Generation of circular dichroism from superposed porphyrin films.

Circular dichroism (CD) was observed from the superposed porphyrin deposited glass plates, which were prepared by the vapor deposition of achiral porphyrin molecules and oriented to one direction by rubbing parallel to the surface of plate. The CD spectra depended on the twisted angle between the plates and the number of plates superposed. The observed CD spectra agreed with the simulated ones by the Mueller matrices superposition calculation using the observed linear dichroism spectra and linear birefringence spectra of each plate.

Critical Detection of Agglomeration of Magnetic Nanoparticles by Magnetic Orientational Linear Dichroism.

Magnetic orientational linear dichroism (MOLD) spectroscopy was found to be useful for detecting the initiation of the agglomeration process of COOH-modified iron-oxide magnetic nanoparticles (MNPs) in water, which was produced by the addition of a small amount of a cationic surfactant or a metal ion. The critical association of MNPs leading to agglomeration was detected from the increase of the maximum MOLD value as well as from the shift of the maximum wavelength of the MOLD spectrum. The magnetic field dependence of MOLD was analyzed by the Langevin equation, and the apparent association numbers of MNPs in the agglomerates were obtained.

Magnetophoretic mole-ratio method in solvent extraction systems.

The magnetophoretic mole-ratio method was applied to the solvent extraction systems of paramagnetic metal ions with bis(2-ethylhexyl)hydrogen phosphate in 2-fluorotoluene. In the extraction of Mn(II), Co(II), Ni(II), Tb(III) and Dy(III), the compositions of the extracted metal complexes were determined from the measurements of the magnetophoretic velocity of a single droplet as a function of the mole ratio of the metal ion and the ligand.

Magnetic Orientational Linear Dichroism Spectra of Magnetic Nanoparticles as a Probe of the Dispersion State.

Magnetic orientational linear dichroism (MOLD) spectra of magnetic nanoparticles (MNPs) in the UV-Vis wavelength region were found to be useful as a probe to detect changes of the dispersion state due to a restriction of the rotational Brownian motion of MNPs; a change of the medium from liquid to resin and the formation of agglomerates in solution. The magnetic-field dependence of MOLD was analyzed by using the Langevin equation, which gave information about the magnetic moment of MNPs.

Electromagnetophoretic Micro-convection around a Droplet in a Capillary.

The electromagnetophoretic behavior of organic droplets in an electrolyte solution was investigated in a silica capillary cell using a superconducting bulk magnet (3.5 T) and a magnetic circuit (2.7 T). The initially dispersed emulsion droplets of dodecane migrated to the wall of the capillary, responding to the direction of an electric current, and coalesced to form smaller and larger droplets after some repeated migrations. When the electric current was applied continuously, the larger droplets became arranged with regular intervals on the wall, and smaller droplets rotated around the larger droplets. These interesting behaviors were analyzed while taking into account the local electric current density determined by the flow velocity of the ionic current around a droplet, which was lowest on the electrode sides of the droplet. The difference in the local electric current density generated the Lorentz-force difference in the medium, which lead to local micro-convection around the droplet, and also the alignment of larger droplets by a repelling effect between the adjacent micro-convections.

Magnetophoretic Mole-Ratio Method.

The principle of the mole-ratio method utilizing magnetophoretic velocimetry was demonstrated for the first time. The feasibility of the magnetophoretic mole-ratio method was studied for the determination of the stoichiometry of the complexes formed between a hydrophobic phosphate ligand adsorbed in mesoporous hydrophobic silica particles and paramagnetic metal ions of Co(II), Tb(III), and Dy(III) in aqueous solutions. The present method is a nonspectroscopic method and carried out by a simple magnetic device.

SERS Measurement of Cysteamine Molecules Stretched by the Electromagnetophoretic Force.

The role of an external force on chemical equilibria is an important subject in mechanobiochemistry. The effect of an electromagnetophoretic force for the stretching of cysteamine molecules was examined by using SERS spectrometry. Polystyrene particles modified with cysteamine were bound to silver nanoparticles adsorbed on the wall of a silica capillary cell. Under a constant magnetic field, when an electric current was applied to the conductive medium in the capillary, the shift of SERS bands and the increase of the trans/gauche ratio of cysteamine were observed, suggesting a molecular conformation change of cysteamine due to the stretching force.

Observation of the Sagnac Effect in the Magnetization of Magnetic Nanoparticles in Water.

A square optical loop used to observe the Sagnac effect was constructed by using a 632.8-nm He-Ne laser, a polarizing beam splitter and three mirrors, combined with a detection system. When a magnetic field was applied from the transversal direction to the beam of the loop, which passed through the sample cell containing magnetic nanoparticles (MNPs) in water, Sagnac interference was observed depending on the concentration of MNPs, indicating evolution of the magnetic birefringence. A possible analytical use of the magnetic Sagnac effect has been suggested.

Chiral Recognition of 2-Alkylalcohols with Magnetic Circular Dichroism Measurement of Porphyrin J-Aggregate on Silica Gel Plate.

Simple chiral recognition method of 2-alkylalcohols on a silica gel plate was proposed by using the induced circular dichroism (ICD) of J-aggregates of diprotonated tetraphenylporphyrin and magnetic circular dichroism (MCD) spectrometry. To the silica gel on a glass slide including a chiral 2-alkylalcohol and 4 M sulfuric acid, the porphyrin in toluene was added and mixed. Then, the glass slide was used for in situ MCD measurement. The observed ICD spectra could recognize well the chirality of the alcohols and the ICD intensity normalized by the MCD intensity of the J-aggregate correlated linearly to the amount of the chiral alcohols in the silica gel.

Modulation of surface plasmon coupled emission (SPCE) by a pulsed magnetic field.

The unique modulation of surface plasmon coupled emission (SPCE) on a Au/Cr/Co/Cr/glass substrate by an external magnetic field has been observed. The most positive regulation was triggered by employing the multilayered substrate with a 7.5 nm-thick Co layer. The new magnetoplasmonic strategy provides a simple way to modulate the SPCE signal.

Zero-velocity magnetophoretic method for the determination of particle magnetic susceptibility.

A simple zero-velocity method to determine the particle magnetic susceptibility by measuring the magnetophoretic velocity was proposed. The principle is that the magnetophoretic velocity of a particle in a liquid medium must be zero when the magnetic susceptibilities of the medium and the particle are equal, or the gravity force and the magnetophoretic force are balanced. By changing the medium magnetic susceptibility and measuring the magnetophoretic velocity of a particle, the particle magnetic susceptibility was determined from the medium magnetic susceptibility under the zero-velocity condition. The feasibility of the method was demonstrated for polystyrene particles using a Dy(III) solution in the horizontal migration mode and different organic solvents in the vertical migration mode.

Continuous separation principles using external microaction forces.

During the past decade, methods for the continuous separation of microparticles with microaction forces have rapidly advanced. Various action forces have been used in designs of both microchannel and capillary continuous separation systems, which depend on properties such as conductivity, permittivity, absorptivity, refractive index, magnetic susceptibility, and compressibility. Particle migration velocity has been used to characterize the particles. Biological cells have been the most interesting targets of these continuous separation methods.

New rotenoids and coumaronochromonoids from the aerial part of Boerhaavia erecta.

From the aerial part of Boerhaavia erecta L., three new rotenoids (3, 8, 10) and two new coumaronochromonoids (6, 11) were isolated, together with ten known compounds. The structure of the new compounds was established by one dimensional (1D)- and 2D-NMR spectroscopy, as well as high resolution-electrospray ionization (HR-ESI)-MS analysis. The absolute configuration of compound 11 was determined by UV circular dichroism spectroscopy. Compounds were evaluated for their cytotoxic activity against HeLa (human epithelial carcinoma), NCI-H460 (human lung cancer) and MCF-7 (human breast cancer) cell lines at the concentration of 100 µg/mL. Rotenoids 3, 4 and 5 showed a strong cytotoxic activity against HeLa cell line and rotenoids 5 and 8 showed good activity against MCF-7 cell line.

Faraday rotation dispersion microscopy imaging of diamagnetic and chiral liquids with pulsed magnetic field.

We have constructed an experimental setup for Faraday rotation dispersion imaging and demonstrated the performance of a novel imaging principle. By using a pulsed magnetic field and a polarized light synchronized to the magnetic field, quantitative Faraday rotation images of diamagnetic organic liquids in glass capillaries were observed. Nonaromatic hydrocarbons, benzene derivatives, and naphthalene derivatives were clearly distinguished by the Faraday rotation images due to the difference in Verdet constants. From the wavelength dispersion of the Faraday rotation images in the visible region, it was found that the resonance wavelength in the UV region, which was estimated based on the Faraday B-term, could be used as characteristic parameters for the imaging of the liquids. Furthermore, simultaneous acquisition of Faraday rotation image and natural optical rotation image was demonstrated for chiral organic liquids.

Laser-photophoretic migration and fractionation of human blood cells.

Laser photophoretic migration behavior of human blood cells in saline solution was investigated under the irradiation of Nd:YAG laser beam (532 nm) in the absence and the presence of the flow in a fused silica capillary. Red blood cells (RBC) were migrated faster than white blood cells (WBC) and blood pellets to the direction of propagation of laser light. The observed photophoretic velocity of RBC was about 11 times faster than those of others. This was understood from the larger photophoretic efficiency of RBC than that of WBC, which was simulated based on the Mie scattering theory. Furthermore, it was found that, during the photophoretic migration, RBCs spontaneously orientated parallel to the migration direction so as to reduce the drag force. Finally, it was demonstrated that RBC and WBC were separated in a micro-channel flow system by the laser photophoresis.

Faraday rotation dispersion measurements of diamagnetic organic liquids and simultaneous determination of natural optical rotatory dispersion using a pulsed magnetic field.

We constructed an apparatus to measure the wavelength dispersion of the Faraday rotation in the visible region, and determined the Verdet constants of diamagnetic organic liquids, including aliphatic compounds, benzene derivatives, and naphthalene derivatives. These three groups were easily distinguished by the magnitudes of their Verdet constants. Based on the theory developed by Serber, we determined the enhancing effect of π*←π transitions on the visible-light Faraday rotation angles observed for aromatic compounds. Furthermore, we propose a novel approach for simultaneously observing Faraday rotation dispersion and natural optical rotatory dispersion.

Alignment and chirality of porphyrin J aggregates formed at the liquid-liquid interface of a centrifugal liquid membrane cell.

Previous direct observations of the J aggregates of diprotonated 5,10,15,20-tetraphenyl-21H,23H-porphine (H4TPP(2+)) formed at the dodecane-water interface in a centrifugal liquid membrane (CLM) cell using conventional CD spectroscopy have shown the existence of circular dichroic signals with a bisignated shape whose sign depends on the rotation direction of the cell. Herein we demonstrate that the determination of the optical Mueller matrix with a two-photoelastic modulator generalized ellipsometer (2-MGE), working in transmission mode, along with the assumption of a two superimposed twin Mueller matrices model (two opposite interfaces in the cylindrical rotation cell) allows us to infer the CD spectra due to overlapping linear polarizations from J aggregates at the front and back liquid-liquid interfaces in the rotating cell. The rotation direction dependence of the CD spectra was thoroughly interpreted by the present model considering the sign and the magnitude of the orientation angle between the front and back J aggregates. The present analysis should help us to understand the optical chirality due to the structural changes in supramolecular and macromolecular systems under flow shear forces as well as changes in birefringence.

Single-molecule lactonization of octadecylrhodamine B at a liquid-liquid interface.

The total internal reflection laser fluorescence microscope method was used to observe the lateral diffusion of a single octadecylrhodamine B (C(18)RB) molecule at the toluene-water interface. The interfacial diffusion constant of single fluorescent cation C(18)RB(+) was obtained from the maximum residence time in a small observation area with pH <2. For pH >3, the maximum residence time was remarkably shortened, indicating that single fluorescent zwitterion C(18)RB(±) rapidly converted to the nonfluorescent lactone at the interface. The lactonization rate was completed within 0.13 ms at the toluene-water interface but slowed to 67 ms at an interface saturated with dimyristoylphosphatidylcholine.

Magnetic-force quartz crystal microbalance for the detection of chemical interactions.

The magnetic-force quartz crystal microbalance (QCM) method was attempted for the dynamic evaluation of chemical interactions. Thiol-modified magnetic particles bound to a QCM gold electrode of less than three layers were pulled by a magnetic force, and the dissociation dynamics of the magnetic particles was measured based on the change in the weight as a function of time under different temperatures. From an analysis of the dissociated layers and the activation energy for the dissociation, the chemical interactions between particles were evaluated.

Brownian motion-magnetophoresis of nano/micro-particles.

A new magnetophoresis method to determine the magnetic susceptibility of single nano/microparticles was developed by applying Brownian motion analysis to determine the size of the particle. This method could measure simultaneously both the magnetophoretic velocity and the radius of the identical single nano/microparticles, which are necessary for the determination of the magnetic susceptibility of the particle. The advantage of this method was demonstrated by the measurement of the diamagnetic susceptibilities of polystyrene particles 500 nm-3 µm in diameter in a paramagnetic 0.5 M manganese(II) chloride solution under a high magnetic field gradient of 5180 T(2) m(-1) generated by a small magnetic circuit.