Microspheres (MS), such as emulsion droplets, multiple emulsions, microparticles, microcapsules, and liposomes, have been utilized in various industries. However, size control of MS is not so easy. Recently, we proposed a novel method for preparing monodispersed emulsion droplets with a coefficient of variation less than 5% from a microfabricated channel (MC) array. In this study, we analyzed a droplet-formation mechanism from a MC using a microscope high-speed camera system. During droplet formation, the dispersed phase passed through the channel inflated on the terrace in a disklike shape, and the droplets were formed in 0.01 s. A droplet-formation mechanism was suggested in which the distorted dispersed phase on the terrace is cut off spontaneously into spherical droplets by interfacial tension. The mechanism is shown to be an adequate model from the viewpoint of interfacial free energy. This emulsification technique exploits the interfacial tension, which is the dominating force on a micrometer scale. It is a promising technique for producing MS requiring extreme monodispersity because of its simplicity.

A novel emulsification method was developed for making monodispersed regular-sized cells. Both oil in water (O/W) and water in oil (W/O) emulsion cells were generated by permeating an internal phase into a continuous phase through a silicon microchannel, which was designed and prepared by using semiconductor technology. The microprocessing of O/W (or W/O) emulsion cells was monitored and controlled with a microscope video system. Regular-sized O/W cells were made by a normal hydrophilic microchannel and a glass plate with use of an appropriate surfactant. On the other hand, W/O emulsion cells were made by a hydrophobic microchannel and a glass plate modified with a silane coupler reagent. Regularsized W/O cells were also obtained; therefore, a suitable combination of organic phase, surfactant, and electrolyte should be carefully selected. There is a possibility for creating artificial biological cells with this method. In the water/triolein and lecithin system, when the amount of oil was decreased on the permeate side, polygon or fiber cell types were created, and each cell contacted its neighbors across a thin oil layer like a biological tissue. JAOCS 74, 317-321 (1997). FIG. 4. Microchannel emulsification for making water in oil (W/O) cells:(A) water permeation through the hydrophilic channel; (B,C) water permeation through the channel, partially wetted by water, in the system: water/triolein with 0.3 wt% sorbitan monooleate; (D) water permeation through the channel, wetted by water, in water/triolein with 0.1 wt% sorbitan monooleate system; (E) breakthrough the microchannel and cell creation in the system: water with 0.75 wt% KCl/kerosene with 3 wt% sorbitan monolaurate; (F) regular-sized W/O cells of 21 µm packed in the closest conformation; (G) the W/O cells observed at a different focus point; (H) W/O cells in the system: water with 0.86 wt% NaCl/oleic acid with 3 wt% sorbitan monolaurate.

The aim of the present study was to investigate the preparation of β-carotene nanodispersions as potential active ingredients for food formulations. Nanodispersions containing β-carotene were obtained by a process based on an emulsification-evaporation technique. The preparation method consisted of emulsifying an organic solution of β-carotene in an aqueous solution containing emulsifier using two different homogenizers (a conventional homogenizer and a microfluidizer), followed by direct solvent evaporation under reduced pressure. The influence of different homogenizing conditions (pressure and cycle) and two organic/aqueous phase ratios on particle size parameters and content of β-carotene was investigated. In addition, the stability of β-carotene nanodispersions was carried out at a storage temperature of 4 °C. The particle size distribution of β-carotene in nanodispersions was demonstrated with a laser diffraction particle size analyzer and the retention of βcarotene in the prepared nanodispersions was studied by high-pressure liquid chromatography. In general, homogenization pressure and cycle had significant (P < 0.05) effects on various particle size parameters. A volume-weighted mean diameter (D4,3) of βcarotene nanoparticles, ranging from 60 to 140 nm, was observed in this study.

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Two major products (adducts A and B) from the reaction of 2-deoxyguanosine (dGuo) with 13-hydroperoxylinoleic acid were detected by liquid chromatography/mass spectrometry (LC/MS). Adducts A and B were also the major products formed enzymatically when dGuo was incubated in the presence of linoleic acid and lipoxygenase. The mass spectral fragmentation patterns of adducts A and B suggested that unique modifications to the nucleoside had been introduced. This resulted in the characterization of a novel bifunctional electrophile, 4-oxo-2-nonenal, as the principal breakdown product of linoleic acid hydroperoxide. In subsequent studies, adduct A was found to be a substituted ethano dGuo adduct that was a mixture of three isomers (A(1)-A(3)) that all decomposed to form adduct B. Adduct A(1) was the hemiacetal form of 3-(2-deoxy-beta-D-erythropentafuranosyl)-3,5,6, 7-tetrahydro-6-hydroxy-7-(heptane-2-one)-9H-imidazo[1, 2-alpha]purine-9-one. Adducts A(2) and A(3) were the diastereomers of the open chain ketone form. Adduct B was the substituted etheno dGuo adduct, 3-(2-deoxy-beta-D-erythropentafuranosyl)imidazo-7-(heptane-2 -one)-9-hydroxy[1,2-alpha]purine, the dehydration product of adducts A(1)-A(3). Identical covalent modifications to dGuo were observed when calf-thymus DNA was treated with 4-oxo-2-nonenal. These data illustrate the diversity of reactive electrophiles produced from the peroxidative decomposition of lipids and have implications in fully assessing the role of lipid peroxidation in mutagenesis and carcinogenesis.

SummaryIn cultivated rice two wild-type alleles, Wx a and Wx b , predominate at the waxy locus, which encodes granulebound starch synthase. The activity of Wx a is 10-fold higher than that of Wx b at the level of both protein and mRNA.Wx b has a ϩ1G to T mutation at the 5Ј splice site of the first intron. Sequence analysis of Wx b transcripts revealed that splicing occurs at the mutant AG/UU site and at two cryptic sites: the first is A/GUU, one base upstream of the original site and the second is AG/GU found approximately 100 bases upstream of the mutant splice site. We introduced single base mutations to the 5Ј splice sites of both Wx a and Wx b , fused with the gus reporter gene and introduced them into rice protoplasts. Analysis of GUS activities and transcripts indicated that a G to T mutation in Wx a reduced GUS activity and the level of spliced RNA. Conversely, a T to G mutation of Wx b restored GUS activity and the level of spliced RNA to that of wild-type Wx a . These results demonstrated that the low level expression of Wx b results from a single base mutation at the 5Ј splice site of the first intron. It is of interest that the Wx b allele of rice carrying the G to T mutation of intron 1 has been conserved in the history of rice cultivation because there is a low amylose content of the seed caused by this mutation.