Crystallographic analysis of an 8-mer p53 peptide analogue complexed with MDM2

The most potent inhibitor of the p53-MDM2 interaction reported to date is an 8-mer p53 peptide analogue (Novartis peptide), which contains 6-chlorotryptophane (Cl-Trp) and phosphonomethylphenylalanine (Pmp) as key residues for the enhanced activity. We report here a crystal structure of the co-complex between MDM2 and the Novartis peptide solved at 1.8 A resolution. The structural basis for the role of the two aromatic residues are delineated by comparing the present structure with crystal structures of the MDM2 co-complex bound to other inhibitors including the wt-p53 peptide itself.     

Inorganic crown: the host-guest chemistry of a high nuclearity 'Celtic-ring' isopolyoxotungstate [H12W36O120]12-

A range of complexes based on the high-nuclearity [W36] isopolyoxotungstate cluster, [H12W36O120]12-, with a triangular topology has been isolated by using the organic cation, protonated triethanolamine. In analogy to an 18-crown-6 crown ether with six oxygen donors on a ring, the cluster can form alkali and alkaline earth metal complexes [M within W36] (M = K+, Rb+, Cs+, NH4+, Sr2+ and Ba2+, 1-6, respectively). Compounds 1-6 were characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy. Comparisons between the structures of 1-6 and 18-crown-6 as well as the symmetry directing influence of the organo-cations in the isolation of the overall cluster architecture are discussed.     

Struktur‐Eigenschafts‐Beziehung von Cu5Pb6O3Cl11, einer gut Kupferionen leitenden Verbindung

Structure‐Behaviour‐Relation of Cu₅Pb₆O₃Cl₁₁, a Good Solid State Ionic Conductor for Cu⁺‐Ions A new compound within the group of coin metal lead(II) oxide halides is found and characterized by X‐ray single crystal structure determination in a temperature range from 120 K to 400 K. Cu₅Pb₆O₃Cl₁₁ shows a new crystal type structure with a = 21.098(4) Å, b = 10.233(2) Å, c = 12.224(2) Å, β = 124.08(3)°, Z = 4 and space group C 2/c (No. 15) at 120 K. There are found isolated oxidic chains built of OPb₄ tetrahedra beside columnar areas consisting of CuCl. In this halidic partial structure are a lot of empty and partially occupied Cl₄‐tetrahedra. This structural characteristic seems to be source of a very good conductivity of copper ions, like in microscopic and nanoscaled composites of Al₂O₃ and AgI.     

Electrokinetics of a poly(N-isopropylacrylamid-co-carboxyacrylamid) soft thin film: evidence of diffuse segment distribution in the swollen state

Streaming current measurements were performed on poly(N-isopropylacrylamid-co-carboxyacrylamid) (PNiPAAM-co-carboxyAAM) soft thin films over a broad range of pH and salt concentration (pH 2.5-10, 0.1-10 mM KCl) at a constant temperature of 22 °C. The films are negatively charged because of the ionization of the carboxylic acid groups in the repeat unit of the copolymer. For a given salt concentration, the absolute value of the streaming current exhibits an unconventional, nonmonotonous dependence on pH with the presence of a maximum at pH ～6.4. This maximum is most pronounced at low electrolyte concentration and gradually disappears with increasing salinity. Complementary ellipsometry data further reveal that the average film thickness increases by a factor of ～2.2 with increasing pH over the whole range of salt concentration examined. The larger the solution salt concentration, the lower the pH value where expansion of the hydrogel layer starts to take place. The dependence of film thickness on pH and electrolyte concentration remarkably follows that obtained for surface conductivity. The streaming current and surface conductivity results could be consistently interpreted on a quantitative basis using the theory we previously derived for the electrokinetics of charged diffuse (heterogeneous) soft thin films complemented here by the derivation of a general expression for the surface conductivity of such systems. In particular, the maximum in streaming current versus pH is unambiguously attributed to the presence of an interphasial gradient in polymer segment density following the heterogeneous expansion of the chains within the film upon swelling with increasing pH. A quantitative inspection of the data further suggests that pK values of ionogenic groups in the film as derived from the streaming current and surface conductivity data differ by ～0.9 pH unit. Such a difference is attributed to the impact of position-dependent hydrophobicity across the film on the degree of ionization of carboxylic sites.     

Die Tris(triisopropylsilyl)pnikogene: Synthese und Charakterisierung von [E(SiiPr3)3] (E = P,As, Sb)

The Tris(triisopropylsilyl)pnikogenes: Synthesis and Characterisation of [E(Si ⁱ Pr₃)₃] (E = P, As, Sb) The compounds [E(SiⁱPr₃)₃] (E = P, As, Sb) ( 1 – 3 ) were prepared in high yields by the reaction of (Na/K)₃E with ⁱPr₃SiCl in DME. They were characterised by ¹H‐, ¹³C‐, ²⁹Si‐ and ³¹P‐NMR spectroscopy, mass spectrometry and single crystal X‐ray diffraction. Compound 1 , recently obtained in a different way, shows an unusual trigonal planar coordination of the central phosphorus atom. However, 2 and 3 , featuring increasing covalence radii of the central atoms, show an increasingly pyramidal structure. 1 – 3 crystallise isotyp in the cubic spacegroup Pa 3, the lattice constants are: 1 : a = 1860.1(2) pm, 2 : a = 1873.6(2) pm, 3 : a = 1897.1(2) pm.     

[La2I2(OH)2(Dibenzo-18-Krone-6)2]I(I3), ein kationischer,dimerer in-cavity-Komplex mit Iodid und Triiodid als Anionen

[La₂I₂(OH)₂(dibenzo-18-crown-6)₂]I(I₃), a Cationic Dimeric in-cavity Complex with Iodide and Triiodide as Anions Single crystals of [La₂I₂(OH)₂(dibenzo-18-crown-6)₂]I(I₃) are obtained from the reaction of LaI₃ and dibenzo-18-crown-6 in acetonitrile. The crystal structure monoclinic, C2/m, Z = 4, T = 293 [100] K, a = 2179(3) [2162.3(3)], b = 1070.3(3) [1069.6(1)], c = 1118.2(3) [1110.6(1)] pm, β = 93.1(1) [92.83(1)]°, R1 = 0.0601 [0.0411], wR2 = 0.1449 [0.1014] contains hydroxide-bridged cationic dimers and iodide as well as triiodide as anions.     

On finite rank perturbations of definitizable operators

It was shown by P. Jonas and H. Langer that a selfadjoint definitizable operator A in a Krein space remains definitizable after a finite rank perturbation in resolvent sense if the perturbed operator B is selfadjoint and the resolvent set ρ(B) is nonempty. It is the aim of this note to prove a more general variant of this perturbation result where the assumption on ρ(B) is dropped. As an application a class of singular ordinary differential operators with indefinite weight functions is studied.