A membrane-associated creatine kinase (EC 2.7.3.2) identified as an acidic species of the non-receptor,peripheral v-proteins in Torpedo acetylcholine receptor membranes

Human liver mRNA isolated from subjects phenotyped as homozygous PiMM or PiZZ α₁-antitrypsin, was translated in a reticulocyte cell-free system, and α₁-antitrypsin identified by immunoprecipitation. In the presence of dog pancreas membranes the translated α₁-antitrypsin appeared as a larger product. Treatment with endo-β-N-glucosaminidase yielded a protein smaller than the reticulocyte translated product, presumably due to removal of the N-terminal signal sequence by membranes and sugar residues by endo-β-N-glucosaminidase. Quantitation of α₁-antitrypsin translated from PiMM and PiZZ livers suggests that both mRNA species were present at the same cellular concentration, and that processing to the core glycosylation stage proceeded at identical rates.     

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Fluxes and compartmentation of potassium and chloride in the green alga Mougeotia

Summary Some ionic relations of the filamentous green alga Mougeotia sp. have been analyzed under different light conditions. Data from influx and efflux measurements using ⁸⁶Rb⁺ and ³⁶Cl^- fit the model of three cellular compartments (cell wall, cytoplasm, vacuole) in series. This result is remarkable, since in a Mougeotia cell at least two thirds of the cytoplasmic compartment are occupied by the cell-filling, flat and nearly rectangular chloroplast which is axially oriented. The chloroplast is concluded to be part of the cytoplasmic flux compartment.Photosynthetically saturating irradiances of continuous white light enhance the active and passive fluxes of K⁺ and Cl^- at the plasmalemma by a factor of 3. Photosystem II is responsible for the light-dependent increase of the uptake of Cl^- (³⁶Cl^-) whereas the uptake of K⁺ (⁸⁶Rb⁺) depends additionally on energy from photosystem I.Ion flux measurements performed after irradiations with red and far-red, respectively, show that the fluxes of K⁺ and Cl^- across the plasmalemma are not affected by the state of phytochrome.     

Stereoselectivity of the in vitro metabolism of thalidomide

The stereoselective metabolism of the former sedative thalidomide and the metabolism of its analogue EM 12 were studied in vitro with liver homogenates. In our study we focused on hydroxylated nonhydrolyzed metabolites of thalidomide. An analytical HPLC method was developed to determine these metabolites directly. The investigations showed a highly stereoselective biotransformation of thalidomide. 5-Hydroxy thalidomide was preferentially formed by (?)-(S)-thalidomide, whereas (+)-(R)-thalidomide was metabolized to two hitherto unknown compounds (Met A and B). Mass spectrometry of these metabolites Met A and B indicated that oxidation or hydroxylation took place in the glutarimide moiety. Biotransformation studies with the more stable thalidomide analogue EM 12 revealed four new metabolites (Met C? F) whose quantities differed in the selected liver homogenate. © 1994 Wiley-Liss, Inc.     

Die Lichtreaktionen der Hydren

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Mhc-DQB repertoire variation in hominoid and Old World primate species.

Comparison of 87 distinct Mhc-DQB sequences, obtained from 13 primate species, demonstrates that five out of eight trans-species Mhc-DQB allele lineages are at least 30 million years old and predate divergence of hominoid and Old World primate species. One lineage may be much older because its members are not only traced back in higher primates, but also are present in a New World primate species. Comparing Mhc-DQB repertoire variation in distinct species, allows one to pinpoint when certain polymorphisms were lost or gained in primate evolution. Heterogeneity observed among members of trans-species Mhc-DQB allele lineages can be explained in major part by point mutations, whereas intraexonic crossing-over is a potent mechanism in generating new allele lineages. The stability of Mhc-DQB polymorphisms is influenced by selective forces because distinct allele lineages appear to have accumulated nucleotide substitutions and amino acid replacements at different rates.     

Preparative and analytical separation of the zopiclone enantiomers and determination of their affinity to the benzodiazepine receptor binding site

We report the preparative separation of rac-zopiclone using malic acid as the resolving agent. Furthermore, two different methods for the analytical determination of zopiclone enantiomers by HPLC on chiral stationary phases are described. The benzodiazepine receptor binding of the isolated enantiomers was investigated. Half-maximal inhibitory concentrations of (+)- and (?)-zopiclone were 21 or 1,130 nmol/liter, respectively, indicating a more than 50 times higher affinity of the (+)-enantiomer toward the receptor. © 1993 Wiley-Liss, Inc.     

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