• Title/Summary/Keyword: Acceptor

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Characterization of Leuconostoc mesenteroides B-742CB Dextransucrase Expressed in Escherichia coli

  • Park, Mi-Ran;Ryu, Hwa-Ja;Kim, Do-Man;Choe, Jun-Yong;John F. Robyt
    • Journal of Microbiology and Biotechnology
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    • v.11 no.4
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    • pp.628-635
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    • 2001
  • Recombinant E. coli DH5$\alpha$ harboring a dextransucrase gene (dsrB742) produced an extracellular dextransucrase in a 2% sucrose medium. The enzyme was purified by DEAE-Sepharose and Phenyl-Sepharose column chromatographies upto a 142.97-fold purification with a 11.11% recovery to near homogeneity. The enzyme had a calculated molecular mass of 168.6 kDa, which was in good agreement with the activity band of 170 kDa on a nondenaturing SDS-PAGE. An expression plasmid was constructed by inserting the dsrB742 into a pRSET expression vector. The activity after expression in E. coli BL21(DE3)pLysS increased about 6.7-fold compared to the extracellular dextransucrase from L. mesenteroides B-742CB. The expressed and purified enzyme from the clone showed similar biochemical properties (acceptor reaction, size of active dextransucrase, optimum pH, and temperature) to B-742CB dextransucrase, however, the ability to synthesize ${\alpha}$-(1$\rightarrow$3) branching decreased in comparison to that of L. mesenteroides B-742CB dextransucrase.

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Determination of Acceptor Concentration by Use of Recording Dynamics of Photorefractive Holograms Under Low-Intensity Condition in LiNbO3

  • Rhee, Bum-Ku;Kim, Bong-Gi;Shin, Seung-Ho
    • Journal of the Optical Society of Korea
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    • v.7 no.3
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    • pp.197-201
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    • 2003
  • We investigated recording dynamics of a holographic grating in the photorefractive LiNbO$_3$ crystal under the low-intensity condition of recording beams. New expressions for the space-charge field and the recording time constant were obtained by solving the Kukhtarev equations under the global space -charge field, which is induced in the previous process of recording and erasing. Their validity can be confirmed by considering the limit that the period of the grating goes to infinity both theoretically and experimentally. It was found that the new expression for the recording time constant allows us to determine acceptor concentration to be $1.2${\times}$10^{21}m^{-3}$ for pure LiNbO$_3$ crystal and 2.5${\times}$$10^{21}m^{-3}$ for the 0.1 mol% iron doped LiNbO$_3$ crystal from the measured ratio of the recording time constant under the extremely large grating condition, in which the diffusion effect can be neglected, to that under the small grating condition.

Photovoltaic Properties of Organic Solar Cell using Zinc phthalocyanine(ZnPc)/$C_{60}$ devices (Zinc phthalocyanine(ZnPc)/$C_(60)$ 소자를 이용한 유기 광소자의 광기전특성)

  • Lee, Ho-Sik;Hur, Sung-Woo;Lee, Won-Jae;Shin, Hoon-Kyu;Kim, Tae-Wan;Kwon, Young-Soo
    • Proceedings of the KIEE Conference
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    • 2004.07c
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    • pp.1712-1714
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    • 2004
  • During the last 20 years organic semiconductors have attracted considerable attention due to their interesting physical properties followed by various technological applications in the area of electronics and opto-electronics. It has been a long time since organic solar cells were expected as a low-cost energy-conversion device. Although practical use of them has not been achieved, technological progress continues. Morphology of the materials, organic/inorganic interface, metal cathodes, molecular packing and structural properties of the donor and acceptor layers are essential for photovoltaic response. We have fabricated solar cell devices based on zinc-phthalocyanine(ZnPc) as donor(D) and fullerine($C_{60}$) as electron acceptor(A) with doped charge transport layers, $Alq_3$ as an electron transport or injection layer. We observed the photovoltaic characteristics of the solar cell devices using the Xe lamp as a light source.

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Extraction of electrical parameters as a function of post-annealing in organic solar cells (유기 태양전지의 후열처리온도에 따른 전기적 Parameter들의 추출)

  • Kim, Dong-Young;Kim, Ji-Hwan;Lee, Hye-Jee;Kim, Hae-Jin;Sohn, Sun-Young
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.06a
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    • pp.460-461
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    • 2009
  • We studied the effects of post-annealing treatment on poly(3-hexylthiophene)(P3HT, donor):[6,6]-phenyl $C_{61}$ butyric acid methyl ester(PCBM, acceptor) blend film as an active layer in the organic solar cells(OSCs). For the formation of the active layer, 3 wt.% P3HT:PCBM solution in chlorobenzene were deposited by spin-coating method. In order to optimize the performance of OSCs, the P3HT crystallization and the redistribution of PCBM cluster at P3HT:PCBM composition as a function of post-annealing condition from room temperature to $200^{\circ}C$ were measured by the Hall effect and the UV-vis Spectrophotometer. We thought that the improved efficiency in the OSCs with post-annealing treatment at $150^{\circ}C$ can be explained by the efficient separation or collection of the photogenerated excitons at donor-acceptor interface by P3HT crystallization.

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A Study on the Optical Property of Al-N-codoped p-type ZnO Thin Films Fabricated by DC Magnetron Sputtering Method

  • Liu, Yan-Yan;Jin, Hu-Jie;Park, Choon-Bae
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.06a
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    • pp.319-320
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    • 2009
  • In this study, high-quality Al-N doped p-type ZnO thin films were deposited on n-type Si (100) wafer or Si coated with buffer layer by DC magnetron sputtering in the mixture of $N_2$ and $O_2$ gas. The target was ceramic ZnO mixed with $Al_2O_3$ (2 wt%). The p-type ZnO thin film showed higher carrier concentration $2.93\times10^{17}cm^{-3}$, lower resistivity of $5.349\;{\Omega}cm$ and mobility of $3.99\;cm^2V^{-1}S^{-1}$, respectively. According to PL spectrum, the Al donor energy level depth ($E_d$) of Al-N codoped p-type ZnO film was reduced to about 51 meV, and the N acceptor energy level depth ($E_a$) was reduced to 63 meV, respectively.

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Kinetics and Mechanism for Alkaline Hydrolysis of C. I. Disperse Blue 79 (C. I. Disperse Blue 79의 알칼리 가수분해 반응속도 및 반응메카니즘)

  • Park, Geon Yong;Park, Chang Hyeok;Park, Byeong Gi
    • Textile Coloration and Finishing
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    • v.13 no.5
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    • pp.24-24
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    • 2001
  • Kinetics and mechanism for alkaline hydrolysis of C. I. Disperse Blue 79(B-79) which is 4-N, N-diacetoxyethyl-2-acylamino-5-ethoxy -2′-bromo-4′,6′-dinitroazobenzene were investigated. The color strength of B-79 in acetone/water solutions of various NaOH concentrations decreased continuously. The hydrolysis rate of B-79 increased with increasing alkali concentration and appeared following first order reaction. The observed rate constants for various concentrations of B-79 showed similar values, and B-79 was hydrolyzed by first order reaction for dye concentration. Therefore, it was confirmed that the overall reaction follow second order kinetics and proceed via S/sub n/2 reaction. From the study on kinetics and spectrometric analysis, it was proposed that the rate determining step of the hydrolysis reaction of B-79 is the nucleophilic substitution reaction - that is the reaction of the rapid attack of $OH^{-}$ on the carbon atom, which is in acceptor ring, adjacent to azo group to break the C-N bond. And it was also found that the final hydrolysis products of B-79 include both the acceptor ring in the form of sodium salt and the donor ring possessing 4-N,N-dihydroxyethyl group converted from 4-N,N-diacetoxyethyl group.