- Email: [email protected]
Modified bacteriorhodopsins as a basis for new optical devices
ELSEVIER
Sensors and Actuators B 38-39 (1997)
B
CHEMICAL
218-221
Modified bacteriorhodopsins as a basis for new optical devices A.A. Khodonov a~*,O.V. Demina b, L.V. Khitrina b, A.D. Kaulen b, P. Silfsten ‘, S. Parkkinen ‘, J. Parkkinen ‘, T. Jaaskelainen d a Department
of Biotechnology, M.V. Lomonosov State Academy of Fine Chemical Technology, Vernadskogo pr-t 86, 117571, Moscow, Russia ’ A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, 119899, Moscow, Russia ‘Department of Information Technology, Lappeenranta University of Technology, PO Box 20, FIN-53851 Lappeenranta, Finland ’ Vaisala Laboratory, University of Joensuu, PO Box 111, FIN-80101 Joensuu, Finland
Abstract The photochemical properties of various bacteriorhodopsin analogs in water suspensions and WA films have been studied and their promise for technological purposes (especially as a basis for colour-imaging and -recognition devices) is shown, Keywords:
Retinal; Bacteriorhodopsin;
Analogs; Opto-electronic
devices; Colonr-recognition
1. Introduction Bacteriorhodopsin (BR) is a light-driven proton pump isolated from Halobacterium saEinarium that weighs 26 kD, discovered in 1971 by Oesterhelt and Stoeckenius. BR is localized in specialized areas of the cell membrane, called purple membranes (PM). It has a chromophore group: a retinal protonated Schiff base bounded by an E-amino group to Lys2i6 -residue [ 13. After absorbing a quantum of light, BR undergoes spectral changes (the photocycle is shown in Fig. 1) and conformational changes in its chromophore and protein part. The main key states (Fig. 1) are the B-state (steady-state, h,, = 570nm, e=63 OOOM-‘cm-‘) andthe M-state (h,, = 412nm, ~=34000M-‘cm-‘). BR’s unique advantages for technological use are: ( 1) availability in bulk amounts, easy isolation and a relatively low price; (2) an extreme stability of the proton pump to illumination, oxygen, a wide range of pH values (O-11), temperature ( - 196 to 7O”C), concentrations of salt and water-glycerol mixtures; (3) preparation of dry film and incorporation into some polymer matrices; (4) the possibility of designing both optical and electric devices using its photocycle or charge-dislocation properties; (5) high quantum efficiency; (6) an extremely fast ‘primary event’ (B + J) of 0.5 ps; (7) the existence of long-living photocycle intermediates (Fig. 1) and the possibility of their slowing down
devices
further by replacement of certain amino-acid residues [ 31, by replacement of the natural retinal chromophore with analogs [ 451, by influence of low temperature, strong external electrical fields, variation of the humidity level or #I, and by action of some chemical additives and reagents. In 1980 the first priority studies on the practical use of BR films as optical memory element:; were carried out in Russia in the Institute of Biophysics RAS at Pushchino in cooperation with the Department of Biotechnology at the State Academy of Fine Chemical Technology [ 21. It was found that BR is a particularly promising photochromic material with a high reversibility quotient, surpassing many materials currently in
M-state * Corresponding author. [email protected]
Tel./Fax:
+7095
437
5.500.
E-mail:
0925-4005/97/$17.00 0 1997 Elsevier Science S.A. All rights reserved P11s0925-4005(97)00074-9
Fig. 1. Photocycle of BR (a water suspension of purple membrane at room temperature and neutral pH) .
A.A. Khodonov et al. /Sensors and Actuators B 38-39 (1997) 218-221
use.The main goal of this work is the comparison of modified analogs of BR as possible materials for new opto-electronic devices.
2. Experimental
Retinal and BR analogs were prepared by methods usedin Ref. [ 51. For investigation of the BR analogs’ photocycle in water suspension, we used a single-beam flash spectrophotometer [ 61. Short laser flashes were used for exciting BR, inducing only one turn of the BR photocycle. Two monochromators before and after the samples were used for filtration of the monitoring beam. Polyvinylalcohol-BR analog films were depositedon conducting glass. The films were covered by a thin layer of gold and a wire was attached to this layer by a drop of silver paint. The electrical responsesof these chips were measuredunder constant illumination and after flashes, both with different wavelengths [ 71.
3. Results and discussion
Our approach includes replacing the natural BR chromophore, retinal, with its analogs [4,5]. We investigated the photocycle of BR analogs in water suspension.Theproperties of the most promising analogs were also investigated after their inclusion in the dry films. At present the interactions of more than 300 polyenic compounds with bacterioopsin have been tested; of these approximately one third were first synthesized and investigated by us. This approach hasextremely important advantages: it makes wide variation of the B- and M-state A,, (for the B-state: 450 to 625 nm) possible, see Table 1. Fig. 2 shows typical curves of the M-state formation and relaxation for thesepigments. Note that the negative band of the differential photoinduced spectrum is similar to the absorption band. The quantum efficiency of the M-state in the photocycle of the most efficient BR analogs (2-5,7, 8) is more than half of the value for BR. Some BR analogs demonstrate deceleration of the M-state + B-state pathway (see for example, Fig. 2, curves 4-6). However, if the N --) BR transition is significantly slower than M +N (Fig. 1) , regeneration of the B-state is slower than the relaxation of the M-state, for example, in BR analog (4) [ 81. The BR analogs studied are promising for use in a new opto-electronic device, which will be used as an element for an optical computer memory as well as for the construction of the colour-image-recognition detector. The photocycle retardation that is observed in some BR analogs is useful for the manufacture of computer memory elements with lightregulated input and output of the information. Rhodopsin is a protein that is responsible for light detection in the human eye. BR is a similar pigment with close width and structure of the absorption and bleaching spectrum. Taking into
219
account that BR is a much more stable molecule than rhodopsin, the former allows BR to be used in technical devices. The reversibility of the BR photocycle makes it possible to use these devices for quite a long time. When different BR analogs are used in matrix elements (pixels), colour sensitivity can be achieved. Considering colour theory, the region of recognizable colours must be defined for the vision device. The results of our investigations into the photochemistry and electrogenesisin a seriesof BR analogs in water suspensions (Fig. 2) have allowed us to design light sensorson the basis of thesepigments incorporated in PVA dry films. Thesefilms have a large amplitude of the electrical responsesand sensitivity to different wavelengths of the excitation light beam. In our experiments, photoresponsesof films = 3 cm’ in area reached some volts at the maximum of spectrum sensitivity [7]. The dependence of the electrical photoresponse on actinic light wavelength was monitored for the films with BR ( 1) and its analogs (2 and 4) [ 71. The difference of the spectral sensitivity of samples anticipated from absorption spectrum was demonstrated. Thus, the possibility of application of BR analogs with different maximum absorption and close kinetic parameters to the construction of colour-recognition detector elements has been shown. However, the potential of BR analog-based
Table 1 Spectral parameters of some BR analogs s-oftitinalogs
NO#
-
i.
&%L.&
4rcxB-*
k&f--@
b-4
Iml
s68
412 425
3.
I
4.
Ii
&A&L..
538
400
506
410
572
415
452
g375
# The retinal analog number corresponds to the code of the BR analog in the text.
220
A.A. Khodonov et al. /Sensors
and Actuators
B 38-39
(1997)
218-221
References [ I] W. Stoeckenius, R. Lazier and R.A. Bogomolni, Bacteriorhodopsin and purple membrane of Halobacteria, Biochim. Biophys. Acta, 505 (1979) 215-279.
[2] H.R. Ivanitsky (ed.), Photosensitive Optical Registration
of Informnfiun,
Biological
Complexes
and
AN SSSR, Pushchino, 1985, p.
209. [3] C. Brauchle, N. Hampp and D. Oesterhelt, Optical applications of bacteriorhodopsin and its mutated variants, Adv. Mater., 3 (1991) 420-428. [4] B.I. Mitsner, A.A. Khodonov, E.K. Zvonkova and R.P. Evstigneeva, Analogs of retinal: synthesis and interaction with bacteriorhodopsin, Bioorgan. Khim. (Rus.), 12 (1986)
5-53.
[S] A.A. Khodonov, S.V. Eremln, J.L. Lockshin, V.I. Shvets, O.V. Den&a, L.V. Khitrina and A.D. Kaulen, Retinal analogs and their application for bacteriorhodopsin investigation, Bioorgan. Khbn. (Rus.), 22 (1996) 745-778.
+--A OH
[6] L.A. Drachev, A.D. Kaulen, L.V. Khitrina and V.P. Skulachev, Fast stagesofphotoelectric processesin biological membranes. 1. Bacteriorhodopsin, Eur. J. Biochem., 117 (1981) 461-470. [7] P. Silfsten, S. Parkkinen, J. Luostarinen, A. Khodonov, T. Jaaskelainen and J. Parkkinen, Color sensitive biosensors for imaging, Proc. 13th Int. Conf Pattern Recognition, ICPR ‘96, Vienna, Austria, 25-30 August, 1996, Vol. 3, Track C, pp, 331-335. [8] L.V. Khitina and Ts.R. Lazarova, Study of 13-cis- and all-transisomers of 4-ketobacteriorhodopsin, Biokhimiya (Rus.), 54 (1989)
136-139. [9] Z. Chen and R.R. Birge, Protein-based artificial retinas, T&tech., 11 (1993)
292-300.
[lo] K. Fukuzawa, Motion-sensitive position sensor using bacteriorhodopsin, Appl. Opt., 33 (1994) ‘1489-7495. [ 1l] Z. Chen, A. Lewis, H. Takei and I, Nebenzahl, Bacteriorhodopsin oriented in polyvinyl alcohol films as an erasable optical storage medium, Appl. Opt., 30 (1991) 5188-5196. [ 121 Q. Wang-Song, C. Zhang, R. Blumer, R.B. Gross, Z. Chen and R.R. Birge, Chemically enhanced bacteriorhodopsin thin-film spatial light modulator, Opt. Mt., IS (1993) 1373-1375. [ 131 Z. Chen, A. Lewis, J. Kumar, S. Tripathy, K. Marx, J. Akkara and D. Kaplan, Second harmonic generation of bactetiorhodopsin and its application for three-dimensional optical memory, Mater. Res. Sot. Synp. Proc., 330 (1994) 263-268. [ 141 N. Hampp, R. Thoma, C. BrauchIe, F.-H. Kreuzer, R. Maurer and D. Oesterhelt, Bacteriorhodopsin variants for optical information processing: a new approach in material science, AIP Conf; Proc., 262 (1992) 181-190. [ 151 K. Tanabe, M. Hikuma, L. Soomi, ‘1. Iwaski, E. Tamiyaand I. Karube, Photoresponse of a reconstituted membrane containing bacteriorhodopsin observed by using an ion-selective field effect transistor, J. Biotech., 10 (1989) 127-134. [16] T. Miyasaka and K. Koyama, Image sensing and processing by a bacteriorhodopsin-based artificial photoreceptor, Appl. Opt., 32 (1993) 63716379.
~lOOpS-&40
mS4
55
4
Fig. 2. Light laser flash-induced (h = 532 nm, t,,* = 15 ns, energy in green light = 50 mJ) optical responsesin water suspensionsof the BR analogs at room temperature (the moment of the flash is indicated by vertical arrows). l-6, optical density changesin arbitraq units (1-5 at 400 nm, 6 at 380 nm). Medium: 100 mM NaCI, 5 mM MES, 3 mM potassium citrate, pH 6.
chips is much wider than this. BR analogs are promising components for various branches of molecular bioelectronics [ 2,3,7,9-161.
Biographies AA. Khodonov is a senior researcher at the Department of Biotechnology at M.V. Lomonosov SAFCT. He is developing new synthetic approaches to retinoid preparation, and investigating the structure of the BR and rhodopsin chromophore centre. He received his :BS and MS degrees in bioorganic chemistry in 1980, and his Ph.D. in bioorganic chemistry in 1984 from M.V. Lomonosov SAFCT.
A.A. Khodonov
et al. /Sensors and Actuators B 38-39 (1997) 218-221
O.V. Demina is a research scientist at the A.N. 3elozersky Institute of Physico-Chemical Biology, Moscow State University (MSU) , She specializes in retinoid analog synthesis. She received her BS and MS degrees in bioorganic chemistry from M.V. Lomonosov SAPCT in 1982 and her Ph.D. in bioorganic chemistry from MSU in 1994.
221
P. Silfsten is a lecturer at Lappeenranta University of Technology and a docent of physics at the University of Joensuu. He specializes in optical spectroscopy. He received his MS and Ph.D. in physics in 1984 and 1991, respectively, from the University of Joensuu.
Institute, MSU. She specializes in BR photochemistry investigations. She received her BS and MS degrees in biology in 1977 and her Ph.D. in biochemistry from MSU in 1983.
S. Parkinnen is a research scientist at Lappeenranta University of Technology. She specializes in molecular biology. She received her BS in biochemistry in 1979, her MS in biochemistry in 1980 and her Ph.D. in microbiology in 1989, all from the University of Kuopio.
A.D. Kaulen is head of the Laboratory of Membrane Photochemistry at A.N. Belozersky Institute, MSU. He specializes in BR photochemistry investigations. He received his BS and MS degrees in biology in 1974, and his Ph.D. and Doctor of Sciences in biochemistry in 1978 and 1990, respectively, from MSU.
J. Parkinnen is a professor in information technology at Lappeenranta University of Technology. He specializes in image analysis, pattern recognition and molecular computing. He received his BS in physics in 1979, his MS in medical physics in 1982 and his Ph.D. in mathematics in 1989, all from the University of Kuopio.
L.V. Khitrina is a senior researcher at A.N. Belozersky
Sensors and Actuators B 38-39 (1997)
B
CHEMICAL
218-221
Modified bacteriorhodopsins as a basis for new optical devices A.A. Khodonov a~*,O.V. Demina b, L.V. Khitrina b, A.D. Kaulen b, P. Silfsten ‘, S. Parkkinen ‘, J. Parkkinen ‘, T. Jaaskelainen d a Department
of Biotechnology, M.V. Lomonosov State Academy of Fine Chemical Technology, Vernadskogo pr-t 86, 117571, Moscow, Russia ’ A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, 119899, Moscow, Russia ‘Department of Information Technology, Lappeenranta University of Technology, PO Box 20, FIN-53851 Lappeenranta, Finland ’ Vaisala Laboratory, University of Joensuu, PO Box 111, FIN-80101 Joensuu, Finland
Abstract The photochemical properties of various bacteriorhodopsin analogs in water suspensions and WA films have been studied and their promise for technological purposes (especially as a basis for colour-imaging and -recognition devices) is shown, Keywords:
Retinal; Bacteriorhodopsin;
Analogs; Opto-electronic
devices; Colonr-recognition
1. Introduction Bacteriorhodopsin (BR) is a light-driven proton pump isolated from Halobacterium saEinarium that weighs 26 kD, discovered in 1971 by Oesterhelt and Stoeckenius. BR is localized in specialized areas of the cell membrane, called purple membranes (PM). It has a chromophore group: a retinal protonated Schiff base bounded by an E-amino group to Lys2i6 -residue [ 13. After absorbing a quantum of light, BR undergoes spectral changes (the photocycle is shown in Fig. 1) and conformational changes in its chromophore and protein part. The main key states (Fig. 1) are the B-state (steady-state, h,, = 570nm, e=63 OOOM-‘cm-‘) andthe M-state (h,, = 412nm, ~=34000M-‘cm-‘). BR’s unique advantages for technological use are: ( 1) availability in bulk amounts, easy isolation and a relatively low price; (2) an extreme stability of the proton pump to illumination, oxygen, a wide range of pH values (O-11), temperature ( - 196 to 7O”C), concentrations of salt and water-glycerol mixtures; (3) preparation of dry film and incorporation into some polymer matrices; (4) the possibility of designing both optical and electric devices using its photocycle or charge-dislocation properties; (5) high quantum efficiency; (6) an extremely fast ‘primary event’ (B + J) of 0.5 ps; (7) the existence of long-living photocycle intermediates (Fig. 1) and the possibility of their slowing down
devices
further by replacement of certain amino-acid residues [ 31, by replacement of the natural retinal chromophore with analogs [ 451, by influence of low temperature, strong external electrical fields, variation of the humidity level or #I, and by action of some chemical additives and reagents. In 1980 the first priority studies on the practical use of BR films as optical memory element:; were carried out in Russia in the Institute of Biophysics RAS at Pushchino in cooperation with the Department of Biotechnology at the State Academy of Fine Chemical Technology [ 21. It was found that BR is a particularly promising photochromic material with a high reversibility quotient, surpassing many materials currently in
M-state * Corresponding author. [email protected]
Tel./Fax:
+7095
437
5.500.
E-mail:
0925-4005/97/$17.00 0 1997 Elsevier Science S.A. All rights reserved P11s0925-4005(97)00074-9
Fig. 1. Photocycle of BR (a water suspension of purple membrane at room temperature and neutral pH) .
A.A. Khodonov et al. /Sensors and Actuators B 38-39 (1997) 218-221
use.The main goal of this work is the comparison of modified analogs of BR as possible materials for new opto-electronic devices.
2. Experimental
Retinal and BR analogs were prepared by methods usedin Ref. [ 51. For investigation of the BR analogs’ photocycle in water suspension, we used a single-beam flash spectrophotometer [ 61. Short laser flashes were used for exciting BR, inducing only one turn of the BR photocycle. Two monochromators before and after the samples were used for filtration of the monitoring beam. Polyvinylalcohol-BR analog films were depositedon conducting glass. The films were covered by a thin layer of gold and a wire was attached to this layer by a drop of silver paint. The electrical responsesof these chips were measuredunder constant illumination and after flashes, both with different wavelengths [ 71.
3. Results and discussion
Our approach includes replacing the natural BR chromophore, retinal, with its analogs [4,5]. We investigated the photocycle of BR analogs in water suspension.Theproperties of the most promising analogs were also investigated after their inclusion in the dry films. At present the interactions of more than 300 polyenic compounds with bacterioopsin have been tested; of these approximately one third were first synthesized and investigated by us. This approach hasextremely important advantages: it makes wide variation of the B- and M-state A,, (for the B-state: 450 to 625 nm) possible, see Table 1. Fig. 2 shows typical curves of the M-state formation and relaxation for thesepigments. Note that the negative band of the differential photoinduced spectrum is similar to the absorption band. The quantum efficiency of the M-state in the photocycle of the most efficient BR analogs (2-5,7, 8) is more than half of the value for BR. Some BR analogs demonstrate deceleration of the M-state + B-state pathway (see for example, Fig. 2, curves 4-6). However, if the N --) BR transition is significantly slower than M +N (Fig. 1) , regeneration of the B-state is slower than the relaxation of the M-state, for example, in BR analog (4) [ 81. The BR analogs studied are promising for use in a new opto-electronic device, which will be used as an element for an optical computer memory as well as for the construction of the colour-image-recognition detector. The photocycle retardation that is observed in some BR analogs is useful for the manufacture of computer memory elements with lightregulated input and output of the information. Rhodopsin is a protein that is responsible for light detection in the human eye. BR is a similar pigment with close width and structure of the absorption and bleaching spectrum. Taking into
219
account that BR is a much more stable molecule than rhodopsin, the former allows BR to be used in technical devices. The reversibility of the BR photocycle makes it possible to use these devices for quite a long time. When different BR analogs are used in matrix elements (pixels), colour sensitivity can be achieved. Considering colour theory, the region of recognizable colours must be defined for the vision device. The results of our investigations into the photochemistry and electrogenesisin a seriesof BR analogs in water suspensions (Fig. 2) have allowed us to design light sensorson the basis of thesepigments incorporated in PVA dry films. Thesefilms have a large amplitude of the electrical responsesand sensitivity to different wavelengths of the excitation light beam. In our experiments, photoresponsesof films = 3 cm’ in area reached some volts at the maximum of spectrum sensitivity [7]. The dependence of the electrical photoresponse on actinic light wavelength was monitored for the films with BR ( 1) and its analogs (2 and 4) [ 71. The difference of the spectral sensitivity of samples anticipated from absorption spectrum was demonstrated. Thus, the possibility of application of BR analogs with different maximum absorption and close kinetic parameters to the construction of colour-recognition detector elements has been shown. However, the potential of BR analog-based
Table 1 Spectral parameters of some BR analogs s-oftitinalogs
NO#
-
i.
&%L.&
4rcxB-*
k&f--@
b-4
Iml
s68
412 425
3.
I
4.
Ii
&A&L..
538
400
506
410
572
415
452
g375
# The retinal analog number corresponds to the code of the BR analog in the text.
220
A.A. Khodonov et al. /Sensors
and Actuators
B 38-39
(1997)
218-221
References [ I] W. Stoeckenius, R. Lazier and R.A. Bogomolni, Bacteriorhodopsin and purple membrane of Halobacteria, Biochim. Biophys. Acta, 505 (1979) 215-279.
[2] H.R. Ivanitsky (ed.), Photosensitive Optical Registration
of Informnfiun,
Biological
Complexes
and
AN SSSR, Pushchino, 1985, p.
209. [3] C. Brauchle, N. Hampp and D. Oesterhelt, Optical applications of bacteriorhodopsin and its mutated variants, Adv. Mater., 3 (1991) 420-428. [4] B.I. Mitsner, A.A. Khodonov, E.K. Zvonkova and R.P. Evstigneeva, Analogs of retinal: synthesis and interaction with bacteriorhodopsin, Bioorgan. Khim. (Rus.), 12 (1986)
5-53.
[S] A.A. Khodonov, S.V. Eremln, J.L. Lockshin, V.I. Shvets, O.V. Den&a, L.V. Khitrina and A.D. Kaulen, Retinal analogs and their application for bacteriorhodopsin investigation, Bioorgan. Khbn. (Rus.), 22 (1996) 745-778.
+--A OH
[6] L.A. Drachev, A.D. Kaulen, L.V. Khitrina and V.P. Skulachev, Fast stagesofphotoelectric processesin biological membranes. 1. Bacteriorhodopsin, Eur. J. Biochem., 117 (1981) 461-470. [7] P. Silfsten, S. Parkkinen, J. Luostarinen, A. Khodonov, T. Jaaskelainen and J. Parkkinen, Color sensitive biosensors for imaging, Proc. 13th Int. Conf Pattern Recognition, ICPR ‘96, Vienna, Austria, 25-30 August, 1996, Vol. 3, Track C, pp, 331-335. [8] L.V. Khitina and Ts.R. Lazarova, Study of 13-cis- and all-transisomers of 4-ketobacteriorhodopsin, Biokhimiya (Rus.), 54 (1989)
136-139. [9] Z. Chen and R.R. Birge, Protein-based artificial retinas, T&tech., 11 (1993)
292-300.
[lo] K. Fukuzawa, Motion-sensitive position sensor using bacteriorhodopsin, Appl. Opt., 33 (1994) ‘1489-7495. [ 1l] Z. Chen, A. Lewis, H. Takei and I, Nebenzahl, Bacteriorhodopsin oriented in polyvinyl alcohol films as an erasable optical storage medium, Appl. Opt., 30 (1991) 5188-5196. [ 121 Q. Wang-Song, C. Zhang, R. Blumer, R.B. Gross, Z. Chen and R.R. Birge, Chemically enhanced bacteriorhodopsin thin-film spatial light modulator, Opt. Mt., IS (1993) 1373-1375. [ 131 Z. Chen, A. Lewis, J. Kumar, S. Tripathy, K. Marx, J. Akkara and D. Kaplan, Second harmonic generation of bactetiorhodopsin and its application for three-dimensional optical memory, Mater. Res. Sot. Synp. Proc., 330 (1994) 263-268. [ 141 N. Hampp, R. Thoma, C. BrauchIe, F.-H. Kreuzer, R. Maurer and D. Oesterhelt, Bacteriorhodopsin variants for optical information processing: a new approach in material science, AIP Conf; Proc., 262 (1992) 181-190. [ 151 K. Tanabe, M. Hikuma, L. Soomi, ‘1. Iwaski, E. Tamiyaand I. Karube, Photoresponse of a reconstituted membrane containing bacteriorhodopsin observed by using an ion-selective field effect transistor, J. Biotech., 10 (1989) 127-134. [16] T. Miyasaka and K. Koyama, Image sensing and processing by a bacteriorhodopsin-based artificial photoreceptor, Appl. Opt., 32 (1993) 63716379.
~lOOpS-&40
mS4
55
4
Fig. 2. Light laser flash-induced (h = 532 nm, t,,* = 15 ns, energy in green light = 50 mJ) optical responsesin water suspensionsof the BR analogs at room temperature (the moment of the flash is indicated by vertical arrows). l-6, optical density changesin arbitraq units (1-5 at 400 nm, 6 at 380 nm). Medium: 100 mM NaCI, 5 mM MES, 3 mM potassium citrate, pH 6.
chips is much wider than this. BR analogs are promising components for various branches of molecular bioelectronics [ 2,3,7,9-161.
Biographies AA. Khodonov is a senior researcher at the Department of Biotechnology at M.V. Lomonosov SAFCT. He is developing new synthetic approaches to retinoid preparation, and investigating the structure of the BR and rhodopsin chromophore centre. He received his :BS and MS degrees in bioorganic chemistry in 1980, and his Ph.D. in bioorganic chemistry in 1984 from M.V. Lomonosov SAFCT.
A.A. Khodonov
et al. /Sensors and Actuators B 38-39 (1997) 218-221
O.V. Demina is a research scientist at the A.N. 3elozersky Institute of Physico-Chemical Biology, Moscow State University (MSU) , She specializes in retinoid analog synthesis. She received her BS and MS degrees in bioorganic chemistry from M.V. Lomonosov SAPCT in 1982 and her Ph.D. in bioorganic chemistry from MSU in 1994.
221
P. Silfsten is a lecturer at Lappeenranta University of Technology and a docent of physics at the University of Joensuu. He specializes in optical spectroscopy. He received his MS and Ph.D. in physics in 1984 and 1991, respectively, from the University of Joensuu.
Institute, MSU. She specializes in BR photochemistry investigations. She received her BS and MS degrees in biology in 1977 and her Ph.D. in biochemistry from MSU in 1983.
S. Parkinnen is a research scientist at Lappeenranta University of Technology. She specializes in molecular biology. She received her BS in biochemistry in 1979, her MS in biochemistry in 1980 and her Ph.D. in microbiology in 1989, all from the University of Kuopio.
A.D. Kaulen is head of the Laboratory of Membrane Photochemistry at A.N. Belozersky Institute, MSU. He specializes in BR photochemistry investigations. He received his BS and MS degrees in biology in 1974, and his Ph.D. and Doctor of Sciences in biochemistry in 1978 and 1990, respectively, from MSU.
J. Parkinnen is a professor in information technology at Lappeenranta University of Technology. He specializes in image analysis, pattern recognition and molecular computing. He received his BS in physics in 1979, his MS in medical physics in 1982 and his Ph.D. in mathematics in 1989, all from the University of Kuopio.
L.V. Khitrina is a senior researcher at A.N. Belozersky