New selenyl linker for solid-phase synthesis of dehydropeptides

A novel linker possessing selenocyanate and masked carboxylic acid was developed for the solid-phase synthesis of dehydropeptides. This linker was used to demonstrate the synthesis of the model compound of RGD-conjugated dehydropeptide.     

Selective colorimetric determination of p-haloaniline in a mixture witho-haloaniline by the reaction with chloranil

Summary p-Haloanilines react with chloranil to develope an intense color (_max: 545 nm), whileo-haloanilines do not. This difference in reaction has been applied to the selective determination ofp-haloanilines in a mixture witho-haloaniline.

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Zusammenfassung p-Halogenaniline geben mit Chloranil eine intensive Farbreaktion (_max= =545 nm), während die entsprechenden o-Verbindungen dies nicht tun. Auf dieser Grundlage wurde eine selektive Bestimmungsmethode für p-halogenierte Aniline in Gemischen mit o-halogenierten Anilinen ausgearbeitet.

     

Origin of enhancement in open-circuit voltage by adding ZnO to nanocrystalline SnO2 in dye-sensitized solar cells

SnO2 + ZnO working electrodes for dye-sensitized solar cells were made by mixing a nanocrystalline SnO2 colloidal dispersion with ZnO or Zn(CH3COO)2. Addition of ZnO or Zn(CH3COO)2 enhanced the open-circuit voltage (V(oc)) of the cells with respect to cells containing only SnO2. Dependence of the electron lifetime in the electrodes on short-circuit photocurrent density (J(sc)) gave evidence against the assumption that the suppression of back electron transfer to the electrolyte is the origin for the V(oc) enhancement by addition of Zn. V(oc) dependence on temperatures indicated a decrease in the combined capacitance of the mixed electrode. The slope of the V(oc) dependence versus the logarithm of J(sc) indicated that the contribution of unpinning of the band to the enhancement of V(oc) could be neglected. From the cyclic voltammograms of the electrodes, the combined capacitance of the mixed electrode was 1 order of magnitude smaller than that of SnO2. The decrease in the combined capacitance in the mixed electrode could be explained by the decrease in the chemical capacitance of SnO2, thus the shift of the conduction band position toward the vacuum level. X-ray photoelectron spectra of Sn 3d(5/2) peaks showed a shift toward lower binding energy with an increasing amount of added Zn. This was attributed to an increase in the surface potential toward the negative direction, which might have resulted from a dipole moment formed by Zn on the surface of SnO2.     

Bicyclic dioxetanes bearing a 4-(benzoazol-2-yl)-3-hydroxyphenyl moiety: chemiluminescence profile for base-induced decomposition in aprotic medium and in aqueous medium

Four bicyclic dioxetanes bearing a 4-(benzothiazol-2-yl)-3-hydroxyphenyl or 4-(benzoxazol-2-yl)-3-hydroxyphenyl group were synthesized. These dioxetanes underwent base-induced decomposition with accompanying emission of light with high efficiency in NaOH/H₂O as well as in tetrabutyl ammonium fluoride (TBAF)/acetonitrile. Among them, benzothiazol-analogs decomposed faster in the aqueous solution than in acetonitrile.     

Asymmetric polymerization of triphenylmethyl methacrylate by optically active anionic catalysts

Triphenylmethyl methacrylate (TrMA) was polymerized with two types of asymmetric anionic catalyst, lithium (R)-N-(1-phenylethyl)anilide (LiAn) and (-)-sparteine–butyllithium complex (Sp–BuLi), at ?78°C. Both catalysts yielded optically active polymers. The polymers obtained with LiAn in toluene and tetrahydrofuran (THF) showed specific rotations [α] of from ?50° to ?90° (in THF). The [α] of the polymer obtained with Sp–BuLi in toluene was positive and increased with polymer yield reaching above +300°s, whereas the polymer obtained in THF showed a low [α] (ca. +7°). Gel permeation chromatograms of both polymers obtained with LiAn and Sp–BuLi in THF exhibited rather narrow molecular weight distributions, whereas those obtained in toluene showed at least two or three components with markedly different molecular weights. The circular dichroism (CD) spectrum of the polymer obtained with Sp–BuLi showed strong positive peaks at 208 and 232 nm and a weak band at 250–280 nm; the polymer produced with LiAn showed a similar spectrum with opposite sign. The poly(methyl methacrylate)s derived from these poly(TrMA)s were highly isotactic but showed negligible rotations ([α] ± 2° in toluene). The polymer of high molecular weight showed clear polarization under a polarizing microscope and the low polymer obtained with LiAn appeared to show flow birefringence in chloroform at room temperature.     

Anionic copolymerization of optically active α-methylbenzyl methacrylate and trityl methacrylate. I. Reactivity of monomers

The monomer reactivity ratios were determined in the anionic copolymerization of (S)- or (RS)-α-methylbenzyl methacrylate (MBMA) and trityl methacrylate (TrMA) with butyllithium at ?78°C, and the stereoregularity of the yielded copolymer was investigated. In the copolymerization of (S)-MBMA (M₁) and TrMA (M₂) in toluene the monomer reactivity ratios were r₁ = 8.55 and r₂ = 0.005. On the other hand, those in the copolymerization of (RS)-MBMA with TrMA were r₁ = 4.30 and r₂ = 0.03. The copolymer of (S)-MBMA and TrMA prepared in toluene was a mixture of two types of copolymer: one consisted mainly of the (S)-MBMA unit and was highly isotactic and the other contained both monomers copiously. The same monomer reactivity ratios, r₁ = 0.39 and r₂ = 0.33, were obtained in the copolymerizations of the (S)-MBMA–TrMA and (RS)-MBMA–TrMA systems in tetrahydrofuran (THF). The microstructures of poly[(S)-MBMA-co-TrMA] and poly-[(RS)-MBMA-co-TrMA] produced in THF were similar where the isotacticity increased with an increase in the content of the TrMA unit.     

Asymmetric selective polymerization of racemic 1,2-diphenylethyl methacrylate with the ethylmagnesium bromide-(−)-sparteine complex

Asymmetric selective (or stereoelective) polymerization of racemic 1,2-diphenylethyl methacrylate (DPEMA) with ethylmagnesium bromide (EtMgBr)-(?)-sparteine catalyst was studied in toluene at ?78°C. In the polymerization (S) enantiomer was consumed preferentially and the enantiomeric excess of initially polymerized (S) enantiomer was consumed preferentially and the enantiomeric excess of initially polymerized DPEMA was greater than 90%. Optically pure (R) monomer was recovered at about 70% polymer yield. Poly(DPEMA) obtained with EtMgBr-(?)-sparteine complex was highly isotactic. It was found in the polymerization of optically active DPEMA that optical rotation of poly(DPEMA) was dependent on the tacticity and that isotactic and syndiotactic poly(DPEMA)s showed opposite optical rotations. Circular dichroism spectra of the optically active polymers were measured.     

Identification of low-abundance proteins of bovine colostral and mature milk using two-dimensional electrophoresis followed by microsequencing and mass spectrometry

We identified several low-abundance proteins of bovine colostrum and mature milk using the immunoabsorption technique and two-dimensional electrophoresis (2-DE) followed by microsequencing and mass spectrometry. Two major milk proteins, beta-casein and immunoglobulin G (IgG), were effectively removed from the milk using immunoabsorbents. Milk samples before and after immunoabsorption were separated by 2-DE. Protein identification of the spots on 2-DE was performed by either gel comparison, microsequencing, matrix-assisted laser desorption/ionization-time of flight mass-spectrometry (MALDI-TOF-MS), peptide mass fingerprinting or peptide sequencing using tandem MS by hybrid quadrupole/orthogonal acceleration time of flight-MS (Q-TOF). Significant differences in protein patterns were observed between the low-abundance proteins of colostrum and mature milk. In addition, several low-abundance proteins including fibrinogen beta-chain, chitinase 3-like 1, alpha-antitrypsin, complement C3 alpha-chain, gelsolin and apolipoprotein H were observed only in colostrum. However, the level of beta-casein fragments increased significantly during this lactation period. alpha-Lactalbumin and beta-lactoglobulin as well as some low-abundance proteins including bovine serum albumin, serotransferrin and lactoferrin were identified in both colostral and mature milk. Low-abundance proteins in bovine colostrum may have special physiologic relevance to the health and development of calves early in lactation.     

Nuclear magnetic resonance studies of isoprenyllithium derived from 1,1-diphenyl-n-butyllithium-3,4-d5, and isoprene

The equimolar reactions of 1,1-diphenyl-n-butyllithium-3,4-d₅ (RLi) with isoprene (I) and isoprene-1,4-d₄ (Id) were carried out in benzene-d₆ quantitatively to give isoprenyllithiums, RILi and RIdLi, respectively. From the NMR spectrum of the RILi it was proposed that the isoprene unit had cis-1,4, cis-4,1 and some unknown structures in benzene-d₆. When RILi was prepared in the presence of about one equivalent of THF to RILi, the anion was considered to include an isoprene unit in cis-1,4, trans-1,4, cis-4,1, and probably 3,4 structures. The same anion was obtained even if an equimolar THF was added afterward to the RILi prepared in benzene-d₆ The RLi was reproduced by the reverse reaction from RILi, when a large excess of THF was added or the temperature of the solution was elevated. The results obtained were correlated with those of anionic polymerizations of isoprene by lithium initiators.     

Essential structure of co-pigment for blue sepal-color development of hydrangea

Blue sepal-color of Hydrangea macrophylla might be due to a supramolecular metal-complex pigment consisting of delphinidin 3-glucoside (1), co-pigments (5-O-caffeoylquinic acid (2), and/or 5-O-p-coumaroylquinic acid (3)) and Al³⁺ in an aqueous solution around pH 4.0. To clarify the mechanism of blue sepal-color development of hydrangea, we tried to reproduce the blue color in vitro by mixing 1 with designed synthetic co-pigments in the presence of Al³⁺ at pH 4.0. We at first succeeded in clarifying the essential functional structure in the co-pigment that could form the stable blue solution. Here, we present the structure of the blue pigment caused by an Al-complex coordinating of 1 at ortho-dihydroxyl groups of the B-ring, 1-hydroxy, 1-carboxylic acid, and the carbonyl residue in the ester at 5-position of 2 and/or 3. The hydrophobic interaction between the aromatic acyl residue at 5-position and the nucleus of 1 may also contribute to stabilize the complex.