Estimation of the lipophilicity of antiarrhythmic and antihypertensive active 1-substituted pyrrolidin-2-one and pyrrolidine derivatives

The lipophilicity of some antiarrhythmic and antihypertensive active 1-[2-hydroxy- or 1-[2-acetoxy-3-(4-aryl-1-piperazinyl)propyl]pyrrolidin-2-one derivatives (1-12) has been investigated. Their lipophilicity (R(MO) and log k') was determined by reversed-phase thin-layer chromatography and reversed-phase high-performance liquid chromatography with mixtures of acetonitrile and Tris buffer as mobile phases. The partition coefficients of compounds 1-12 (log P(ScilogP)) were also calculated with the ScilogP program. Comparison of R(MO), log k' and calculated log D(7.0 ScilogP) values enabled calculation of clog D(7.0 TLC) and clog D(7.0 HPLC) values. Preliminary quantitative structure-activity relationship studies indicated that for active compounds there is a dependence between affinity for alpha(2)-adrenoceptors and their clog D(7.0 HPLC) values.     

Structural and binding study of modified siRNAs with the Argonaute 2 PAZ domain by NMR spectroscopy

By using high-resolution NMR spectroscopy, the structures of a natural short interfering RNA (siRNA) and of several altritol nucleic acid (ANA)-modified siRNAs were determined. The interaction of modified siRNAs with the PAZ domain of the Argonaute 2 protein of Drosophila melanogaster was also studied. The structures show that the modified siRNA duplexes (ANA/RNA) adopt a geometry very similar to the naturally occurring A-type siRNA duplex. All ribose residues, except for the 3' overhang, show 3'-endo conformation. The six-membered altritol sugar in ANA occurs in a chair conformation with the nucleobase in an axial position. In all siRNA duplexes, two overhanging nucleotides at the 3' end enhance the stability of the first neighboring base pair by a stacking interaction. The first overhanging nucleotide has a rather fixed position, whereas the second overhanging nucleotide shows larger flexibility. NMR binding studies of the PAZ domain with ANA-modified siRNAs demonstrate that modifications in the double-stranded region of the antisense strand have some small effects on the binding affinity as compared with the unmodified siRNA. Modification of the 3' overhang with thymidine (dTdT) residues shows a sixfold increase in the binding affinity compared with the unmodified siRNA (relative binding affinity of 17% compared with dTdT-modified overhang), whereas modification of the 3' overhang with ANA largely decreases the binding affinity.     

Study of the intensity of M+, M2+ and MO+ signals in ICP-MS as a function of instrumental parameters

In addition to peaks from singly charged ions (M⁺), signals from oxide (MO⁺), hydroxide (MOH⁺) and doubly charged (M²⁺) ions, which may lead to spectral overlap interferences, are observed in ICP-MS spectra. Using a VG PlasmaQuad ratios of MO⁺/M⁺, MOH⁺/M⁺ and M²⁺/M⁺ were determined for a number of elements, covering a wide range of atomic masses, first and second ionisation energies and chemical properties. The temporal stability of the MO⁺/M⁺ and M²⁺/M⁺ ratios was investigated. The correlation between the ratios of MO⁺/M⁺ and M²⁺/M⁺ with the M-O bond strength and the difference between the second and the first ionisation energy respectively is discussed. The influence of several instrumental parameters, associated with sample introduction and plasma operation, on the M⁺, M²⁺ and MO⁺ signals and on the MO⁺/M⁺ and M²⁺/M⁺ ratios is studied. Simple qualitative explanations are given in order to explain some of the observed results. No quantitative results are given for the MO⁺/M⁺ and M²⁺/M⁺ ratios as the experiments pointed out that they are influenced to a large extent by several instrumental parameters.     

Ca3Al2Ge3O12:Cr3+的光谱性质及晶场参数计算

为了解Cr3 离子在钙铝锗酸盐Ca3Al2Ge3O12石榴石中的光谱性质,合成了Ca3Al2Ge3O12:Cr3 多晶材料;测量了其X射线衍射图,漫反射光谱,激发、发射光谱等;分析了Cr3 离子在钙铝锗酸盐中的发光特性;计算了其晶场强度(Dq/B),Stokes位移(ΔEs)及黄昆-里斯因子(S)等.在450nm激发下,Ca3Al2Ge3O12:Cr3 室温发射光谱主要由三个宽带及附加其上的弱R线构成,分别对应于Cr3 离子的4T1、4T2、2T2到4A2能级跃迁.低温时R线变得强而锐.通过计算,Dq/B=2.43,ΔEs=1884cm-1,S=5.21.表明在Ca3Al2Ge3O12中Cr3 离子处于较弱的晶场强度,电子-声子耦合较强,为发展可调谐激光材料提供重要线索.     

Effect of the Porous Structure of the Support and Modifying Cation on the Catalytic Properties of the Co/SiO2·M n + System in the Hydrogenation of Carbon Monoxide to Give Hydrocarbons

Data are given on the activity and selectivity of formation of C₅₊ hydrocarbons in the Fischer–Tropsch synthesis depending on mean diameter of support pores (1.6-907 nm). The formation of C₅₊ hydrocarbons was found to be a function of the mean support pore diameter. The optimal value was 8-12.6 nm. The output and selectivity of formation of the hydrocarbons are also functions of the introduced cation.