Bacteriorhodopsin as a Photochromic Retinal Protein for Optical Memories

Cellular and organellar membrane-associated proteins in haloarchaea: Perspectives on the physiological significance and biotechnological applications

“…Furthermore, the photoelectronic aspect of bacteriorhodopsin, i.e., lightdriven proton translocation and the high speed of the photocycles (~10 ms), also make retinal proteins outstanding candidates for photo-and bio-sensors [115], nonlinear optical filtering and light switching [84]. BR may also be used for seawater desalination [10]. It is also a candidate for use in gene therapy in neuroscience and has recently attracted tremendous interest [116118].…”

Approaches for biological and biomimetic energy conversion

“…Some of the earliest work (16) found that surfaces coated with the protein could produce a transient signal similar in behavior to normal photoreceptors; this phenomena has been shown to function at a variety of electrolyte͞ electrode interfaces (22,23). Although these findings were quickly extended into efforts to make artificial retinas (24) and protein-based optical storage devices (25)(26)(27)(28)(29), issues of interfacing the proteins with conventional semiconductors led to the development of synthetic or modified bacteriorhodopsin devices using organic cations. ʈ PSI has been used recently as an optical trigger for a retinal prosthesis (31).…”

Photosensitive protein patterning with electrophoretic deposition

“…To achieve these applications, especially image sensors, micropatterning of bR-sensing site arrays that range in size from several micrometers to hundreds of micrometers is essential. However, conventional microfabrication processes consisting of photolithography and etching cannot be applied for bR because bR is not an inorganic material but a biomaterial, thus it is denatured by high-temperature (> 90 • C) heating and its structure is broken by the alcohols used for cleansing photoresists [6]. Thus, most previous studies report on the improvements of bR photosensitivity with chemical treatments or new device structures [6,7], whereas studies on image sensors have been few due to the difficulty of bR micro-patterning [2,3].…”

“…In the developed process, the desired area of the electrode for immobilizing bR is defined by a hydrophobic surface and the undesired area of the electrode is covered with the hydrophobic polymer Cytop, which repels bR. After the micro-fabrication process, bR is selectively formed on the defined areas using electrophoretic deposition because bR is negatively charged in the neutral pH solution [6], and the positive potential moves bR and deposits bR film on a substrate. The advantage of this process is that microfabrication is not processed after bR deposition, which prevents bR from denaturing.…”