Gerhard Höhne

Dissociation behavior of ionized valeramide: Part III. An unprecedented temperature effect on the C3/C2 branching ratio and its implications for metastable ion dissociations

Abstract The competing formations of C 2 - and C 3 -fragments in the unimolecular decay of mass-selected valeramide cation-radicals are analyzed in detail. It turns out that the different branching ratios observed in the various experiments are due not only to the internal energy of the ions but also to that of the neutral precursors. The latter is manifested by a pronounced effect of the temperature of the ion source on the C 3 /C 2 branching ratios in the metastable ion spectra of ionized valeramide. Exploratory studies indicate that the effect is not limited to valeramide in that similar temperature phenomena are observed for the metastable molecular ions of hexanoic acid and its amide.Abstract The competing formations of C 2 - and C 3 -fragments in the unimolecular decay of mass-selected valeramide cation-radicals are analyzed in detail. It turns out that the different branching ratios observed in the various experiments are due not only to the internal energy of the ions but also to that of the neutral precursors. The latter is manifested by a pronounced effect of the temperature of the ion source on the C 3 /C 2 branching ratios in the metastable ion spectra of ionized valeramide. Exploratory studies indicate that the effect is not limited to valeramide in that similar temperature phenomena are observed for the metastable molecular ions of hexanoic acid and its amide.

Size-exclusion chromatography performed in capillaries: Studies by liquid chromatography–mass spectrometry

Miniaturization of the chromatographic column led to increased sensitivity and shortened time of analysis. In our work we applied 300 microm I.D. capillaries packed with a novel stationary phase Superdex Peptide for the size-exclusion chromatography, capable of separating molecules within the mass range of 0.1-7 kDa. Here we proved that such capillary columns can operate effectively at high sensitivity. Several peptide mixtures were efficiently chromatographed and analyzed on line with electrospray ionization mass spectrometry as a detection technique. A CNBr peptide map, derived from human globin alpha subunit, was effectively separated using this method. These fragments are difficult to elute from the reversed-phase column at low pH, therefore, such approach can be considered as a complementary to other separation techniques, in particular for analyzing hydrophobic components and complex mixtures.

Determination of nociceptin-orphanin FQ metabolites by capillary LC-MS

Nociceptin-orphanin FQ (OFQ/N) is a newly discovered peptide involved in pain transmission. The method is described to identify metabolic pathway of this neuropeptide in the spinal cord of rats using capillary size-exclusion liquid chromatography coupled to electrospray ionization mass spectrometry. The applied technique is rapid and selective, and allows for simultaneous measurement and quantitation of several fragments in the incubation mixture.

Chinese whip scorpion using 2-ketones in defense secretion (Arachnida: Uropygi)

SummaryNorth American as well as East Asian whip scorpions of the generaMastigoproctus andTypopeltis are known to use acetic acid and caprylic acid as a defense mechanism. In the secretion from defense glands of a ChineseTypopeltis species, 2-ketones (2-heptanone, 2-octanone, and 2-nonanone) were identified as constituents for the first time. While acetic acid is also present as a secretory product, no caprylic acid has been found.