Synthesis of EDTA core dendrimers through a consecutive esterification-CuAAC process

A novel class of thermostable G0 and G1-dendrimers was synthesized from the coupling of both propargyl and azido esters derived from EDTA through copper catalyzed azide-alkyne cycloaddition. The branching and size in these compounds were controlled by a simple azide-alkyne group position change in the CuAAC reaction in conjunction with the use of 1,3-diazido-propan-2-ol as a polyfunctional compound.     

High temperature enthalpy increment and thermodynamic functions of U2Ti

This study investigated thermodynamic properties of uranium–titanium alloy to determine its suitability for storage of hydrogen isotopes. The enthalpy increments of U₂Ti were measured using a high temperature inverse drop calorimeter in the temperature range of 299–1,169 K. Temperature dependence of the molar enthalpy increment and molar heat capacity is expressed in the form $ H^\circ_{\text{m}} (T) - H^\circ_{\text{m}} (298.15\,{\text{K}})({\text{J }}\,{\text{mol}}^{ - 1} ) = 23.236(T/{\text{K}}) + 53.292 \times 10^{ - 3} (T/{\text{K}})^{2} - 21.294 \times 10^{5} ({\text{K}}/T) - 4523 $ and $ C^\circ_{\text{p,m}} ({\text{J}}\,{\text{K}}^{ - 1} \,{\text{g}}^{ - 1} ) = 23.236 + 10.6584 \times 10^{ - 2} (T/{\text{K}}) + 21.294 \times 10^{5} ({\text{K}}/T)^{2} (300 \le T/{\text{K}} \le 900) $ , respectively. A set of self consistent thermodynamic functions such as entropy, Gibbs energy function, heat capacity, and Gibbs energy and enthalpy values for U₂Ti have been computed using data obtained in this study and required data from the literature.     

Computational studies on the structures and energies of the tautomers of 1-amino-3-nitrotriazol-5-one-2-oxide

Molecular orbital calculations at the DFT-B3LYP/aug-cc-pVDZ level were performed for the possible tautomers of 1-amino-3-nitro-1,2,4-triazol-5-one-2-oxide. We have examined the substitution effects of amino and nitro groups by comparing calculated geometries, relative energies, and electrostatic potentials of model molecules. The optimized structures, vibrational frequencies, and thermodynamic values for triazol-5-one-N-oxides were obtained in their ground state. The results show 1H, 4H tautomers to be most stable. Detonation velocity and detonation pressure were evaluated by the Kamlet and Jacob equations based on the predicted density and the calculated heat of explosion. Explosive properties appear to be promising compared with those of 1,3,5-trinitro-1,3,5-triazine (D = 8.75 km/s, P = 34.7 Gpa) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (D = 8.96 km/s, P = 35.96 Gpa), 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (D = 9.20 km/s, P = 42.0 Gpa) and octanitrocubane (D = 9.90 km/s, P = 48.45 GPa). The designed triazol-5-one-N-oxides satisfy the criteria of high energy density materials.     

Separation and Analysis of Nucleic Acids and Their Constituents by Ion-Exclusion and Ion-Exchange Column Chromatography

The recent commercial development of high pressure liquid chromatographic instruments, and the availability of small and uniformly sized resin beads has enhanced the role of column chromatography for the rapid assay of nucleic acid components. A major advancement in the purification and analysis has been due to the recent demonstration that the ion exclusion is more or equally effective than the ion exchange as a separation principle for the resolution of purine and pyrimidine bases, nucleosides, deoxynucleosides and nucleotides^1–3. This article deals with the recent applications of separation principles that have been employed for the separation of nucleic acid constituents. The reader is referred to two review articles of Cohn for the earlier works on this subject^{4, 5}. Separations by chromatography and electrophoresis on paper and thin layers are not described here; several monographs and review articles are available in the literature^6–12.The reader is also referred to a recent methodological study for the base analysis of ribopolynucleotides by chemical tritium labeling which utilizes two dimensional chromatography on thin layers of cellulose as a separation means^{13, 14}.     

Simple approach to study biomolecule adsorption in polymeric microfluidic channels

Herein a simple analytical method is presented for the characterization of biomolecule adsorption on cyclo olefin polymer (COP, trade name: Zeonor^®) substrates which are widely used in microfluidic lab-on-a-chip devices. These Zeonor^® substrates do not possess native functional groups for specific reactions with biomolecules. Therefore, depending on the application, such substrates must be functionalized by surface chemistry methods to either enhance or suppress biomolecular adsorption. This work demonstrates a microfluidic method for evaluating the adsorption of antibodies and oligonucleotides surfaces. The method uses centrifugal microfluidic flow-through chips and can easily be implemented using common equipment such as a spin coater. The working principle is very simple. The user adds 40 L of the solution containing the sample to the starting side of a microfluidic channel, where it is moved through by centrifugal force. Some molecules are adsorbed in the channel. The sample is then collected at the other end in a small reservoir and the biomolecule concentration is measured. As a pilot application, we characterized the adsorption of goat anti-human IgG and a 20-mer DNA on Zeonor^®, and on three types of functionalized Zeonor: 3-aminopropyltriethoxysilane (APTES) modified surface with mainly positive charge, negatively charged surface with immobilized bovine serum albumin (BSA), and neutral, hydrogel-like film with polyethylene glycol (PEG) characteristics. This simple analytical approach adds to the fundamental understanding of the interaction forces in real, microfluidic systems. This method provides a straightforward and rapid way to screen surface compositions and chemistry, and relate these to their effects on the sensitivity and resistance to non-specific binding of bioassays using them. In an additional set of experiments, the surface area of the channels in this universal microfluidic chip was increased by precision milling of microscale trenches. This modified surface was then coated with APTES and tested for its potential to serve as a unique protein dilution feature.     

Catalyst Type and Concentration Dependence in Catalytic Transfer Hydrogenolysis of α,β-Unsaturated Carbonyls and Nitriles Via Ammonium Formate

The catalytic reduction of a variety of α, β-unsaturated compounds into saturated analogs in the presence of other reducible moieties is described using ammonium formate as a hydrogen source. The rate dependence on the concentration of Pd-C catalyst as well as on 5% Pd-BaSO4 and Ra-Ni are also characterized.     

Zinc-Mediated Facile and Efficient Chemoselective S-Alkylation of 5-Aryl-1,3,4-oxadiazole-2-thiols in the Absence of Base

Zinc-mediated facile and efficient chemoselective S-alkylation of 5-aryl 1,3,4-oxadiazole-2-thiols in the presence of a catalytic amount of tetra butyl ammonium iodide was described. The reaction was performed under neutral conditions. The chemoselectivity of the alkylation was confirmed by NMR spectroscopy and x-ray crystallography.     

Isolation and biological evaluation of chromone alkaloid dysoline,a new regioisomer of rohitukine from Dysoxylum binectariferum

The chromone alkaloid dysoline (1), a new regioisomer of rohitukine (2) along with rohitukine and rohitukine-N-oxide (3) were isolated from the stem barks of Dysoxylum binectariferum. The structure of dysoline (1) was determined by extensive 2D-NMR studies and the absolute configuration was established by NOESY and CD spectra. Dysoline (1) consisted of a 5,7-dihydroxy-2-methylchromone nucleus substituted with a 2′-hydroxylated N-Me piperidine ring at the C-6 position. Dysoline differs from rohitukine by the position of the piperidine ring on the chromone nucleus. Dysoline displayed promising cytotoxicity in HT1080 fibrosarcoma cells with an IC₅₀ of 0.21 μM, and also displayed significant inhibition of proinflammatory cytokines TNF-α and IL-6.     

Proton‐Assisted Hydrogen Activation on Polyhedral Cations

The treatment of [1,1‐(PR₃)₂‐3‐(Py)‐closo‐1,2‐RhSB₉H₈] (PR₃=PMe₃ ( 2 ) or PPh₃ and PMe₃ ( 3 ); Py=pyridine) with triflic acid (TfOH) affords [1,3‐μ‐(H)‐1,1‐(PR₃)₂‐3‐(Py)‐1,2‐RhSB₉H₈]⁺ (PR₃=PMe₃ ( 4 ) or PMe₃ and PPh₃ ( 5 )). These products result from the protonation of the 11‐vertex closo‐cages along the Rh(1)? B(3) edge. These unusual cationic rhodathiaboranes are stable in solution and in the solid state and they have been fully characterized by multinuclear NMR spectroscopy. In addition, compound 5 was characterized by single‐crystal X‐ray diffraction. One remarkable feature in these structures is the presence of three {Rh(PPh₃)(PMe₃)}‐to‐{ηⁿ‐SB₉H₈(Py)} (n=4 or 5) conformers in the unit cell, thus giving an uncommon case of conformational isomerism. [1,1‐(PPh₃)₂‐3‐(Py)‐closo‐1,2‐RhSB₉H₈] ( 1 ), that is, the bis‐PPh₃‐ligated analogue of compounds 2 and 3 , is also protonated by TfOH, but, in marked contrast, the resulting cation, [1,3‐μ‐(H)‐1,1‐(PPh₃)₂‐3‐(Py)‐1,2‐RhSB₉H₈]⁺ ( 6 ), is attacked by a triflate anion with the release of a PPh₃ ligand and the formation of [8,8‐(OTf)(PPh₃)‐9‐(Py)‐nido‐8,7‐RhSB₉H₉] ( 9 ). The result is an equilibrium that involves cationic species 6 , neutral OTf‐ligated compound 9 , and [HPPh₃]⁺, which is formed upon protonation of the released PPh₃ ligand. The resulting ionic system reacts readily with H₂ to give cationic species [8,8,8‐(H)(PPh₃)₂‐9‐(Py)‐nido‐8,7‐RhSB₉H₉]⁺ ( 7 ). This reactivity is markedly higher than that previously found for compound 1 and it introduces a new example of proton‐assisted H₂ activation that occurs on a polyhedral boron‐containing compound.