Preparations of bacteriorhodopsin variants having increased memory time, and their use

A process for the storage and non-destructive reading of information in a composition

• said composition containing at least one purple membrane variant in which more than 50% of a bacteriorhodopsin variant is converted at room temperature into a photoproduct having an absorption maximum which is shifted spectrally by at least 10 nm compared with the absorption maximum of the initial state by irradiation with light having a wavelength in the region of the absorption band of the initial state, where the photoproduct can be converted back into the initial state by irradiation with light having a wavelength in the region of its absorption band, wherein
• the configuration of the photoproduct which is a retinal is modified compared with the configuration of the retinal of the initial state and is different from 13-cis;
• or a Schiff base bond of the retinal has been hydrolyzed;
• and the photoproduct has a memory time of more than one day at room temperature;
• and the photoproduct allows at least 104 write/erase cycles with retention of at least 50% of the original contrast ratio;
• and a pH of the composition is between 3 and 11;
• and a water content of the composition is between 1% and 30% by weight, based on the total weight of the composition;
• and auxiliaries for modulation of the proton mobility are present in a concentration of between 1% and 80% by weight, based on the amount of a purple membrane variant employed;
• wherein the auxiliaries used to modulate the proton mobility are at least one substance selected from the group consisting of glycerol, glycols, mono-, di-, and polysaccharides and mono- or polyfunctional alcohols;
• and
• optionally matrix materials are present in a concentration of up to 10% by weight, based on the total weight of the composition;
• said process comprising the steps of
• storing the information by irradiation of the composition with linear-polarized light having a wavelength in the region of the absorption maximum of the initial state of the bacteriorhodopsin variant present in the composition, and
• detecting the information stored in this way by determining the change in the polarization state of a linear-polarized photochemically inactive detection beam after it has passed through the composition, where the detection beam is polarized neither perpendicular nor parallel to the polarization direction of the recording light.