Bacteriorhodopsin-Based Volumetric Optical Memory

Jeffrey Stuart and Robert R. Birge

W. M. Keck Center for Molecular Electronics, Syracuse University, 111 College Place, Syracuse, NY 13244-4100, USA


Computer applications have evolved to a level of sophistication that demands not only a powerful processor, but tremendous amounts of memory. The memory-intensive nature of many software applications, especially those which manipulate graphics and image data, requires that memory be handled quickly and efficiently, with high-volume through-put. Three-dimensional optical memories have often been suggested as a way to address issues like these, but to date, volumetric architectures have been plagued by problems with destructive write and read processes. However, they hold the potential to provide as much as a thousand-fold improvement in memory storage capacity over current technology. A three-dimensional optical memory based on the photoactive protein bacteriorhodopsin (BR) may be able to avoid such problems. By utilizing the branched portion of the photocycle, access is gained to a long lived photointermediate which can serve as an active element for memory storage. This intermediate, denoted as the Q-state, is accessed as a result of the sequential absorption of two photons, the first to initiate the BR photocycle, and the second to drive the protein into the branched photocycle a few milliseconds later. Two factors allow unwanted photochemistry (i.e. destructive write and read processes) to be avoided: (1) The Q-state, produced via absorption of red light by the O-state, is strongly blue-shifted with respect to other intermediates in the photocycle; and (2) The architecture employs no simultaneous two photon processes. The latter is especially important in that the need for large powerful lasers typical of two-photon based architectures is eliminated.

A bacteriorhodopsin-based volumetric memory is currently in development at the W. M. Keck Center for Molecular Electronics at Syracuse University. The presentation will focus on the BR branched photocycle memory architecture, as well as the ongoing efforts in prototype development, optimization, and protein characterization at Syracuse University.