The S. cerevisiae outwardly-rectifying potassium channel (DUK1) identifies a new family of channels with duplicated pore domains.

Potassium channel subunits have six or two transmembrane segments in addition to a conserved pore-forming (P) domain; four subunits come together to form a channel. A gene was identified in S. cerevisiae (J0911) encoding a protein with eight probable membrane-spanning segments and two such P regions. This protein (Duk1p) is a potassium channel because Xenopus oocytes injected with the corresponding RNA express potassium currents activated by depolarization that are not seen in control oocytes. Similar potassium currents were recorded from wildtype S. cerevisiae spheroplasts, but not from those in which the DUK1 locus had been disrupted. Cells carrying the duk1 delta 1::HIS disruption in addition to a chimeric gene comprising DUK1 behind the GAL1 promoter showed outward currents when grown in galactose, but not when grown in glucose. Additional sequences with the duplicate pore motif were found in C. elegans, suggesting that these proteins represent a novel structural family of potassium channel proteins

Determination of C-Reactive protein by an improved turbidimetric assay

An improved turbidimetric assay for the measurement of C-reactive protein (CRP) has been evaluated in six laboratories on various analytical systems (Boehringer Mannheim Hitachi systems 704, 717, 747, 911, 917 and on Keysys® analyzer). Compared to the previous test version this assay has better transferability of results from instrument to instrument, less lipemia and gammopathy interference, a better linearity in the lower concentration range, the applicability of EDTA plasma or heparin plasma and a satisfactory recovery of target values according to CRM 470 standardization. The detection limit of the Tina-quant® CRP assay is 1.9 mg/l CRP. Median values of CVs within run of lower than 2.5% and between day of lower than 3.3% were obtained. A survey with 50 human pool sera revealed a good transferability of results obtained in different laboratories and on different analytical systems. Method comparison studies between the Tina-quant® CRP assay and fixed-time nephelometry, rate nephelometry and turbidimetry were in reasonable agreement (± 10%) throughout the entire measuring range. No drift effect was noticed with the tubing system on Boehringer Mannheim/Hitachi 747 analyzers. The reagent and calibration stability was extended to 12 weeks. The Tina-quant® CRP assay enables the precise, accurate, rapid and convenient determination of CRP used for routine clinical chemistry and STAT purposes