Modification-free photocontrol of β-lactam conversion with spatiotemporal resolution.

β-Lactams can be converted into β-amino acids by β-lactamase, a bacterial enzyme, leading to significant change in the biological function of the substrate molecules. Here we describe a method for photocontrol of β-lactam conversion without gene nor enzyme modification. This is achieved by the addition of a cationic photosensitive surfactant, AzoTAB, to a gene expression medium containing DNA coding for β-lactamase, the enzyme capable of the desired conversion. In the absence of UV (365 nm) or after illumination by blue light (480 nm) for 4 min, conversion of β-lactam is strongly reduced while the application of UV for 4 min results in a strong enhancement of substrate conversion. Several cycles of activation/inhibition are obtained upon successive UV/blue light illuminations. When both reconstituted photoresponsive gene expression medium and β-lactamase substrate are encapsulated in independent microfluidic chambers, selective UV illumination results in spatially resolved activation of substrate conversion.