Aspects of protein-DNA interactions: a review of quantitative thermodynamic theory for modelling synthetic circuits utilising LacI and CI repressors, IPTG and the reporter gene lacZ.

Protein-DNA interactions are central to the control of gene expression across all forms of life. The development of approaches to rigorously model such interactions has often been hindered both by a lack of quantitative binding data and by the difficulty in accounting for parameters relevant to the intracellular situation, such as DNA looping and thermodynamic non-ideality. Here, we review these considerations by developing a thermodynamically based mathematical model that attempts to simulate the functioning of an Escherichia coli expression system incorporating two of the best characterised prokaryotic DNA binding proteins, Lac repressor and lambda CI repressor.

Analysis of the phase behavior of the aqueous poly(ethylene glycol)-Ficoll system.

The PEG-Ficoll polymer phase system is one that has been overlooked in the past for biotechnology applications because of the stability of its emulsions. However, new applications, such as emulsion coating of cells, are appearing that rely on this very property. Ficoll is highly polydisperse and multimodal with three distinct Ficoll peaks in gel permeation chromatography.