A silaproline‐containing dipeptide

The silaproline‐containing dipeptide N‐(3,3‐di­methyl‐1‐pivaloyl‐1‐aza‐3‐sila‐5‐cyclo­pentyl­carbonyl)‐l ‐alanine iso­propyl­amide, C₁₇H₃₃N₃O₃Si, has two independent molecules in the asymmetric unit and each adopts a β‐II folded conformation, where the amide on the terminal C interacts intramolecularly with the pivaloyl O atom. The five‐membered silaproline ring is C^β‐puckered, an infrequent conformation for the homol­ogous proline ring.     

Towards a holographic model of color-flavor locking phase

Journal of High Energy Physics - We examine the prospects for testing SO(10) Yukawa-unified supersymmetric models during the first year of LHC running at $ \sqrt s = 7\,{\text{TeV}} $ , assuming...     

Simultaneous Determination of Carvedilol,Enalaprilat, and Perindoprilat in Human Plasma Using LC–MS/MS and Its Application to a Pharmacokinetic Pilot Study

Chromatographia - A method for the extraction and quantification of carvedilol, enalaprilat, and perindoprilat in 50 µL human plasma, using high-performance liquid chromatography with...     

Metal-Organic Framework (MOF) Morphology Control by Design

Exerting morphological control over metal-organic frameworks (MOFs) is critical for determining their catalytic performance and to optimize their packing behavior in areas from separations to fuel gas storage. A mechanism-based approach to tailor the morphology of MOFs is introduced and experimentally demonstrated for five cubic Zn₄O-based MOFs. This methodology provides three key features: 1) computational screening for selection of appropriate additives to change crystal morphology based on knowledge of the crystal structure alone; 2) use of additive to metal cluster geometric relationships to achieve morphologies expressing desired crystallographic facets; 3) potential for suppression of interpenetration for certain phases.     

Electrochemical structure‐switching sensing using nanoplasmonic devices

In this article, the implementation of electrochemical plasmonic nanostructures functionalized with DNA‐based structure‐switching sensors is presented. eNanoSPR devices with open and microfluidic measurement cells are developed on the base of nanohole arrays in 100 nm gold film and applied for combined microscopic and electrochemical surface plasmon (eSPR) visualization. eSPR voltammograms and spectroscopy are performed using planar three electrode schematic with plasmonic nanostructure operated as working electrode. Limit of detection of eNanoSPR devices for oligonucleotide hybridization is estimated in the low nanomolar and applications for structure‐switching electro‐plasmonic sensing in complex liquids are discussed.     

New advances in the understanding of the in-source decay fragmentation of peptides in MALDI-TOF-MS

In-source decay (ISD) is a rapid fragmentation occurring in the matrix-assisted laser desorption/ionization (MALDI) source before the ion extraction. Despite the increasing interest for peptides de novo sequencing by ISD, the influence of the matrix and of the peptide itself is not yet fully understood. Here we compare matrices with high ISD efficiencies to gain deeper insight in the ISD fragmentation process(es). The major ISD fragments are the c- and z-ions, but other types of fragments are also observed, and their origin is studied here. Two main pathways lead to fragmentation in the source: a radical-induced pathway that leads to c-, z-, w-, and d- ions, and a thermally activated pathway that leads to y-, b-, and a-ions. A detailed analysis of the ISD spectra of selected peptides revealed that (1) the extents of the two in-source pathways are differently favored depending on the matrix used, that (2) the presence of a positive/negative charge on the radical-induced fragments is necessary for their observation in positive/negative mode, respectively, and that (3), for a same peptide, the patterns of the different types of fragments differ according to the matrix used.     

Nonequilibrium Wetting

When a nonequilibrium growing interface in the presence of a wall is considered a nonequilibrium wetting transition may take place. This transition can be studied through Langevin equations or discrete growth models. In the first case, the Kardar-Parisi-Zhang equation, which defines a very robust universality class for nonequilibrium moving interfaces, with a soft-wall potential is considered. While in the second, microscopic models, in the corresponding universality class, with evaporation and deposition of particles in the presence of hard-wall are studied. Equilibrium wetting is related to a particular case of the problem, it corresponds to the Edwards-Wilkinson equation with a potential in the continuum approach or to the fulfillment of detailed balance in the microscopic models. In this review we present the analytical and numerical methods used to investigate the problem and the very rich behavior that is observed with them.     

Adsorption of Large Organic Molecules on Clean and Hydroxylated Rutile TiO2(110) Surfaces

Behavior of large organic molecules equipped with spacer groups (Violet Landers, VL) on the TiO₂(110)‐(1×1) surfaces is investigated by means of high‐resolution scanning tunneling microscopy (STM). Two distinct adsorption geometries are observed. We demonstrate that the molecule adsorption morphology can be alternated by well‐controlled STM tip‐induced manipulation. It is used to probe the mobility of molecules and reveals locking in one of the analyzed adsorption sites, thus allow to enhance or reduce the mobility along the [001] direction. Field induced hydrogen desorption is used to perform lateral STM manipulation on a hydroxyl‐free surface, which provides insight into the influence of surface hydroxyl groups on the molecule behavior. The ability to image with submolecular resolution both the central board and the spacer groups of the VL molecule is demonstrated.     

Physical properties of hemoglobin-poly(acrylamide) hydrogel-based oxygen carriers: effect of reaction pH

This work examines the physical properties of bovine hemoglobin (BHb) chemically cross-linked to a pH responsive polymer (poly(acrylamide)) with the goal of taking advantage of the polymer's pH sensitivity to generate low-P50 oxygen carriers for application in physiological conditions characterized by deviations from normal pH. BHb-hydrogel-based oxygen carriers encapsulating 10-16 g/dL BHb displayed P50s < 10 mmHg when encapsulated inside of liposomes (i.e. Hb-LGs) and <15 mmHg in the absence of a lipid bilayer (i.e. Hb-NHPs), when synthesized at pHs less than normal physiological pH. The results of this work suggest that synthesis of Hb-LGs/Hb-NHPs under different pH conditions affect the ionization of BHb and the flexibility of the polymer chains to which BHb is chemically cross-linked. The degree of BHb cross-linking to the polymer matrix and the chain flexibility of the polymer influences the oxygen affinity and cooperativity of the oxygen carrier by influencing how easy it is for the Hb molecule to change conformations between the R and T states. The magnitude of the zeta potential of Hb-LGs and Hb-NHPs was shown to be within the range of stored red blood cells and within the range of limited flocculation. Taken together, this work describes the preparation and characterization of oxygen carriers with increased oxygen affinities compared to those of red blood cells.     

Comparison of analytical strategies for the chromatographic and mass spectrometric measurement of brominated flame retardants: 1. Polybrominated diphenylethers

The chromatographic and mass spectrometric (MS) behaviors of 49 polybrominated diphenylether (PBDE) homologues toward various techniques is investigated. Special attention is paid to chromatographic separation, ionization processes, and signal acquisition modes. Different liquid chromatographic (LC) separation systems and gas chromatographic (GC) temperature program parameters are studied. For LC-MS experiments, the ionization efficiencies of electrospray, atmospheric pressure chemical ionization, and atmospheric pressure photoionization (APPI) are evaluated. For GC-MS experiments, negative chemical ionization with ammonia as reagent gas as well as negative and positive electron impact (EI) ionization are studied. Thus, fragmentation pathways of PBDEs are investigated, with the main objective being to determine the sensitivity/specificity balance of each tested technique with respect to their potential respective application (parent compound focusing, metabolite identification, and screening of analogue compounds). Finally, performances of the different tested techniques are compared and evaluated in terms of detection limits on standard solutions for each homologue group. In terms of ionization, EI remains the best compromise between sensitivity and specificity with possible complementary applications in MS-MS and high-resolution MS. Nevertheless, APPI appears to be a promising alternative.