In this issue: Biotechnology Journal 10/2010

Self‐association chromatography Bankston and Carta , Biotechnol. J. 2010, 5, 1028–1039 Bankston and Carta , Biotechnol. J. 2010, 5, 1040–1049 Apolipoprotein A‐IMilano (apoA‐I M ) is a major component of high density lipoprotein (HDL) involved in cholesterol transport. When oxidized, apoA‐I M consists of a homodimer and reversibly self‐associates to higher order oligomers. It is not only a potential therapeutic protein, but also a useful model to study associating proteins. Giorgio Carta and Theresa Bankston from the University of Virginia (Charlottesville, VA, USA) have studied the separation behavior during anion exchange chromatography in two consecutive papers of this issue. While one explains the effects of urea and salt concentration on the binding characteristics, the other studies the kinetics of adsorption on anion exchangers with different pore sizes. By developing a mechanistic model of the process, they can predict separation of the protein. These models are of special importance to develop separation processes for industrial applications. Cell patterning Puttaswamy et al., Biotechnol. J. 2010, 5, 1005–1015 Negative dielectrophoretic (n‐DEP) cell manipulation is an efficient way to pattern human liver cells on micro‐electrode arrays. It employs electric fields that move the cells to a desired place because they are less polarizable than the surrounding medium. Excessive charging of the cellular membrane, the non‐physiological medium and shear stress due to the liquid flow might compromise the cell viability. Researchers from Taiwan have now developed a low conductivity medium containing essential components of DMEM medium at low concentration, suitable for DEP‐based cell manipulation at low voltage and frequency. Here the cells show high viability and cell adhesion. They developed a microchip prototype with a well‐defined positioning of titanium electrode arrays on a glass substrate. These cells on the chip now mimic the lobular morphology of real liver tissue (see cover image). Green tea metabolism Schantz et al., Biotechnol. J. 2010, 5, 1050–1059 It is well know that green tea polyphenols have a beneficial health effect, which is primarily accounted to the presence of catechins. However, there is not much known on their degradation in the intestine. Therefore authors from Kaiserlautern, Germany, have studied the microbial metabolism and chemical stability of these polyphenols using a well‐established ex vivo model. Fresh ileal fluids from probands were incubated for 24 h under anaerobic conditions with different catechins. Then, the metabolites were analysed by HPLC‐photodiode array detection and tandem mass spectrometry. Interestingly the same metabolites were detected, although the microbiota were substantially different. The authors concluded that microbiota‐dependent liberation of the metabolites occurs before these compounds reach the colon.