Anthralin: primary products of its redox reactions.

One-electron reduction significantly enhances the ability of anthralin, 1, to act as a hydrogen atom donor. On annealing of an MTHF glass in which the radical anion of anthralin, 1*-, is generated radiolytically, this species decays mainly by loss of H* to give the anthralyl anion, 2- . On the other hand, radicals formed on radiolysis of matrices that are suitable for the generation of radical anions or cations are capable to abstract H* from anthralin to give the anthralyl radical, 2* . Both 2- and 2* are obtained simultaneously by mesolytic cleavage of the radical anion of the anthralin dimer. Contrary to general assumptions, the anthralyl radical is found to be much more reactive toward oxygen than the anion. All intermediates are characterized spectroscopically and by reference to quantum chemical calculations. Attempts to generate the radical cation of anthralin by X-irradiation of an Ar matrix containing anthralin led also to significant formation of its radical anion, i.e., anthralin acts apparently as an efficient electron trap in such experiments.

Detection of TAP-tagged proteins in Western blot, confocal laser scanning microscopy and FACS using the ZZ-domain.

Tandem affinity purification of protein complexes has become an important tool in the field of proteomic research. Analysis of the proper intracellular localization of TAP-tagged proteins by immunohistochemistry by specific antibodies is often impossible due to the simultaneous detection of the endogenously synthesized native protein. Here we show that the highly specific interaction of the ZZ-domain of Protein A, which constitutes part of the original TAP-tag, to rabbit IgGs can be used to detect TAP-tagged proteins in fixated cells by Confocal Laser Scanning Microscopy just by the use of labeled secondary antibodies. In addition, such interactions can be exploited for the analysis of transfected cells in FACS and Western blot experiments. Thus, we present valuable tools for the analysis of recombinant proteins on the basis of IgG-ZZ interactions, which can be used even if target specific first antibodies are not available or lack sufficient specificity.

Mechanistic aspects of alloxan diabetogenic activity: a key role of keto-enol inversion of dialuric acid on ionization.

The inversion of the keto-enol stability order of dialuric acid on ionization was calculated and verified experimentally. The radical cations in both forms were characterized. The spectrum of the keto form was observed upon direct ionization of dialuric acid under matrix conditions, whereas the enol form was formed upon a sequential electron-proton-proton attachment to alloxan under acidic aqueous condition. Facilitation of the one-electron oxidation of dialuric acid upon its enolization can result in a more effective formation of superoxide radical anion in the process of its auto-oxidation. This process is discussed in reference to the alloxan diabetogenic action. Both neutral keto and enol forms are energetically close, and under favorable conditions, the auto-oxidation of dialuric acid could involve participation of the enol form.