Manipulation of Ion Types via Gas-Phase Ion/Ion Chemistry for the Structural Characterization of the Glycan Moiety on Gangliosides.

Gangliosides are the most abundant glycolipid among eukaryotic cell membranes and consist of a glycan head moiety containing one or more sialic acids and a ceramide chain. The analysis of the glycan moieties among different subclass gangliosides, including GM, GD, and GT gangliosides, remains a challenge for shotgun lipidomics. Here, we present a novel shotgun lipidomics approach employing gas-phase ion/ion chemistry.

In-Depth Structural Characterization and Quantification of Cerebrosides and Glycosphingosines with Gas-Phase Ion Chemistry.

Cerebrosides (n-HexCer) and glycosphingosines (n-HexSph) constitute two sphingolipid subclasses. Both are comprised of a monosaccharide headgroup (glucose or galactose in mammalian cells) linked via either an α- or β-glycosidic linkage to the sphingoid backbone (n = α or β, depending upon the nature of the linkage to the anomeric carbon of the sugar). Cerebrosides have an additional amide-bonded fatty acyl chain linked to the sphingoid backbone.

Sensitive Energetics from the -Amination of 4-Nitro-1,2,3-Triazole.

Energetic N-amino-C-nitro compounds 1-amino-4-nitro-1,2,3-triazole and 2-amino-4-nitro-1,2,3-triazole are characterized for the first time as energetic materials. These compounds were characterized chemically by nuclear magnetic resonance (NMR), Infrared spectroscopy and X-ray crystallography. Compounds were also characterized energetically by differential scanning calorimetry (DSC), impact, and friction and found to possess sensitivities and performances classifying them as primary explosives with PETN-like performance.

Lewis-Acid-assisted Hydrogen Atom Transfer to Manganese(V)-Oxo Corrole through Valence Tautomerization.

The kinetics of formation of the valence tautomers (tpfc)Mn(O-LA)] [where LA=Zn, Ca, Sc, Yb, B(CF), and trifluoroacetic acid (TFA); tpfc=5,10,15-tris(pentafluorophenyl) corrole] from (tpfc)Mn(O) were followed by UV/Vis spectroscopy, giving second-order rate constants ranging over five orders of magnitude from 10 for Ca to 10  m  s for Sc. Hydrogen atom transfer (HAT) rates from 2,4-di--butyl phenol (2,4-DTBP) to the various Lewis acid valence tautomers of manganese oxo corrole complexes were evaluated and compared. For LA=TFA, Sc, or Yb, the rate constants of HAT were comparable to unactivated (tpfc)Mn(O).

9 Structure and function of isoprenylcysteine carboxylmethyltransferase (Icmt): A key enzyme in CaaX processing.

Proteins that terminate in a C-terminal CaaX motif undergo three sequential posttranslational modifications: isoprenylation of the cysteine residue, endoproteolysis of the -aaX residues, and methylation of the isoprenylated cysteine by an isoprenylcysteine carboxylmethyltransferase (Icmt). Among the proteins that contain this CaaX sequence are the Ras superfamily of G-proteins and other signal transduction proteins, the nuclear lamins, and the yeasta-factor mating pheromone. Icmt is a mechanistically intriguing enzyme that is unique among S-adenosyl-l-methionine (SAM)-dependent methyltransferases in that it is an integral membrane enzyme localized to the endoplasmic reticulum.