Adsorptive stripping voltammetry of sex hormones at the static mercury drop electrode

Controlled adsorptive accumulation of testosterone, methyltestosterone and progesterone on the static mercury drop electrode provides the basis for direct stripping measurement of these compounds ar nanomolar concentrations. The adsorptive stripping behavior is evaluated with respect to preconcentration time and potential, stripping mode, concentration dependence, drop size and other variables. With 5-min accumulation, peak current enhancements of 45, 18 anal 12 are observed for 5 × 10^?8 M testosterone, progesterone and methyltestosterone, respectively, relative to direct pulse voltammetry. Detection limits are 1.6 × 10^?10 M for testosterone, 2 × 10^?10 M for progesterone and 3.3 × 10^?10 M for methyltestosterone with 15-min preconcentration. The relative standard deviation for 8 × 10^?8 M progesterone is 3.4% (n=8). Applicability to direct measurements of methyltestosterone in pharmaceutical formulations is assessed.     

Electric field gradient at the Hf site and the phase transition in HfV2

The electric quadrupole interaction at the Hf site in the cubic HfV₂ compound, which shows lattice instability when cooled below 120 K, has been studied using the 482 keV (5/2⁺) state in¹⁸¹Ta. The time differential perturbed angular correlation (TDPAC) studies involving (133+136)-482 keV - cascade at room temperature show that only a fraction of¹⁸¹Ta nuclei see a cubic symmetry while the remaining experience a weak, randomly oriented, electric quadrupole interaction described by a Gaussian frequency distribution with _Q=6.1±1.0 Mrad/sec and the relative width =0.5. There is a dramatic change in TDPAC pattern indicating a phase transition when the compound is cooled down to 77 K. At this temperature the quadrupole interaction frequency is found to be _Q=40.6±3.0 Mrad/sec with =0.35. The experimentally observed EFG both at the Hf and the V sites are compared to the theoretical estimates based on point charge model.     

Complexation of palladium cyanide with imidazolidine-2-thione and its derivatives

Summary Pd(CN)₂ reacts with imidazolidine-2-thione (Imt), 1,3-diazinane-2-thione(Diaz), 1,3-diazipnane-2-thione (Diap) and their derivatives to yield complexes of stoichiometry [PdL₂(CN)₂] or [PdL(CN)₂] (L = Imt, Diaz or Diap and L = Imt having N-Me, Et or Pr substituents), which were characterized by elemental analysis, i.r., ¹H and ¹³C n.m.r. spectroscopy. Both mono- and bis ligand complexes are thought to be square planar with the monoligand binding to metal via sulphur (bridging) and the bis ligand via the monodentate thione group. The ¹³C enriched Pd(¹³CN)₂ complex was prepared and the ¹³C n.m.r. recorded. The C-2 resonance of ¹³C n.m.r. of Imt, Diaz or Diap complexes of the copper(I), silver(I), gold(I) and palladium(II) were compared.     

Triosmium clusters derived from the reactions of thioureas with dodecacarbonyltriosmium: Crystal structures of [Os3(CO)11{η 1-SC(NMe2)2}], [Os3(CO)9(μ-OH)(μ-OMeOCO){η 1-SC(NMe2)2}] and [(μ-H)Os3(CO)9{μ 3-NHC(S)NH2}]

The reaction of [Os₃(CO)₁₂] with tetramethylthiourea in the presence of a methanolic solution of Me₃NO·2H₂O at 60° yields the compounds [Os₃(CO)₁₁{η ¹-SC(NMe₂)₂}] (1) in 56% yield and [Os₃(CO)₉(μ-OH)(μ-MeOCO){η ¹-SC(NMe₂)₂}] (2) in 10% yield in which the tetramethylthiourea ligand is coordinatedvia the sulfur atom at an equatorial position. Compound2 is a 50 e^? cluster with two metal-metal bonds and the hydroxy and methoxycarbonyl ligands bridging the open metal-metal edge. In contrast, the analogous reaction of [Os₃(CO)₁₂] with thiourea gives the compounts [(μ-H)Os₃(CO)₁₀{μ-NHC(S)NH₂}] (3) in 8% yield and [(μ-H)Os₃(CO)₉{₃-NHC(S)NH₂}] (4) in 30% yield. In3, the thioureato ligand bridges two osmium atomsvia the sulfur atom, whereas in4 in addition to the sulfur bridge, one of the nitrogen atoms of thioureato moiety bonds to the remaining osmium atom. The decacarbonyl compounds 3 can also be obtained in 50% yield from the reaction of [Os₃(CO)₁₀(MeCN)₂] with thiourea at ambient temperature. Compound3 converts to4 (65%) photochemically. Compound1 reacts with PPh₃ and acetonitrile at ambient temperature to give the simple substitution products [Os₃(CO)₁₁(PPh₃)] and [Os₃(CO)₁₁(MeCN)], respectively, while with pyridine, the oxidative addition product [(μ-H)Os₃(CO)₁₀(μ-NC₅H₄] is formed at 80°C. All the new compounds are characterized by IR,¹-H-NMR and elemental analysis together with the X-ray crystal structures of1,2 and4. Compound1 crystallizes in the triclinic space group P $P\bar 1$ with unit cell parametersa = 8.626(3) Å,b = 11.639(3) Å,c = 12.568(3_ Å,α = 84.67(2)°,β = 75.36(2)°,γ = 79.49(3)°,V = 1199(1) ų, andZ = 2. Least-squares refinement of 4585 reflections gave a final agreement factor ofR = 0.0766 (R _w = 0.0823). Compound2 crystallizes in the monoclinic space group P2_1/n with unit cell parametersa = 9.149(5) Å,b = 17.483(5) Å,c = 15.094(4) Å,β = 91.75(2)°,V = 2413(2) ų, andZ = 4. Least-squares refinement of 3632 reflections gave a final agreement factor ofR = 0.0603 (R _w = 0.0802). Compound4 crystallizes in the monoclinic space group C2/c with unit cell parametersa = 13.915(7) Å,b = 14.718(6) Å,c = 17.109(6) Å,β = 100.44(3)°,V = 3446(5) ų, andZ = 8. Least-squares refinement of 2910 reflections gave a final agreement factor ofR = 0.0763 (R _w = 0.0863).     

4‐[3‐(3,4‐Di­methoxy­phenyl)­prop‐2‐enoyl]­phenyl methacryl­ate and 4‐[3‐(2‐bromo­phenyl)­prop‐2‐enoyl]­phenyl methacryl­ate

Chalcones (α,β‐unsaturated ketones) are effective antitumour agents. It has been proved that having halogen or methoxy groups substituted in various positions of the phenyl ring enhances the activity of chalcones many times. The title compounds, C₂₁H₂₀O₅ and C₁₉H₁₅BrO₃, respectively, were chosen for crystallographic study in order to determine their structures and conformations. In both compounds, the keto group is in the s‐cis conformation and is almost planar. There are weak intramolecular interactions in both structures.     

The estimation of the iodine number in edible and industrial oils by radioiodine

Summary The iodine number of twenty-two samples of different fats and oils is determined by ¹³¹I, according to the radiometric method. The values obtained for such samples lie between 7.2 and 154.9. The method is applicable with reproducible results and is recommended to cover any stage of unsaturation.

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Zusammenfassung Die Jodzahl von 22 Proben verschiedener Öle und Fette wird radiometrisch unter Benutzung von Jod-131 bestimmt. Die erhaltenen Werte liegen zwischen 7,2 und 154,9. Das Verfahren liefert reproduzierbare Ergebnisse und ist für jeden Grad von Ungesättigtheit anwendbar.

     

Dramatic 5'-residue effect on conformer distribution of short oligonucleotide retro models of the cisplatin-DNA cross-link: implications for the Lippard and cross-link distorted base pair steps present in cisplatin-DNA duplex adducts

The cisplatin anticancer drug preferentially attacks the GG sequence of DNA duplexes. Virtually all DNAs containing the key G*G* lesion (G* = N7 platinated G) have large distortions in the cross-link (G*G*) base pair (bp) step and also in the adjacent Lippard (XG*) bp step, making the adducts very different from B-form DNA in the XG*G* region. The XG*G* strand in duplexes also differs in several ways from single-strand (ss) models with G*G* and XG*G* sequences. In the duplex, the X residue has an N sugar, the 5'-G* and 3'-G* bases have slight "R" canting (3'-G* H8 atom toward the 5'-G* base), and there is no or weak H-bonding by the NH3 ligands. In most XG*G* ss models, X has an S sugar, the 5'-G* base normally cants strongly toward the 3'-G* base (L canting), and the NH3 forms an H-bond. Well-defined ss models exist in the solid state, but dynamic motion obscures the properties of the ss models in solution. In this work, we employ retro models (better defined, less dynamic ss models) to understand the differences between duplex and ss models. The retro models in this study lack carrier ligand NH's, thus eliminating H-bonding. To correlate previous ss solid-state models with our solution work, we constructed hybrid molecules by overlaying parts of known structures. The combined model and experimental information indicates that the X N-pucker is not favorable in L-canted ss models, that X residue steric effects (not H-bonding) favor L canting in ss models, that X N-pucker is needed for favorable WC hydrogen bonding and stacking interactions in duplexes, and that X N-pucker minimizes X base clashes with bases in the complementary strand in duplexes. The R canting minimizing clashes between the X and G* residues of the Lippard bp step (independent of X pucker) and the repositioning of the X residue base caused by the change from S-pucker to N-pucker together lead to the unusual features of the Lippard bp step in the duplex.     

Investigations of regio- and stereoselectivities in the synthesis of cytotoxic isoxazolidines through 1,3-dipolar cycloadditions of nitrones to dipolarophiles bearing an allylic oxygen

Regio- and stereoselectivities in cycloadditions of nitrones to dipolarophiles bearing an allylic oxygen, which furnishes substituted-isoxazolidine analogs of the furanose ring of nucleosides, have been investigated. Although the obtained regioselectivities are anticipated, a rationalization of the preferred formation of endo-cycloadducts necessitates the involvement of an allylic oxygen in secondary interaction. The obtained isoxazolidines display cytotoxic activities against a number of human cancer cell lines.     

R7-binding protein targets the G protein β5/R7-regulator of G protein signaling complex to lipid rafts in neuronal cells and brain

Background  

Heterotrimeric guanine nucleotide-binding regulatory proteins (G proteins), composed of Gα, Gβ, and Gγ subunits, are positioned at the inner face of the plasma membrane and relay signals from activated G protein-coupled cell surface receptors to various signaling pathways. Gβ5 is the most structurally divergent Gβ isoform and forms tight heterodimers with regulator of G protein signalling (RGS) proteins of the R7 subfamily (R7-RGS). The subcellular localization of Gβ 5/R7-RGS protein complexes is regulated by the palmitoylation status of the associated R7-binding protein (R7BP), a recently discovered SNARE-like protein. We investigate here whether R7BP controls the targeting of Gβ5/R7-RGS complexes to lipid rafts, cholesterol-rich membrane microdomains where conventional heterotrimeric G proteins and some effector proteins are concentrated in neurons and brain.