• Journal of Photoscience
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• v.9 no.2
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• pp.1-4
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• 2002

Hula-twist is a volume-conserving photoisomerization reaction mechanism postulated in 1985 to account for the rapid photoisomerization of the retinyl chromophore in rhodopsin. The requisite stereochemical consequence of simultaneous isomerization of a double bond and an adjacent single bond has recently been demonstrated in isomerization of pre-vitamin D in an organic glass and by many other examples of organic systems already reported in the literature This paper reports the consequence in applying the mechanism to the primary photochemical process of several photosensitive biopigments: bilirubin, photoactive yellow protein, bacteriorhodopsin and rhodopsin. It is shown that the anchored nature of the chromophores must first be taken into consideration.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.114-115
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• 2000

Halobacterium halobium에서 추출한 Bacteriorhodopsin(bR)을 고분자 물질에 첨가해 박막화하였다. 이 단백질 박막 소자의 photodynamic특성을 이용하여 광 switching system을 구성하였다. 광 switch system은 pump광을 이용해 B상태와 M상태에서 축퇴4광파 혼합방식으로 구성했다. Red, blue, violet 광원을 사용하여 B상태와 M상태 격자를 형성하고 on-off되는 위상공액신호를 측정했다. (중략)

• Journal of Photoscience
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• v.9 no.2
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• pp.317-319
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• 2002

All-optical switching has been demonstrated in bacteriorhodopsin (bR) based on nonlinear intensity induced excited state absorption. The transmission of a cw probe laser beam at 410 nm corresponding to the peak absorption of M state through a bR film is switched by a pulsed pump laser beam at 570 nm that corresponds to the maximum initial 8 state absorption. The switching characteristics have been analyzed using the rate equation approach considering all the six intermediate states (B, K, L, M, N and 0) in the bR photocycle. The switching characteristics are shown to be sensitive to life time of the M state, absorption cross-section of the 8 state at probe wavelength ($\sigma$ $\_$Bp/) and peak pump intensity. It has been shown that the probe laser beam can be completely switched off (100 % modulation) by the pump laser beam at relatively low pump powers, for $\sigma$$\_$Bp/ = O. The switching characteristics have been used to design all-optical NOT, OR, AND and the universal NOR and NAND logic gates for optical computing with two pulsed pump laser beams.

• Journal of Photoscience
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• v.9 no.2
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• pp.293-295
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• 2002

The structural stability of bacteriorhodopsin (bR) solubilized by Triton X-100 (TX-100) was studied by measuring the denaturation kinetics in the dark and under illumination, and compared with the structural stability of bR solubilized by octyl-${\beta}$-glucoside (OG). In the dark, bR solubilized by TX- 100 was more stable than bR solubilized by OG. Under illumination, bR solubilized by TX-100 showed light-induced denaturation in the same manner as bR solubilized by OG. These results in the dark well correlated with the experimental results of the visible CD band. Although solubilized bR in the TX-100 concentration range of 2-50 mM showed almost identical positive CD band and did not denature in the dark at 35$^{\circ}$C, the kinetic constant of the photobleaching increased with the increase of TX-100 concentration. These results suggested that photo-intermediates of solubilized bR are destabilized by TX-100 micelles.

• Journal of Photoscience
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• v.9 no.2
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• pp.114-117
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• 2002

Ultraviolet resonance Raman (UVRR) spectroscopy was used to elucidate the dynamic change of the protein structure of bacteriorhodopsin (BR) during the photocycle. The photointermediates minus light- adapted (LA) BR difference spectra show Trp difference signals, which are assigned to Trp189 or Trp182 on helix F by using the mutants, W182F and W189F. The Difference signals of Trp 182 indicates an increase in hydrogen bonding strength at the indole nitrogen and a large change in the side chain conformation (X$\^$2,1/ torsion angle) in the M$_1$ \longrightarrow M$_2$ transition. On the other hand, Trp189 shows an increased hydrophobic interaction. These results suggest that the tilt of helix F occurs in the M$_1$\longrightarrow M$_2$ transition. In the M$_2$ \longrightarrow N transition, the hydrophobic interaction of Trp182 decreases drastically, The decrease in hydrophobic interaction of Trp182 in the N state suggests an invasion of water molecules that promote the proton transfer from Asp96 to the Schiff base. Structural reorganization of the protein after the tilt of helix F may be important for efficient reprotonation of the Schiff base.

• Journal of Photoscience
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• v.2 no.1
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• pp.19-25
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• 1995

Picosecond time-resolved and static protein fluorescence spectra and absorption spectra of octopus rhodopsin, a photorecepting protein, are measured and compared with those of bacteriorhodopsin, a photon-induced proton pumping protein, to understand the protein conformations and functions of octopus rhodopsin and its deprotonated photocycle intermediate. The bluer and weaker absorption of retinal indicates that octopus rhodopsin is better in thermal noise suppression but less efficient in light harvesting than bacteriorhodopsin. The protein fluorescence of octopus rhodopsin shows the characteristic of Trp only and the uantum efficiency and lifetime variations may result primarily from variations in the coupling strength with the retinal. The stronger intensity by four times and larger red shift by 12 nm of fluorescence suggest that octopus rhodopsin has more open and looser structure compared with bacteriorhodopsin. Fluorescence decay profiles reveal two decay components of 300 ps (60%) and 2 ns (40%). The deprotonation of protonated Schiff's base increases the shorter decay time to 500 ps and enhances the fluorescence intensity by 20%. The fluorescence and its decay time from Trp residues near retinal are influenced more by the deprotonation. The increase of fluorescence intimates that protein structure becomes loosened and relaxed further by the deprotonation of protonated Schiff's base. The driving force of sequential changes initiated by absorption of a photon is too exhausted after the deprotonation to return the intermediate to the ground state of the begun rhodopsin form.

• 한국생물공학회:학술대회논문집
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• 2005.10a
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• pp.376-376
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• 2005

• Journal of Photoscience
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• v.2 no.2
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• pp.69-72
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• 1995

Dry orderly oriented purple membrane from Halobacterium halobium was obtained by a new technique of preparation. This oriented purple membrane film was very stable, nearly permanently, and showed long term reproducibility with respect to its photochemical behavior. In addition, we have investigated the photooptical properties in terms of the M$_{412}$ intermediate of the bacteriorhodopsin photocycle with respect to the humidity of the film. The relative optical density, i.e. its apparent concentration of the M$_{412}$ intermediate was decreased with the humidity increase as a function of the intensity of the exciting flash within our experimental range. It is suggested that the bound water molecules play an important role in the structure of the bacteriorhodopsin.

• 한국생물공학회:학술대회논문집
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• 2003.10a
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• pp.665-665
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• 2003

• Journal of Photoscience
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• v.9 no.2
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• pp.110-113
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• 2002

We demonstrate here a dynamic structure of bacteriorhodopsin (bR) as revealed by $^{13}$ C NMR studies on [3_$^{13}$ C]_,[1-$^{13}$ C]Ala- and/or Val-labeled wild type and a variety of site-directed mutants at ambient temperature. For this purpose, well-resolved (up to twelve) I$^{13}$ C NMR peaks were assigned with reference to the displacement of peaks due to the conformation-dependent I$^{13}$ C chemical shifts and reduced peak-intensities due to site-directed mutations. Revealed bR structure was not rigid as anticipated from 2D crystals of hexagonal array but a dynamically heterogeneous, undergoing a variety of local fluctuations depending upon specific site with frequency range of 10$^2$ -10$^{8}$ Hz. In particular, dynamics- dependent suppression of peaks turned out to be very sensitive to the motion of 10$^{-4}$ s and 10$^{-5}$ s interfered with frequency of magic angle spinning and proton decoupling, respectively. It is also noteworthy that such dynamic feature is strongly dependent upon the manner of 2D crystalline packing: $^{13}$ C NMR peaks of monomeric bR yielded either highly broadened or completely suppressed signals, depending upon the type of $^{13}$ C-labeled amino-acid residues.