Aromatic formulas in ambient PM samples from Hong Kong determined using FT-ICR ultrahigh-resolution mass spectrometry.

Many aromatic compounds (e.g., polycyclic aromatic hydrocarbons (PAHs)) found in atmospheric aerosols are toxic and exist in both unsubstituted and substituted forms.

Generation and Characterization of Gas-Phase Doubly Charged Biradical Peptide Ions (M).

The gas-phase chemistry of peptide radical ions is attracting considerable interest in the fields of biology and mass spectrometry owing to its capability to provide sequence information on peptides and proteins. In this study, we observed that doubly charged peptide ions (M) can be produced from the collision-induced dissociation (CID) of Hg(II)-adducted peptide ions. The chemical nature and, thus, the dissociation pathways of this hydrogen-deficient biradical M species is intriguing.

Membrane funnel-based spray ionization for protein/peptide analysis by Fourier transform ion cyclotron resonance mass spectrometry.

Rationale: Samples analyzed in proteomic studies by nanoelectrospray ionization (nanoESI) are extremely limited in quantity requiring careful sample handling to prevent loss upon transfer and to maintain sample concentration. To alleviate the operational process and reduce the cost of nanoESI, it is essential to develop more robust, simple and sensitive analytical variants of the process. Membrane funnel-based spray was developed for analysis of proteins/peptides in this study.

Development of miniaturized sorbent membrane funnel-based spray platform for biological analysis.

In this work, a miniaturized solid-phase extraction (SPE) platform, called sorbent membrane funnel, which permits in situ cleanup prior to membrane funnel-based spray analysis was developed. The fabrication of funnel and the mounting of SPE sorbent were simple and straightforward by a homemade punching system. Using different sorbents, the SPE sorbent funnel has been successfully applied in spray analysis of drug molecules spiked in human plasma, trypsin digested solution of bovine serum albumin in the presence of high concentration of chaotropic reagents, and phosphopeptides in the tryptic digested solution of casein.

Reaction pathways of Sc+ (3D, 1D) and Fe+ (6D, 4F) with acetone in the gas phase: metal ion oxidation and acetone deethanization.

The reactions of Sc(+) ((3)D, (1)D) and Fe(+) ((6)D, (4)F) with acetone have been investigated in both high- and low-spin states using density functional theory. Our calculations have indicated that oxidation of Sc(+) by acetone can take place by (1) metal-mediated H migration, (2) direct methyl-H shift and/or (3) C=O insertion. The most energetically favorable pathway is metal-mediated H migration followed by intramolecular ScO(+) rotation and dissociation.

Reaction pathways of Rh+ (3F and 1D) with CH3OCH3 in the gas phase.

Rationale: The mass spectrometric studies of transition metal ion-ether reactions are informative in elucidating the principles of metal ion mediated demethanation and dehydrogenation. In order to obtain a deeper understanding of the role of metal ions, it is essential to explore the detailed reaction mechanisms of these reactions, here studied using Rh(+) and dimethyl ether as a model system.

Methods: The gas-phase demethanation and dehydrogenation pathways of dimethyl ether mediated by Rh(+) ((3)F and (1)D) were investigated by density functional theory in conjunction with the Stuttgart RSC + 6-311 + G(d) basis set.

Transition metal ions: charge carriers that mediate the electron capture dissociation pathways of peptides.

Electron capture dissociation (ECD) of model peptides adducted with first row divalent transition metal ions, including Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), and Zn(2+), were investigated. Model peptides with general sequence of ZGGGXGGGZ were used as probes to unveil the ECD mechanism of metalated peptides, where X is either V or W; and Z is either R or N. Peptides metalated with different divalent transition metal ions were found to generate different ECD tandem mass spectra.

Determination of closantel and rafoxanide in animal tissues by online anionic mixed-mode solid-phase extraction followed by isotope dilution liquid chromatography tandem mass spectrometry.

A rapid and high-throughput isotope dilution LC-MS/MS method with online sample pre-concentration and clean-up using anionic mixed-mode SPE was described for the determination of closantel and rafoxanide in edible bovine and ovine tissues. Tissue samples were extracted with acetonitrile and acetone mixture (60:40, v/v). Sample pre-concentration, clean-up and analysis were completed simultaneously with the online MAX SPE LC-MS/MS system.

Formation of peptide radical cations (m+·) in electron capture dissociation of peptides adducted with group IIB metal ions.

Peptides adducted with different divalent Group IIB metal ions (Zn(2+), Cd(2+), and Hg(2+)) were found to give very different ECD mass spectra. ECD of Zn(2+) adducted peptides gave series of c-/z-type fragment ions with and without metal ions. ECD of Cd(2+) and Hg(2+) adducted model peptides gave mostly a-type fragment ions with M(+•) and fragment ions corresponding to losses of neutral side chain from M(+•).

Quantitative analysis of closantel and rafoxanide in bovine and ovine muscles by high-performance liquid chromatography with fluorescence detection.

An HPLC method with a fluorescence detector (HPLC-FLD) was described for the quantitative determination of closantel and rafoxanide in bovine and ovine muscles. A structural analog closely related to rafoxanide, viz., N-[4-(4-chlorophenoxy)phenyl]-2-hydroxy-3,5-diiodobenzamide, was synthesized as an internal standard.

Screening of closantel and rafoxanide in animal muscles by HPLC with fluorescence detection and confirmation using MS.

A sensitive and selective LC-FLD method was described for determination of closantel and rafoxanide in bovine and ovine muscles. Bovine and ovine muscles were extracted with ACN and acetone mixture (80:20, v/v). After cleanup with Oasis MAX SPE cartridges, the sample was analyzed by LC-FLD using the control point approach.

Highly efficient energy transfer in subphthalocyanine-BODIPY conjugates.

Two novel subphthalocyanines substituted axially with a BODIPY or distyryl BODIPY moiety have been synthesized. Both systems exhibit a highly efficient photoinduced energy transfer process, either from the excited BODIPY to the subphthalocyanine core (for the former) or from the excited subphthalocyanine to the distyryl BODIPY unit (for the latter).