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Measurements of the electrical conductivity of n-octadecane in the liquid and solid phases are reported. The results indicate that ion transport predominates in the liquid phase and may also be important in the solid. An electrolytic purification process has been observed in both phases. The situation in the solid is complicated because defects formed in the solid during solidification from the melt appear to facilitate the transport of ions, causing the conductivity of the solid to be higher than expected.

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The protein components of three industrial recombinant expression systems: Escherichia coli, Saccharomyces cerevisiae, and a mammalian cell culture supernatant of CHO cells were characterized in terms of their molecular weight, isoelectric point, and relative surface hydrophobicity. Identification of individual proteins was done by reference to their position in protein band profiles by polyacrylamide gel electrophoresis (PAGE) of the crude material. This permitted a rapid and facile assignment of quantitative values for these three parameters to all the major protein components in these materials. Because it is the indigenous proteins in expression systems that will form the bulk of any impurities in the product, once the values of these parameters are known for any target recombinant protein, the data obtained will enable appropriate expression systems to be chosen for minimizing amounts of potential contaminants and reducing downstream processing requirements and costs. The data will also indicate which fractionation steps (i.e., charge, size or hydrophobicity-based) are likely to be best for distinguishing between target and contaminant proteins, thus aiding and early removal of the maximum quantities of undesired protein to bring subsequent bioseparation steps down in scale and cost and up in terms of efficiency.

The currents flowing along two crystal directions, viz. parallel with and perpendicular to the molecular axis, were monitored but an apparent anisotropy in the conduction properties was removed by a voltage conditioning procedure. It is concluded that n-octadecane does not show an intrinsic DC conduction process when pure, defect-free crystals are grown. The voltage step-responses of the crystals do, however, show the logarithmic time dependence which is common to a wide range of insulators and semiconductors. Comparisons are made with results presented previously on liquid and polycrystalline n-octadecane.