• Journal of Photoscience
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• 제3권2호
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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.

• 한국염색가공학회지
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• 제19권3호
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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.

• 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.

• Journal of Photoscience
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• 제9권2호
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• pp.130-133
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• 2002

The last step in the photocycle of photoactive yellow protein (PYP) is a spontaneous recovery of the dark state from the active state in which the p-coumaric acid chromophore is thermally isomerized, concomitantly with the deprotona- tion of the chtomophore and the refolding of the protein moicty. For the purpose of understanding the mechanism of the thermal back-isomerization, we have investigated the rate-determining step by analyzing mutant PYPs of Met100, which was previously shown to play a major role in facilitating the reaction (1). The mutation to Lys, Leu, Ala, or Glu decelerated the dark state recovery by 1 to 3 three orders of magnitude. By evaluating temperature-dependence and pH-dependence of the kinetics of the dark state recovery, it was found that the retardation by mutations resulted from elevation of the activation enthalpy ( H$\^$┿/) and that the pKa of the chromophore, which was affected by the mutation, is in a linier correlation with the amplitude of the rate constants. It was, therefore, deduced from the correlation that the free energy for crossing the activated state in the dark recovery process is proportional to the free energy for the deprotonation of the chromophore, identifying the rate-determining step as the deprotonation of the chromophore. (1) Devanathan, S. Genick, U. K. Canestrelli, I. L. Meyer, T. E. Cusanovich, M. A. Getzoff, E. D. Tollin, G., Biochemistry 1998, 37, 11563 - 11568

• 한국세라믹학회지
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• 제46권6호
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• pp.615-620
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• 2009

The present research was performed to determine the optimal firing condition and holding time for malayaite crystal, which is responsible for the stable pink-red coloration in glaze at high temperatures, using Cr$Cl_3$ as chromophore for the synthesis of $Cr_2O_3-SnO_2-CaO-SiO_2$ system pigments. The malayaite crystal was influenced by the raw materials used for synthesis, firing temperature, and holding time. Thus there are differences in the crystal phase and in the coloration according to the condition of synthesis. When Cr$Cl_3$ was used as chromophore, the pigment could be synthesized at lower temperatures, because Cr$Cl_3$ melts at $1500{^{\circ}C}$, which is much lower than the temperature at which $Cr_2O_3$ melts (higher than $2435{^{\circ}C}$). And the employed Cr ion showed a change in oxidation state. When a mineralizer was used to improve the employment of malayaite and the Cr ion, and the low temperature was maintained at which the malayaite crystal is produced, the production of malayaite crystal was promoted and the employment of chromophore was also promoted in the oxidation state of Cr (IV). The results of the experiment showed that the optimal firing condition was 18 h of holding time at $800{^{\circ}C}$, using Cr$Cl_3$ as chromophore, followed by 2 h at the raised temperature of $1150{^{\circ}C}$. The change in coloration of the Cr (IV) employed by malayaite showed a very rich color of red. Thus it was possible to effectively synthesize sphene-pink pigments with more red tint at a low temperature.

• 한국미생물·생명공학회지
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• 제19권6호
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• pp.604-609
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• 1991

토양에서 분리한 Streptomyces nigrifaciens GMT-497호무터 G(+) bacteria에만 강한 항균활성을 갖는 항생물질 MT-497을 용매추출, silica column chromatography와 재결정화를 통하여 분리 정제하였다. MT-497의 UV, 융점, 원소분석, IR spectrum, $^1H-NMR$과 구성아미노산 분석을 통해 actinocin chromophore와 threonine, proline, methyl valine, sarcosine, aspartic acid로 구성된 peptide을 갖는 actinomvcin계열의 항생물질로 동정하였다.

• Bulletin of the Korean Chemical Society
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• 제33권1호
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• pp.137-142
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• 2012

The convergent synthetic strategy for the emissive dendrimers having the chromophore at core via the coppercatalyzed 1,3-dipolar cycloaddition reaction between alkyne and azide was described. 2,7-Diazido-9,9-dioctyl-9H-fluorene, designed to serve as the core in dendrimer, was stitched with the alkyne-functionalized Frechettype and PAMAM dendrons by the click chemistry leading to the formation of the corresponding fluorescent dendrimers in high yields. The preliminary photoluminescence studies indicated that 2,7-diazido-9,9-dioctyl-9H-fluorene showed no fluorescence due to the quenching effect from the electron-rich ${\alpha}$-nitrogen of the azido group but the dendrimers fluoresced due to the elimination of the quenching through the formation of the triazole ring.

• Journal of Photoscience
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• 제9권2호
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• pp.302-304
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• 2002

pharaonis phoborhodopsin (ppR), a photophobic sensor of haloalkaliphilic bacteria, Natronobacterium phar-aonis, has retinal as a chromophore covalently bound to Lys in G-helix via a protonated Schiff base (PSB), as is the same as bacteriorhodopsin (bR). For ppR, the corresponding counter-ion is Asp residue (Asp75) located in C-helix. Here we investigated the influence of the protonated state of this counter-ion and its location on the chromophore configuration. Under alkaline condition, the chromophore configuration of D75E mutant was analyzed by HPLC. D75E had a much larger content of 13-cis isomer: the ratio of 13-cis to all-trans was 6:4 while the wild-type had this ratio of 1 :9. On the other hand, under acidic condition where Glu was associated, D75E had no 13-cis retinal isomer. Mutants whose Asp75 was replaced by neutral amino acids (D75N and D75Q) did not contain 13-cis retinal. Furthermore, retinal isomer compositions and the change in the visible ab- sorption spectra (indicating the dissociation state of Glu75) were measured under varying pH, and these were almost the same dependencies. These results indicate that an important factor determining the 13-cis isomer content is the presence of negative charge of the counter-ion against PSB, but not the size of this residue. Com- parison between the wild-type and D75E in alkaline solutions indicates the influence of the location of the counter-ion.

• 폴리머
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• 제36권6호
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• pp.795-802
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• 2012

소수성 고분자 표면을 화학적 처리를 통해 활성화시키고 화학반응을 통해 발색단을 도입하는 연구를 진행하였다. 2-Triphenylstannylthioethyl acrylate를 자외선 조사시켜 고분자 필름을 만들었다. 필름 표면에 노출된 주석치환체를 불소이온으로 처리하여 SH를 형성함으로써 필름표면에 많은 SH를 생성시켰고 적외석 흡수스펙트럼으로 이를 확인하였다. 아크릴 유도체로 만든 발색단 물질을 노출된 SH와 반응시켜 필름 표면에 여러 발색단을 도입할 수 있었고 이를 자외선-가시광선 흡수스펙트럼으로 관찰할 수 있었다. 2-Triphenylstannylthioethyl acrylate와 tris(hydroxymethyl) ethane에서 유도된 triacrylate를 혼합하여 얻은 광경화 필름에서 단분자 함량 변화에 따른 SH의 표면 노출량을 변화시킬 수 있음을 흡수스펙트럼을 통해 관찰하였다. 유사하게, 2-tributylstannylthioethyl acrylate를 이용한 광경화 필름을 만들어 표면반응 연구를 진행하였다. 이 경우, 불소이온 처리를 통한 표면 활성화는 약 5분 이내로 빠르게 진행되었다. 이소시안 작용기를 갖는 발색단을 합성하여 필름과 반응시켜 표면에 발색단 도입하는 비교연구를 진행하였다. 아크릴 유도체가 표면 SH와 반응이 24시간 이상을 요구하는 반면 이소시안 유도체는 10분 이내에 결합반응이 완료되었다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.88.1-88.1
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• 2010

Organic dyes, because of their many advantages, such as high molar extinction coefficients, convenience of customized molecular design for desired photophysical and photochemical properties, inexpensiveness with no transition metals contained, and environment-friendliness, are suitable as photosensitizers for the Dye-sensitized Solar Cell (DSSC). The efficiency of DSSC based on metal-free organic dyes is known to be much lower than that of Ru dyes generally, but a high solar energy-to-electricity conversion efficiency of up to 8% in full sunlight has been achieved by Ito et al. using an indoline dye. This result suggests that smartly designed and synthesized metal-free organic dyes are also highly competitive candidates for photosensitizers of DSSCs with their advantages mentioned above. Recently, the performance of DSSC based on metal-free organic dyes has been remarkably improved by several groups. We had reported the novel organic dye with double electron acceptor chromophore, which was a new strategy to design an efficient photosensitizer for DSSC. To verify the strategy, we synthesized organic dyes whose geometries, electronic structures and optical properties were derived from preceding density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations. In this paper, we successfully synthesized the chromophore containing multi-acceptor push-pull system from triphenylamine with thiophene moieties as a bridge unit. Organic dyes with a single electron acceptor and double acceptor system were also synthesized for comparison purposes. The photovoltaic performances of these dyes were compared, and the recombination dark current curves and the incident photon-to-current (IPCE) efficiencies were also measured in order to characterize the effects of the multi-anchoring groups on the open-circuit voltage and the short-circuit current. In order to match specifications required for practical applications to be implemented outdoors, light soaking and thermal stability tests of these DSSCs, performed under $100mWcm^{-2}$ and $60^{\circ}C$ for 1000h.