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The precise diagnosis for bovine spongiform encephalopathy (BSE) is crucial for preventing new transmission to humans. Several testing procedures are reported for determining protease-resistant prion protein in various tissues as a major hallmark of prion diseases such as BSE, scrapie, and Creutzfeldt–Jakob disease. However, contamination of materials from tissues or degradation of the specimens sometimes disturbs the accuracy of the assay. Here, we have developed a novel method for solid-phase immunoassay of the disease-specific conformational isoform, PrP Sc , using filtration blotting of protein in the presence of sodium dodecyl sulfate (SDS) followed by a filtration-based immunoassay with a single anti-prion protein antibody, together with the improved fractionation procedure involving high concentrations of surfactant/detergent. The SDS/heat treatment renders unfolded PrP Sc quantitative retention on a polyvinylidene difluoride filter and allows enhancement of the analyte signal with immunodetection; thus, all of the tested specimens are determined with 100% accuracy. In addition, the immunoassay is completed in approximately 1 h, indicating its usefulness not only for the screening of BSE specimens but probably also for the postmortem BSE diagnosis of fallen stock as the antibody recognizes the core part of PrP Sc . The solid-phase immunoassay method, including the filtration blotting with SDS, would be applicable to determining even more sensitively proteins other than PrP Sc , especially those having rigid conformations.

It is thought that sodium dodecyl sulfate (SDS), an anionic detergent, binds to hydrophobic moieties of peptide to destroy the conformational structure of protein. Because of this property, it is involved in many biochemical procedures such as separations of protein and proteolytic digestion. In the course of our study on a solid-phase protein assay, we found that SDS acts as an effective reagent for protein blotting onto a hydrophobic membrane of polyvinylidene difluoride with a manifold dot-blot apparatus. At least 0.1% SDS in an acid–ethanol blotting solution, while reducing the bias of pronounced interferers for protein assay to protein–membrane interaction, quantitatively retains protein on the membrane. Presumably, protein denatures by SDS to become an unfolded state and adsorbs into the membrane by hydrophobic interaction, even in the presence of excess SDS. Therefore, bolts stained with a pyrogallol red–molybdate complex (Pyromolex) reagent unreactive to the membrane allowed a precise protein determination without significant interference of materials, especially detergents in the sample solution. The filtration-blotting with SDS would be a crucial procedure for quantitative analyses such as immunoblotting in detergent-containing samples, together with the solid-phase protein assay with limited sample volumes, such as 20 μL or less.

In genome and cDNA sequencing projects, current cycle sequencing often encounters difficult-to-sequence templates which have unique secondary structures due to GC-rich composition or repeated regions. Due to the formation of stable secondary structures, remarkable decreases in fluorescent signals are observed in cycle sequencing reactions. It is not easy to determine the nucleotide sequences of these regions. Although several modifications of sequencing reactions have been tried to overcome these problems, some unreadable regions remain as gaps in genome sequencing projects. Here, we further developed transcriptional sequencing technology and evaluated the sequencing accuracy in these regions. The method was successively applied to artificial GC cluster templates and putative secondary structure-forming templates from genomic and cDNA clones. Our results indicate that transcriptional sequencing is a powerful and accurate method for GC-rich regions, simple sequence repeats, hairpins (inverted repeats), tandem repeat DNA templates, and gap-closing in draft sequencing data.