Catalytic activity of thiacalix[4]arenetetrasulfonate metal complexes on modified anion-exchangers for ascorbic acid oxidation.

The catalysis of ascorbic acid (AsA) oxidation by anion-exchangers modified with metal complexes of thiacalix[4]arenetetrasulfonate (Me-TCAS[4]A-500, Me=Mn(3+), Fe(3+), Co(3+), Ce(4+), Cu(2+), Zn(2+), Ni(2+), and H2) were investigated. Me-TCAS[4]A-500 (Me=Mn(3+), Fe(3+), Ce(4+), and Cu(2+)) all exhibited the ability to catalyze the oxidative reaction of AsA to dehydroascorbic acid. However, in the presence of high concentrations of AsA, only Cu(2+)-TCAS[4]A-500 was capable of complete oxidation of the acid.

(15)N-Labeled ionic probes for bioanalytical mass spectrometry.

An effective La-complex-based probe ionization method is reported. Novel stable isotopically labeled probes containing the (15)N-labeled 2,6-bis(oxazolin-2-yl)pyridine (pybox) ligand, succinimide-tetramethylpybox (NHS-TMpybox), maleimide-tetramethylpybox (Mal-TMpybox), and 4-(tetramethylpybox)-butyl bromoacetate (BrAc-TMpybox), have been synthesized and their value in analyzing large complex molecules has been studied. The value of the (15)N-labeled pybox-La complex in ionizing various compounds, including bioactive peptides by cold-spray ionization mass spectrometry is emphasized.