Research Update: A minimal region of squid reflectin for vapor-induced light scattering

Reflectins are a family of proteins found in the light manipulating cells of cephalopods.These proteins are made up of a series of conserved repeats that contain highlyrepresented amino acids thought to be important for function. Previous studiesdemonstrated that recombinant reflectins cast into thin films produced structural colorsthat could be dynamically modulated via changing environmental conditions. In this study,we demonstrate light scattering from reflectin films following exposure to a series ofwater vapor pulses. Analysis of film surface topography shows that the induction of lightscatter is accompanied by self-assembly of reflectins into micro- and nanoscale features.Using a reductionist strategy, we determine which reflectin repeats and sub-repeats arenecessary for these events following water vapor pulsing. With this approach, we identifya singly represented, 23-amino acid region in reflectins as being sufficient torecapitulate the light scattering properties observed in thin films of the full-lengthprotein. Finally, the aqueous stability of reflectin films is leveraged to show thatpre-exposure to buffers of varying pH can modulate the ability of water vapor pulses toinduce light scatter and protein self-assembly