Frontal Affinity Chromatography (FAC)
Continuous methods and flow processing for chemical synthesis and biological evaluation are both now well established and documented. Our ultimate aim is to produce coordinated systems to achieve “Make & Screen” in flow, hence integrating of these devices in one single laboratory environment. When this powerful tool is combined with appropriate automated synthesis systems and design software, then a true closed loop discovery platform will be attained.
FAC is a biophysical method where the target macromolecule is immobilised on a polymeric support; the binding affinity of a compound can be measured by comparing its retention to that of a control. In our opinion, this simple and robust method is an ideal evaluation method that may be plugged in-line to our existing flow chemistry platforms.
Principle of Frontal Affinity Chromatography
Our proof of concept work was published early 2013, in which a library of GABAA agonists, including zolpidem (Stilnox, Ambien) and alpidem, were synthesised using flow chemistry. Binding affinities towards Human Serum Albumin (HSA, the most abundant protein in plasma) were accurately determined and in accordance with the literature. Furthermore, a simple ranking method based on aliquots automatically prepared via the flow platform showed good correlation with binding affinities and potential for full integration with our flow equipment.
Current FAC-MS set-up
We are now using Mass Spectrometry as detection system, which enables the injection of mixtures for competitive studies, and virtually detects any compound with no need of pre-labelling. Our current set-up is now applied to a medicinal chemistry programme in epigenetics: the discovery of bromodomains modulators. This research project is being run in collaboration with SGC (Structural Consortium Genomics, Oxford, www.thesgc.org), which kindly provides proteins of interest and cross-validates data.
Flow chemistry synthesis of zolpidem, alpidem and other GABAA agonists and their biological evaluation through the use of in-line frontal affinity chromatography L. Guetzoyan, N. Nikbin, I.R. Baxendale, S.V. Ley, Chem. Sci., 2013, 4, 764-769.