A high power,widely tunable infrared source based on stimulated electronic Raman scattering in caesium vapour

Dye lasers pumped by the second harmonic of a ruby laser have been used to produce tunable stimulated electronic Raman scattering in caesium vapour. Using three different Raman transitions, the infrared tuning ranges were 2.5–4.75 μm, 5.67–8.65 μm and 11.7–15 μm with powers of up to 25kW, 7 kW and 2 kW respectively.     

Electron-impact and thermal fragmentation patterns of some cyclic fluoroethers

The mass spectra of cyclic fluoroethers of the general formula (n = 1 to 4) are reported and discussed. Although these spectra show many similar features, those for which n = 3 and 4 contain intense peaks at m/e 63 which are only of relatively low intensity in the spectra of the other two. A similarity between the electron-impact and thermal fragmentation patterns of these compounds is noted.     

Ionization and dissociation of some perfluoroalkylene-linked silanes and cyclic siloxanes under electron-impact

The mass spectra of two silanes and two cyclic siloxanes of the general formulae HSi(CH₃)₂-C₆H₄? (CF₂)_n? C₆H₄(CH₃)₂SiH and (n = 2 and 3) are reported and discussed. Although some major differences are apparent between the spectra of the two silanes, the fragmentation patterns of the cyclic siloxanes are largely identical.     

Fragmentation studies of noncovalent sugar-sugar complexes by infrared atmospheric pressure MALDI

An investigation of sugar-sugar noncovalent complex fragmentation was conducted using a 2.94 microm Er:YAG laser for infrared (IR) atmospheric pressure matrix-assisted laser desorption/ionization (AP MALDI) on an ion trap mass spectrometer (ITMS). This approach allowed the analysis of weak noncovalent complexes between a variety of biologically relevant oligosaccharides. The strength of interaction varied with different sugar structures, potentially due to varying strength of hydrogen bonding networks. In some cases, fragmentation of intramolecular sugar bonds preceded breakdown of the noncovalent complex. This result appeared primarily when complexes contained sugars with at least one sialic acid. Globotrios dimers also showed intramolecular fragmentation in preference to breakdown of the noncovalent dimer. This technique will allow further study of sugar-sugar interactions known to play a role in cellular interactions.     

Authentication of paintings by Ralph A. Blakelock through neutron activation autoradiography

Following his mental collapse at the end of the nineteenth century the paintings of Ralph A. Blakelock suddenly began to bring exceptionally high prices. Not surprisingly, therefore, many forgeries attributed to him were produced in the early twentieth century. In fact, some experts consider him to have been the most widely forged American painter. At Brookhaven National Laboratory a group of paintings attributed to him have been studied by thermal neutron activation autoradiography combined with solid state high resolution gamma-ray spectroscopy. Most of the paintings studied were of unquestioned authenticity coming from the collection of the Metropolitan Museum of Art, the National Collection of Fine Art of the Smithsonian Institution, the Sheldon Memorial Art Gallery of the University of Nebraska, and two private collectors with well established histories of acquisition. These included paintings produced by Blakelock both before and after his breakdown. In general a number of characteristic consistencies in the types of pigments and media used and how they were employed in these paintings were revealed by the activation study. Of course, major differences exist between his early and later work. However, a lack of these characteristics and hidden overpainted details which are not revealed in conventional X-ray radiographs have provided evidence that two of the paintings attributed to Ralph Blakelock are the work of other artists. Some paintings of Blakelock's contemporaries George Inness and Albert Ryder have also been investigated. Research supported by the U.S. Atomic Energy Commission.     

Fragmentation of cationized phosphotyrosine containing peptides by atmospheric pressure MALDI/Ion trap mass spectrometry

An investigation of phosphate loss from sodium-cationized phosphotyrosine containing peptide ions was conducted using liquid infrared (2.94 microm) atmospheric pressure matrix-assisted laser desorption/ionization (AP MALDI) coupled to an ion trap mass spectrometer (ITMS). Previous experiments in our laboratory explored the fragmentation patterns of protonated phosphotyrosine containing peptides, which experience a loss of 98 Da under CID conditions in the ITMS. This loss of 98 Da is unexpected for phosphotyrosine, given the structure of its side chain. Phosphate loss from phosphotyrosine residues seems to be dependent on the presence of arginine or lysine residues in the peptide sequence. In the absence of a basic residue, the protonated phosphotyrosine peptides do not undergo losses of HPO(3) (Delta 80 Da) nor HPO(3) + H(2)O (Delta 98 Da) in their CID spectra. However, sodium cationized phosphotyrosine containing peptides that do not contain arginine or lysine residues within their sequences do undergo losses of HPO(3) (Delta 80 Da) and HPO(3) + H(2)O (Delta 98 Da) in their CID spectra.     

Miniaturized linear time-of-flight mass spectrometer with pulsed extraction

Improved resolution for a miniaturized instrument is demonstrated at high masses using a pulsed extraction, 3(") linear time-of-flight (TOF) mass analyzer. This illustrates the utility of a small and simple mass spectrometer for biological/medical analyses. Current and future applications suggested by this instrument include rapid mass spectral reading of oligonucleotides that differ in one base (single nucleotide polymorphisms), distinction of biomarker signatures from different species of bacterial spores (biological weapons detection) and point-of-care instruments for proteomics-based diagnostics. We have incorporated a two-stage, pulsed-extraction design that places the focal plane of the ions at the detector channel plate surface. The ions are accelerated to a total energy of 12 keV to enable detection of high-mass proteins in a design that incorporates a floatable flight tube set at the voltage of the front channel plate of the detector. The resultant elimination of post-acceleration at the detector is intended to improve mass resolution by reducing the difference in arrival times between ions and their neutral products. Resolutions of one part in 1200 at m/z 4500 and one part in 600 at m/z 12 000 have been achieved. Proteins with molecular masses up to 66 000 Da, mixtures of oligonucleotides, and biological spores have all been successfully measured, results that increase the potential use of this TOF analyzer.     

Molecular weight determination of underivatized oligodeoxyribonucleotides by positive-ion matrix-assisted ultraviolet laser-desorption mass spectrometry

A Wiley-McLaren type time-of-flight mass spectrometer has been used for molecular weight measurements of several unprotected oligodeoxyribonucleotides using matrix-assisted UV laser desorption. Approximately 10 to 100 pmol of sample was required for recording their positive-ion mass spectra with a mass resolution in the range of 150 to 300 (Full width at half maximum) (FWHM). Little fragmentation was observed.     

Fission fragment angular distributions in 16O+181Ta

Time of flight and energy of fission fragments were measured using pulsed beam. Fission fragment mass and energy integrated angular distributions were extracted. Fission fragment anisotropy was explained in the framework of saddle point model.