Cobalt(II) Complexes of Nitrile‐Functionalized Ionic Liquids

A series of nitrile‐functionalized ionic liquids were found to exhibit temperature‐dependent miscibility (thermomorphism) with the lower alcohols. Their coordinating abilities toward cobalt(II) ions were investigated through the dissolution process of cobalt(II) bis(trifluoromethylsulfonyl)imide and were found to depend on the donor abilities of the nitrile group. The crystal structures of the cobalt(II) solvates [Co(C₁C_1CNPyr)₂(Tf₂N)₄] and [Co(C₁C_2CNPyr)₆][Tf₂N]₈, which were isolated from ionic‐liquid solutions, gave an insight into the coordination chemistry of functionalized ionic liquids. Smooth layers of cobalt metal could be obtained by electrodeposition of the cobalt‐containing ionic liquids.     

Optimization of N‐methyl‐N‐[tert‐butyldimethylsilyl]trifluoroacetamide as a derivatization agent for determining isotopic enrichment of glycerol in very‐low density lipoproteins

Stable isotope kinetic studies play an important role in the study of very‐low density lipoprotein (VLDL) metabolism, including basic and clinical research. Today, [1,1,2,3,3‐²H₅]glycerol is the most cost‐effective alternative to measure glycerol and triglyceride kinetics. Recycling of glycerol from glycolysis and gluconeogenesis may lead to incompletely labelled tracer molecules. Many existing methods for the measurement of glycerol isotopic enrichment involve the production of glycerol derivatives that result in fragmentation of the glycerol molecule after ionization. It would be favourable to measure the intact tracer molecule since incompletely labelled tracer molecules may be measured as fully labelled. The number of methods available to measure the intact tracer in biological samples is limited. The aim of this project was to develop a gas chromatography/mass spectrometry (GC/MS) method for glycerol enrichment that measures the intact glycerol backbone and is suitable for electron ionization (EI), which is widely available. A previously published method for N‐methyl‐N‐[tert‐butyldimethylsilyl]trifluoroacetamide (MTBSTFA) derivatization was significantly improved; we produced a stable derivative and increased recovery 27‐fold in standards. We used the optimized MTBSTFA method in VLDL‐triglyceride and found that further modification was required to take matrix effects into account. We now have a robust method to measure glycerol isotopic enrichment by GC/EI‐MS that can be used to rule out the known problem of tracer recycling in studies of VLDL kinetics. Copyright © 2010 John Wiley & Sons, Ltd.     

Characterization of metal-labelled peptides by matrix-assisted laser desorption/ionization mass spectrometry and tandem mass spectrometry

Metal labelling of peptides and proteins using high-affinity metal-chelating compounds has found widespread applications in the medical and bioanalytical fields. In the present study we investigated the analysis of peptides derivatized either with cysteine- or amino group-directed metal-bound DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) chelators in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The metal complexes of DOTA were shown to be stable under MALDI-MS conditions. The introduction of the metal label led in a number of cases to significantly increased signal-to-noise (S/N) values and thus improved sensitivity of the labelled peptides compared to their unlabelled counterparts, especially for multiply labelled peptides. The presence of the labels did alter the tandem mass spectrometric (MS/MS) behaviour, namely the formation of sequence specific a-, b- and y-ion series, in dependence of the position of the label within the peptide sequence. For cysteine-derivatized peptides several label-specific reporter ions and characteristic immonium ions could be identified. Amino-directed labelling led only to the formation of characteristic immonium ions in ε-amino groups of lysine, whereas N-terminal labelling in some cases led to the formation of a(1)- and b(1)-ions. The results clearly show that MALDI-MS is suitable for the analysis of metal-labelled peptides, which was also confirmed in liquid chromatography (LC)/MALDI-based identification of proteins in a model protein mixture labelled with Cys-reactive DOTA. Here, in comparison to a run with alkylated cysteines, more than 50% more cysteine-containing peptides were identified.     

An electrochemical and structural investigation of silicon nanowires as negative electrode for Li-ion batteries

The electrochemical and structural responses of silicon nanowires deposited by chemical vapor deposition are investigated. Transmission electron microscopy and X-ray diffraction experiments show the electrochemical lithiation of SiNWs is not a quantitative process in good agreement with cycling experiments performed as a function of cycling limits. The SiNWs are not deeply lithiated as revealed by TEM micrographs. Our results suggest the existence of two well-defined lithiation steps, first at ∼0.2 V into amorphous silicon and then into crystalline silicon at ∼0.1 V. Cycling SiNWs above 100 mV avoid the lithiation of c-Si which preserves the silicon 3-D architecture and results in good cycling performances. A stable capacity value of ∼500 mAh g⁻¹ is achieved over at least 50 cycles.     

Alloying of electrodeposited silicon with lithium—a principal study of applicability as anode material for lithium ion batteries

The possibility to electrodeposit silicon directly on a copper current collector out of organic electrolyte and ionic liquid was investigated with the aim to alloy the deposited silicon with lithium to prove the possible use as negative electrode in lithium ion batteries. Cyclovoltammetric analyses have shown in comparison to electrodes containing high crystalline silicon similar behaviour during the electrochemical alloying and dealloying process. SEM analyses have shown a particle size of the deposited silicon in submicron range.     

Effects of bundling on the properties of the SPC water model

Simultaneous representation of molecules at an all-atom and coarse-grained level, as required by multiscaling molecular dynamics simulations, poses problems for the treatment of small molecules. If more than one of these molecules are mapped to a single coarse-grained interaction site, unrestricted movement in the all-atom representation can make a meaningful correspondence of the coordinates between the two representations impossible. Restricting the relative movement of molecules mapped to the same coarse-grained interaction site solves that problem, but will have consequences for the properties of the model. Here we investigate the effects of introducing bundling to the common simple point charge (SPC) water model and present a bundled water model that preserves important properties of SPC water relevant for multiscaling.     

Lineshapes in quasi-elastic scattering from species hopping between non-equivalent surface sites

We present an analytic model applied to quasi-elastic scattering from an adsorbed surface species undergoing jump diffusion between adsorption sites described by a Bravais lattice combined with a basis of multiple points. The model allows for hops between adsorption sites which are both symmetrically and energetically inequivalent. We give results for 1-D hopping, which are applicable to a species jumping between the top and bridge sites along the [11?0] direction on an fcc-(110) surface or for jumps along a step edge. In 2-D, results for hopping between fcc and hcp hollow sites and between the bridge sites of an fcc-(111) surface are presented. These examples give characteristic signatures which will allow these forms of motion to be recognized in experimental data and will enable the underlying physical parameters to be extracted by comparison with the analytical forms derived here.     

Calorimetric investigations of the influence of waste aluminosilicate on the hydration of different cements

The aim of this work is to compare the influence of addition of waste aluminosilicate catalyst on the initial periods of hydration of different cements, i.e. calcium aluminate cements of different composition and Portland cement, basing on the calorimetric studies. Cement pastes containing up to 25 mass% of additive were studied, where the water/(cement+additive) ratio was 0.5. An attempt was undertaken to explain the mechanism of action of introduced aluminosilicate in the system of hydrating cement, particularly in the case of calcium aluminate cement pastes. It was found that the presence of fine-grained additive caused in all studied cases the increase of the amount of released heat in the first period after the addition of water. In the case of aluminate cements with aluminosilicate addition, a significant reduction of induction time and faster precipitation of hydration products were observed compared to the reference sample (without additive). In the experimental conditions, the additive caused the acceleration of aluminate cements hydration, and the mechanism of its action is probably complex and can encompass: nucleative action of small grains and formation of new chemical compounds.     

Mid‐IR Spectroscopy and Structural Features of Protonated Carbonic Acid in the Gas Phase

An anti trihydroxycarbenium ion is revealed to be the gas‐phase structure of protonated carbonic acid by IR multiple‐photon dissociation spectroscopy (see picture for calculated structure and comparison of experimental and computed spectra). Deprotonation yields anti‐H₂CO₃ with a nominal gas‐phase basicity of 724 kJ mol^?1.