Time-resolved in-cell IR spectroscopy on the bacterial chloride pump NMHR

In-cell spectroscopic techniques have become a powerful tool to overcome the drawbacks of studying proteins isolated from their native environment. This advancement is of major importance especially for membrane proteins since the recreation of a stabilizing environment using lipids or nanodiscs is challenging and varies substantially from in-vivo conditions, influencing the protein mechanism. A method well-suited for the investigation of the light-induced structural changes of photoreceptors is presented by infrared difference spectroscopy, allowing to detect changes in the cofactor, side chains and secondary structure. In pioneering studies, Fourier transform infrared (FTIR) spectroscopy using the attenuated total reflection (ATR) mode was successfully established to study light-induced changes in soluble blue-light sensors in living E. coli cells.