Synthesis of steroidal dendrimers modified by ‘click’ chemistry with PAMAM dendrons as unimolecular micelles

Novel Fréchet–PAMAM hybrid dendrimers linked by triazole units as unimolecular micelles with a hydrophobic core surrounded by a hydrophilic shell were prepared. The dendritic cores with 3 and 6 alkyne terminal groups were synthesized from 1,3,5-tribromomethyl-benzene (tBrMeB), in one case by direct coupling with 17α-ethynylestradiol (EE); in the second one the tBrMeB was reacted with bis(hydroxymethyl) phenol followed by chlorination of the hydroxyl groups and subsequent coupling to EE. With this strategy, the core can be grown by further substitutions of bis(hydroxymethyl) phenol over the halogenated terminals as Fréchet dendrimer. The hydrophilic shells used were PAMAM type dendrons of 0.5 and 1.5 generations with azide as focal point and tert-butyl ester as end groups. The unimolecular micelles were obtained by cycloaddition between an azide in the selected dendron and the alkyne terminal in the hydrophobic core to obtain a 1,4-disubstituted 1,2,3-triazole. Once the coupling was achieved, the tert-butyl ester groups were hydrolyzed in trifluoroacetic acid and the corresponding dendrimers with carboxylic acid as end groups were completely soluble in phosphate buffer solutions of pH 7.0, 7.4, and 8.0. All hybrid dendrimers were characterized by High Resolution Mass Spectrometry, ¹H and ¹³C NMR, and FTIR.     

The free solution mobility of DNA in Tris-acetate-EDTA buffers of different concentrations,with and without added NaCl

The free solution mobility of a high-molecular-weight DNA, linear pUC19, and a 20-bp oligomer called dsA5 have been studied as a function of Tris-acetate-EDTA (TAE) buffer concentration, with and without added NaCl. The two DNAs migrate as separate peaks during capillary electrophoresis, because the mobility of linear pUC19 is higher than that of the 20-bp oligomer. In TAE buffers ranging from 10-400 mM in concentration, the migration times and peak areas of the two DNAs are independent of whether they are electrophoresed separately or in mixtures, indicating that DNA-DNA and DNA-buffer interactions are absent in these solutions. The migration times of the two DNAs vary and the peak areas are not additive when the TAE buffer concentration is reduced to 5 mM or below, indicating that DNA-DNA and DNA-buffer interactions are occurring at very low TAE buffer concentrations. The mobilities of linear pUC19 and dsA5 decrease slowly with increasing conductivity or ionic strength when the conductivity is increased by increasing the TAE buffer concentration. When the Tris buffer concentration is held constant and the conductivity is increased by adding various concentrations of NaCl to the solution, the mobilities of linear pUC19 and dsA5 first increase slightly, then become independent of solution conductivity (or ionic strength), and finally decrease when the NaCl concentration is increased above approximately 50 mM. The mobility variations observed in the various TAE and TAE-NaCl solutions are described qualitatively by Manning's theory, although quantitative agreement is not achieved. The free solution mobilities of single-stranded pUC19 and two 20-base oligonucleotides have also been measured. The free solution mobility of single-stranded pUC19 is approximately 15% lower than that of native pUC19, in agreement with other results in the literature. Somewhat surprisingly, the mobilities of the single- and double-stranded 20-mers are equal to each other in TAE buffers with and without added NaCl.     

[M(bpy)3] (M = Fe,Ru, Os): New Crystalline Materials from the reductive electrocrystallization of [M(bpy)3](PF6)2

Reductive electrocrystallization at a constant current density (11.0–11.5 μA/cm²) of millimolar solutions of [M(bpy)₃](PF₆)₂, where M = Fe, Ru, or Os, and bpy = 2,2′-bipyridine in acetonitrile containing 0.1M Bu₄NPF₆ results in the formation of dark crystals on the Pt cathode. The crystals grow as long, thin, and shiny needles having a hexagonal cross section of 0.1–0.5 mm in diameter. Combustion microanalyses results are consistent with the composition for [Fe(bpy)₃], [Ru(bpy)₃], and [Os(bpy)₃]. In addition, the chromophores are conserved, as confirmed by recording both the electronic and the ¹H-NMR spectra after reoxidation of the electrocrystals in humid air. The spectra are identical to those for authentic samples of [Fe(bpy)₃]²⁺, [Ru(bpy)₃]²⁺, and [Os(bpy)₃]²⁺. A ratio of 2.0 ± 0.1 e^?/molecule is observed upon completion of the controlled potential electrolysis of a solution of [M(bpy)₃]²⁺, which results in the precipitation of a dark solid and the almost complete fading of the color of the original solution. Unexpectedly, the crystals do not exhibit an ESR signal. These data indicate the formation of novel materials, crystalline [Fe(bpy)₃], [Ru(bpy)₃], and [Os(bpy)₃].     

Characterization of singlet ground and low-lying electronic excited states of phosphaethyne and isophosphaethyne

The singlet ground ((approximate)X(1)Sigma1+) and excited (1Sigma-,1Delta) states of HCP and HPC have been systematically investigated using ab initio molecular electronic structure theory. For the ground state, geometries of the two linear stationary points have been optimized and physical properties have been predicted utilizing restricted self-consistent field theory, coupled cluster theory with single and double excitations (CCSD), CCSD with perturbative triple corrections [CCSD(T)], and CCSD with partial iterative triple excitations (CCSDT-3 and CC3). Physical properties computed for the global minimum ((approximate)X(1)Sigma+HCP) include harmonic vibrational frequencies with the cc-pV5Z CCSD(T) method of omega1=3344 cm(-1), omega2=689 cm(-1), and omega3=1298 cm(-1). Linear HPC, a stationary point of Hessian index 2, is predicted to lie 75.2 kcal mol(-1) above the global minimum HCP. The dissociation energy D0[HCP((approximate)X(1)Sigma+)-->H(2S)+CP(X2Sigma+)] of HCP is predicted to be 119.0 kcal mol(-1), which is very close to the experimental lower limit of 119.1 kcal mol(-1). Eight singlet excited states were examined and their physical properties were determined employing three equation-of-motion coupled cluster methods (EOM-CCSD, EOM-CCSDT-3, and EOM-CC3). Four stationary points were located on the lowest-lying excited state potential energy surface, 1Sigma- -->1A", with excitation energies Te of 101.4 kcal mol(-1) (1A"HCP), 104.6 kcal mol(-1)(1Sigma-HCP), 122.3 kcal mol(-1)(1A" HPC), and 171.6 kcal mol(-1)(1Sigma-HPC) at the cc-pVQZ EOM-CCSDT-3 level of theory. The physical properties of the 1A" state with a predicted bond angle of 129.5 degrees compare well with the experimentally reported first singlet state ((approximate)A1A"). The excitation energy predicted for this excitation is T0=99.4 kcal mol(-1) (34 800 cm(-1),4.31 eV), in essentially perfect agreement with the experimental value of T0=99.3 kcal mol(-1)(34 746 cm(-1),4.308 eV). For the second lowest-lying excited singlet surface, 1Delta-->1A', four stationary points were found with Te values of 111.2 kcal mol(-1) (2(1)A' HCP), 112.4 kcal mol(-1) (1Delta HPC), 125.6 kcal mol(-1)(2(1)A' HCP), and 177.8 kcal mol(-1)(1Delta HPC). The predicted CP bond length and frequencies of the 2(1)A' state with a bond angle of 89.8 degrees (1.707 A, 666 and 979 cm(-1)) compare reasonably well with those for the experimentally reported (approximate)C(1)A' state (1.69 A, 615 and 969 cm(-1)). However, the excitation energy and bond angle do not agree well: theoretical values of 108.7 kcal mol(-1) and 89.8 degrees versus experimental values of 115.1 kcal mol(-1) and 113 degrees. of 115.1 kcal mol(-1) and 113 degrees.     

Fermentation of “Quick Fiber” produced from a modified corn-milling process into ethanol and recovery of corn fiber oil

Approximately 9% of the 9.7 billion bushels of corn harvested in the United States was used for fuel ethanol production in 2002, half of which was prepared for fermentation by dry grinding. The University of Illinois has developed a modified dry grind process that allows recovery of the fiber fractions prior to fermentation. We report here on conversion of this fiber (Quick Fiber [QF]) to ethanol. QF was analyzed and found to contain 32%wt glucans and 65%wt total carbohydrates. QF was pretreated with dilute acid and converted into ethanol using either ethanologenic Escherichia coli strain FBR5 or Saccharomyces cerevisiae. For the bacterial fermentation the liquid fraction was fermented, and for the yeast fermentation both liquid and solids were fermented. For the bacterial fermentation, the final ethanol concentration was 30 g/L, a yield of 0.44 g ethanol/g of sugar(s) initially present in the hydrolysate, which is 85% of the theoretical yield. The ethanol yield with yeast was 0.096 gal/bu of processed corn assuming a QF yield of 3.04 lb/bu. The residuals from the fermentations were also evaluated as a source of corn fiber oil, which has value as a nutraceutical. Corn fiber oil yields were 8.28%wt for solids recovered following prtetreatment.     

Functional Tethered Bilayer Lipid Membranes on Aluminum Oxide

Tethered bilayer lipid membranes are established as well‐suited model membrane systems adaptable to different surfaces, for example, gold and silicon. These solid supported membranes are highly flexible in their tethering and lipid parts and can thus be optimized for functional incorporation of membrane proteins. The excellent sealing properties of the tethered membranes allow incorporated ion‐channel proteins to be investigated. Preparation of ultrasmooth aluminum oxide by sputtering and synthesis of new tethering lipids with phosphonic acid anchor groups enable formation of an electrically sealing membrane on this surface. This process is monitored by electrochemical impedance spectroscopy and by surface plasmon resonance spectroscopy. High sealing performance of the membrane and functional incorporation of the ion carrier valinomycin are demonstrated.     

Moran's genetics model via electric networks

Using the electric approach, we derive exact and asymptotic closed form formulas for hitting times in symmetric cases of the Moran's genetics model.