Study on the Gas-Phase Reactivity of Charged Pyridynes.

The reactivities of three isomeric, charged -pyridynes, the 1,2-, 2,3-, and 3,4-didehydropyridinium cations, were examined in the gas phase using Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry. The structures of selected product ions were probed using collision-activated dissociation (CAD) experiments in a linear quadrupole ion trap (LQIT) mass spectrometer. Mechanisms based on quantum chemical calculations are proposed for the formation of all major products.

Identification of Protonated Sulfone and Aromatic Carboxylic Acid Functionalities in Organic Molecules by Using Ion-Molecule Reactions Followed by Collisionally Activated Dissociation in a Linear Quadrupole Ion Trap Mass Spectrometer.

Gas-phase reactivity of protonated model compounds with different functional groups toward trimethoxymethylsilane (TMMS) was studied to explore the utility of this reagent in mass spectrometric identification of specific functionalities for potentially rapid characterization of drug metabolites. Only protonated analytes with a carboxylic acid, a sulfone, or a sulfonamide functionality formed diagnostic adducts that had lost a methanol molecule upon reactions with TMMS. Collisionally activated dissociation (CAD) of these methanol-eliminated adduct ions (MS experiments) produced characteristic fragment ions of m/z 75, 105, and 123 for sulfones, while an additional methanol elimination was observed for carboxylic acids and sulfonamides.

Laser-Induced Acoustic Desorption/Electron Ionization of Amino Acids and Small Peptides.

Laser-induced acoustic desorption (LIAD) allows for desorption of neutral nonvolatile compounds independent of their volatility or thermal stability. Many different ionization methods have been coupled with LIAD. Hence, this setup provides a better control over the types of ions formed than other mass spectrometry evaporation/ionization methods commonly used to characterize biomolecules, such as ESI or MALDI.

Gas-phase Reactivity of meta-Benzyne Analogs Toward Small Oligonucleotides of Differing Lengths.

The gas-phase reactivity of two aromatic carbon-centered σ,σ-biradicals (meta-benzyne analogs) and a related monoradical towards small oligonucleotides of differing lengths was investigated in a Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer coupled with laser-induced acoustic desorption (LIAD). The mono- and biradicals were positively charged to allow for manipulation in the mass spectrometer. The oligonucleotides were evaporated into the gas phase as intact neutral molecules by using LIAD.

Identification of the Phenol Functionality in Deprotonated Monomeric and Dimeric Lignin Degradation Products via Tandem Mass Spectrometry Based on Ion-Molecule Reactions with Diethylmethoxyborane.

Conversion of lignin into smaller molecules provides a promising alternate and sustainable source for the valuable chemicals currently derived from crude oil. Better understanding of the chemical composition of the resulting product mixtures is essential for the optimization of such conversion processes. However, these mixtures are complex and contain isomeric molecules with a wide variety of functionalities, which makes their characterization challenging.

Gas-phase ion-molecule reactions for the identification of the sulfone functionality in protonated analytes in a linear quadrupole ion trap mass spectrometer.

Rationale: The oxidation of sulfur atoms is an important biotransformation pathway for many sulfur-containing drugs. In order to rapidly identify the sulfone functionality in drug metabolites, a tandem mass spectrometric method based on ion-molecule reactions was developed.

Methods: A phosphorus-containing reagent, trimethyl phosphite (TMP), was allowed to react with protonated analytes with various functionalities in a linear quadrupole ion trap mass spectrometer.

Identification of N-Oxide and Sulfoxide Functionalities in Protonated Drug Metabolites by Using Ion-Molecule Reactions Followed by Collisionally Activated Dissociation in a Linear Quadrupole Ion Trap Mass Spectrometer.

The in vivo oxidation of sulfur and nitrogen atoms in many drugs into sulfoxide and N-oxide functionalities is a common biotransformation process. Unfortunately, the unambiguous identification of these metabolites can be challenging. In the present study, ion-molecule reactions of tris(dimethylamino)borane followed by collisionally activated dissociation (CAD) in an ion trap mass spectrometer are demonstrated to allow the identification of N-oxide and sulfoxide functionalities in protonated polyfunctional drug metabolites.

A Mimivirus Enzyme that Participates in Viral Entry.

Mimivirus was initially identified as a bacterium because its dense, 125-nm-long fibers stained Gram-positively. These fibers probably play a role during the infection of some host cells. The normal hosts of Mimivirus are unknown, but in the laboratory Mimivirus is usually propagated in amoeba.

Citrate-stabilized gold nanorods.

Stable aqueous dispersions of citrate-stabilized gold nanorods (cit-GNRs) have been prepared in scalable fashion by surfactant exchange from cetyltrimethylammonium bromide (CTAB)-stabilized GNRs, using polystyrenesulfonate (PSS) as a detergent. The surfactant exchange process was monitored by infrared spectroscopy, surface-enhanced Raman scattering (SERS), and X-ray photoelectron spectroscopy (XPS). The latter established the quantitative displacement of CTAB (by PSS) and of PSS (by citrate).