Über die Bildung der Resultante und des grössten gemeinsamen Theilers zweier ganzer rationaler Functionen einer Variablen.

Ohne Zusammenfassung     

The structure of melanins and melanogenesis—I The structure of melanin in Sepia

Melanin from Sepia officinalis is a natural polymer containing many carboxylic groups. It is present in the ink sac of the animal as the Mg and Ca salt. Purified sepiomelanin is able to combine with cations and, to a less extent with anions; by heating CO₂ is evolved. A formula closely related to ... [---C₈H₅O₂N---C₈H₄O₂N·COOH---]_x... is suggested for sepiomelanin and its derivatives.

Owing to the presence of a tyrosinase in the ink sack it is possible that 2-carboxy-2,3-dihydroindole-5,6-quinone (dopachrome) plays an important part in the biological process of polymerization.     

The structure of melanins and melanogenesis—III The structure of sepiomelanin

New degradation products of sepiomelanin have been obtained. Alkali fusion yields, in addition to other compounds, 5,6-dihydroxyindole, 5,6-dihydroxyindole-2-carboxylic acid, 4-methyl-cathechol and a compound, which is probably 5,6-dihydroxyindole-4,7-dicarboxylic acid. These products constitute the first proof of the indole structure of a natural melanin. The carboxyl group of 5,6-dihydroxyindole-2-carboxylic acid is not formed during alkali fusion, but pre-exists in the macromolecule. Cysteic acid, taurine, glycine and aspartic acid were obtained by oxidation of sepiomelanin with hydrogen peroxide in acetic acid. The formation of cysteic acid indicates that sepiomelanin is bound to the protein by means of cysteine. Taurine is clearly an artifact generated by decarboxylation of cysteine. Glycine and aspartic acid probably are derived from the pyrrole moiety of the indole units: they also result from the oxidation of 5,6-dihydroxyindole-2-carboxylic acid.

Oxidation of methylated sepiomelanin yields 3-carbomethoxypyrrole-2,5-dicarboxylic acid and 5-carbomethoxypyrrole-2,3-dicarboxylic acid; isolation of the former further proves the presence of pyrrole units in sepiomelanin, whereas formation of the latter is further evidence that some indole (probably dopachrome) units of the macromolecule have a carboxyl group in position 2.     

Catalytic Antibodies by Fluorescence Screening

A series of eleven immunizations against transition-state analogs were carried out to improve the catalytic properties of Ab 9D9, a catalytic antibody that catalyzes a fluorogenic retro-Diels-Alder reaction liberating nitroxyl. By a direct fluorescence assay of cell-culture supernatant, eight new hybridoma cell lines producing catalytic antibodies for the reaction were readily identified among more than 14000 individual samples. Our results demonstrate that early catalysis screening by fluorescence allows an efficient survey of large antibody libraries, and may lead to rapid and significant improvement in catalysis.     

AFM and STM characterization of thiol and thiophene functionalized SWNTs: pitfalls in the use of chemical markers to determine the extent of sidewall functionalization in SWNTs

Thiol- and thiophene-functionalized SWNTs prepared via the reaction of a substituted amine with fluoronanotubes show similar levels of sidewall functionalization, however, the use of Au nanoparticles as chemical markers for AFM gives misleading results for substituent distribution since STM shows the thiol substituents grouped in bands while the thiophene substituents uniformly distributed along the SWNTs.     

Schottky groups and maximal representations

We describe a construction of Schottky type subgroups of automorphism groups of partially cyclically ordered sets. We apply this construction to the Shilov boundary of a Hermitian symmetric space and show that in this setting Schottky subgroups correspond to maximal representations of fundamental groups of surfaces with boundary. As an application, we construct explicit fundamental domains for the action of maximal representations into \(\mathrm {Sp}(2n,\mathbb {R})\) on \(\mathbb {RP}^{2n-1}\).     

CE of phytosiderophores and related metal species in plants

Phytosiderophores (PS) and the closely related substance nicotianamine (NA) are key substances in metal uptake into graminaceous plants. Here, the CE separation of these substances and related metal species is demonstrated. In particular, the three PS 2'-deoxymugineic acid (DMA), mugineic acid (MA), and 3-epi-hydroxymugineic acid (epi-HMA), and NA, are separated using MES/Tris buffer at pH 7.3. Moreover, three Fe(III) species of the different PS are separated without any stability problems, which are often present in chromatographic analyses. Also divalent metal species of Cu, Ni, and Zn with the ligands DMA and NA are separated with the same method. By using a special, zwitterionic CE capillary, even the separation of two isomeric Fe(III) chelates with the ligand ethylenediamine-N,N'-bis(o-hydroxyphenyl)acetic acid (EDDHA) is possible (i.e., meso-Fe(III)-EDDHA and rac-Fe(III)-EDDHA), and for fast separations of NA and respective divalent and trivalent metal species, a polymer CE microchip with suppressed EOF is described. The proposed CE method is applicable to real plant samples, and enables to detect changes of metal species (Cu-DMA, Ni-NA), which are directly correlated to biological processes.     

High-temperature immobilized-cell ultrafiltration reactors

The possibility of preparing polymeric membranes filled with enzymes or whole cells, using traditional techniques such as phase inversion, appears of particular industrial interest. Experimental results are reported which describe the preparation and characterization of various UF polymeric membranes filled with the thermophilic microorganism Caldariella acidophila, which has unusual chemical and thermal resistance.