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High Content Screening
Once we have discovered a bioactive compound it is important to elucidate its mode of action. Since a cellular organism is a complex system this is not an easy task. There is no general protocol available how to proceed, and most methods rely on the chemical modification of the compound which often alters the binding affinities. In the Department of Chemical Biology we therefore developed high Content Screening tools that are generally applicable to get hints about the mode of action and do not rely on chemical modification of the compound of interest.
The first method is based on phenotypic changes of mammalian cells that are induced when they are incubated with a bioactive compound. Using fluorescence and immunofluorescence labeling techniques a set of cellular proteins and structures is made visible and alterations of incubated cells can be documented by automated microscopy then. Selected parameters from High Content Image Analysis are then taken to form a profile that is typical for the mode of action of a compound. By comparing profiles of a new compound with profiles of a set of reference compounds whose modes of action are already known this approach gives hints about the mode of action of the new compound.
The second method relies on changes in the morphology of cells that can be monitored over time by measuring electrical impedance in cultures that are incubated with the compound of interest. The resulting curves are rather complex and are typical for the mode of action of a compound. By comparing the impedance curve of a new compound with curves of our reference library we can again get hints about the mode of action of the new compound.
The HCS methods developed in the CBIO department were used in many collaborative projects and helped to elucidate the mode of action of natural products. Two representative examples from 2013 are:
 Synthesis and biological evaluation of paleo-soraphens.
Lu HH, Raja A, Franke R, Landsberg D, Sasse F, Kalesse M.
Angew Chem Int Ed Engl. 2013 Dec 16;52(51):13549-52. doi: 10.1002/anie.201305331. Epub 2013 Nov 7.
 Total synthesis and biological evaluation of jerantinine e.
Frei R, Staedler D, Raja A, Franke R, Sasse F, Gerber-Lemaire S, Waser J.
Angew Chem Int Ed Engl. 2013 Dec 9;52(50):13373-6. doi: 10.1002/anie.201305533. Epub 2013 Oct 14.