Plasticization of a polymer layer harnessed to a silicon microcantilever as a highly sensitive and selective means to detect nitroaromatic derivatives

A new approach to the chemo‐mechanical detection of trace amounts of nitroaromatics, even in the presence of high concentrations of background materials, is presented. The detection scheme is based on the plasticization of an aminopropyl silane layer that is harnessed to a silicon beam following its reaction with nitroaromatic systems. The reaction‐induced plasticization attenuates the temperature induced bending of the polymer‐beam sandwich, offering a simple and very sensitive tool for the detection of nitroaromatic systems. Using this approach, it was possible to detect a sample of 100 pg TNT even in the presence of a ～10⁹ fold excess of a background material such as acetonitrile. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2124–2130     

Microcantilevers as gas‐phase sensing platforms: Simplification and optimization of the production of polymer coated porous‐silicon‐over‐silicon microcantilevers

The asymmetric roughening of silicon microcantilevers using different vapor stain‐etching conditions is studied with the aim of optimizing face selective coating of microcantilevers by polymers through simple dipping. The effect of roughening is studied by following the time‐dependent guest‐induced bending of silicone microcantilevers coated with a poly‐4‐vinylpyridine sensing layer. A correlation between the surface roughness of the microcantilevers and their time‐dependent guest‐induced bending is gained from combining high resolution scanning electron microscopy studies of the surface of the microcantilevers as well as their cross‐sections with time‐dependent guest‐induced microcantilever bending. The purpose of the present work is to lay the foundations for a small and relatively simple gas‐phase sensing tool based on a microcantilever platform capable of offering wide range sensing capabilities. © 2013 Wiley Periodicals, 2014 , 52, 141–146     

Selective Inhibition of Aggregation and Toxicity of a Tau‐Derived Peptide using Its Glycosylated Analogues

Protein glycosylation is a ubiquitous post‐translational modification that regulates the folding and function of many proteins. Misfolding of protein monomers and their toxic aggregation are the hallmark of many prevalent diseases. Thus, understanding the role of glycans in protein aggregation is highly important and could contribute both to unraveling the pathology of protein misfolding diseases as well as providing a means for modifying their course for therapeutic purposes. Using β‐O‐linked glycosylated variants of the highly studied Tau‐derived hexapeptide motif VQIVYK, which served as a simplified amyloid model, we demonstrate that amyloid formation and toxicity can be strongly attenuated by a glycan unit, depending on the nature of the glycan itself. Importantly, we show for the first time that not only do glycans hinder self‐aggregation, but the glycosylated peptides are capable of inhibiting aggregation of the non‐modified corresponding amyloid scaffold.     

On partitions of {1,…,2m + 1}\{k} into differences d,…,d + m − 1: Extended Langford sequences of large defect

It is shown that for m = 2d ? 1, 2d, 2d + 1, and d ≥ 1, the set {1, 2,…, 2m + 2}, ? {2,k} can be partitioned into differences d,d + 1,…,d + m ? 1 whenever (m,k) ≡ (0,0), (1,d + 1), (2, 1), (3,d) (mod (4,2)) and (d,m,k) ≠ (1,1,3), (2,3,7) (where (x,y) ≡ (u,ν) mod (m,n) iff x ≡ u (mod m) and y ≡ ν (mod n)). It is also shown that if m ≥ 2d ? 1 and m ? [2d + 2, 8d ? 5], then the set {1, 2, …, 2m + 1} ? {k} can be partitioned into differences d,d + 1,…,d + m ? 1 whenever (m,k) ≡ (0, 1), (1,d), (2,0), (3,d + 1) mod (4,2). Finally, for d = 4 we obtain a complete result for when {1,…,2m + 1} ? {k} can be partitioned into differences 4,5,…,m + 3. © 2004 Wiley Periodicals, Inc.     

Symmetrical gas-phase dissociation of noncovalent protein complexes via surface collisions

Previous gas-phase dissociation experiments of protein-protein complexes have resulted in product ion distributions that are asymmetric by charge and mass, providing limited insight into the chemical nature of subunit organization and interaction. In these experiments, a symmetric charge distribution results from an "energy sudden" collision of protein-protein complexes with a surface, indicating that it may be possible to probe the suboligomeric structure of noncovalent complexes in the gas phase. It is proposed that energy sudden surface activation of cytochrome C homodimers results in dissociation without significant unfolding of one of the monomeric subunits. Previously proposed mechanisms for the dissociation of protein-protein complexes are discussed in the context of these results. These experiments demonstrate the potential to preserve the structural details of subunit interaction within a protein-protein complex and help elucidate the asymmetric nature of macromolecular dissociation in the gas phase.     

Manifestations of the roton mode in dipolar Bose-Einstein condensates

We investigate the structure of trapped Bose-Einstein condensates (BECs) with long-range anisotropic dipolar interactions. We find that a small perturbation in the trapping potential can lead to dramatic changes in the condensate's density profile for sufficiently large dipolar interaction strengths and trap aspect ratios. By employing perturbation theory, we relate these oscillations to a previously identified "rotonlike" mode in dipolar BECs. The same physics is responsible for radial density oscillations in vortex states of dipolar BECs that have been predicted previously.     

Enumerating traceless matrices over compact discrete valuation rings

We show that the non-separable Banach space SL∞ is primary. This is achieved by directly solving the infinite-dimensional factorization problem in SL∞. In particular, we bypass Bourgain’s localization method.     

A new action photoelectron spectroscopy for anions

We present a new experimental approach, in which anion photodetachment spectroscopy is recorded with electrons of fixed kinetic energy. This approach circumvents some shortcomings of the zero electron kinetic energy method. Our method is based on a modified magnetic bottle photoelectron spectrometer (MBPES). A tunable laser is used to detach electrons from mass selected anions, drifting collinearly with the 40 cm MBPES drift tube. To avoid Doppler broadening, a low voltage pulse removes the velocity component of anions from the detached electrons. Spectra are recorded by collecting the wavelength dependence of electron-signal at a predetermined TOF window, corresponding to a specific electron-kinetic energy. We call this approach PEACE, denoting photoelectron action spectroscopy at constant kinetic energy. Our best resolution is 0.65 meV for 1.5 meV electrons. We present a PEACE spectrum of HgCl(-) together with the corresponding simulated theoretical spectrum. The method is similar in resolution and data collection rates to the slow electron velocity map imaging technique recently introduced by Neumark and co-workers.