bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heterogeneous Photocatalytic Reactions on Semiconductor Materials. III. Effect of pH and Cu2+ Ions on the Photo-Fenton Type Reaction
Authors: Fujihira Masamichi , Satoh Yoshiharu , Osa Tetsuo 
Published: July 2006

Abstract
The effect of pH and Cu2+ ions on the heterogeneous photocatalytic oxidation of toluenes by H2O2 formed from dissolved O2 in the presence of illuminated TiO2 powders, i.e. “the photo-Fenton type reaction,” was investigated. At low and high pH, a total amount of products increased drastically compared with that of the additive free system (pH 7). In the acidic region (aqueous H2SO4), side-chain oxidation prevailed over cresol formation and benzaldehyde was formed quite selectively at pH 1. Oxidation of the side chain in preference to hydroxylation of aromatic ring was also observed in the alkaline region (aqueous NaOH). By adding Cu2+ ion to the aqueous H2SO4 (pH 1 and 2), the yield of benzaldehyde increased further and cresols, benzyl alcohol, and bibenzyl were formed newly in high yields. At high Cu2+ concentrations (pH 2), the cresol formation in preference to the side-chain oxidation was attained. The observation was in good agreement with the Fenton reaction reported in which Cu2+ and Fe3+ ions are added as oxidants for the intermediate products, such as hydroxycyclohexadienyl and benzyl radicals, formed by HO· attack to toluene. Cu2+ ion was more preferable to Fe3+ ion as the oxidant, since “short circuiting” by Cu2+ due to the reversible redox reaction at semiconductor particles was much lower than that by Fe3+. By adding a large amount of Cl− ions to the Cu2+–H2SO4 aqueous system, no oxidation of toluene resulted.
Preparation and Physical Properties of EuC2 and Its Solid Solutions, RxEu1−xC2 (R=La and Gd)
Authors: Sakai Tetsuo , Adachi Gin-ya , Yoshida Takeshi , Ueno Shin-ya , Shiokawa Jiro 
Published: July 2006

Abstract
A cubic-tetragonal phase transformation of EuC2 was observed at 623 K. The phase transition temperatures of metal dicarbides (MC2) were discussed in terms of the band structure proposed by previous authors. The compound EuC2 was a ferromagnet with a zero field curie temperature of 20 K, which was close to the value expected from the Curie temperature vs. nearest neighbor Eu–Eu distance relation for the Eu chalcogenides. The solid solutions, LaxEu1−xC2, became ferromagnetic at low temperatures over the whole composition range, while the solid solutions, GdxEu1−xC2, have continuously changed the kind of magnetic order from ferromagnetic to antiferromagnetic. All the effective moments obtained for RxEu1−xC2 were in good agreement with the theoretical values of Eu2+ and R3+ contained. The electrical resistivities of EuC2 and its solid solutions had a sharp peak near the Curie temperature. When magnetic field was applied, the peak became broader and shifted to higher temperature.
Protolytic Kinetics of Some Pyridine Derivatives in Non-buffered Aqueous Solution
Authors: Ando Isao , Ujimoto Kikujiro , Kurihara Hirondo 
Published: July 2006

Abstract
The deprotonation rates of the conjugate acids of 2,2′-bipyridine and pyridine, and the protonation rates of 2-aminopyridine and 4-aminopyridine were measured in non-buffered aqueous solution by means of a stopped-flow pH jump method. These pyridine derivatives showed quite slow protolytic behavior, similar to that of 1,10-phenanthroline and cyclopentadienes: the deprotonation rate constants of conjugate acids of 2,2′-bipyridine and pyridine are (4.8±0.7)×10−1 and (6.0±2.2)×10−2 s−1, respectively. The deprotonation rates of barbituric acid and acetylcyclopentadiene as authentic samples were also measured. Their deprotonation rate constants are in good agreement with the literature values, this demonstrates the validity and the applicability of the stopped-flow pH jump method. This method is superior to the NMR method for the determination of the protontransfer rates of azaaromatic compounds.
Highly Aggregated State of the Dye with the Detergent in the Premicellar Region as Revealed by Resonance Raman Spectra
Authors: Katsumata Masaaki , Kasatani Kazuo , Kawasaki Masahiro , Sato Hiroyasu 
Published: July 2006

Abstract
Resonance Raman spectra of 3,3′-diethylthiacarbocyanine iodide–sodium dodecyl sulfate (SDS) system are characterized by [SDS]-dependent change of band intensities. The change was much larger than that accompanied with the shift of monomer-dimer equilibrium in the aqueous solution. The spectra for [SDS]&lt;&lt;critical micelle concentration (cmc) resemble that of the dye in the solid state, indicating the highly-aggregated state of the dye caused by the interaction with the detergent.
Characterization of Prussian Blue Analogs of the Type M3[Fe(CN)5CO]2·xH2O
Authors: Inoue Hidenari , Kawai Takashi , Nagao Masaki , Yanagisawa Saburo 
Published: July 2006

Abstract
A series of compounds of the type M3[Fe(CN)5CO]2·xH2O (M=Mn, Co, Ni, Cu, and Zn) have been studied by means of the X-ray diffraction powder patterns, magnetic measurements, infrared, electronic, and M\ddotossbauer spectra. Three compounds M3[Fe(CN)5CO]2·xH2O (M=Mn, Co, and Ni) crystallize in the face-centered cubic system. Copper compound Cu3[Fe(CN)5CO]2·18.5H2O belongs to the tetragonal system, zinc compound Zn3[Fe(CN)5CO]2·13.5H2O being amorphous. The structure of these compounds is described as a three-dimensional framework of two octahedral coordination units FeC6 in the low spin state and MN10⁄3O8⁄3 in the high spin state. The back donation in the Fe(CN)5CO3− moiety is enhanced by the bridge formation through CN− and CO ligands, i.e. upon the formation of M3[Fe(CN)5CO]2·xH2O from the corresponding sodium salt.
Crystallographic Data for New Phases in the CaSO3–H2O System
Authors: Arai Yasuo , Yasue Tamotsu , Nagata Norifumi , Shiino Hiroaki 
Published: July 2006

Abstract
Among the three modifications of calcium sulfite hemihydrate, two of them, hexagonal β-CaSO3·1/2H2O with a rhombohedral lattice and γ-CaSO3·1/2H2O with a simple triangular hexagonal lattice, were found in the authors’ recent work. By heating α- and/or γ-hemihydrate at 330–360 °C in a nitrogen atmosphere, the orthorhombic anhydrate α-CaSO3 was formed, with lattice constants of 6.472, 15.93, and 23.44 Å for a, b, and c respectively, while the body-centered tetragonal anhydrate β-CaSO3, with lattice constants of 15.68 and 19.44 Å for a and c respectively, was formed by heating the β-hemihydrate. The dehydration of three hemihydrates and the hydration of two anhydrates were discussed. The phase relationships in the CaSO3–H2O system were summarized as follows:
α-CaSO3·1⁄2H2O\oversetDehydration (360°C)\undersetHydration(30°C)\ightleftarrowsα-CaSO3+1⁄2H2O;
β-CaSO3·1⁄2H2O\oversetDehydration (360°C)\undersetHydration (30°C)\ightleftarrowsβ-CaSO3+1⁄2H2O;
γ-CaSO3·1⁄2H2O\xrightarrowDehydration (330°C)α-CaSO2+1⁄2H2O;
γ-CaSO3·1⁄2H2O\xrightarrowTransformation (in water at 20°C)
β-CaSO3·1⁄2H2OO\xrightarrowTransformation (in water at 20°C)α-CaSO3·1⁄2H2O.
An Ab Initio MO Calculation for the Bonding Structure of [Ni(CN)4]2−
Authors: Sano Mitsuru , Kashiwagi Hiroshi , Yamatera Hideo 
Published: July 2006

Abstract
An ab initio MO calculation of [Ni(CN)4]2− has been carried out with a double zeta basis set. The nickel-cyanide interactions are discussed and the electronic change occurring on the coordination of CN− to Ni2+ is shown by using the MO contours and the electron-density difference map. The map shows σ donation from the cyanide orbitals and π back-donation from the metal dxy orbital.
Solubility Isotherms of Systems Containing Optically Active Tris(ethylenediamine)cobalt(III) Ion. III. Quaternary System, (Λ-[Co(en)3]3+, Δ-[Co(en)3]3+, H+)–(R,R)-C4H4O62−–H2O, at 25 °C
Authors: Fuyuhiro Akira , Yamanari Kazuaki , Shimura Yoichi 
Published: July 2006

Abstract
A part of quaternary solubility isotherm, (Λ-[Co(en)3]3+, Δ-[Co(en)3]3+, H+)–(R,R)-C4H4O62−–H2O, CH+≤C(R,R)-C4H4O62−, was determined at 25 °C. It was found that three double salts Λ- and Δ[Co(en)3](d-C4H5O6)· (d-C4H4O6)·nH2O and Λ-[Co(en)3]0.48 ·Δ-[Co(en)3]0.52(d-C4H4O6)1.5·5H2O exist, three invariant points appearing. The yield for optical resolution of [Co(en)3]3+ found to be constant regardless of [H+]. The existence of complete ternary system containing double salts, Λ-[Co(en)3](d-C4H5O6)(d-C4H4O6)–Δ-[Co(en)3](d-C4H5O6)(d-C4H4O6)–H2O, was found and the solubilities of Λ- and Δ-[Co(en)3](d-C4H5O6)(d-C4H4O6) were measured at 5–65 °C.
Cation Exchange Separation of Metal Ions Using HF–H3BO3 Media
Authors: Adachi Takeo 
Published: July 2006

Abstract
Using hydrofluoric–boric acid media, a new cation exchange method for the mutual separation of metals which form stable fluoride complexes has been developed. The addition of boric acid to a hydrofluoric acid solution reduces the free fluoride ion concentration to about one hundredth because of the formation of fluoroboric acid. This reduction of the free fluoride ion concentration makes it easy to control the formation of metal fluoride complexes, favoring their separation. As the fluoroboric acid has a buffer action relating to the fluoride ion concentration, the distribution coefficients of metal ions are not affected by the increase in the concentrations of metal ions, even at a low concentration of fluoride ions in the solution. By the use of hydrofluoric–boric acid media, such metals as zirconium, titanium, aluminium, and uranium can be separated from each other. The distribution coefficients of eighteen metals were investigated both in hydrofluoric acid and hydrofluoric–boric acid solutions.
Preparation and Physicochemical Properties of New Linear μ-Oxo Bridged Ruthenium(IV) and Osmium(IV) Porphyrin Dimers
Authors: Sugimoto Hiroshi , Higashi Teruaki , Mori Masayasu , Nagano Motoi , Yoshida Zen-ichi , Ogoshi Hisanobu 
Published: July 2006

Abstract
μ-Oxo-bis[(hydroxo)(octaethylporphyrinato)ruthenium(IV)] was prepared by the oxidation of (carbonyl)(octaethylporphyrinato)ruthenium(II) with t-butyl hydroperoxide in good yield. Facile replacement of the hydroxyl group with various anions afforded μ-oxo dimer complexes formulated as [{RuIV(oep)X}2O] (X=Cl, Br, and OCOCH3). The same type of osmium complexes, [{OsIV(oep)(OCH3)}O], {[OsIV(oep)(OCH3)}O{OsIV(oep)(OH)}], and [{OsIV(oep)(OH)}2O] were obtained from the air oxidation product of (carbonyl)(methanol)(octaethylporphyrinato)osmium(II) in the presence of 2,3-dimethylindole. These complexes are diamagnetic. The 1H NMR data are in conformity with the linear oxo-bridged dimer structure which was proved by X-ray crystallography with [{RuIV(oep)(OH)}2O]. The redox potentials were measured by the cyclic voltammetry. These complexes showed three distinct quasi-reversible redox couples assignable to metalII/ metalIII, metalIII/metalIV, and porphyrin ligand oxidation, respectively. Significantly lower redox values and anomalous spectral features indicate a strong pπ-dπ interaction between the bridging oxygen atom and the two quadrivalent metal ions.
A Kinetic Study on Reduction of 9,9′-Bifluorenylidene by Sodium Isopropoxide
Authors: Kajigaeshi Shoji , Fujisaki Shizuo , Nakashige Yasuhiko , Murakami Sadaaki 
Published: July 2006

Abstract
The kinetics and mechanism of reduction of 9,9′-bifluorenylidene (1) by sodium isopropoxide (2) in isopropyl alcohol to yield 9,9′-bifluorenyl (3) were investigated spectrophotometrically. The kinetic data suggest that the reduction proceeds autocatalytically, the reduction product 3 acting as the catalyst. It was found that
1\xrightarrow[2]k13 (1) 1+3\xrightarrow[2]k23+3 (2)
Reactions 1 and 2 are of the first order with respect to 1, but that the former is of the third order with respect to 2, whereas the latter is of the first. The fourth- and third-order rate constants, k1 and k2, for Reactions 1 and 2 were determined to be 3.0×10−5 dm9 mol−3 s−1 and 1.1×103 dm6 mol−2 s−1, respectively, at 130 °C. Probable mechanisms for Reactions 1 and 2 have been offered on the basis of the reaction order for each molecular species involved.
Hydrolysis of Carbohydrates in the Presence of a Reversed Micelle. III. Hydrolysis of Dextrin in Benzene
Authors: Arai Kenichiro , Ogiwara Yoshitaka 
Published: July 2006

Abstract
The secondary solubilization of dextrin in a dodecylbenzenesulfonic acid (DBSH) reversed micelle in benzene containing a small amount of water was examined; a perfectly clear solution was obtained. The solution showed a CMC of DBSH, estimated by the method of Methylene Blue methachromasis, just like that of sucrose-containing similar reversed-micelle system. The hydrolysis of the dextrin in the system was investigated; the maximum rate enhancement of 285-fold was obtained on the basis of the reaction in DBSH aqueous solution. The CMC and the reaction rate showed changes similar to those in the case of sucrose-containing similar reversed-micelle system with changing the amount of water solubilized, but they showed different changes with changing the concentration of the substrate. These different changes were supposed to result from the differences in the molecular weights of the substrates. These results suggested that the rate enhancement mechanism due to solvent effect and micelle effect which was proposed for the hydrolysis of sucrose in the presence of a DBSH reversed micelle operates in the hydrolysis of the high molecular weight substrate such as dextrin.
Photooxygenation Reaction and Chemiluminescence of (Arylmethylenehydrazono)triphenylphosphoranes. Possible Generation of Phospha-1,2-dioxetanes
Authors: Suzuki Nobutaka , Sano Kaniti , Wakatsuki Satoshi , Izawa Yasuji 
Published: July 2006

Abstract
Photosensitized oxygenation of (benzylidenehydrazono)-, (diphenylmethylenehydrazono)-, (9-fluorenylidenehydrazono)-, (9-xanthenylidenehydrazono)-, and (10-methyl-9,10-dihydroacridin-9-ylidenehydrazono)triphenylphosphoranes at −78 °C gave the corresponding carbonyl compounds and triphenylphosphine oxide and also gave light emission upon warming-up to room temperature.
Furan Derivatives. IV. On the Effects of Substituents in the Syntheses of 4,5-Dihydro-3H-naphtho[1,8-bc]furans
Authors: Horaguchi Sakaaki , Hara Mamoru , Suzuki Tsuneo 
Published: July 2006

Abstract
The reaction of (8-oxo-5,6,7,8-tetrahydro-1-naphthyloxy)acetic acids with acetic anhydride and sodium acetate give a mixture of 4,5-dihydro-3H-naphtho[1,8-bc]furans and lactones. The relative yields of 4,5-dihydro-3H-naphtho[1,8-bc]furans and lactones varied according to kinds of substituents on the benzene ring of (8-oxo-5,6,7,8-tetrahydro-1-naphthyloxy)acetic acids. Substituents which make the methylene group approach closer to the carbony carbon atom of (8-oxo-5,6,7,8-tetrahydro-1-naphthyloxy)acetic acids by a steric effect seem to favor the production of 4,5-dihydro-3H-naphtho[1,8-bc]furans. On the other hand, substituents which make the methylene group separate from the carbonyl carbon atom seem to favor the production of lactones. An electron-withdrawing chlorine atom on the benzene ring of (8-oxo-5,6,7,8-tetrahydro-1-naphthyloxy)acetic acids also favors the production of 4,5-dihydro-3H-naphtho[1,8-bc]furans.
Functionalization of trans-Decalin. V. A Synthesis of (±)-Nootkatone and (±)-Valencene from 4β,4aβ-Dimethyl-Δ6,7-octalin-1-one Ethylene Acetal
Authors: Torii Sigeru , Inokuchi Tsutomu , Handa Ko 
Published: July 2006

Abstract
A synthesis of (±)-nootkatone (1) and (±)-valencene (18) starting from 4β,4aβ-dimethyl-Δ6,7-octalin-1-one ethylene acetal (2) is described. Epoxidation of the double bond of 2 followed by regiospecific reduction of the oxirane ring at the C-6 position gave the corresponding C-7 alcohol 4. Oxidation of 4 and subsequent methoxycarbonylation at the C-6 position afforded methyl 1,1-ethylenedioxy-4β,4aβ-dimethyl-7-oxodecalin-6-carboxylate (6) in good yield. The keto ester 6 was converted to methyl 1,1-ethylenedioxy-4β,4aβ-dimethyldecalin-6α-carboxylate (10b) by the reduction with NaBH4 followed by dehydration and subsequent hydrogenation over PtO2 and epimerization of the 6β-methoxycarbonyl group with MeONa in MeOH. Deacetalization of 10b followed by reduction and dehydration afforded methyl 4β,4aβ-dimethyl-Δ1(8a)-octalin-6α-carboxylate (15). The conversion of 15 into (±)-18 was carried out directly by the reaction with salt-free methylenetriphenylphosphorane in refluxing tetrahydrofuran (76%) or by hydrolysis of 15 followed by methylation with MeLi, and subsequent Wittig reaction (60%). The allylic oxidation of (±)-18 with CrO3·(pyridine)2 complex gave the desired (±)-1, smoothly.
Synthesis and Stereochemistry of Hypusine, a New Amino Acid in Bovine Brain.
Authors: Shiba Tetsuo , Akiyama Hitoshi , Umeda Isao , Okada Satoshi , Wakamiya Tateaki 
Published: July 2006

Abstract
Hypusine, a new basic amino acid occurring in the homogenate of bovine brain tissue, was synthesized to determine the absolute structure. Nα-Benzyloxycarbonyl-l-lysine benzyl ester was coupled with (S)- or (R)-4-benzyloxycarbonylamino-1-bromo-2-butanol derived from l- or d-malic acid, respectively. The products were deprotected by catalytic hydrogenation. One of the synthetic compounds, i.e., (2S,9R)-2,11-diamino-9-hydroxy-7-azaundecanoic acid, was completely identical with natural hypusine in all respects.
Preparation of Homologs of l-2-Amino-5-(p-methoxyphenyl)pentanoic Acid
Authors: Kosui Nobuo , Waki Michinori , Kato Tetsuo , Izumiya Nobuo 
Published: July 2006

Abstract
Lower and higher homologs, l-2-amino-4-(p-methoxyphenyl)butanoic acid (l-Amb) and l-2-amino-6-(p-methoxyphenyl)hexanoic acid (l-Amh), of l-2-amino-5-(p-methoxyphenyl)pentanoic acid were prepared by optical resolution of N-acetyl-Dl-Amb and of N-acetyl-Dl-Amh with Aspergillus acylase. N-Acetyl-Dl-Amb or N-acetyl-Dl-Amh was synthesized from [2-(p-methoxyphenyl)ethyl or butyl](acetamido)malonic acid by heating with p-xylene.
The Configurations of Benzylmethyl(o- or p-tolyl)silylmethylamine and the Stereochemistry of the Reactions of Benzylmethylmethoxyphenylsilane with Some Organometallic Agents
Authors: Terunuma Daiyo , Senda Kazuhisa , Sanazawa Masato , Nohira Hiroyuki 
Published: July 2006

Abstract
Optically active α-amino organosilanes such as benzylmethyl(o- or p-tolyl)silylmethylamine were converted into benzylmethylphenyl(o- or p-tolyl)silane, of which the configurations had been known. From these observations, it was found that (+)- and (−)-benzylmethyl(o- or p-tolyl)silylmethylamine has S and R configuration respectively. Furthermore, the stereochemistry of the reaction of benzylmethyl(methoxy)phenylsilane with some organometallic agents was investigated.
Branched-chain Sugars. XXVIII. Synthesis of 2-C-Methyl-l-glyceraldehyde, 2-C-Methyl-d-erythrose, and 3-C-Methyl-l-erythrose Derivatives
Authors: Yoshimura Juji , Hara Kazutoshi , Yamaura Masanori , Mikami Kazutoshi , Hashimoto Hironobu 
Published: July 2006

Abstract
As synthons for the synthesis of bicyclomycin, the title compounds were derived from 1,2:5,6-di-O-isopropylidene-3-C-methyl-α-d-allofuranose by the descendent method.
Solvent Effects on the Isomerization of 1-Pentene Catalyzed by Cationic Platinum Complexes
Authors: Kanai Hiroyoshi , Hirako Osamu 
Published: July 2006

Abstract
The isomerization of 1-pentene with [PtH(PPh3)3]X (X=SO4H, ClO4) occurred only in ethers. The decrease in the concentrations of 1-pentene and the platinum complexes leads to high cis-selectivity.
Thermolysis of 6-Hydroxyimino-1,3,5-tri-t-butyl-5-methyl-1,3-cyclohexadiene
Authors: Okazaki Renji , Watanabe Masako , Inamoto Naoki 
Published: July 2006

Abstract
Mechanism of the thermolysis of the titile compound has been proposed, which begins with a homolytic cleavage leading to t-butyl radical and 2,4-di-t-butyl-6-methyl-1-nitrosobenzene. The reaction of the nitrosobenzene with t-butyl radical generated from photolysis of 2,2′-dimethyl-2,2′-azopropane is also described.
The Influence of Additives on the Decomposition of an Alkaline Manganate(VII) Solution
Authors: Narita Eiichi , Hashimoto Tatsuhiko , Yoshida Sakae , Okabe Taijiro 
Published: July 2006

Abstract
The decomposition of manganate(VII) in an alkaline solution was significantly enhanced by the addition of hydrous manganese(IV) oxide or metal ions, such as Ni(II) and Co(II). On the other hand, the inhibitive effect of the tellurate(VI) ion on the decomposition was found even in the presence of the additives described above.
The Crystal Structure of Bis(methyl 3-benzylidenedithiocarbazato)nickel(II)
Authors: Uechi Tetsuo , Oniki Takayuki 
Published: July 2006

Abstract
The title compound crystallizes in the monoclinic space group P21/a with two molecules in a unit cell of dimensions; a=21.479(5), b=4.2092(6), c=14.257(3) Å, and β=129.53(2)°. The structure was refined by block-diagonal least-squares procedures to give a final R value of 0.032 for 1693 reflections with I&gt;3σ(I) collected on a four-circle X-ray diffractometer. The complex consists of two methyl 3-benzylidenethiocarbazate groups, each bound to the central Ni atom through the thiol S atom and the hydrazine N atom, to yield a five-membered chelate ring. The NiN2S2 moiety is trans square-planar, with Ni–S and Ni–N bond distances of 2.1767(9) and 1.927(3) Å respectively. An examination of the bond distances and the planarity of the molecule revealed a delocalization of the π electrons over the chelate ring. The intra-molecular contact of S···H is 2.35(4) Å, which indicates a definite C–H···S interaction or hydrogen bonding.
Polymerization of Silicic Acid Adsorbed on Aluminium Hydroxide
Authors: Yokoyama Takushi , Nakamura Osamu , Tarutani Toshikazu 
Published: July 2006

Abstract
Factors controlling the absorption of silicic acid on aluminium hydroxide from aqueous solution and the polymerization of adsorbed silicic acid were studied. Measurements included the amount of silicic acid adsorbed on aluminium hydroxide, the amount and size distribution of the polysilicic acid formed, and the differential thermal analysis curve of aluminium hydroxide which had adsorbed silicic acid. The adsorption and the polymerization of silicic acid are affected by pH, the relative amounts of silicic acid and aluminium hydroxide, the reaction time between monosilicic acid and aluminium hydroxide, and the formation of amorphous aluminosilicate. The amount of adsorbed silicic acid and the rate of its polymerization are maximum at pH 9.0–9.5. A part of adsorbed monosilicic acid reacts with aluminium hydroxide to form an aluminosilicate. In an early stage of the polymerization of the adsorbed silicic acid, the polymerization mainly proceeds by the reactions between monosilicic acids and between monosilicic and polysilicic acids; the particle sizes of polysilicic acids gradually increase with time. When the polymer particles grow large enough to touch neighboring polymers, the growth rate of polymer particles becomes faster due to the polymer-polymer reactions.
Kinetic Study on Conformational Changes of Poly(l-lysine) in Sodium Alkyl Sulfate Solutions. Effects of Surfactant Chain Length and Added NaCl
Authors: Takeda Kunio , Iba Akira , Shirahama Keishiro 
Published: July 2006

Abstract
The conformational changes of poly(l-lysine) (PLL) were observed in alkyl sulfate solutions by a circular dichroic method. PLL forms a β-structure in sodium dodecyl sulfate solution with an apparent first-order rate constant of 3.0×10−2 s−1 (20 °C). In sodium octyl sulfate (SOS) solution, PLL assumes the α-helix within a certain concentration range of the surfactant, above which the β-structure is favored. The rate of coil to β-structure transition slows down with increase in hydrophobic interaction between surfactants and PLL. The presence of sodium ions decreases the rate of coil to α-helix transition by about two orders of magnitude (2.0×10−1 s−1 salt free to 3.0×10−3 s−1 in the presence of 2.0×10−2 mol/dm3 NaCl at 20 °C). These phenomena are explained in terms of a rearrangement process of bound surfactants adjusting for a free energy minimum; a stronger binding force brings about a slower rearrangement rate.