometry for the characterisation of cyclic phosphazenes

Cyclic phosphazenes with different substituents were synthesised and investigated by liquid chromatography (LC) and electrospray ionisation mass spectrometry (ESI-MS). Hexachlorocyclotriphosphazene was functionalised with aliphatic substituents as alcohols and amines, leading to product mixtures, which were subsequently analysed. In contrast to classical methods of structural analysis such as nuclear magnetic resonance (NMR) spectroscopy or X-ray crystallography, which are restricted to pure compounds, these complex mixtures can favourably be analysed by means of LC/ESI-MS. The main products could be separated from by-products and, moreover, all the components of the unknown mixture were unambiguously identified by accurate mass measurements. For all compounds with different side-chain ratios, remaining chlorine atoms or hydroxyl groups and even for spiro or ansa products, molecular structures could be suggested.     

Theoretical studies of the tunneling splitting of malonaldehyde using the multiconfiguration time-dependent Hartree approach

Full dimensional multi-configuration time-dependent Hartree calculations of the zero point energy and the tunneling splitting of malonaldehyde using a recently published potential energy surface [Y. Wang, B. J. Braams, J. M. Bowman, S. Carter, and D. P. Tew, J. Chem. Phys. 128, 224314 (2008)] are reported. The potential energy surface has been approximated by a modified version of the n-mode representation and careful convergence check has been performed to ensure accurate results. The obtained value for the splitting (23.4 cm(-1)) is in acceptable agreement with the experimental value of 21.583 cm(-1). The computed zero-point-energy is 14,670 cm(-1) which is lower than previous results of Wang et al., but likely to be about 4 cm(-1) too low because of shortcomings of the n-mode representation of the potential. The energies reported in this abstract contain a correction to account for neglected vibrational angular momentum terms.