Three-dimensional data storage using the photochromic protein bacteriorhodopsin

A three-dimensional computer memory architecture based on the optical properties of the integral membrane protein bacteriorhodopsin has been previously proposed. However, confirmation of the very important branched photocycle property of this protein has not been shown. Data confirming the existence of a branched photocycle by writing a long term stable bit of information within the center of a cube of protein is presented. The stable photoproduct is formed by pulsing a 635 nm laser followed by an intersecting 690 nm laser pulse. At the point of intersection a stable branched photo-product appears. We found that at elevated temperatures the rate of production of the stable photoproduct is greatly increased and therefore the experiments are performed at 40°C. Data representing absorbance changes at 690 nm due to the bacteriorhodopsin photocycle at 40°C is presented. This information is required to set the timing of the light pulses required to write a bit. Then the pulse-pulse experiment is performed with a corresponding increase in transmission observed during the 690 nm light pulse. This confirms the production of the stable photoproduct. The experiment is then repeated with both lasers pulsing simultaneously. If the photoproduct is formed from a branch off of the photocycle, the simultaneous pulses should form much less photoproduct, despite an equivalent number of photons. Data showing this result is presented confirming the branched production of the stable photoproduct, thus proving the three dimensional computer memory architecture