There have been many methods and proteins researched for use in computer applications in recent years. However ,among the most promising approches,and thje focus of this seminar is 3D optical RAM storage using the light sensitive protein bacteriorhodopsin.
Bacteriorhodopsin is the light-harvesting protein found in the membrane of a microorganism called Halobacterium halobium. This bacterium grows in salt marshes where the salt concentration is roughly six times the salt concentration in seawater. When the oxygen becomes too low to sustain respiration, the purple membrane, where the bacteriorhodopsin, resides is grown. The protein, upon the absorption of light, pumps a proton across the membrane, generating a chemical and osmotic potential that serves as an alternative source of energy. In this fashion, the Halobacterium can, when the need arises, switch over from respiration to photosynthesis; this is a very unique characteristic.
Survival in the harsh environment of the salt marsh, where temperatures exceed 150 degrees Fahrenheit for extended periods of time, requires a durable protein that resists thermal and photochemical degradation. Bacteriorhodopsin, then, has provided scientists with a protein that defies the conventional logic that proteins are too fragile and unstable for use in computing devices. and natural selection have provided scientists with a natural protein which can survive environments so harsh that few semiconductor devices could survive in such conditions.
Among the major advantages of using bacteriorhodopsin for computer applications are:
• long-term stability and resistance to thermal and photochemical degradation
• a cyclicity (the number of times it can be photochemically cycled) which exceeds 106, a value considerably higher than most synthetic photochromic materials
• high quantum yields (efficient use of light) which permits the use of low light levels for switching/activating
• wavelength-independent quantum yields
• high two-photon cross sections, permitting activation in the infared and three-dimensional memory architectures
• generation of a signal upon photoconversion, permitting electronic state assignment ability to form thin films or oriented polymer cubes containing bacteriorhodopsin with excellent optical properties.
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