Catalytic flow-injection determination of copper at nanogram levels by using color formation of N-phenyl-p-phenylenediamine with m-phenylenediamine in the presence of pyridine and ammonia as activators

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.     

Novel real-time sensors to quantitatively assess in vivo inositol 1,4,5-trisphosphate production in intact cells

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.     

Interaction of cubosomes with plasma components resulting in the destabilization of cubosomes in plasma

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.     

Gas-phase generation of highly reactive hexatriyne-bridged [6n]paracyclophynes

[6n]Paracyclophenediynes 2a-d (n = 3-6) having [4.3.2]propellatriene units were prepared as precursors of the corresponding [6n]paracyclophynes. Laser irradiation of 2a-d produced the negative ions of [6n]paracyclophynes 1a-d (n = 3-6) by extrusion of the indan fragments, which were detected by time-of-flight mass spectrometry.