- Phenylalanine ammonia lyase catalyzed synthesis of amino acids by an MIO-cofactor independent pathway
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Phenylalanine ammonia lyases (PALs) belong to a family of 4-methylideneimidazole-5-one (MIO) cofactor dependent enzymes which are responsible for the conversion of L-phenylalanine into trans-cinnamic acid in eukaryotic and prokaryotic organisms. Under conditions of high ammonia concentration, this deamination reaction is reversible and hence there is considerable interest in the development of PALs as biocatalysts for the enantioselective synthesis of non-natural amino acids. Herein the discovery of a previously unobserved competing MIO-independent reaction pathway, which proceeds in a non-stereoselective manner and results in the generation of both L- and D-phenylalanine derivatives, is described. The mechanism of the MIO-independent pathway is explored through isotopic-labeling studies and mutagenesis of key active-site residues. The results obtained are consistent with amino acid deamination occurring by a stepwise E1cB elimination mechanism. All manner of things: A competing MIO-independent (MIO=4-methylideneimidazole-5-one) reaction pathway has been identified for phenylalanine ammonia lyases (PALs), which proceeds in a non-stereoselective manner, resulting in the generation of D-phenylalanine derivatives. The mechanism of D-amino acid formation is explored through isotopic-labeling studies and mutagenesis of key active-site residues.
- Lovelock, Sarah L.,Lloyd, Richard C.,Turner, Nicholas J.
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supporting information
p. 4652 - 4656
(2014/05/20)
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- Fluorine Radiolabelling Process
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The invention relates to a process for producing a process for producing an 18F-labelled compound, the process comprising treating a compound of formula (I) wherein EDG is an electron-donating group selected from —OH, —OR4, —NHR5 and —NR55R5; R1, R2, X1 and X2 are as defined herein; and R3 is selected from H, X3 and X4, wherein X3 is a monodentate cleavable surrogate group, and X4 is a bidentate cleavable surrogate group which is bonded (a) to said X1 or X2 and (b) to the ring carbon atom para to EDG; with [18F]fluoride in the presence of an oxidant, thereby producing, when R3 in the compound of formula (I) is H, an 18F-labelled compound of formula (II), wherein EDG is as defined above and R1, R2, X1 and X2 are as defined herein; or thereby producing, when R3 in the compound of formula (I) is said monodentate cleavable surrogate group X3, a compound of formula (IIa), wherein EDG′ is O, NR5, —NR55R5 or [OR4]+, and wherein R4, R5, R55, R1, R2, X1, X2 and X3 are as defined herein; or thereby producing, when R3 in the compound of formula (I) is said bidentate cleavable surrogate group X4, a compound of formula (IIc) or a compound of formula (IId), wherein EDG′ is O, NR5, —NR55R5 or [OR4]+, and wherein R4, R5, R55, R1, R2, X1, X2 and X4 are as defined herein
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Paragraph 0521
(2013/07/31)
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- FLUORINE RADIOLABELLING PROCESS
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The invention relates to a process for producing a process for producing an 18F-labelled compound, the process comprising treating a compound of formula (I): wherein EDG is an electron-donating group selected from -OH, -OR4, -NHR5 and -NR55R5; R1, R2, X1 and X2 are as defined herein; and R3 is selected from H, X3 and X4, wherein X3 is a monodentate cleavable surrogate group, and X4 is a bidentate cleavable surrogate group which is bonded (a) to said X or X and (b) to the ring carbon atom para to EDG; with [18F]fluoride in the presence of an oxidant, thereby producing, when R3 in the compound of formula (I) is H, an 18F-labelled compound of formula (II), wherein EDG is as defined above and R1, R2, X1 and X2 are as defined herein; or thereby producing, when R3 in the compound of formula (I) is said monodentate cleavable surrogate group X4, a compound of formula (Ilc), wherein EDG' is O, NR5, -NR55R5 or [OR4]+, and wherein R4, R5, R55, R1, R2, X1, X2 and X3 are as defined herein; or thereby producing, when R3 in the compound of formula (I) is said bidentate cleavable surrogate group X4, a compound of formula (IIc) or a compound of formula (IId), wherein EDG' is O, NR5, -NR55R5 or [OR4]+, and wherein R4, R5, R55, R1, R2, X1, X2 and X4 are as defined herein.
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Page/Page column 100
(2012/02/01)
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- Identification of phenylalanine 3-hydroxylase for meta -tyrosine biosynthesis
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Phenylalanine hydroxylase (PheH) is an iron(II)-dependent enzyme that catalyzes the hydroxylation of aromatic amino acid l-phenylalanine (l-Phe) to l-tyrosine (l-Tyr). The enzymatic modification has been demonstrated to be highly regiospecific, forming proteinogenic para-Tyr (p-Tyr) exclusively. Here we biochemically characterized the first example of a phenylalanine 3-hydroxylase (Phe3H) that catalyzes the synthesis of meta-Tyr (m-Tyr) from Phe. Subsequent mutagenesis studies revealed that two residues in the active site of Phe3H (Cys187 and Thr202) contribute to C-3 rather than C-4 hydroxylation of the phenyl ring. This work sets the stage for the mechanistic and structural study of regiospecific control of the substrate hydroxylation by PheH.
- Zhang, Wenjun,Ames, Brian D.,Walsh, Christopher T.
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scheme or table
p. 5401 - 5403
(2012/06/15)
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- SUBSTITUTED HYDROXYPHENYLAMINE COMPOUNDS
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The present invention relates to new substituted hydroxyphenylamine based modulators of hormone and/or pigment levels, pharmaceutical compositions thereof, and methods of use thereof. Formula (I).
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Page/Page column 41
(2010/06/11)
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- Kinetic of adsorption and of photocatalytic degradation of phenylalanine effect of pH and light intensity
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Phenylalanine (Phe) was chosen to study the TiO2 photocatalytic degradation of amino acids, which are at the origin of the formation of odorous compounds after chlorination. The photocatalytic degradation has been investigated in aqueous solutions containing TiO2 suspensions as photocatalyst, in order to assess the influence of various parameters, such as adsorption, initial concentration, pH and radiant flux on the photocatalytic process. Results showed no correlation between dark adsorption and photocatalytic degradation. A multilayer kinetic was observed in the dark with a monolayer corresponding to less that 1% of OH covered, whereas Langmuir-Hinshelwood model seems to modelize the photocatalytic disappearance of Phe. However, even if the form of the curve is similar to L-H model, the degradation of phenylalanine is not a kinetic of L-H as we could plan it by considering the adsorption of the phenylalanine in the dark. The study of the mineralization of carbon and nitrogen showed that nitrogen atoms were predominantly photoconverted into NH4+ and a total mineralization of nitrogen and carbon seems occur. The identification of the by-products by LC-MS reveal mono- and di-hydroxylation and nitrogen-carbon (N-C) cleavage. The effect of pH showed an increase of adsorption under acid pH but a decrease of disappearance rate. The more efficient degradation was found at basic pH. The evolution of hydroxylated compounds of phenylalanine as a function of conversion revealed the presence of more hydroxylated compounds at natural pH and at basic pH compared to acid pH suggesting a modification of mechanism with solution pH. The effect of the radiant flux evaluated under different initial concentration of phenylalanine allowed us to determine that Κ increases by increasing the radiant flux, whereas Κ decreases or remains constant from about a value of 3.5 mW/cm2. The disappearance rate as a function of radiant flux has been showed to reach a maximal value corresponding to a maximal quantum yield of 1.6%.
- Elsellami,Vocanson,Dappozze,Puzenat,Pa?sse,Houas,Guillard
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experimental part
p. 142 - 148
(2011/10/12)
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- Optimized synthesis of L-m-tyrosine suitable for chemical scale-up
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This paper demonstrates how L-m-tyrosine 1 can be synthesized on larger-scale via enzyme-catalyzed kinetic resolution of N-acyl m-tyrosine methyl ester 4. N-Acyl m-tyrosme methyl ester 4 was prepared by a modification of Erlenmeyer's azalactone synthesis followed by hydrogenation of the resultant dehydroamino acid 12. The optimized four-step synthesis utilizes cheap and readily available starting materials and circumvents difficult purification protocols.
- Humphrey, Cara E.,Furegati, Markus,Laumen, Kurt,Vecchia, Luigi La,Leuten, Thomas,Constanze D Mueller-Hartwieg,Voegtle, Markus
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p. 1069 - 1075
(2012/12/30)
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- Ingredients contribute to variation in production of reactive oxygen species by areca quid
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Areca quid (AQ) chewing has been implicated an independent risk factor for the development of oral cancer. Taiwanese areca quid (AQ) refers to a combination of areca nut (AN), lime, and inflorescence of Piper betle Linn. (IPB) or Piper betle leaf (PBL). Studies of AQ in other countries reported that AN extract combined with lime generates reactive oxygen species (ROS), such as hydroxyl radical (HO? ), known to be a contributing factor in oral mucosa damage. To determine whether HO? is formed in the oral cavity during AQ chewing, the formation of meta -tyrosine ( m -Tyr) and ortho -tyrosine ( o -Tyr) from l -phenylalanine (Phe) was confirmed. It was demonstrated that combined aqueous extracts of AN, lime, metal ions (such as Cu 2+ and Fe 2+ ), and IPB or PBL produced HO?. Thus, the yield of HO? significantly increases when higher amounts of IPB or lime are added and also when Cu 2+ and Fe 2+ are increased. Further, the omission of any one of these ingredients significantly reduces the formation of HO ?. Our results found that chewing AQ with IPB generated significantly higher HO? than chewing AQ with PBL, and may result in greater oxidative damage to the surrounding oral mucosa. Copyright Taylor & Francis Group, LLC.
- Chen, Ping-Ho,Tsai, Chi-Cheng,Lin, Ying-Chu,Ko, Ying-Chin,Yang, Yi-Hsin,Shieh, Tien-Yu,Ho, Pei-Shan,Li, Chien-Ming,Min-Shan Ko, Albert,Chen, Chung-Ho
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p. 1055 - 1069
(2007/10/03)
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- Synthesis of (-)-quinocarcin by directed condensation of α-amino aldehydes
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An enantioselective synthesis of the natural antiproliferative agent quinocarcin was achieved by the directed condensation of optically active α-amino aldehyde intermediates. Condensation of the N-protected α-amino aldehyde 1, prepared in eight steps (19% yield) from (R,R)-pseudoephedrine glycinamide, with the C-protected α-amino aldehyde derivative 2, prepared in seven steps (34% yield) from (R,R)-pseudoephedrine glycinamide, afforded the corresponding imine in quantitative yield. Without isolation, direct treatment of this imine intermediate with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and hydrogen cyanide led to cleavage of the fluorenylmethoxycarbonyl (Fmoc) protective group followed by addition of cyanide (Strecker reaction) to form the bis-amino nitriles 3 as a mixture of diastereomers, in 91% yield. Treatment of the diastereomers 3 with trimethylsilyl cyanide and zinc chloride in 2,2,2-trifluoroethanol at 60 °C led to stepwise cyclization to form the tetracyclic product 4 (42% yield from 1 and 2). The latter intermediate was transformed into (-)-quinocarcin (1) in five steps (45% yield). The yield of quinocarcin was 19% from 1 and 2 (7 steps), and 4% from pseudoephedrine glycinamide (15 steps). Copyright
- Kwon, Soojin,Myers, Andrew G.
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p. 16796 - 16797
(2007/10/03)
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- Formation of a hydroxyl radical from riboflavin sodium phosphate by photo-illumination
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Photo-illumination of riboflavin sodium phosphate (Rp) with phenylalanine produced significant levels of o-tyrosine, m-tyrosine and p- tyrosine as hydroxylated products. The hydroxylation of Rp was pH-dependent, and the maximum rate was around pH 4.5. Replacement of air with nitrogen prevented the formation of tyrosine isomers while the addition of superoxide dismutase or catalase to this system prevented hydroxylation. The tyrosine formation by the system was significantly prevented by hydroxyl radical (HO·) scavengers such as potassium iodide, potassium bromide, thiourea and sodium formate. No free iron and cupric ions were detected in the reaction mixture by inductively-coupled plasma atomic emission spectrometry. The above results suggest that the formation of HO· may occur in the photochemical reaction system in the presence of Rp under aerobic conditions, and that a superoxide radical and hydrogen peroxide may be involved in HO· formation.
- Ishimitsu, Susumu,Mishima, Ikuko,Tsuji, Sumiko,Shibata, Tadashi
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p. 2107 - 2109
(2007/10/03)
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- Formation of a hydroxyl radical from tar dye by photo-illumination
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When indigo carmine (B-2) was illuminated in the presence of phenylalanine in 0.1 M citrate buffer (pH 4.0), p-tyrosine, m-tyrosine and o-tyrosine were identified as hydroxylated products. However, ten other food colors did not form tyrosine isomers. The hydroxylation of B-2 was pH-dependent, and the maximum rate was found at around pH 4.0. Replacement of air with nitrogen gas completely prevented the formation of tyrosine isomers and the decomposition of B-2. In contrast, oxygen gas accelerated both the hydroxylation and the decomposition. The addition of superoxide dismutase or catalase to this system prevented hydroxylation. Chemical scavengers of the hydroxyl radical (HO·) prevented the hydroxylation. On the other hand, a singlet oxygen scavenger had no significant effect. The above results suggest that the formation of HO· may occur in the photochemical reaction system in the presence of B-2 under aerobic conditions, and that a superoxide radical and hydrogen peroxide may he involved in the HO· formation.
- Ishimitsu,Ohmori,Tsuji,Shibata
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p. 1810 - 1812
(2007/10/03)
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- Aromatic hydroxylations by flavins: Evidence on direct attack of phenylalamine by flavin radical species
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In 0.05 - 12.0 N acidic solutions, the 5-ethyl-3-methyllumiflavosemiquinone 5 (and/or 5H+) spontaneously arose from the corresponding flavinium cation 4. Raising the temperature from 20 to 50°C, considerably increased the reaction rates with no significant changes in the yields of 5 (5H+). The spontaneous one-electron reduction of 4 requires a coupling with a one-electron oxidation of another flavin such as 5-ethyl-4(a)-hydroxy-3-methyl-4(a),5-dihydroflavin pseudobase 1. The latter, being in equilibrium with 4, can be oxidized to give the transient 5-ethyl-4(a)-hydroxy-3-methyllumiflavin radical 2. This is the protonated form of a flavinoxy radical 3(a,b), a product of a homolysis of the O-O bond in a dihydroflavin hydroperoxide. As an alternative to the homolysis mentioned, the one-electron oxidation of 1 provides the principle to develop a new hydroxylating model system that does not require a dihydroflavin hydroperoxide as a starting compound. Using phenylalanine as a test substrate, the anaerobic formation of tyrosine and its o- and m-hydroxyphenylalanine isomers was established. This achievement is a strong experimental support for the hypothesis that flavin radical species like 2 may directly attack an aromatic. Evidence was obtained on some accumulation of an intermediate that is not a hydroxycyclohexadienyl radical. It was shown to react in a secondary, oxidative chain reaction, remarkably increasing the yields of aromatic hydroxylation without any further supply of flavin.
- Mager,Tu
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p. 5287 - 5298
(2007/10/02)
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- A novel hydroxylation of aromatics in a flavin-initiated chain reaction
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In aqueous acidic solutions, the 5-ethyl-3-methyllumiflavinium cation 5 was spontaneously transformed into the dihydroflavin pseudobase radical 6 and the flavosemiquinone 7. In attacking an aromatic like phenylalanine, 6 was mainly reconverted to 5 which, ultimately, could lead to an anaerobic accumulation of 7 in yields of 95 ± 5%. In the immediate presence of O2 and/or H2O2, 7 was rapidly and continuously reoxidized to 5 which, consequently, gave a continued production of 6 increasing the hydroxylating ability of the system. The oxidants also had a second distinct effect in converting an intermediate X in a chain reaction to further increase the yields of hydroxyphenylalanines. As illustrated by the results obtained with O2 and H2O2 under comparable conditions, the efficiency of this chain reaction proved to be significantly influenced by the nature of the oxidant. These new findings imply that hydroxyl radicals arising in a homolysis of the O-O bond in a dihydroflavin hydroperoxide should not be taken for granted as the primary attacking species in the hydroxylation of an aromatic. From a practical point of view it is noticed that the hydroxylating ability of the new flavin / H2O2 system surpasses that of any other known, flavin-free chemical system.
- Mager, Humphrey I. X.,Tu, Shiao-Chun
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p. 6759 - 6766
(2007/10/02)
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- Phenylalanine: Its *OH and SO4(1-*)-Induced Oxidation and Decarboxylation. A Pulse Radiolysis and Product Analysis Study
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Phenylalanine has been oxidized by radiolytically generated hydroxyl and sulfate radicals, the ensuing intermediates and their reactions have been studied by pulse radiolysis and product analysis in the absence and presence of oxidants such as Fe(CN)6(3-) and O2.Upon OH radical attack, hydroxycyclohexadienyl-type radicals are mainly formed while H-abstraction reactions can be neglected.In the presence of Fe(CN)6(3-) these radicals are for the most part oxidized to the corresponding tyrosines (80percent), except for the ipso-OH-adduct radicals (ca. 20percent=.It is concluded that *OH-addition is almost random, but with a slight avoidance of the meta-position relative to the ortho-, para- and ipso-positions.Oxygen adds reversibly to the OH-adduct radicals (kf = 1.8x108 dm3 mol-1 s-1, kr = 5.4x104 s-1).In this case, tyrosine formation occurs by HO2*-elimination.However, due to side reactions, tyrosine formation only reaches 52percent of the OH radical yield.The tyrosine yield drops to 10percent in the absence of an oxidant.Upon SO4(1-*)-attack, decarboxylation becomes a major process (33percent of SO4(1-*) alongside the production of tyrosines (43percent).Here, with Fe(CN)6(3-) as the oxidant the formation of p-Tyr (18.5percent) and m-Tyr (16.5percent) is preferred over o-Tyr formation (8.5percent).It is believed that in analogy to other systems a radical cation is formed immediately upon SO4(1-*)-attack which either reacts with water under the formation of hydroxycyclohexadienyl-type ("OH-adduct") radicals, or decarboxylates after intramolecular electron transfer.The radical cation can also arise indirectly through H(1+)-calalysed water elimination from the *OH-adduct radicals.At pH 2 and a dose rate of 0.0046 Gy s-1 CO2 formation matches the OH radical yield when *OH is the attacking radical.Below pH 2, G(CO2) decreases with falling pH.This indicates the occurrence of another, unimolecular, pathway under these conditions competing effectively with decarboxylation.This appears to be a relatively slow deprotonation reaction of the carboxyl-protonated phenylalanine radical cation which gives rise to the benzyl-type radical. Key words: Amino acid; phenylalanine; pulse radiolysis; peroxy radicals; sulfate radical.
- Wang, Degui,Schuchmann, Heinz-Peter,Sonntag, Clemens von
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p. 761 - 770
(2007/10/02)
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- Antibiotics napsamycins A-D, process for their production and their use as pharmaceuticals
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This invention relates to new antibacterial antibiotics Napsamycins A - D of the formula Napsamycin A :R1 = H, R2 = uracil Napsamycin B :R1 = CH3, R2 = uracil Napsamycin C :R1 = H, R2 = dihydrouracil Napsamycin D :R1 = CH3, R2 = dihydrouracil from a strain of Streptomyces candidus, Y-82,11372 (DSM 5940).
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- OXIDATION OF L-PHENYLALANINE BY THE MODIFIED UDENFRIEND SYSTEM
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L-phenylalanine is oxidized by oxygen into 3,4-dihydroxyphenylalanine (DOPA) at 40 deg C with Fe(2+) EDTA as a catalyst.For the reduction of Fe(3+) species, electrons are released from the cathode of an electrochemical cell.
- Blanchard, M.,Bouchoule, C.,Djaneye-Boundjou, G.,Canesson, P.
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p. 2177 - 2178
(2007/10/02)
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- HYDROXYLATION REACTION OF AROMATIC RINGS IN AQUEOUS SOLUTION INDUCED BY HYDROGEN-OXYGEN FLAME
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It was found that direct hydroxylation of aromatic rings proceeded in aqueous solution of phenyl-containing amino acids by using hydrogen-oxygen flame and that the active species of the reaction could be considered as hydroxyl radicals generated in the burning flame.
- Takasaki, Michiaki,Nomoto, Shinya,Harada, Kaoru
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p. 1629 - 1632
(2007/10/02)
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