| Summary: | 碩士 === 國立臺灣大學 === 生化科技學系 === 101 === Retinal-binding proteins (RBPs) are composed of seven-transmembrane α helix, which form a binding pocket to secure a photosensing retinal molecule. RBPs response to light illumination after abosorbing maximally at a specific wavelength and exhibit different visual colors. Our laboratory reported six new RBPs from a halophilic archaea, Haloarucla marismortui, and constructed a mutated protein named Highly-Expressed Bacteriorhodopsin (HEBR) from of one of the RBPs, HmBRI, and found it to have exceptional high expression efficiency and high stability, as well as a
slower photocycle recovery rate. In addition, HEBR showed purple to yellow color changing when exposure to light, and the degree of such color changing was pH-dependent. Photocycle measurement unveiled that the accumulation of an
important intermediate state, M state, is proportional to the increasing of pH value and consequently the color changing. In addition, by chemical reaction equilibrium, we
introduced light intensity as another variable to describe such pheromone.
Furthermore, this study calibrated the visual color changing with a professional standard color card with software, and quantified them as RGB values. Based on thecorrelation between HEBR color changing, pH value and light intensity, a series of HEBR under different pH was shown to report different light intensity and we proposed to use it as a battery-free light intensity indicator. Furthermore, HEBR also could serve as pH indicator by the color changing under certain light intensity.
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