Electrochemical Recovery of Silver from Lead Alloys in Chloride Melts

Electrochemical separation of lead-silver alloys into the constituents by thin-layer electrolysis in molten electrolytes, with bismuth as metal separator, is studied. It is proposed to determine the extent of component recovery by potentiometry.     

Characterization of a new qQq-FTICR mass spectrometer for post-translational modification analysis and top-down tandem mass spectrometry of whole proteins

The use of a new electrospray qQq Fourier transform ion cyclotron mass spectrometer (qQq-FTICR MS) instrument for biologic applications is described. This qQq-FTICR mass spectrometer was designed for the study of post-translationally modified proteins and for top-down analysis of biologically relevant protein samples. The utility of the instrument for the analysis of phosphorylation, a common and important post-translational modification, was investigated. Phosphorylation was chosen as an example because it is ubiquitous and challenging to analyze. In addition, the use of the instrument for top-down sequencing of proteins was explored since this instrument offers particular advantages to this approach. Top-down sequencing was performed on different proteins, including commercially available proteins and biologically derived samples such as the human E2 ubiquitin conjugating enzyme, UbCH10. A good sequence tag was obtained for the human UbCH10, allowing the unambiguous identification of the protein. The instrument was built with a commercially produced front end: a focusing rf-only quadrupole (Q0), followed by a resolving quadrupole (Q1), and a LINAC quadrupole collision cell (Q2), in combination with an FTICR mass analyzer. It has utility in the analysis of samples found in substoichiometric concentrations, as ions can be isolated in the mass resolving Q1 and accumulated in Q2 before analysis in the ICR cell. The speed and efficacy of the Q2 cooling and fragmentation was demonstrated on an LCMS-compatible time scale, and detection limits for phosphopeptides in the 10 amol/muL range (pM) were demonstrated. The instrument was designed to make several fragmentation methods available, including nozzle-skimmer fragmentation, Q2 collisionally activated dissociation (Q2 CAD), multipole storage assisted dissociation (MSAD), electron capture dissociation (ECD), infrared multiphoton induced dissociation (IRMPD), and sustained off resonance irradiation (SORI) CAD, thus allowing a variety of MS(n) experiments. A particularly useful aspect of the system was the use of Q1 to isolate ions from complex mixtures with narrow windows of isolation less than 1 m/z. These features enable top-down protein analysis experiments as well structural characterization of minor components of complex mixtures.     

Separation and determination of homogenous fatty alcohol ethoxylates by liquid chromatography with mulitstage mass spectrometry

Alcohol ethoxylates (AEs) are a significant component of a stream of surfactants directed to the aquatic environment. The aim of this work was the investigation of the dependence of the analytical signals of homogeneous AE homologues on liquid chromatography with tandem mass spectrometry conditions, as well as the separation of AEs from the water matrix and, on this basis, the development of an analytical procedure suitable for the determination of AEs in environmental samples. Homogeneous homologues containing dodecyl moiety and 2–9 oxyethylene subunits were investigated. The analytical signals of the investigated homologues were optimized in terms of concentration of ammonium acetate in the mobile phase (optimum 5 mM) and a column temperature (optimum 35°C) of the liquid chromatography with tandem mass spectrometry system. A separation of AEs from the water matrix by liquid–liquid extraction (ethyl acetate, chloroform) or solid‐phase extraction (C₁₈, styrene divinylbenzene, H‐RX) was investigated. In a model investigation, the best recoveries (>90%) were obtained with a styrene divinylbenzene cartridge eluted with a 1:1 mixture of chloroform and methanol. However, much worse recoveries were obtained from the river water sample. Better results were obtained for liquid–liquid extraction with ethyl acetate. Recoveries of 62–80% were obtained for homologues having 4–9 oxyethylene subunits, at the lowest spike.     

Intense picosecond X-Ray pulses from laser plasmas by use of nanostructured "Velvet" targets

We describe the optical, radiative, and laser-plasma physics of a new type of nanostructured surface especially promising as a very high absorption target for high-peak-power subpicosecond laser-matter interaction. This oriented-nanowire material, irradiated by 1 ps pulses at intensities up to 10(17) W cm(-2), produces picosecond soft x-ray pulses 50x more efficiently than do solid targets. We compare this to "smoke" or metallic clusters, and solid nanogroove-grating surfaces; the "metal-velvet" targets combine the high yield of smoke targets with the brief emission of grating surfaces.     

Theoretical study of thermoelectronic laser energy conversion: II. Characteristics of optical discharge

The dependences of the parameters of a continuous optical discharge in an interelectrode space of a thermoelectronic laser energy converter on the gas pressure, electron emission current, and discharge current are studied. The current-voltage characteristics of the discharge are calculated.     

Local atomic and electronic structure of quantum dots based on Mn- and Co-doped ZnS

Solid solutions of zinc sulfide with manganese and cobalt are synthesized. Based on the analysis of X-ray diffraction profiles the conclusion is drawn about the formation of a hexagonal wurtzite type structure in the synthesized quantum dot (QD) solutions. The average crystallite sizes are 8 nm and 22 nm for the samples with manganese and cobalt respectively. Results of IR and optical spectroscopy are consistent with the powder X-ray diffraction and X-ray fluorescence data. The question about particle aggregation in isopropanol and DMF solutions is considered. The QD structures based on ZnS particles doped with Mn and Co transition metal atoms are modeled. The possibility to apply X-ray absorption near edge structure (XANES) spectroscopy to verify the atomic structure parameters around the positions of doping transition metal atoms in QDs of the ZnS family is shown. Partial densities of ZnS:Mn and ZnS:Co electronic states are calculated.     

Characteristics of xenon flash lamps in short-flash operation

Journal of Applied Spectroscopy -     

Electron capture dissociation distinguishes a single D-amino acid in a protein and probes the tertiary structure

First results are reported on the application of ECD in analysis of 2+ and 3+ ions of stereoisomers of Trp-cage (NLYIQWLKDGGPSSGRPPPS), the smallest and fastest-folding protein, which exhibits a tightly folded tertiary structure in solution. The chiral recognition based on the ratios of the abundances of z(18) and z(19) fragments in ECD of 2+ ions was excellent even for a single amino acid (Tyr) D-substitution (R(chiral) = 8.6). The chiral effect decreased with an increase of temperature at the electrospray ion source, as well as at a higher degree of ionization, 3+ ions (R(chiral) = 1.5). A general approach is suggested for charge localization in n+ ions by analysis of ECD mass spectra of (n + 1)+ ions. Application of this approach to 3+ Trp-cage ions revealed the protonation probability order in 2+ ions: Arg(16) > Gln(5) > approximately N-terminus. The ECD results for native form of the 2+ ions favor the preservation of the solution-phase tertiary structure, and chiral recognition through the interaction between the charges and the neutral bond network. Conversely, ECD of 3+ ions supports the dominance of ionic hydrogen bonding which determines a different gas-phase structure than found in solution. Vibrational activation of 2+ ions indicated greater stability of the native form, but the fragmentation patterns did not provide stereoisomer differentiation, thus underlying the special position of ECD among other MS/MS fragmentation techniques. Further ECD studies should yield more structural information as well as quantitative single-amino acid D/L content measurements in proteins.     

Electron capture dissociation of b (2+) peptide fragments reveals the presence of the acylium ion structure

Electron capture dissociation (ECD) of peptides and their fragments has now been extended to b ( n) ( 2+) ions, where it also produced far more structural information than collisional activation. Interestingly, b ( n) ( 2+) ions revealed abundant loss of CO from radical monocations and the presence of c ((n - 1)) ( +.) fragments. The CO loss from peptide radical cations is unusual and was attributed to neutralization of the -C identical with O(+) group in the acylium ion structure, supported by the observation of c ( (n - 1)) ( +.) ions that can only be formed from an open-chain ion. These characteristic features were most prominent for b ( 12)( 2+) ions of renin substrate and least prominent for b ( n) ( 2+) ions of substance P (n = 9,10). Totally, out of seven b ( n) ( 2+) ions studied, CO loss above 3% level was present in all spectra as well as c ( (n - 1))( +.) fragments of three species, suggesting that the acylium ion structure plays a significant role for at least some b ( 2+) ions. This is an unexpected result in view of the literature data for small, singly charged b ions, for which the protonated oxazolone structure is favoured in ab initio calculations. Apparently, more studies are required before extrapolating the small molecule results to large species. The CO loss in ECD can be used for distinguishing between b and y ions in the MS/MS spectrum of larger molecules.