• Bulletin of the Korean Chemical Society
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• 제18권12호
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• pp.1260-1264
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• 1997

The phase-transfer reagent (PTC), ethyl tri-n-octylammonium bromide (ETABr), strongly catalyzes the reaction of p-nitrophenyldiphenylphosphinate (p-NPDPIN) with benzimidazole (BI) and its anion (BI-). In ETABr solutions, the dephosphorylation reactions exhibit higer than first order kinetics with respect to the nucleophile, BI, and ETABr, suggesting that reactions are occuring in small aggregates of the three species including the substrate, whereas the reaction of p-NPDPIN with OH- is not catalyzed by ETABr. This behavior for the drastic rate-enhancement of the dephosphorylation is refered as 'aggregation complex model' for reactions of hydrophobic organic phosphinates with benzimidazole in hydrophobic quarternary ammonium salt solutions.

• 한국환경과학회지
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• 제24권8호
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• pp.981-992
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• 2015

This study is mainly focused on micellar effect of tetradecyltrimethyl ammonium bromide(TTABr) solution including alkylbenzimidazole(R-BI) on dephosphorylation of diphenyl-4-nitrophenylphosphinate(DPNPIN) in carbonate buffer(pH 10.7). Dephosphorylation of DPNPIN is accelerated by $BI^{\Theta}$ ion in $10^2$ M Carbonate buffer(pH 10.7) of $4{\times}10^{-4}$ M TTABr solution up to 80 times as compared with the reaction in Carbonate buffer by no benzimidazole(BI) solution of TTABr. The value of pseudo first order rate constant($k_{\psi}$) of the reaction in TTABr solution reached a maximum rate constant increasing micelle concentration. The reaction mediated by $R-BI^{\Theta}$ in micellar solutions are obviously slower than those by $BI^{\Theta}$, and the reaction rate were decreased with increase of lengths of alkyl groups. It seems due to steric effect of alkyl groups of $R-BI^{\Theta}$ in Stern layer of micellar solution. The surfactant reagent, TTABr, strongly catalyzes the reaction of DPNPIN with R-BI and its anion($R-BI^{\Theta}$) in Carbonate buffer(pH 10.7). For example, $4{\times}10^{-4}$ M TTABr in $1{\times}10^{-4}$ M BI solution increase the rate constant($k_{\psi}=99.7{\times}10^{-4}1/sec$) of the dephosphorylation by a factor ca. 28, when compared with reaction($k_{\psi}=3.5{\times}10^{-4}1/sec$) in BI solution(without TTABr). And no TTABr solution, in BI solution increase the rate constant($k_{\psi}=3.5{\times}10^{-4}1/sec$) of the dephosphorylation by a factor ca. 39, when compared with reaction ($k_{\psi}=1.0{\times}10^{-5}1/sec$) in water solution(without BI).

• 한국환경과학회지
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• 제14권2호
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• pp.241-249
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• 2005

This study deals with micellar effects on dephosphorylation of diphenyl-4- nitrophenylphosphate (DPNPPH), diphenyl-4-nitrophenylphosphinate (DPNPlN) and isopropylphenyl-4-nitrophenyl phosphinate (IPNPlN) mediated by $OH^\Theta$ or o-iodosobenzoate ion $(IB^\Theta)$ in aqueous and CTAX solutions. Dephosphorylation of DPNPPH, DPNPIN and IPNPIN mediated by $OH^\Theta$ or o-iodosobenzoate ion $(IB^\Theta)$ is relatively slow in aqueous solution. The reactions in CTAX micellar solutions are, however, much accelerated because CTAX micelles can accommodate both reactants in their Stem layer in which they can easily react, while hydrophilic $OH^\Theta\;(or\;IB^\Theta)$ and hydrophobic substrates are not mixed in water. Even though the concentrations $(>10^{-3}\;M)\;of\;OH^\Theta\;(or\;IB^\Theta)$ in CTAX solutions are much larger amounts than those $(6\times10^{-6}\;M)$ of substrates, the rate constants of the dephosphorylations are largely influenced by the change of concentration of the ions, which means that the reactions are not followed by the pseudo first order kinetics. In comparison to effect of the counter ions of CTAX in the reactions, CTACI is more effective on the dephosphorylation of substrates than CTABr due to easier expelling of $Cl^\Theta$ ion by $OH^\Theta\;(or\;IB^\Theta)$ ion from the micelle, because of easier solvation of $Cl^\Theta$ ion by water molecules. The reactivity of IPNPlN with $OH^\Theta\;(or\;IB^\Theta)$ is lower than that of DPNPlN. The reason seems that the 'bulky' isopropyl group of IPNPIN hinders the attack of the nucleophiles.

• BMB Reports
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• 제28권6호
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• pp.552-555
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• 1995

Treatment of microsomal vesicles isolated from etiolated Pisum sativum L cv. Alaska epicotyl tissue with agents inhibiting protein dephosphorylation, namely NaF and/or ATP, resulted in increased binding of the phytotropin NPA to the putative auxin efflux carriers localized on the plasma membrane. The phytotropin effect was especially conspicuous if the vesicles were simultaneously treated with Triton X-100. Kinetic analysis of the binding indicated the existance of two distinct sites for NPA, each having different affinities. Increased binding of the phytotropin to the membrane where protein dephosphorylation was inhibited was attributable to the increased ligand affinity of both sites. Treatment of tissue segments with flubride was found to enhance in vivo auxin transport. Implications of covalent modification of the auxin efflux carrier complex for the regulation of membrane transport of auxin molecules are discussed.

• Bulletin of the Korean Chemical Society
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• 제18권4호
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• pp.428-432
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• 1997

The dephosphorylation specificity of protein phosphatase 2A (PP2A), calcineurin (PP2B) and protein phosphatase 2C (PP2C) were studied in vitro using myelin basic protein (MBP) as a model substrate which was fully phosphorylated at multiple sites by protein kinase C (PKC) or cyclic AMP-dependent protein kinase (PKA). In order to determine the site specificity of phosphates in myelin basic protein, the protein was digested with trypsin and the radioactive phosphopeptide fragments were isolated by high performance liquid chromatography (HPLC) on reversed-phase column. Subsequent analysis and/or sequential manual Edman degradation of the purified phosphopeptides revealed that Thr-65 and Ser-115 were most extensively phophorylated by PKA and Ser-55 by PKC. For the dephosphorylation kinetics, the phosphorylated MBP was treated with calcineurin or PP2C with various time intervals and the reaction was terminated by direct tryptic digest. Both Thr-65 and Ser-115 residues were dephosphorylated more rapidly than any other ones by phosphatases. However it can be differentiated further by first-order kinetics that the PP2B dephosphorylated both Thr-65 and Ser-115 with almost same manner, whereas PP2C dephosphorylated somewhat preferentially the Ser-115.

• 한국환경과학회지
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• 제21권5호
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• pp.585-596
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• 2012

This study is mainly focused on micellar effect of cetyltrimethyl ammonium bromide(CTABr) solution including alkylbenzimidazole(R-BI) on dephosphorylation of isopropyl-4-nitrophenylphosphinate(IPNPIN) in carbonate buffer(pH 10.7). The reactions of IPNPIN with R-$BI^{\ominus}$ are strongly catalyzed by the micelles of CTABr. Dephosphorylation of IPNPIN is accelerated by $BI^{\ominus}$ ion in $10^{-2}$ M carbonate buffer(pH 10.7) of $4{\times}10^{-3}$ M CTABr solution up to 89 times as compared with the reaction in carbonate buffer by no benzimidazole(BI) solution of $4{\times}10^{-3}$ M CTABr. The value of pseudo first order rate constant($k_{\Psi}$) of the reaction in CTABr solution reached a maximum rate constant increasing micelle concentration. Such rate maxima are typical of micellar catalyzed bimolecular reactions. The reaction mediated by R-$BI^{\ominus}$ in micellar solutions are obviously slower than those by $BI^{\ominus}$, and the reaction rate were decreased with increase of lengths of alkyl groups. It seems due to steric effect of alkyl groups of R-$BI^{\ominus}$ in Stern layer of micellar solution. The surfactant reagent, CTABr, strongly catalyzes the reaction of IPNPIN with R-BI and its anion(R-$BI^{\ominus}$) in carbonate buffer(pH 10.7). For example, $4{\times}10^{-3}$ M CTABr in $1{\times}10^{-4}$ M BI solution increase the rate constant($k_{\Psi}=98.5{\times}10^{-3}\;sec^{-1}$) of the dephosphorylation by a factor ca.25, when compared with reaction($k_{\Psi}=3.9{\times}10^{-4}\;sec^{-1}$) in $1{\times}10^{-4}$ M BI solution(without CTABr). And no CTABr solution, in $1{\times}10^{-4}$ M BI solution increase the rate constant($k_{\Psi}=3.9{\times}10^{-4}\;sec^{-1}$) of the dephosphorylation by a factor ca.39, when compared with reaction ($k_{\Psi}=1.0{\times}10^{-5}\;sec^{-1}$) in water solution(without BI). This predicts that the reactivities of R-$BI^{\ominus}$ in the micellar pseudophase are much smaller than that of $BI^{\ominus}$. Due to the hydrophobicity and steric effect of alkyl group substituents, these groups would penetrate into the core of the micelle for stabilization by van der Waals interaction with long alkyl groups of CTABr.

• 한국환경과학회지
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• 제19권5호
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• pp.565-575
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• 2010

This study is mainly focused on micellar effect of cetylpyridinium chloride(CPyCl) solution including alkylbenzimidazole(R-BI) on dephosphorylation of diphenyl-4-nitrophenylphosphinate(DPNPIN) in carbonate buffer(pH 10.7). The reactions of DPNPIN with R-BI$^{\ominus}$ are strongly catalyzed by the micelles of CPyCl. Dephosphorylation of DPNPIN is accelerated by BI$^{\ominus}$ ion in $10^{-2}M$ carbonate buffer(pH 10.7) of $4{\times}10^{-3}M$ CPyCl solution up to 100 times as compared with the reaction in carbonate buffer by no BI solution of $4{\times}10^{-3}M$ CPyCl. The value of pseudo first order rate constant($k^m_{BI}$) of the reaction in CPyCl solution reached a maximum rate constant increasing micelle concentration. Such rate maxima are typical of micellar catalyzed bimolecular reactions. The reaction mediated by R-BI$^{\ominus}$ in micellar solutions are obviously slower than those by BI$^{\ominus}$, and the reaction rate were decreased with increase of lengths of alkyl groups. It seems due to steric effect of alkyl groups of R-BI$^{\ominus}$ in Stern layer of micellar solution. The surfactant reagent, cetylpyridinium chloride(CPyCl), strongly catalyzes the reaction of diphenyl-4-nitrophenylphosphinate(DPNPIN) with alkylbenzimidazole (R-BI) and its anion(R-BI$^{\ominus}$) in carbonate buffer(pH 10.7). For example, $4{\times}10^{-3}M$ CPyCl in $1{\times}10^{-4}M$ BI solution increase the rate constant ($k_{\Psi}=1.0{\times}10^{-2}sec^{-1}$) of the dephosphorylation by a factor ca.14, when compared with reaction ($k_{\Psi}=7.3{\times}10^{-4}sec^{-1}$) in $1{\times}10^{-4}M$ BI solution(without CPyCl). And no CPyCl solution, in $1{\times}10^{-4}M$ BI solution increase the rate constant ($k_{\Psi}=7.3{\times}10^{-4}sec^{-1}$) of the dephosphorylation by a factor ca.36, when compared with reaction ($k_{\Psi}=2.0{\times}10^{-5}sec^{-1}$) in water solution(without BI). This predicts that the reactivities of R-BI$^{\ominus}$ in the micellar pseudophase are much smaller than that of BI$^{\ominus}$. Due to the hydrophobicity and steric effect of alkyl group substituents, these groups would penetrate into the core of the micelle for stabilization by van der Waals interaction with long alkyl groups of CPyCl.

• Bulletin of the Korean Chemical Society
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• 제35권11호
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• pp.3385-3388
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• 2014

• 대한화학회지
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• 제41권4호
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• pp.205-209
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• 1997

신경수초 염기성 단백질(MBP)에 대한 탈인산화의 자리 특이성에 대한 연구를 시험관에서 수행하였다. MBP에서 인산화된 자리를 알아내기 위해서 MBP를 단백질 키나제 C로 인산화 시키고 단백질 탈인산화 효소 PP2A로 탈인산화시켰다. 인산화된 MBP는 트립신으로 잘라내어서 역상 HPLC 크로마토그래피로 펩티드 조각들을 분리하였다. 각 조각들을 섬광 계측한 후 일부 펩티드의 아미노산 서열을 결정하였다. 일곱 개의 방사능을 보이는 펩티드 조각이 검출되었으며 두번째 조각($P_2$)의 $Ser^{55}$에 해당하는 아미노산이 인산화 반응에 가장 큰 민감도를 보였다. 그러나 탈인산화는 다섯번째 고작($P_5$)의 인산이 가장 잘 방출되는 것으로 나타났다. 이 결과는 MBP가 단백질 탈인산화 반응에 적절한 기질임을 보여주고 있다.

• Applied Biological Chemistry
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• 제38권3호
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• pp.254-258
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• 1995

탈인산화 정도를 달리한 전카제인 또는 ${\beta}$- 및 ${\kappa}$-카제인을 사용하여 여러 종류의 카제인 미셀계를 합성하여 탈인산화하지 않은 카제인으로 제조한 미셀계와 에탄올에 대한 안정성을 비교하였다. 탈인산화한 전카제인으로 만든 미셀은 천연 전카제인으로 제조한 인공 카제인보다 에탄올에 대한 안정성이 낮았으며, 탈인산화 정도가 클수록 에탄올 안정성이 낮게 나타났다. 탈인산화한 ${\kappa}$-카제인을 사용하여 제조한 인공 카제인 미셀은 탈인산화하지 않은 ${\kappa}$-카제인을 사용한 미셀보다 에탄올에 대한 안정성이 낮았고, 또한 탈인산화가 많이 된 ${\beta}$-카제인으로 만든 미셀계일수록 에탄올 안정성이 낮았다. 탈지유의 에탄올에 대한 안정성은 탈인산화가 많이 될수록 감소하였으나 감소의 폭이 좁은 특징을 보였으며, 합성한 카제인 미셀계는 pH $6.3{\sim}7.2$ 범위에서 pH가 상승함에 따라 에탄을 안정성이 높아져 카제인의 인산기가 미셀의 안정성에 중요한 역할을 함을 시사하였다.