• Journal of Microbiology and Biotechnology
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• v.16 no.9
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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.

• Journal of the Korean Chemical Society
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• v.26 no.2
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• pp.99-106
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• 1982

The ketone chromophore of 1-Acetyl-1-methyl-2-cyclopentene (1) was replaced by nitrile, carboxylic acid and acetamide group, and their photochemical reactions were investigated. While the ${\beta},\;{\gamma}$-unsaturated ketone 1 afforded 1,2 ar 1,3-Acyl shift product, these replaced chromophores did not afford any monomeric rearranged products. 1-Cyano-1-methyl-2-cyclohexene also afforded no product anology of the 1,2-acyl shift reaction. The replacement of the ketone chromophore by nitrile, carboxylic acid and carboxamide has greatly altered the photochemistry of ${\beta},\;{\gamma}$-unsaturated ketones.

• Macromolecular Research
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• v.12 no.5
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• pp.484-489
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• 2004

We have prepared a phenothiazine-based nonlinear optical (NLO) chromophore that displays a fairly high microscopic nonlinearity through intramolecular charge transfer. The phenothiazine unit plays important roles of contributing its high electron donating ability and connecting the resonance pathway through a conjugative effect in the cyclized ring adjacent to the aromatic ring. Theoretical calculations and an absorption spectroscopic study provided useful information concerning the microscopic nonlinearity of the chromophores. We investigated the electro-optic (EO) properties of the guest-host systems in amorphous polycarbonate containing the synthesized chromophores at different concentrations under different poling temperatures. A real-time pole and probe method provided a much greater amount of information regarding how the EO properties can arise and how they can be optimized.

• Bulletin of the Korean Chemical Society
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• v.30 no.4
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• pp.882-886
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• 2009

The electrode contact poling is one of the efficient tools to induce a stable polar order of nonlinear optical (NLO) chromophores in the solid film. Self-assembled NLO chromophores with high electro-optic (E-O) activities were utilized for quantitative determination of the chromophore order induced under contact poling by spectroscopic changes. We found that NLO chromophores rarely decompose under the high electric field during contact poling. The absorption spectra were de-convoluted into a sum of Gaussian components to separate energy transitions for a binary composite system which contains a secondary guest chromophore AJC146 in the self-assembled chromophore HDFD. Poling efficiency was significantly improved in the binary system compared to the individual components.

• Journal of Photoscience
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• v.3 no.2
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• pp.71-76
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• 1996

Anil K. Singh, Mrunalini M. Kapil, Department of Chemistry, Indian Institute of Technology Bombay - 400076, INDIA Purple membrane (PM, $\lambda$$_{max}$ 570 nm) of H. halobium on treatment with sulphuric acid changes its colour to blue ($\lambda$$_{max}$ 608 nm). The purple chromophore can be regenerated from the blue chromophore by exogeneous addition of anions such as CI$^-$ and HPO$_4^{2-}$. Chloride ion is found to be more effective than the dibasic phosphate ion in regenerating the purple chromophore. Nevertheless, one thing common to the anion regeneration is that both CI$^-$ and HPO$_4^{2-}$ show marked pH effect. At pH 1.0 the efficiency of regeneration of the purple chromophore is greater than at pH 2.0, for the same anion concentration. Fluorescence and circular dichroic studies indicate that the proteins do not undergo drastic changes at the secondary' or tertiary structure level and the native structure is preserved during this transition. However, chromophoric-site interactions between retinal and the apoprotein are affected during this colour transition. A molecular mechanism is advanced for this transition.

• Textile Coloration and Finishing
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• v.19 no.3
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• pp.6-11
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• 2007

The indigoid-type dyes based on isatin $\alpha-chloride$ were synthesized and the dyes were discussed with relevance to the "H-chromophore" or "cross-conjugated chromophore". The color-changed properties of the dyes were also investigated by means of visible absorption spectra. The novel dyes from isatin $\alpha-chloride$ are of theoretical interest and such dyes can be used as continuous pH indicators in acid/base titrimetric analyses.

• Bulletin of the Korean Chemical Society
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• v.6 no.5
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• pp.300-303
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• 1985

To understand the nature of the linkage between chromophore and apoprotein in the photoreceptor of Stentor coeruleus, a conformational analysis has been carried out on the dipeptide amides linked to the chromophore hypericin using an empirical potential function. The conformational energies for the dipeptide amides of Glu (OHyp)-X-NHMe, where X = Leu, Phe, Asp, and Tyr, have been calculated to investigate the influence of peptide residues in stabilizing conformers. It was found that the increase of acidity of hypericin upon photoexcitation may be facilitated by the formation of intramolecular hydrogen bonds between hydroxyl groups of hypericin and carbonyl groups of peptide backbone, and that the stabilities of dipeptide amides do not significantly depend on peptide residues directly linked to chromophore.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.132-132
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• 2003

Second-order nonlinear optical(NLO) materials have been extensively studied for applications in photonic devices, such as frequency doubling and electro-optical(EO) modulation, because of their large optical nonlinearity, excellent processibility, low dielectric constant, and high laser damage thresholds. The poling behaviour of NLO chromophore in organic/inorganic matrixes showed the randomization of poled NLO chromophore in the absence of poling Held. The liquid crystal molecules in a droplet showed a long-range orientational order along a director. Therefore, liquid crystal effects on poling behaviour of NLO chromophore dispersed in organically modified inorganic sol-gel materials were investigated. Using sol-gel process for the development of NLO material has received increasing attention, Organically modifked inorganic NLO sol-Eel materials are obtained via incorporation of the organic NLO active chromophore into an alkoxysilane based inorganic network. One of the most important thing in this works was that tetraethoxysilane(TEOS) and methyltrimathoxysilane(HTMS) were used as precursor followed by hydrolysis and condensation without using any acidic catalyst during the process. The NLO chromophores in the liquid crystal nanodomains were well mixed with I/O hybrid matrix, deposited on transparent ITO-coated glasses. The poling behaviour of liquid crystal effects of NLO chromophore dispersed in I/O hybrid matrix were investigated by UV-vis spectroscopy. Size distribution and morphology of the NLO chromophores doped in the liquid crystal nanodomains dispersed in I/O hybrid matrix were investigated by SEM.

• Bulletin of the Korean Chemical Society
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• v.27 no.12
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• pp.1940-1960
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• 2006

Theoretical descriptions of two-dimensional (2D) vibrational and electronic spectroscopy are presented. By using a coupled multi-chromophore model, some examples of 2D spectroscopic studies of peptide solution structure determination and excitation transfer process in electronically coupled multi-chromophore system are discussed. A few remarks on perspectives of this research area are given.

• Proceedings of the Optical Society of Korea Conference
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• 2002.11a
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• pp.274-275
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• 2002