Proton-translocating retinal protein
The invention relates to proton-translocating retinal proteins which exhibit a photocycle which is retarded as compared with the wild type and whose all-trans retinal contents in the light-adapted and dark-adapted states do not differ from each other by more than 10%. The invention furthermore relates to a photochromic composition and to the use of the proton-translocating retinal proteins and the photochromic composition.
1. A photochromic composition comprising:
(i) a proton-translocating retinal protein that is a mutein of a Halobacterium salinarium bacteriorhodopsin, which exhibits a retarded photocycle (type 1 mutation) and whose all-trans retinal contents in the light-adapted and dark-adapted states do not differ from each other by more than 10% (type 2 mutation), wherein said muteins comprises SEQ ID NO:1 except for one or more amino acid substitutions at a position selected from the group consisting of D38, D102, and D104 (type 1 mutation) and one or more amino acid substitutions at a position selected from the group consisting of V49, A53, L93, M118, G122, S141, and M145 (type 2 mutation);
(ii) at least one additive selected from a stabilizer, a foam formation-diminishing additive, a UV light-absorbing additive and a buffering substance;
and
(iii) at least one additional component selected from glycerol, an organic polymer and an organic solvent.
2. The photochromic composition of claim 1 wherein the retinal protein is present in the form of a purple membrane.
3. A photochromic composition comprising:
(i) a proton-translocating retinal protein that is a mutein of a Halobacterium salinarium bacteriorhodopsin, SEQ ID NO:1, which exhibits a retarded photocycle (type 1 mutation) and whose all-trans retinal contents in the light-adapted and dark-adapted states do not differ from each other by more than 10% (type 2 mutation), wherein said mutein comprises SEQ ID NO:1 except for the amino acid substitutions D96N (type 1 mutation) and M145F (type 2 mutation);
(ii) at least one additive selected from a stabilizer, a foam formation-diminishing additive, a UV light-absorbing additive and a buffering substance;
and
(iii) at least one additional component selected from glycerol, an organic polymer and an organic solvent.
4. The photochromic composition of claim 3 wherein the retinal protein is present in the form of a purple membrane.
5. The photochromic composition of claim 1 wherein the proton-translocating retinal protein exhibits a retinal isomer composition of at least 60% all-trans retinal in both the light-adapted and dark-adapted states.
6. The photochromic composition of claim 2 wherein the density of the purple membrane is between 1.10 and 1.20 g/cm 3 .
7. The photochromic composition of claim 6 wherein the density of the purple membrane is from 1.175 to 1.185 g/cm 3 .
8. The photochromic composition of claim 3 wherein the proton-translocating retinal protein exhibits a retinal isomer composition of at least 60% all-trans retinal in both the light-adapted and dark-adapted states.
9. The photochromic composition of claim 4 wherein the density of the purple membrane is between 1.10 and 1.20 g/cm 3 .
10. The photochromic composition of claim 9 wherein the density of the purple membrane is from 1.175 to 1.185 g/cm 3 .