While magnetic and semi-conductor based information storage devices have been in use since the middle 1950's, today's computers and volumes of information require increasingly more efficient and faster methods of storing data. While the speed of integrated circuit random access memory (RAM) has increased steadily over the past ten to fifteen years, the limits of these systems are rapidly approaching. In response to the rapidly changing face of computing and demand for
· physically smaller,
· greater capacity,
A number of alternative methods to integrated circuit information storage have surfaced recently. Among the most promising of the new alternatives are
optical memory storage devices, and
· protein-based optical memory storage using
reaction centers, cytochrome c, photosystems I and II, phycobiliproteins, and phytochrome.
This article focuses mainly on
protein-based optical memory storage using the photosensitive
protein bacteriorhodopsin with the two-photon method of exciting the molecules, but briefly describes what is involved in the other two. Bacteriorhodopsin is a light-harvesting protein from bacteria that live in salt marshes that has shown some promise as a feasible optical data storage. The current work is to hybridize this biological molecule with the solid state components of a typical computer.
Under this effort, a bacteriorhodopsin-based, three dimensional (3-D) memory device was developed and fabricated. Advances were made in both prototype development and materials enhancement. Bacteriorhodopsin in its native form (i. e., the wild-type protein that has not been altered either genetically or chemically) is incapable of the efficient operation. This fact guided the research effort toward three major objectives: (1) Optimization of the protein with respect to operation in the 3-D optical memory, (2) Optimization of the polymer matrix that encapsulates the protein, thereby comprising the memory media, and (3) Fabrication of prototype 3-D optical memories geared toward use with not only the native protein, but also chemically and genetically manipulated forms. Directed evolution (DE) was selected as the best way to optimize the protein. This genetic engineering technique offers the opportunity to explore mutations that otherwise would be overlooked by more pragmatic approaches. Additionally, advances in polymer matrix optimization have been made with respect to long-term stability, shrinkage, and optical clarity. Lastly, a prototype device was made under this effort that represents the first true step toward a commercially viable optical memory.