A high performance low magnetic field internal electrospray ionization-fourier transform ion cyclotron resonance mass spectrometer

A new in-magnetic field electrospray ionization (ESI) and Fourier transform ion cyclotron resonance mass spectrometer has been constructed and evaluated. This system is characterized by the use of multiple concentric cryopanels to achieve ultrahigh vacuum in the ion cyclotron resonance cell region, a probe-mounted internal ESI source, and a novel in-field shutter. Initial experiments demonstrate high resolution mass measurement capability at a field strength of 1 T. Mass resolution of 700,000 has been obtained for the 3+ charge state of Met-Lys-bradykinin (at m/z 440) generated by electrospray ionization. When electron impact ionization was employed, resolution in excess of 9,200,000 was achieved for nitrogen molecular ions (N ₂ ⁺ ). Isotopic resolution for molecular ions of bovine ubiquitin (MW=8565 µ) also was achieved by using small ion populations.     

Global existence for degenerate parabolic equations with a non-local forcing

We establish local existence and comparison for a model problem which incorporates the effects of non-linear diffusion, convection and reaction. The reaction term to be considered contains a non-local dependence, and we show that local solutions can be obtained via monotone limits of solutions to appropriately regularized problems. Utilizing this construction, it is further shown that, under conditions of either ‘weak reaction’ or ‘sufficiently small’ initial mass, solutions exist for all time. Finally, we provide an alternative analysis of global existence and investigate blow up in finite time for the case of power law diffusion and convection. These results show the extent to which the assumption of weak reaction may be relaxed and still obtain global existence. © 1997 by B. G. Teubner Stuttgart–John Wiley & Sons Ltd.     

Improved processes of molybdenum-99 production

Two improved processes of⁹⁹Mo production have been developed on laboratory scale. The first one allows to purify Mo of natural isotopic composition from tungsten impurities from 64 to <10 ppm by using preferential adsorption of tungsten on hydrated tin(IV) oxide (SnO₂ nH₂O) before irradiation in a nuclear reactor. The second process deals with the separation of pure fission product⁹⁹Mo from²³⁵U irradiated in a reactor. Two versions of separation process for production of fission⁹⁹Mo have been developed. Both versions start with the dissolution of²³⁵U oxide target in nitric acid and are based on sequential use of alumina and anion exchange resin AG® 1-X8 columns. The yield of⁹⁹Mo in both versions is 80–89%.     

Improved isotopic abundance measurements for high resolution fourier transform ion cyclotron resonance mass spectra via time-domain data extraction

The simultaneous high resolution and accurate mass measurements possible with Fourier transform ion cyclotron resonance mass spectrometry coupled with the gentle ionization of electrospray hold attractions for protein, peptide, and oligonucleotide characterization, including multistage-mass spectrometry measurements for assignment of fragment masses and greater confidence in structural measurements. The detection of cyclotron motion over extended periods of time (in some cases for several minutes) allows higher resolution and mass accuracy. Generally, signal duration has been considered to be limited primarily by background pressure, with ion-neutral collisions leading to the reduction and dephasing of cyclotron motion, causing signal loss. However, recent theoretical work has shown that the ion cloud stability that is a prerequisite for high performance measurements is highly dependent on the electric field generated by the ion cloud, thus giving rise to a minimum number of charges or ions required for extended time-domain signals. The effects of ion population on ion cloud stability and signal duration, and the subsequent effects on resolution and measured isotopic abundances are reported. Individual time-domain signals for bovine insulin isotopic peaks were extracted to allow a comparison of the damping rates for each of these ion clouds and the measured time-domain amplitude maxima are shown to provide a better match with the theoretically predicted isotopic abundances for insulin. These results show that different damping rates of ions of very similar mass, but different ion cloud population sizes, can have dramatic effects on the observed isotopic patterns. Additionally, more accurate, high resolution spectra can be produced by correcting for the effects of the different damping rates that are observed for different ion population sizes.     

Ethyl and isopropyl 4‐ferrocenylbenzoate

The title compounds, [Fe(C₅H₅)(C₁₄H₁₃O₂)] and [Fe(C₅H₅)(C₁₅H₁₅O₂)], respectively, contain the ferrocenyl η⁵(C₅H₄) and phenyl­ene –C₆H₄– rings in a nearly coplanar arrangement, with interplanar angles of 6.88 (12) and 10.5 (2)°, respectively. Molecules of the ethyl ester form dimers through η⁵(C₅H₅)C—H⋯O=C hydrogen bonds, with graph set R(20), and, together with Csp³—H⋯π(C₅H₅) interactions, generate a one‐dimensional column (irregular ladder). Molecules of the iso­propyl ester aggregate through η⁵(C₅H₅)C—H⋯π(C₆H₄) interactions.     

[Ethylene-1,2-bis(diphenylphosphine)-P,P′]dinitratoplatinum(II) and cis-bis[(diphenylphosphinomethyl)diphenylphosphine oxide-O,P]platinum(II) dinitrate dihydrate

In [Pt(dppe)(NO₃)₂], where dppe is ethyl­ene-1,2-bis­(di­phenyl­phosphine) (C₂₆H₂₄P₂), the Pt atom is coordinated by the two P atoms and by two O atoms of the two nitrate ions. The mol­ecule has a distorted square-planar geometry, with one of the nitrate groups directed on each side of the plane. The cation in cis-[Pt(dppmO-O,P)₂](NO₃)₂·2H₂O, where dppmO is bis­(di­phenyl­phosphino­methyl)­di­phenyl­phosphine oxide (C₂₅H₂₂OP₂), comprises two five-membered chelate rings, each dppmO ligand being coordinated to platinum through one P atom and the O atom. The larger P—Pt—P angle of 102.25 (4)° is due to steric interactions between the two phenyl groups on each P atom.     

A high transmission hemispherical energy analyzer for ion spectrometry

A hemispherical energy analyzer was constructed by using a novel approach to control the fringing electrostatic field. It provides several properties useful in ion spectrometers: namely, rather simple fabrication and compact size, high transmission efficiency at moderate resolution, and the capability to adjust resolution by changing the intersphere potentials. A computer program was developed to evaluate ion trajectories through the hemispherical analyzer. Data obtained from the trajectories were used to predict the characteristics of the analyzer. Experiments performed to determine the kinetic energy dependence of the absolute transmission and the resolution functions are in accord with theoretical calculations.