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81.
A spectrophotometric flow-injection method for determining copper(II) has been developed. It is based on the catalytic effect of copper(II) on the oxidative coupling of N-phenyl-p-phenylenediamine with m-phenylenediamine in the presence of hydrogen peroxide. Pyridine and ammonia as activators increased the absorbance for the copper(II)-catalyzed coloration, and the dye formed was stabilized by adding a non-ionic surfactant. The working range of the method was 0.1-2.0 ng ml(-1) of cooper(II) with a relative standard deviation 2.4% at a sampling rate of 30 h(-1). Interference from iron(III) was effectively suppressed by citric acid. Copper in natural water samples can be determined easily. 相似文献
82.
Takashi Hirota Kenji Sasaki Yohsuke Tashima Taiji Nakayama 《Journal of heterocyclic chemistry》1991,28(2):263-267
Syntheses of 2,3-dihydrobenzofuro[2,3-e]imidazo[1,2-c]pyrimidine and its 5-substituted derivatives, corresponding to B-nor-6-oxa-11,13,15-triazasteroids, are described. These products and their precursors were screened to evaluate the antidepressive activity. 相似文献
83.
Qi ZM Matsuda N Santos J Yoshida T Takatsu A Kato K 《Journal of colloid and interface science》2004,271(1):249-253
Broadband, time-resolved optical waveguide (OWG) spectroscopy has been used for in situ, real-time investigation into the self-assembly of metal nanoparticle monolayers. The OWG spectroscopy makes it possible to use the transverse electric (TE) and transverse magnetic (TM) modes to measure surface plasmon absorption of immobilized metal nanoparticles in two directions, parallel and normal to the waveguide surface. Therefore, this technique can provide direction-dependent information on the metal nanoparticles at the interface. In this paper, a 50-microm-thick glass plate was used as a slab waveguide and the kinetics of Au nanoparticle adsorption on a hemoglobin-functionalized glass substrate was examined in the early stage of self-assembly. The findings show that with the TE mode the surface plasmon resonance (SPR) behavior for immobilized Au nanoparticles is different from that with the TM mode. 相似文献
84.
(+-)-3,3,7-Trimethyl-2,9-dioxatricyclo[4.2.1.04, 7]noname and (+-)-3,3,7-trimethyl-2,9-dioxatricyclo[3.3.1.04, 7] nonane were synthesized. The latter was shown to be (+-)-lineatin, an ambrosia beetle pheromone. 相似文献
85.
86.
Sugimoto K Nishida M Otsuka M Makino K Ohkubo K Mori Y Morii T 《Chemistry & biology》2004,11(4):475-485
Real-time observation of messenger molecules in individual intact cells is essential for physiological studies of signaling mechanisms. We have developed a novel inositol 1,4,5-trisphosphate (IP(3)) sensor based on the pleckstrin homology (PH) domain from phospholipase C (PLC) delta. The environmentally sensitive fluorophore 6-bromoacetyl-2-dimethyl-aminonaphtalene was conjugated to the genetically introduced cysteine at the mouth of the IP(3) binding pocket for enhanced IP(3) selectivity and for rapid and direct visualization of intracellular IP(3) > or = 0.5 microM as fluorescence emission decreased. The probe, tagged with arginine-rich sequences for efficient translocation into various cell types, revealed a major contribution of Ca2+ influx to PLC-mediated IP(3) production that boosts Ca2+ release from endoplasmic reticulum. Thus, our IP(3) probe was extremely effective to quantitatively assess real-time physiological IP(3) production via those pathways formed only in the intact cellular configuration. 相似文献
87.
Synthesis and characterization of 6-O-acyl-2-O-alpha-D-glucopyranosyl-L-ascorbic acids with a branched-acyl chain 总被引:3,自引:0,他引:3
We previously reported the chemical synthesis of a series of novel monoacylated vitamin C derivatives, 6-O-acyl-2-O-alpha-D-glucopyranosyl-L-ascorbic acids (6-Acyl-AA-2G) possessing a straight-acyl chain of varying length from C(4) to C(18), as effective skin antioxidants. In this paper, we describe branched type of 6-Acyl-AA-2G derivatives (6-bAcyl-AA-2G) synthesized by use of a 2-branched-chain fatty acid anhydride as an acyl donor. The stability of 6-bAcyl-AA-2G in neutral solution was much higher than that of 6-Acyl-AA-2G, while they were susceptible to enzymatic hydrolysis for exerting vitamin C effect. These branched derivatives as well as 6-Acyl-AA-2G increased the radical scavenging activity against 1, 1-diphenyl-2-picrylhydrazyl and the lipophilicity in octanol/water-partitioning systems with increasing length of their acyl group. In addition, the 6-bAcyl-AA-2G derivative with an acyl chain of C(12), 6-bDode-AA-2G had the excellent solubility to various solvents, suggesting easy handling in cosmetic use. These characteristics of 6-bAcyl-AA-2G may be available for skin care application as an effective antioxidant. 相似文献
88.
Leesajakul W Nakano M Taniguchi A Handa T 《Colloids and surfaces. B, Biointerfaces》2004,34(4):253-258
Cubosomes are novel dispersed nanoparticles with bicontinuous cubic phases of monoolein in their interior. We investigated their disintegration process in plasma by in vitro and in vivo studies. Cubosomes were incubated with whole plasma or plasma components such as HDL, LDL, and albumin. The lypolysis study indicated lipolytic activity of whole plasma towards cubosomes. Gel filtration chromatography revealed that HDL, LDL and albumin interacted with cubosomes. HDL affected cubosomes’ integrity and gave rise to smaller particles which contained the components of both cubosomes and HDL. Upon incubation with LDL, cubosomes fused with LDL. Albumin was shown to take up monoolein out of the particles. Cubosomes were disintegrated by whole plasma as a result of the interaction with plasma components. It was concluded that in vivo observation of a long circulation time of a hydrophobic substance in cubosomes was due to the sustained behavior of cubosome remnant particles. 相似文献
89.
Kiyokawa T Kanaori K Tajima K Kawaguchi M Mizuno T Oku J Tanaka T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(14):3548-3554
The alpha-helical coiled coils have a representative amino acid sequence of (abcdefg)(n) heptad repeats. We previously reported that two peptides named IZ-2A and IZ-2W formed an (IZ-2A)(2)/IZ-2W heterotrimer with an Ala-Ala-Trp interaction in the hydrophobic core. In this paper, we describe the selective formation of AAB- and ABC-type heterotrimers. To increase the selectivity of the AAB-type heterotrimeric formation, Lys residues at the f position were mutated to either an Ala or a Gln residue to form IZ-2A(fA) or IZ-2W(fQ). Separately, both IZ-2A(fA) and IZ-2W(fQ) have a random structure at pH 7 and 20 degrees C. However, together IZ-2A(fA) and IZ-2W(fQ) form a 2:1 complex with a thermal transition midpoint (Tm) of 48 degrees C. This procedure was applied to prepare the ABC-type heterotrimer, in which two sets of Ala-Ala-Trp interactions were designed in the hydrophobic core. Interhelical interaction between the e and g positions and the alpha-helical propensity of the amino acid at the f position were also considered in the design. The resultant three peptides selectively formed the ABC-type heterotrimer with a Tm of 51 degrees C. Other peptide combinations had random coil properties. 相似文献
90.
Highly optically pure enantiomers of (E)-6-isopropyl-3,9-dimethyl-5,8-decadienyl acetate, the sex pheromone of the yellow scale (Aniodiella citrina), were stereoselectively from synthesized from(R)-(+)-citronellic acid. Only the (s)-enantiomer was bioactive. 相似文献