Cyclo[n]pyrroles: size and site-specific binding to G-quadruplexes

Inhibiting the enzyme telomerase by stabilizing the G-quadruplex has potential in anticancer drug design. Diprotonated cyclo[n]pyrroles represent a set of expanded porphyrin analogues with structures similar to that of telomestatin, a natural product known to bind to and stabilize G-quadruplexes. As a first step toward testing whether cyclo[n]pyrroles display a similar function, a series of diprotonated cyclo[n]pyrroles (where n = 6, 7, and 8) was each added to the human telomere repeat sequence d(T(2)AG(3))(4) and examined with mass spectrometry, ion mobility, and molecular dynamics calculations. Nano-ESI-MS indicated that the smaller the cyclo[n]pyrrole, the more strongly it binds to the telomeric sequence. It was also found that cyclo[6]pyrrole bound to d(T(2)AG(3))(4) better than octaethylporphyrin, a finding rationalized by cyclo[6]pyrrole having a 2+ charge, while octaethylporphyrin bears no charge. Ion mobility measurements were used to measure the collision cross section of each d(T(2)AG(3))(4)/cyclo[n]pyrrole complex. Only one peak was observed in the arrival time distributions for all complexes, and the experimental cross sections indicated that only structures with d(T(2)AG(3))(4) in an antiparallel G-quadruplex arrangement and each cyclo[n]pyrrole externally stacked below the G-quartets occur under these experimental conditions. When the cyclo[n]pyrroles were intercalated or nonspecifically bound to the quadruplex, or if conformations different than antiparallel were considered for d(T(2)AG(3))(4), the theoretical cross sections did not match experiment. On this basis, it is inferred that (1) external stacking represents the dominant binding mode for the interaction of cyclo[n]pyrroles with d(T(2)AG(3))(4) and (2) the overall size and charge of the cyclo[n]pyrroles play important roles in defining the binding strength.     

Surface confined ionic liquid as a stationary phase for HPLC

Trimethoxysilane "ionosilane" derivatives of room temperature ionic liquids based on alkylimidazolium bromides were synthesized for attachment to silica support material. The derivatives 1-methyl-3-(trimethoxysilylpropyl)imidazolium bromide and 1-butyl-3-(trimethoxysilylpropyl)imidazolium bromide were used to modify the surface of 3 microm diameter silica particles to act as the stationary phase for HPLC. The modified particles were characterized by thermogravimetric analysis (TGA) and (13)C and (29)Si NMR spectroscopies. The surface modification procedure rendered particles with a surface coverage of 0.84 micromol m(-2) for the alkylimidazolium bromide. The ionic liquid moiety was predominantly attached to the silica surface through two siloxane bonds of the ionosilane derivative (63%). Columns packed with the modified silica material were tested under HPLC conditions. Preliminary evaluation of the stationary phase for HPLC was performed using aromatic carboxylic acids as model compounds. The separation mechanism appears to involve multiple interactions including ion exchange, hydrophobic interaction, and other electrostatic interactions.     

Imaging nanostructures with scanning photoionization microscopy

We report detailed studies of local electronic properties in nanostructured thin metallic films using scanning photoionization microscopy. This novel form of microscopy combines the advantages of diffraction-limited optical excitation with the ability to detect both photons and low kinetic energy photoelectrons, permitting sensitive characterization of heterogeneous surfaces under vacuum conditions. Using this technique, correlated measurements of multiphoton photoemission cross section and optical penetration depth are reported for Au films supported on Pt. These results present a first step toward combining confocal fluorescence or Raman microscopy with time-resolved photoelectron imaging spectroscopy in complex metal film environments, which should be ideally suited to investigating local plasmonic effects in nanostructures.     

Ether- and alcohol-functionalized task-specific ionic liquids: attractive properties and applications

In recent years, the designer nature of ionic liquids (ILs) has driven their exploration and exploitation in countless fields among the physical and chemical sciences. A fair measure of the tremendous attention placed on these fluids has been attributed to their inherent designer nature. And yet, there are relatively few examples of reviews that emphasize this vital aspect in an exhaustive or meaningful way. In this critical review, we systematically survey the physicochemical properties of the collective library of ether- and alcohol-functionalized ILs, highlighting the impact of ionic structure on features such as viscosity, phase behavior/transitions, density, thermostability, electrochemical properties, and polarity (e.g. hydrophilicity, hydrogen bonding capability). In the latter portions of this review, we emphasize the attractive applications of these functionalized ILs across a range of disciplines, including their use as electrolytes or functional fluids for electrochemistry, extractions, biphasic systems, gas separations, carbon capture, carbohydrate dissolution (particularly, the (ligno)celluloses), polymer chemistry, antimicrobial and antielectrostatic agents, organic synthesis, biomolecular stabilization and activation, and nanoscience. Finally, this review discusses anion-functionalized ILs, including sulfur- and oxygen-functionalized analogs, as well as choline-based deep eutectic solvents (DESs), an emerging class of fluids which can be sensibly categorized as semi-molecular cousins to the IL. Finally, the toxicity and biodegradability of ether- and alcohol-functionalized ILs are discussed and cautiously evaluated in light of recent reports. By carefully summarizing literature examples on the properties and applications of oxy-functional designer ILs up till now, it is our intent that this review offers a barometer for gauging future advances in the field as well as a trigger to spur further contemplation of these seemingly inexhaustible and--relative to their potential--virtually untouched fluids. It is abundantly clear that these remarkable fluidic materials are here to stay, just as certain design rules are slowly beginning to emerge. However, in fairness, serendipity also still plays an undeniable role, highlighting the need for both expanded in silico studies and a beacon to attract bright, young researchers to the field (406 references).     

New reactivity of the uranyl ion: ring opening polymerisation of epoxides

The uranyl aryloxide, [UO(2)(OAr)(2)(THF)(2)], and uranyl chloride, [UO(2)Cl(2)(THF)(3)] or [UO(2)Cl(2)(THF)(2)](2) act as pre-catalysts for the ring opening polymerization of propylene oxide and cyclohexene oxide. Coordination of the monomers has been investigated using (1)H EXSY spectroscopy and kinetic and thermodynamic parameters reported. NMR analyses of the polymers suggest a bimetallic mechanism for the polymerization.     

Magnetically gated microelectrodes

Microelectrodes fabricated in the center of single-coil microelectromagnetic traps are described. Magnetic particles are then used to reversibly gate transport of an electroactive species to the surface of the electrode or as a means to produce an ON/OFF bioelectrocatalytic glucose sensor.     

Heuristic solution methods for the stochastic flow shop problem

We investigate the stochastic flow shop problem with m machines and general distributions for processing times. No analytic method exists for solving this problem, so we looked instead at heuristic methods. We devised three constructive procedures with modest computational requirements, each based on approaches that have been successful at solving the deterministic counterpart. We compared the performance of these procedures experimentally on a set of test problems and found that all of them achieve near-optimal performance.     

A Personal Perspective on the Last Half-Century of Critical Phenomena

One of the crowning achievements of mathematical, statistical physics over the past half century has been the discovery of the many aspects of structure of the critical point. It has been an exciting time and was only possible through the combined efforts of many excellent people. This article contains brief reviews of some of the parts in which I have been most interested and to which I have made some contributions.