Formation of (bn-1 + H2O) ions by collisional activation of MALDI-formed peptide [M + H]+ ions in a QqTOF mass spectrometer.

Collisional activation of [M + H](+) parent ions from peptides of n amino acid residues may yield a rearrangement that involves loss of the C-terminal amino acid residue to produce (b(n-1) + H(2)O) daughters. We have studied this reaction by a retrospective examination of the m/z spectra of two collections of data. The first set comprised 398 peptides from coat protein digests of a number of plant viruses by various enzymes, where conditions in the tryptic digests were chosen so as to produce many missed cleavages.

Environmental chemistry and toxicology of polychlorinated n-alkanes.

Polychlorinated-n-alkanes (PCAs) or chlorinated paraffins consist of C10 to C30 n-alkanes with chlorine content from 30% to 70% by mass. PCAs are used as high-temperature lubricants, plasticizers, flame retardants, and additives in adhesives, paints, rubber, and sealants. This review presents the existing data on the environmental chemistry and toxicology of PCAs and a preliminary exposure and risk assessment.

Characterization of three major toxaphene congeners in arctic ringed seal by electron ionization and electron capture negative ion mass spectrometry.

Three environmentally significant chlorinated bornane (CHB) congeners were extracted from Arviat ringed seal blubber and identified by using gas chromatography/mass spectrometry (HRGC/HRECNIMS (CH4), low resolution EIMS, and linked field scanning). They are referred to as TS2 (Parlar#39, B8-531) [2-exo,3-endo,5-exo,6,6,8b,9c,10c (or 10a)-octachlorobornane], TS3 (Parlar#40, B8-1414) [2-endo,3-exo,5-endo,6-exo,8c,9b,10a,10c (or 10b)-octachlorobornane] and TS4 (Parlar#42, Toxicant A, B8-806/809) [2-exo,3-endo,6,6,8b,8c,9c,10c (or 10a)-octachlorobornane/2-exo,3-endo,6,6,8b,9b,9c,10a (or 10b)-octachlorobornane]. This is the first time Toxicant A, known to be the most toxic CHB congener in technical toxaphene, has been found in any significant concentration in a marine mammal.

Preparation and properties of pure, full-length IclR protein of Escherichia coli. Use of time-of-flight mass spectrometry to investigate the problems encountered.

IclR protein, the repressor of the aceBAK operon of Escherichia coli, has been examined by time-of-flight mass spectrometry, with ionization by matrix assisted laser desorption or by electrospray. The purified protein was found to have a smaller mass than that predicted from the base sequence of the cloned iclR gene. Additional measurements were made on mixtures of peptides derived from IclR by treatment with trypsin and cyanogen bromide.

Mass spectrometric studies of the toxaphene components 2-exo,3-endo,5-exo,6-endo,8,8,10,10-octachlorobornane (T2) and 2-exo,3-endo,5-exo,6-endo,8,8,9,10,10-nonachlorobornane (T12).

The electron capture negative ion mass spectra of the title compounds show prominent [M-Cl]- ions, and low-abundance ions formed by further elimination of HCl or Cl2. The electron ionization positive ion mass spectra are complex, but structurally informative fragmentations are observed. In particular, fragmentations involving elimination of C2H2Cl2, and not of C2H4, C2H3Cl, C2HCl3 or C2Cl4, indicate that two chlorines are bound to the C2-C3 and C5-C6 units of a norbornane skeleton.