1H NMR and IR Spectroscopic Study of the Structure of the Major Component of the 99mTc HMPAO (Hexamethylpropyleneamino Oxime) Radiopharmaceutical Preparation

d,l-Hexamethylpropyleneamino oxime (HMPAO) was synthesized and isolated from a mixture of d,l - and meso-isomers. The structure of the conformers was studied using ¹H NMR spectroscopy over a broad range of pH. A method for estimating the amount of meso-form present in the mixture of isomers was proposed. It was shown that specific features of the IR spectra depend on the structure of the isomers and on the difference between the packing of molecules in the crystal lattice.     

Structural, textural, and electronic properties of a nanosized mesoporous ZnxTi1-xO2-) solid solution prepared by a supercritical drying route

Mesoporous nanosized TiO2 and Zn(x)Ti(1-x)O(2-x) solid solution having a Zn content below 10 mol % with a particles size between 13 and 17 nm are prepared by a template-free sol-gel method followed by high-temperature supercritical drying in 2-propanol. The structural, textural, and electronic properties of the obtained nanomaterials are methodically investigated by using XRD, SEM, TEM, ED, HREM, EDX, ICP-OES, N(2) adsorption-desorption, Raman spectroscopy, and diffuse reflectance UV-vis spectroscopy. It is shown that the proposed synthesis technique leads to the formation of a Zn(x)Ti(1-x)O(2-x) solid solution based on the anatase crystal structure rather than a two-phase sample. High-resolution electron microscopy and electron diffraction indicate that the distribution of zinc atoms over the anatase structure does not lead to a considerable deformation of the crystal structure.     

Chemical biology of protein lipidation: semi-synthesis and structure elucidation of prenylated RabGTPases

Rab/Ypt guanosine triphosphatases (GTPases) represent a family of key membrane traffic regulators in eukaryotic cells. For their function Rab/Ypt proteins require double modification with two covalently bound geranylgeranyl lipid moieties at the C-terminus. Generally, prenylated proteins are very difficult to obtain by recombinant or enzymatic methods. We generated prenylated RabGTPases using a combination of chemical synthesis and protein engineering. This semi-synthesis depends largely on the availability of functionalized prenylated peptides corresponding to the proteins' native structure or modifications. We developed solution phase and solid phase strategies for the generation of peptides corresponding to the prenylated C-terminus of Rab7 GTPase in preparative amounts enabling us to crystallize the mono-prenylated Ypt1:RabGDI complex. The structure of the complex provides a structural basis for the ability of RabGDI to inhibit the release of nucleotide by Rab proteins and a molecular basis for understanding a RabGDI mutant that causes mental retardation in humans.     

Highly Efficient One‐Pot Preparation of 1,2,4‐Oxadiazoles in the Presence of Diazabicycloundecene

New highly efficient method for the cyclization of acylamidoximes in the presence of diazabicycloundecene was developed and incorporated into a general and practical one‐pot synthesis of 1,2,4‐oxadiazoles (11 examples, 85–97% yields).     

Kinetic Study of Propylene Hydrogenation over Pt/Al2O3 by Parahydrogen-Induced Polarization

Parahydrogen-induced polarization has been successfully used for a kinetic study of propylene hydrogenation over a Pt/Al₂O₃ catalyst. It was shown that the reaction orders with respect to hydrogen are different for the pairwise and the non-pairwise hydrogen addition and are equal to 0.7 and 0.1, respectively. This observation of different reaction orders confirms the coexistence of different types of active sites which are responsible for the overall and the pairwise hydrogen addition to the propylene C=C double bond. Moreover, 0.7 reaction order with respect to H₂ for pairwise hydrogen addition indicates that the contribution of pairwise addition depends on the concentration of molecular hydrogen. Therefore, this observation can be developed into a practical tool for producing fluids with highly polarized nuclear spins by changing the hydrogen concentration.     

Four-component stereoselective synthesis of tetracyano-substituted piperidines

Research on Chemical Intermediates - A novel four-component stereoselective synthesis of polysubstituted piperidines is reported. The Knoevenagel–Michael–Mannich cascade of two...     

Mathematical Model of Speeds Change Device on the Basis of Switched Differential Mechanisms

International Applied Mechanics - The geometry and kinematics of a dynamic system with several degrees of freedom and controllable friction clutches are considered. The necessary kinematic...