• Journal of Microbiology and Biotechnology
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• 제16권9호
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• pp.1441-1447
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• 2006

The light perception and phototransformation of phytochromes are the first process of the phytochrome-mediated light signal transduction. The chromophore ligation and its photochromism of various site-specific and deletion mutants of pea phytochrome A and bacterial phytochrome-like protein (Cph1) were analyzed in vitro. Serial truncation mutants from the N-terminus and C-terminus indicated that the minimal N-terminal domain for the chromophore ligation spans from the residue 78 to 399 of pea phytochrome A. Site-specific mutants indicated that several residues are critical for the chromophore ligation and/or photochromism. Histidine-324 appears to serve as an anchimeric residue for photochromism through its H-bonding function. Isoleucine-80 and arginine-383 playa critical role for the chromophore ligation and photochromism. Arginine-383 is presumably involved in the stabilization of the Pfr form of pea phytochrome A. Apparently, the amphiphilic ${\alpha}$-helix centered around the residue-391 is in the chromophore pocket and critical for the chromophore ligation.

• 한국염색가공학회지
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• 제3권3호
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• pp.1-5
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• 1991

Cationic azo dyes were synthesized by coupling aniline and its derivatives with 2,4-dimethyl imidazole as a coupler, and their photochromic behavior was investigated. The dyes exhibited little photochromism on wool, but to a considerable degree on Dacron T92(anionic modified polyester), the photochromism being prominent for the dye with electron-releasing substituent on diazo component. Little photochromism on wool can be attributed to a decreased mobility of dye by the various interactions between the dye and wool molecules, which interferes the cis-trans isomeriation of dye. On Dacron T92 there can not be any obstacle for the cis-trans isomerization of dye, hence reversible color change may occur. The electron-releasing substituent on diazo component may be helpful for the photochromism of dye by increasing the n-electron density of phenyl ring, which can stabilize the cis-form of the dye by the interaction with the positive charge of imidazole ring.

• 한국안광학회지
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• 제8권1호
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• pp.59-64
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• 2003

Photochoromic lens에 광을 조사하면 darkening 상태와 fading상태에서photo-transmittance는 감소한다. 광의 조사를 제거하면 fading 상태가 되어 photo-transmittance는 원래 상태로 회복하는 가역과정을 갖는다. 자체 제작한 Photochoromic lens에서 darkening과 fading 과정에서 Photochromism의 분광측색계를 이용하여 CIE $L^*a^*b^*$의 색 좌표을 얻는다. darkening과 fading상태에서 색 좌표($a^*-b^*$)는 일차 곡선이고 (-) 기울기를 이며, 선형적으로 변한다. 색 좌표 이동량은 Blue ${\rightarrow}$ Yellow, Red ${\rightarrow}$ Green형태이다. fading상태에서 색 좌표는 darkening 상태보다 $b^*$ 값이 낮고, Photochromism 좌표의 이동은 darkening 상태와 반대로 이동한다. Photochoromic lens에 대한 Photochoromism 평가 방법은 darkening과 fading에 대한 색 좌표 이동으로 이용 할 수 있다.

• Journal of Photoscience
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• 제7권4호
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• pp.131-133
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• 2000

A Styrene-derived polymer having pendent phenoxyanthraquinones for photochromism was prepared by AIBN-initiated radical polymerization. Syntgesus of the monomers was straightforward and the polymer was obtained in 65% yield. Photoinduced rearrangement from the “trans” quinone forms to the “ana” quinone forms readily occurred both in solution and in film when the polymer was irradiated with UV light.

• Bulletin of the Korean Chemical Society
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• 제24권4호
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• pp.441-445
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• 2003

We synthesized three copolymers bearing photochromic spiropyran dye and chalcone moiety in the side chain for studying the dynamic properties of their photochromism. They contain methacrylate-spiropyran (MAspiropyran) and methacrylate-chalcone (MA-chalcone) with the different concentration. The photosensitivity of the newly synthesized copolymers was investigated by using UV-Vis absorption spectroscopy. We observed photodimerization and photochromic behavior under UV irradiation at the same time. The effect of photocrosslink on the rate and stability of photochromism in three copolymers was considered in this study. This study might be helpful to design photochromic materials for irreversible optical memory by virtue of photocrosslinking reaction.

• Macromolecular Research
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• 제13권3호
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• pp.180-186
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• 2005

A novel bifunctional dye composed of spirobenzopyran and a cinnamoyl moiety was prepared and its photochromic behavior under the illumination of monochromatic UV light was investigated. This colorless bifunctional dye exhibits typical photochromism in both the film and in solution, through the structural and geometrical transformation from spirobenzopyran to merocyanine accompanied by a photocrosslinking reaction between the cinnamoyl moieties. Two kinds of photochemical reaction were selectively achieved by irradiation with monochromatic UV light at wavelengths of 275 and 365 nm, respectively. The effect of the selective photochemical reaction on the photochromism of the dye and its decaying behavior was investigated.

• Bulletin of the Korean Chemical Society
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• 제29권4호
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• pp.827-832
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• 2008

A new diarylethene compound with donor and acceptor substituent was synthesized from 2,3-bis(2-methylbenzo[b]thiophene-3-yl)hexafluorocyclopentene (BTF) over 5 steps. The donor-acceptor structured BTF compound (TBTFE) showed spectral change to a longer wavelength through photochromism with a high cyclization quantum yield (0.56). The 3,4-ethylenedioxythiophene (T) and carboethoxy (E) groups directly connected to BTF unit promoted electrical change accompanied with the photoisomerization of the BTF unit. Photo-induced electrical switching was achieved from a photocell containing TBTFE doped polymer film, which showed reversible and stable current change over repeated cycles by the alternative UV/Vis irradiation, as estimated by the I-V plot.

• 한국식물학회:학술대회논문집
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• 한국식물학회 1998년도 The 12th Symposium on Plant Biotechnology Vol.12
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• pp.83-96
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• 1998

The plant pigment proteins phytochromes are a molecular light sensor or switch for photomorphogenesis involving a variety of growth and developmental responses of plants to red and far-red wavelength light. Underscoring the photomorphogenesis mediated by phytochromes is the light signal transduction at molecular and cellular levels. For example, a number of genes activated by the phytochrome-mediated signal transduction cascade have been identified and characterized, especially in Arabidopsis thaliana. The light sensor/switch function of phytochromes are based on photochromism of the covalently linked tetrapyrrole chromophore between the two photoreversible forms, Pr and Pfr. The photochromism of phytochromes involves photoisomerization of the tetrapyrrole chromophore. The "photosensor" Pr-form ("switch off" conformation) of phytochromes strongly absorbs 660 nm red light, whereas the "switch on" Pfr-conformation preferentially absorbs 730 nm far-red light. The latter is generally considered to be responsible for eliciting transduction cascades of the red light signal for various responses of plants to red light including positive or negative expression of light-responsive genes in plant nuclei and chloroplasts. In this paper, we discuss the structure-function of phytochromes in plant growth and development, with a few examples of biotechnological implications.

• 한국안광학회지
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• 제7권2호
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• pp.169-174
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• 2002

Photochromic lens의 광감성 평가 방법을 만들고, 이를 적용시키기 위하여 Photochromic lens에 UV light source을 조사하였다. UV light 광원을 조사 전과 후의 darkening과 fading 상태의 transmittance(T%)의 파장 의존성을 spectrophotometer, light source, power meter, detecter로 구성된 광학적 장치로 측정한다. 조사 직전의 최대 $T%{\times}{\lambda}$ 면적과 saturated state면적의 상대적 비율을 이용한다. Photochromic lens에서 조사시간 의존성의 평가는 darkening 효율도 ($K_d$)값 ($(1-C_1/A_1)/t_{on}$과 fading 효율도($K_f$)값 ($(C_2/A_2)/t_{on}$을 도입하였다. Darkening과 fading 상태에서 transmittance(T%)의 파장의존성은 $T_m+T_1{\exp}[-(x_0-t)/a]$의 형태를 갖는다. Photochromic lens에서 광감성의 평가 parameter Z, $K_d$, $K_f$를 적용한 결과 각 평가 지수 값을 얻을 수 있다.

• Fibers and Polymers
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• 제2권3호
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• pp.117-121
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• 2001

Liquid crystalline spiroxazine derivatives have been synthesized. The spiroxazines obtained were characterized by H-NMR, IR spectroscopy, UV and GC-MS.