Electrostatically mediated adsorption by nanodiamond and nanocarbon particles

Nanodiamond (ND) and other nanocarbon particles are popular platforms for the immobilization of molecular species. In the present research, factors affecting adsorption and desorption of propidium iodide (PI) dye, chosen as a charged molecule model, on ND and sp ² carbon nanoparticles were studied, with a size ranging from 75 to 4,305 nm. It was found that adsorption of PI molecules, as characterized by ultraviolet–visible spectroscopy, on ND particles is strongly influenced by sorbent-sorbate electrostatic interactions. Different types of NDs with a negative zeta potential were found to adsorb positively charged PI molecules, while no PI adsorption was observed for NDs with a positive zeta potential. The type and density of surface groups of negatively charged NDs greatly influenced the degree and capacity of the PI adsorbed. Ozone-purified NDs had the highest capacity for PI adsorption, due to its greater density of oxygen containing groups, i.e., acid anhydrides and carboxyls, as assessed by TDMS and TOF–SIMS. Single wall nanohorns and carbon onion particles were found to adsorb PI regardless of their zeta potential; this is likely due to π bonding between the aromatic rings of PI and the graphitic surface of the materials and the internal cavity of the horns.     

Virtual screening using a conformationally flexible target protein: models for ligand binding to p38α MAPK

We have used virtual screening to develop models for the binding of aryl substituted heterocycles to p38α MAPK. Virtual screening was conducted on a number of p38α MAPK crystal structures using a library of 46 known p38α MAPK inhibitors containing a heterocyclic core substituted by pyridine and fluorophenyl rings (structurally related to SB203580) and a set of decoy compounds. Multiple protonation states and tautomers of active and decoy compounds were considered. Each docking model was evaluated using receiver operating characteristic (ROC) curves and enrichment factors. The two best performing single crystal structures were found to be 1BL7 and 2EWA, with enrichment factors of 14.1 and 13.0 at 2 % of the virtual screen respectively. Ensembles of up to four receptors of similar conformations were generated, generally giving good or very good performances with high ROC AUCs and good enrichment. The 1BL7-2EWA ensemble was able to outperform each of its constituent receptors and gave high enrichment factors of 17.3, 12.0, 8.0 at 2, 5 and 10 % respectively, of the virtual screen. A ROC AUC of 0.94 was obtained for this ensemble. This method may be applied to other proteins where there are a large number of inhibitor classes with different binding site conformations.     

Atom-Transfer Cyclization with CuSO(4)/KBH(4): A Formal "Activators Generated by Electron Transfer" Process Also Applicable to Atom-Transfer Polymerization

The 4-exo and 5-exo-trig atom-transfer cyclizations of 1, 8a-e, 9, 12, and 13 can be mediated with as little as 0.05 mol % of Cu(TPMA)SO(4)·5H(2)O in the presence of 2.5 mol % of borohydride salts in 10 min at room temperature in air. This formal "activators generated by electron transfer" (AGET) procedure utilizes a cheap and oxidatively stable copper source (CuSO(4)·5H(2)O) and can be carried out in environmentally benign solvents (EtOH). It is possible to alter the product distribution in the 5-endo radical-polar crossover reactions of 10a,b and 11 by tailoring the amount of borohydride. Cyclization onto alkynes 14 and 15 is also possible in only 20 min. Controlled radical polymerization of styrene, with increased rates over conventional atom-transfer radical polymerization (ATRP), can be carried out in a controlled fashion (Mn, PDI) using either CuBr or CuSO(4)·5H(2)O and Bu(4)NBH(4).     

From solid state to solution: advancing chemistry of Bi-Bi and Bi-Rh paddlewheel carboxylates

The first successful high-yield solution synthesis of homobimetallic Bi(2)(O(2)CCF(3))(4) (1), as well as heterobimetallic BiRh(O(2)CCF(3))(4) (2) and BiRh(O(2)CCF(2)CF(3))(4) (3), complexes is reported. It is based on one-pot reduction reactions starting from Bi(III) and Rh(II) carboxylates and using Bi metal as a reducing agent. The presence of small amounts of diphenyl ether was found to facilitate this reaction, most probably because of its good solubilizing and π-stabilizing abilities. The latter is illustrated by the isolation and structural characterization of a π-adduct of 1 with diphenyl ether, [Bi(2)(O(2)CCF(3))(4)·1/2Ph(2)O]. Importantly, the new approach expands to solution the chemistry of Bi(II) that was previously limited to the solid state only. The solution procedure developed for the preparation of heterometallic BiRh(O(2)CCF(3))(4) is now one step shorter and gives the product in excellent yield compared with the previously reported method based on sublimation-deposition technique. It is also performed on a greater scale (~10-20 times) and makes further scale-up feasible, if needed. Moreover, it eliminates the isolation of the hard-to-handle unsolvated Bi(II) trifluoroacetate used earlier as a starting material. A new polymorph of BiRh(O(2)CCF(3))(4) (2) was crystallized from solution in this work. The solution approach was also applied to the synthesis of a new heterobimetallic carboxylate with perfluorinated propionate ligands, BiRh(O(2)CCF(2)CF(3))(4) (3). All products are fully characterized by spectroscopic and single crystal X-ray diffraction methods. Complexes 2 and 3 exhibit similar solid state structures based on heterobimetallic paddlewheel units forming infinite 1D chains through intermolecular Rh···O interactions.     

Measurements of L-shell X-ray emission lines of neonlike europium on an electron beam ion trap

We report a measurement of the two X-ray transitions that proceed from the and (1s²2s_1/22p⁶3p_1/2)_{J = 1} upper levels to the (1s²2s²2p⁶)_{J = 0} ground level in neonlike Eu⁵³⁺ (Z = 63), that is,  near the previously documented avoided crossing of the two upper levels at Z = 68. The measurement was carried out using the calorimeter spectrometer on the Livermore EBIT-I electron beam ion trap. It affirms the trends set by the neighboring neonlike ions both in terms of the relative intensity of the two lines and in terms of the magnitude of disagreement with theoretical energy level predictions.     

Force Deployment in a Conventional Theatre-level Military Engagement

This paper is concerned with the study of force deployment in a conventional theatre-level military engagement. First, it discusses some of the governing parameters that affect the modelling. A non-linear programming model is then developed to describe the combat dynamics. Sensitivity analysis on the optimal solution is also discussed. The merit of the model is demonstrated by applying the formulation to study the effect of various sustainment policies on the outcome of a battle.     

Adsorption kinetics of surfactant mixtures from micellar solutions as studied by maximum bubble pressure technique

The adsorption kinetics of micellar solutions of anionic/cationic SDS/DATB mixtures with mixing ratios of 10/1 and 10/2, respectively, are studied experimentally by means of the maximum bubble pressure method. For long adsorption times the adsorption of the highly surface-active anionic/cationic complex leads to a decrease of dynamic surface tension in comparison to the single SDS system. However, the situation is the reverse for short adsorption times where the dynamic surface tension is increased by addition of the cationic surfactant, although the overall concentration is increased. This unexpected behavior is explained by partial solubilization of free SDS molecules into micelles formed by SDS/DTAB complexes. With increasing overall concentration, when eventually the CMC of SDS is reached, the anionic/cationic complex itself is solubilized by SDS micelles. Finally, no complex micelles, which for their part can solubilize an excess of SDS molecules, are present. Hence, the dynamic properties of the solution are no longer influenced by the depletion of SDS molecules and the mixture tends to behave like a pure SDS solution.     

Alterations in mitochondrial and apoptosis-regulating gene expression in photodynamic therapy-resistant variants of HT29 colon carcinoma cells

Photodynamic therapy (PDT) is a novel cancer therapy inducing irreversible photodamage to tumor tissue via photosensitizer-mediated oxidative cytotoxicity. The cellular and molecular responses associated with PDT are only partially understood. We have reported previously the generation of several photosensitizer-specific PDT-resistant cell variants of HT29 human colon adenocarcinoma cells by selecting cells from sequential PDT treatment using different photosensitizers. In this report, we describe the use of messenger RNA (mRNA) differential display to identify genes that were differentially expressed in the parental HT29 cells compared with their resistant variants. In comparison with parental HT29 cells, mRNA expression was increased in the PDT-resistant cell variants for BNIP3, estrogen receptor-binding fragment-associated gene 9, Myh-1c, cytoplasmic dynein light chain 1, small membrane protein I and differential dependent protein. In contrast, expression in the PDT-resistant variants was downregulated for NNX3, human HepG2 3' region Mbol complementary DNA, glutamate dehydrogenase, hepatoma-derived growth factor and the mitochondrial genes coding for 16S ribosomal RNA (rRNA) and nicotinamide adenine dinucleotide (NADH) dehydrogenase subunit 4. The reduction for mitochondrial 16S rRNA in the PDT-resistant variants was confirmed by Northern blotting, and the elevated expression of the proapoptotic BNIP3 in the PDT-resistant variants was confirmed by Northern and Western blotting analysis. We also examined the expression of some additional apoptosis-regulating genes using Western blotting. We show an increased expression of Bcl-2 and heat shock protein 27 and a downregulation of Bax in the PDT-resistant variants. In addition, the mutant p53 levels in the parental HT29 cells were reduced substantially in the PDT-resistant variants. We suggest that the altered expression in several mitochondrial and apoptosis-regulating genes contributes to PDT resistance.     

Optimisation of microdialysis sampling recovery by varying inner cannula geometry

In vitro microdialysis recoveries of glucose were evaluated and optimised by varying the inner cannula dimensions for a concentric type microdialysis probe. The recovery was shown to be significantly dependent on the outer radius of the inner cannula (r alpha). Increasing r alpha by 50% while holding all other microdialysis variables constant caused a 26% increase in recovery under the conditions tested. Mass transport modeling of microdialysis sampling showed that the magnitude of the recovery change in response to changes in r alpha may depend on other experimental variables such as effective dialysis length, membrane dimensions, membrane type and medium composition. These data indicate that microdialysis recovery may be substantially improved by optimising the outer diameter of the inner cannula. These data also suggest that in order to fully characterise and compare data from microdialysis experiments, r alpha should become one of the reported variables.     

Allylic stereocontrol of the intramolecular Diels-Alder reaction

The stereochemical outcome of the intramolecular Diels-Alder reaction of ester-linked 1,3,8-nonatrienes can be controlled by substituents about a stereogenic center attached to C1. The scope and limitations of this approach have been investigated, with variation in substrate structure about the allylic stereocenter and the dienophile. The stereochemical outcomes of these reactions are explained by reference to B3 LYP/6-31G(d) transition structures. New insights into the conformational preferences of allylic alcohol derivatives are reported, results which allow an explanation of the differing levels of pi-diastereofacial selectivity and cis/trans (i.e. endo/exo) selectivity from the reaction.