Chemistry

Kinetic studies on Cr(III)-binding behavior of collagen fiber functionalized by amino- and carboxyl-terminated hyperbranched polyamide
Two kinds of insoluble collagen fiber (CF) were prepared by grafting amino- and carboxyl-terminated hyperbranched polyamide into collagen fiber using the cross-linking and terminal groups modification methods: (1) grafting amino terminated hyperbranched polyamide to CF by glutaraldehyde, and condensation of the resulting carboxyl with glyoxylic acid. Their structures were characterized by FT-IR...


Infrared spectroscopy of CHCl2+ molecular dications
Different isomers of the CHCl2+ dications were studied using infrared predissociation spectroscopy with helium and neon tagging in a low-temperature trapping experiment. It is shown that H–C–Cl2+ isomers form the dominant portion of the trapped dications that were detected by IRPD spectroscopy. Other possible isomers, such as H–Cl–C2+, are depleted by a proton transfer reaction with the...
An historical approach to the effects of elastic collisions in radiofrequency devices and recent developments
After an historical review of several approaches to predict the spatial and energy distributions of ions confined in a Paul trap and subjected to collisions with neutrals, the paper focuses on the temporal invariance method. Two improvements of this method are studied. The first one is used to probe the shape of the equilibrium distribution around a given value of the dynamic state of the ion. ...


Fifty years of desorption ionization of nonvolatile compounds
During the past 50 years, mass spectrometry has advanced from a small molecule method to one critical to understanding biological processes. The ability to analyze compounds as large as protein complexes did not happen with any single invention, but occurred in steps. Thus, electrospray ionization can be traced to Zeleny (1917) and Dole (1968), but also to Colby and Evans (1973) with the demons...
Selective cleavage upon ETD of peptides containing disulfide or nitrogen–nitrogen bonds
Site-selective bond cleavage is an interesting but infrequently observed process in gas phase ions. We report the comparison of highly efficient and specific NN and SS cleavages in peptides modified at their N- or C-terminal with tags that contain a disulfide or a hydrazine-type bond. Preferential NN or SS cleavage occurs upon electron transfer dissociation (ETD) of the doubly-protonated modifi...


Direct analysis of complex mixtures by mass spectrometry
Mixture analysis can provide information on individual components if the sample is first subjected to chromatographic separation. Two critical capabilities, soft ionization and the ability to mass-select and then dissociate ions of a particular m/z, coalesced in 1975, allowing direct analysis of complex mixtures by mass spectrometry. Chemical ionization was used as the soft ionization method an...
Gas-phase conformations of small polyprolines and their fragment ions by IRMPD spectroscopy
Infrared multiple-photon dissociation (IRMPD) spectroscopy has been used to examine the gas-phase conformations of a series of short protonated polyproline ions (Pro3–Pro6), their CID/IRMPD fragmentation pathways, and the associated fragment identities. Consistent with previous findings, and in combination with density functional theory (DFT) and MM/MD methods, a series of conformers for the ...

Proton affinity of dipeptides containing alanine and diaminobutyric acid
Thermochemical properties, including the proton affinity, the gas-phase basicity, and the protonation entropy, were determined for the acetylated unnatural amino acid, 2,3-diaminobutyric acid, AcDab and two isomeric dipeptides containing alanine (Ala) and Dab AcAlaDab and AcDabAla. The experiments were carried out using a triple quadrupole mass spectrometer. The extended Cooks kinetic method wa...
Years of Fourier transform ion cyclotron resonance mass spectrometry
This article reviews the development of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) in several respects: (a) a strong static magnetic field serves to convert ion mass-to-charge ratio into cyclotron frequency. Because frequency is the most accurately measurable property, ICR MS inherently offers higher mass resolution and mass accuracy than any other mass analyzer. (b...

Survival yield comparison between ESI and SAII: Mechanistic implications
The survival yield (SY) method is commonly used in mass spectrometry to determine the energy deposited into ions by an ionization process. SY is the fraction of intact molecular ions that remain after fragmentation. In this study, we compared the fragmentation of three different thermometer ions as a function of various inlet voltages on an Orbitrap Exactive mass spectrometer using solvent assi...
Experimental evaluation of micro-ion trap mass spectrometer geometries
We describe a new fabrication method, simulations, and experimental results for micromachined cylindrical ion trap (μ-CIT) arrays for use in miniaturized mass spectrometers. The micromachined μ-CIT arrays were fabricated in a silicon-on-insulator (SOI) substrate, and a variety of trap geometries were incorporated into a single μ-CIT array chip to allow fast iterative measurements of the diff...

Characterization of geometry deviation effects on ion trap mass analysis: A comparison study
A high precision electric field simulation method is employed to investigate micron-size geometry deviation effects on the electric field distributions as well as on mass resolutions in linear ion traps. Translational and angular displacements within three linear ion traps with different electrode geometries, hyperbolic, circular and rectangular electrodes, were studied. It is found that the li...
SIMS methodology for probing the fate and dispersion of catalytically active molecules
Secondary ion mass spectrometry (SIMS) with 520keV A u 400 4 + projectiles operating in event-by-event bombardment/detection mode was applied to investigate pyrolized mixtures of catalyst (vitamin B12) and carbon supports (carbon black). The specimens are alternative cathode materials to platinum for fuel cells. The goal was to understand the effect of temperature on the chemical en...
Comparison of VUV radiation induced fragmentation of thymidine and uridine nucleosides – The effect of methyl and hydroxyl groups
Fragmentation of thymidine and uridine nucleosides followed by vacuum ultraviolet radiation was compared using time-of-flight (TOF) mass spectroscopy. TOF spectra of 5-methyluridine were also measured in order to investigate the effect of the 5-methyl group of the base and the 2′-hydroxyl group of the sugar moiety on the fragmentation. It was observed that uridine fragments more extensively t...
Sub-eV ion deposition utilizing soft-landing ion mobility for controlled ion, ion cluster, and charged nanoparticle deposition
Sub-eV ion deposition via soft-landing ion mobility has been utilized for a variety of applications. It has allowed for the deposition of a dielectric material onto graphene without introducing defects into the lattice structure. This deposition technique has also been used for surface enhanced Raman studies. Deposited silver has also been used as an alternative MALDI matrix for low mass compou...