Precipitation of sword bean proteins by heating and addition of magnesium chloride in a crude extract

<p>Sword bean (<i>Canavalia gladiata</i>) seeds are a traditional food in Asian countries. In this study, we aimed to determine the optimal methods for the precipitation of sword bean proteins useful for the food development. The soaking time for sword beans was determined by comparing it with that for soybeans. Sword bean proteins were extracted from dried seeds in distilled water using novel methods. We found that most proteins could be precipitated by heating the extract at more than 90 °C. Interestingly, adding magnesium chloride to the extract at lower temperatures induced specific precipitation of a single protein with a molecular weight of approximately 48 kDa. The molecular weight and N-terminal sequence of the precipitated protein was identical to that of canavalin. These data suggested that canavalin was precipitated by the addition of magnesium chloride to the extract. Our results provide important insights into the production of processed foods from sword bean.</p

Long-Lived Photoinduced Charge Separation in Inclusion Complexes Composed of a Phenothiazine-Bridged Cyclic Porphyrin Dimer and Fullerenes

C₆₀, [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM), lithium-cation-encapsulated C₆₀ (Li⁺@C₆₀), and [6,6]-diphenyl-C₆₂-bis­(butyric acid methyl ester) (bis-PCBM) were included into a phenothiazine-bridged cyclic free-base porphyrin dimer (H₄-Ptz-CPD_Py(TEO)) in a polar solvent (benzonitrile) with large association constants of 1.3 × 10⁶, 6.4 × 10⁵, 3.2 × 10⁶, and 2.5 × 10⁵ M^–1, respectively. Based on the electrochemical data, the lowest energy levels of the charge-separated (CS) states for the inclusion complexes of H₄-Ptz-CPD_Py(TEO) with C₆₀, PCBM, Li⁺@C₆₀, and bis-PCBM (designated as C₆₀⊂H₄-Ptz-CPD_Py(TEO), PCBM⊂H₄-Ptz-CPD_Py(TEO), Li⁺@C₆₀⊂H₄-Ptz-CPD_Py(TEO), and bis-PCBM⊂H₄-Ptz-CPD_Py(TEO)) composed of the phenothiazine donor and fullerene acceptors were determined to be 1.30, 1.40, 0.66, and 1.51 eV, respectively. Both C₆₀⊂H₄-Ptz-CPD_Py(TEO) and PCBM⊂H₄-Ptz-CPD_Py(TEO) underwent electron transfer upon photoexcitation of the porphyrin and fullerene chromophores, and the resultant photoinduced CS states comprised the phenothiazine cation and the fullerene anions with lifetimes of 0.71 ms determined by time-resolved transient absorption spectra. Li⁺@C₆₀⊂H₄-Ptz-CPD_Py(TEO) also afforded a similar CS state with a lifetime of 0.56 ms. These lifetimes are the longest values ever reported for the CS states of phenothiazine–fullerene complexes in solution. The spin states of these long-lived CS states were assigned to be triplet by ESR spectroscopy. The remarkably long CS lifetimes are attributable mainly to the lower CS energies than the triplet energies of the phenothiazine, fullerenes, and porphyrin moieties and the spin-forbidden slow back-electron-transfer processes. On the other hand, the photoinduced CS state of bis-PCBM⊂H₄-Ptz-CPD_Py(TEO) was quenched rapidly by fast back electron transfer due to the relatively high CS energy comparable to the triplet energies of the porphyrin and fullerene

Blue Fluorescence from BF₂ Complexes of <i>N,O</i>-Benzamide Ligands: Synthesis, Structure, and Photophysical Properties

Small molecules having intense luminescence properties are required to promote biological and organic material applications. We prepared five types of benzamides having pyridine, pyridazine, pyrazine, and pyrimidine rings and successfully converted them into three types of the difluoroboronated complexes, Py@BAs, as novel blue fluorophores. Py@BA having a pyridine moiety (2-Py@BA) showed no fluorescence in solution, whereas Py@BAs of pyridazine and pyrazine moieties (2,3-Py@BA and 2,5-Py@BA, respectively) emitted blue fluorescence with quantum yields of ca. 0.1. Transient absorption measurements using laser flash photolysis of the Py@BAs revealed the triplet formation of 2,3- and 2,5-Py@BAs, while little transient signal was observed for 2-Py@BA. Therefore, the deactivation processes from the lowest excited singlet state of fluorescent 2,3- and 2,5-Py@BAs consist of fluorescence and intersystem crossing to the triplet state while that of the nonfluorescent Py@BA is governed almost entirely by internal conversion to the ground state. Conversely, in the solid state, 2-Py@BA emitted intense fluorescence with a fluorescence quantum yield as high as 0.66, whereas 2,3- and 2,5-Py@BAs showed fluorescence with quantum yields of ca. 0.2. The crystal structure of 2-Py@BA took a herringbone packing motif, whereas those for 2,3- and 2,5-Py@BAs were two-dimensional sheetlike. On the basis of the difference in crystal structures, the emission mechanism in the solid state was discussed

Phenothiazine-Bridged Cyclic Porphyrin Dimers as High-Affinity Hosts for Fullerenes and Linear Array of C₆₀ in Self-Assembled Porphyrin Nanotube

Free-bases and a nickel­(II) complex of phenothiazine-bridged cyclic porphyrin dimers bearing self-assembling 4-pyridyl groups (M₂-Ptz-CPD_Py(OC_<i>n</i>); M = H₂ or Ni, OC_<i>n</i> = OC₆ or OC₃) at opposite <i>meso</i>-positions have been prepared as host molecules for fullerenes. The free-base dimer (H₄-Ptz-CPD_Py(OC₆)) includes fullerenes with remarkably high association constants such as 3.9 ± 0.7 × 10⁶ M^–1 for C₆₀ and 7.4 ± 0.8 × 10⁷ M^–1 for C₇₀ in toluene. This C₆₀ affinity is the highest value ever among reported receptors composed of free-base porphyrins. The nickel dimer (Ni₂-Ptz-CPD_Py(OC₆)) also shows high affinities for C₆₀ (1.3 ± 0.2 × 10⁶ M^–1) and C₇₀ (over 10⁷ M^–1). In the crystal structure of the inclusion complex of C₆₀ within H₄-Ptz-CPD_py(OC₃), the C₆₀ molecule is located just above the centers of the porphyrins. The two porphyrin planes are almost parallel to each other and the center-to-center distance (12.454 Å) is close to the optimal separation (∼12.5 Å) for C₆₀ inclusion. The cyclic porphyrin dimer forms a nanotube through its self-assembly induced by C–H···N hydrogen bonds between porphyrin β-CH groups and pyridyl nitrogens as well as π–π interactions of the pyridyl groups. The C₆₀ molecules are linearly arranged in the inner channel of this nanotube

Synthesis of 2‑Iodoazulenes by the Iododeboronation of Azulen-2-ylboronic Acid Pinacol Esters with Copper(I) Iodide

Azulen-2-ylboronic acid pinacol ester, prepared by iridium-catalyzed C–H borylation of azulene, efficiently underwent iododeboronation with a stoichiometric amount of copper­(I) iodide. This reaction allowed the synthesis of 2-iodoazulene in only two steps starting from azulene. This methodology was successfully applied to analogous azulenes

New Insights into the Electronic Structure and Reactivity of One-Electron Oxidized Copper(II)-(Disalicylidene)diamine Complexes

The neutral and one-electron oxidized Cu­(II) six-membered chelate <b>1,3-Salcn</b> (<b>1,3-Salcn</b> = <i>N,N</i>′-bis­(3,5-di-<i>tert</i>-butylsalicylidene)-1,3-cyclohexanediamine) complexes have been investigated and compared with the five-membered chelate <b>1,2-Salcn</b> (<i>N,N</i>′-bis­(3,5-di-<i>tert</i>-butylsalicylidene)-1,2-cyclohexane-(1<i>R,</i>2<i>R</i>)-diamine) complexes. Cyclic voltammetry of Cu<b>(1,3-Salcn)</b> showed two reversible redox waves at 0.48 and 0.68 V, which are only 0.03 V higher than those of Cu<b>(1,2-Salcn)</b>. Reaction of Cu<b>(1,3-Salcn)</b> with 1 equiv of AgSbF₆ afforded the oxidized complex which exists as a ligand-based radical species in solution and in the solid state. The X-ray crystal structure of the oxidized complex, [Cu<b>(1,3-Salcn)</b>]<b>SbF</b>_<b>6</b>, exhibited an asymmetric metal binding environment with a longer Cu–O bond and quinoid distortion in the phenolate moiety on one side, demonstrating at least partial ligand radical localization in the solid state. The ligand oxidation is also supported by XPS and temperature dependent magnetic susceptibility. The electronic structure of the [Cu<b>(1,3-Salcn)</b>]^<b>+</b> complex was further probed by UV–vis–NIR, resonance Raman, and electron paramagnetic resonance (EPR) measurements, and by theoretical calculations, indicating that the phenoxyl radical electron is relatively localized on one phenolate moiety in the molecule. The reactivity of [Cu<b>(1,3-Salcn)</b>]^<b>+</b> with benzyl alcohol was also studied. Quantitative conversion of benzyl alcohol to benzaldehyde was observed, with a faster reaction rate in comparison with [Cu<b>(1,2-Salcn)</b>]^<b>+</b>. The kinetic isotope effect (KIE = <i>k</i>(H)/<i>k</i>(D)) of benzyl alcohol oxidation by [Cu<b>(1,3-Salcn)</b>]^<b>+</b> was estimated to be 13, which is smaller than the value reported for [Cu<b>(1,2-Salcn)</b>]^<b>+</b>. The activation energy difference between [Cu<b>(1,2-Salcn)</b>]^<b>+</b> and [Cu<b>(1,3-Salcn)</b>]^<b>+</b> was in good agreement with the energy calculated from KIE. This correlation suggests that the Cu­(II)-phenoxyl radical species, characterized for [Cu­(<b>1,2-salcn</b>)]⁺ is more reactive for hydrogen abstraction from benzyl alcohol in comparison to the 1:1 mixture of Cu­(III)-phenolate and Cu­(II)-phenoxyl radical species, [Cu<b>(1,2-Salcn)</b>]^<b>+</b>. Thus, the Cu­(II)-phenoxyl radical species accelerates benzyl alcohol oxidation in comparison with the Cu­(III)-phenolate ground state complex, in spite of the similar activated intermediate and oxidation pathway

Influence of Ligand Flexibility on the Electronic Structure of Oxidized Ni^III-Phenoxide Complexes

One-electron-oxidized Ni^III-phenoxide complexes with salen-type ligands, [Ni­(salen)­py₂]²⁺ (<b>[1</b>^<b>en</b><b>-py]</b>^<b>2+</b>) and [Ni­(1,2-salcn)­py₂]²⁺ (<b>[1</b>^<b>cn</b><b>-py]</b>^<b>2+</b>), with a five-membered chelate dinitrogen backbone and [Ni­(salpn)­py₂]²⁺ (<b>[2</b>^<b>pn</b><b>-py]</b>^<b>2+</b>), with a six-membered chelate backbone, have been characterized with a combination of experimental and theoretical methods. The five-membered chelate complexes <b>[1</b>^<b>en</b><b>-py]</b>^<b>2+</b> and <b>[1</b>^<b>cn</b><b>-py]</b>^<b>2+</b> were assigned as Ni^III-phenoxyl radical species, while the six-membered chelate complex <b>[2</b>^<b>pn</b><b>-py]</b>^<b>2+</b> was concluded to be a Ni^II-bis­(phenoxyl radical) species with metal-centered reduction in the course of the one-electron oxidation of the Ni^III-phenoxide complex <b>[2</b>^<b>pn</b><b>-py]</b>^<b>+</b>. Thus, the oxidation state of the one-electron-oxidized Ni^III salen-type complexes depends on the chelate ring size of the dinitrogen backbone