Preparation and Reactions of Optically Active 4-Hydroxy-1,3-dioxolanes: 2-Hydroxy Aldehyde Equivalents

The preparation and reactions of optically and chemically stable (S)-4-hydroxy-1,3-dioxolane 3 as a 2-hydroxy aldehyde equivalent were explored. Hydroxydioxolane 3 was prepared by reduction of ketodioxolane 2 which was obtained from (S)-2-hydroxycarboxylic acid 1. The reactions of 3 with triethyl phosphonoacetate and organometallic reagents were carried out. These and other conversions gave synthetically and biologically useful products in moderate to good chemical and moderate stereochemical yields.     

Convenient,One-Step Syntheses of 2-Fluoroveratrole And 2-Fluoroveratraldehyde

Metalated veratraldehyde and veratrole were quenched with perchloryl fluoride to provide one-step syntheses of 2-fluoroveratraldehyde and 2-fluoroveratrole, respectively. Previous syntheses of these precursors to 2-fluorodopamine and 5-fluoronorepinephrine are multi-step processess which involve introduction of fluorine at an early stage. Perchloryl fluoride is a potentially hazardous reagent, and should be used only on an appropriate (millimolar) scale with precautions.     

Thiolated dendrimers as multi-point binding headgroups for DNA immobilization on gold

The synthesis of multithiolated DNA molecules that can be used to produce self-assembled monolayers of single-stranded DNA oligonucleotides on gold substrates is described. Generation 3 polyamidoamine (PAMAM) dendrimers were conjugated to DNA oligomers and functionalized with ~30 protected thiol groups. The protected thiol groups-thioacetate groups-allowed the dendrimer-DNA constructs to be stored in a buffer solution for at least 2 months before deprotection without any observable decrease in their ability to assemble into functional layers. The monolayers formed using these multithiolated DNA probe strands demonstrate target capture efficiencies comparable to those of analogous monolayers assembled with DNA functionalized with single thiol groups. A functional advantage of using dendrimer headgroups is the resistance to probe strand loss in prolonged exposure to buffer solutions at a high temperature (95 °C).     

The effect of interfacial microstructure on the lipid oxidation stability of oil-in-water emulsions

Novel rattle-type magnetic mesoporous carbon spheres are successfully prepared using composite spheres with Fe(3)O(4) as core and mesoporous SiO(2) as shell plus solid SiO(2) as a middle layer as templates. These rattle-type spheres possess the magnetization strength of as high as 37.5 emu/g, high and tunable specific surface areas (382-512.6 m(2)/g) due to mesoporous carbon shells. This magnetic rattle-type structure and the readily accessible mesoporous shell are very favoring for the fast adsorption and release of guest objects triggered by external stimulus, for example, the spheres showed very good adsorptive property to dye.     

Reveal E. coli 2.0 method for detection of Escherichia coli O157:H7 in raw beef

Reveal E. coli 2.0 is a new lateral-flow immunodiagnostic test for detection of E. coli O157:H7 and O157:NM in raw beef trim and ground beef. Compared with the original Reveal E. coli O157:H7 assay, the new test utilizes a unique antibody combination resulting in improved test specificity. The device architecture and test procedure have also been modified, and a single enrichment protocol was developed which allows the test to be performed at any point during an enrichment period of 12 to 20 h. Results of inclusivity and exclusivity testing showed that the test is specific for E. coli serotypes O157:H7 and O157:NM, with the exception of two strains of O157:H38 and one strain of O157:H43 which produced positive reactions. In internal and independent laboratory trials comparing the Reveal 2.0 method to the U.S. Department of Agriculture-Food Safety and Inspection Service reference culture procedure for detection of E. coli O157:H7 in 65 and 375 g raw beef trim and ground beef samples, there were no statistically significant differences in method performance with the exception of a single internal trial with 375 g ground beef samples in which the Reveal method produced significantly more positive results. There were no unconfirmed positive results by the Reveal assay, for specificity of 100%. Results of ruggedness testing showed that the Reveal test produces accurate results even with substantial deviation in sample volume or device incubation time or temperature. However, addition of the promoter reagent to the test sample prior to introducing the test device is essential to proper test performance.     

Study of the surface morphology of polyisobutylene-based block copolymers by atomic force microscopy

This paper reports the investigation of the nanostructured surface morphology of linear polystyrene-block-polyisobutylene-block-polystyrene (SIBS) triblock copolymers and novel arborescent SIBS block copolymers by Atomic Force Microscopy (AFM) in the tapping mode. Thin films spin coated from toluene onto silicon wafers were studied. The nanostructured morphology of the block copolymers varied with the hard polystyrene (PS) and soft polyisobutylene (PIB) segment composition, ranging from spherical to lamellar nanometer-sized discreet PS phases dispersed in a continuous PIB matrix. Annealing the samples resulted in well developed/ordered structures. The arborescent blocks had irregularly distributed PS phases in the PIB matrix. Annealing had a dramatic effect on the morphology which still remained irregular. Three-dimensional AFM image and section analysis indicated the presence of a height difference between PIB (high-lying plateaus or hills) and PS (low-lying plateaus or valleys) in the block copolymers, which became more prominent during annealing. It is theorized that the rubbery PIB chains are able to relax, thereby protruding from the surface, anchored by the physically crosslinked PS phases.