MPI System with Bore Sizes of 75 mm and 100 mm Using Permanent Magnets and FMMD Technique.

We present two magnetic particle imaging (MPI) systems with bore sizes of 75 mm and 100 mm, respectively, using three-dimensionally arranged permanent magnets for excitation and frequency mixing magnetic detection (FMMD) coils for detection. A rotational and a translational stage were combined to move the field free line (FFL) and acquire the MPI signal, thereby enabling simultaneous overall translation and rotational movement. With this concept, the complex coil system used in many MPI systems, with its high energy consumption to generate the drive field, can be replaced. The characteristic signal of superparamagnetic iron oxide (SPIO) nanoparticles was generated via movement of the FFL and acquired using the FMMD coil. The positions of the stages and the occurrence of the f1 + 2f2 harmonics were mapped to reconstruct the spatial location of the SPIO. Image reconstruction was performed using Radon and inverse Radon transformations. As a result, the presented method based on mechanical movement of permanent magnets can be used to measure the MPI, even for samples as large as 100 mm. Our research could pave the way for further technological developments to make the equipment human size, which is one of the ultimate goals of MPI.

A Novel Field-Free Line Generator for Mechanically Scanned Magnetic Particle Imaging.

In this study, we propose an efficient field-free line (FFL) generator for mechanically driven FFL magnetic particle imaging (MPI) applications. The novel FFL generator comprises pairs of Halbach arrays and bar magnets. The proposed design generates high-gradient FFLs with low-mass permanent magnets, realizing fine spatial resolutions in MPI. We investigate the magnetic field generated using simulations and experiments. Our results show that the FFL generator yields a high gradient of 4.76 T/m at a cylindrical field of view of 30 mm diameter and a 70 mm open bore. A spatial resolution of less than 3.5 mm was obtained in the mechanically driven FFL-MPI.

Is the biotransformation of chlorinated dibenzo-p-dioxins by Sphingomonas wittichii RW1 governed by thermodynamic factors?

Density functional theory (DFT) calculations were used to explore the relationship between the biotransformation of dibenzo-p-dioxin and selected chlorinated derivatives by resting cells of Sphingomonas wittichii RW1 and measuring the thermodynamic properties of the biotransformation substrates. Sphingomonas wittichii RW1 can aerobically catabolize dibenzo-p-dioxin as well as 2,7-dichloro-, 1,2,3-trichloro-, 1,2,3,4-tetrachloro-, and 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin; however, neither the 2,3,7-trichloro- nor the 1,2,3,7,8-pentachlorodibenzo-p-dioxin was transformed to its corresponding metabolic intermediate. The experimental biotransformation rates established were apparently governed by the selected thermodynamic properties of the substrates tested.

Analysis of beta amyloid peptides employing the small probe molecules.

We herein describe an analytical method employing a small molecule array for the characterization of similar proteins based on ligand binding. In this study, 2 different beta amyloids (Abeta(1-40) and (1-42)) were selected as the model compounds. Their primary structures are identical except for 2 additional C-terminal amino acids. However, many studies have observed different biological and chemical characteristics of these peptides. Thus, the ability to distinguish these 2 peptides is important in the diagnosis and development of treatments for related disorders such as Alzheimer's disease. However, strong non-specific binding is usually observed, even when specific antibodies for each peptide are employed. In this study, Abeta(1-40) and Abeta(1-42) peptides were immobilized on a typical 96-well microplate. Twenty different small probe molecules (modified amino acids conjugated with FITC) were applied to the peptides acting as the secondary antibodies and labeling compounds. The results show that specific binding patterns occurred according to Abeta type and the analysis of the patterns can be used to distinguish these 2 similar peptides.

Detection of two different influenza A viruses using a nitrocellulose membrane and a magnetic biosensor.

Here we describe a new analytical method for the detection of two influenza A viruses by nitrocellulose membrane and magnetic sensors that employ a special frequency mixing technique. The combination of the nitrocellulose membrane and magnetic bead detection permits a rapid assay procedure and excludes two steps (the development of color and the stop reaction) required for usual immunochemical detection methods such as ELISA. Quantitative virus detection was performed using magnetic beads conjugated with secondary antibody. The results were compared with conventional assay methods and with a dot-blot assay with fluorescence compound (FITC). Under optimum conditions, our new assay procedure is capable of detecting picograms of virus per well. This new method combining the nitrocellulose membrane and magnetic bead detection reduces analytical time and allows stable and repeatable analyses of samples in point-of-care applications.

Centrifugal enhancement of Kaposi's sarcoma-associated virus infection of human endothelial cells in vitro.

In order to improve the efficiency of infection of primary human endothelial cells in vitro of Kaposi's sarcoma-associated herpesvirus (KSHV), the effect of low speed centrifugation was investigated. The recombinant KSHV, BAC36, was used to examine the centrifugal enhancement of KSHV. Infectivity was estimated by green fluorescent protein (GFP) expression and real-time RT-PCR. The enhancement of infectivity was dependent upon the time and force of centrifugation in human umbilical vein endothelial cells (HUVECs). Centrifugation enhanced the infectivity of KSHV by up to 70 fold compared to non-centrifugal control infection for the same period of time; viral mRNA expression was also enhanced by centrifugation. HUVECs that were centrifuged before infection with KSHV displayed no enhancement in infectivity; therefore, enhancement is believed to occur during centrifugation. In addition, the mechanisms of infection including the initial viral attachment to cells, lipid rafts, and clathrin-mediated and caveolae endocytosis appear to be similar in KSHV infection with and without centrifugal enhancement. These results show that low speed centrifugation could be a useful tool for improving the efficiency of KSHV infection in vitro.

Effect of heavy metals on the biodegradation of dibenzofuran in liquid medium.

The effect of heavy metals on the degradation of dibenzofuran by Sphingomonas wittichii RW1 was determined in liquid cultures. The results showed that 10mg/L cadmium, mercury and copper not only affected the growth of RW1 with dibenzofuran but also the ability of resting cells to degrade this compound. Growth and degradation were strongly inhibited by mercury, even at 1mg/L, while the inhibitory effect of cadmium and copper at the same concentration or at 5mg/L were negligible. In contrast, arsenic and lead did not affect degradation or growth, even at very high concentrations of 100mg/L. Subsequent analyses additionally revealed that concentrations of arsenic and lead remained unchanged following incubation, while those of cadmium, mercury and copper decreased significantly.

Biological removal of polychlorinated dibenzo-p-dioxins from incinerator fly ash by Sphingomonas wittichii RW1.

The ability of Sphingomonas wittichii strain RW1 to remove polychlorinated dibenzo-p-dioxins (PCDDs) from fly ash was investigated. All experiments were carried out in a slurry-phase system. Preliminary studies with resting cells of strain RW1 in a model fly ash system showed the complete removal of dibenzofuran (DF) and 81% of dibenzo-p-dioxin (DD). Incubation of real fly ash collected from municipal waste incinerators with strain RW1 for 15 days resulted in a 75.5% reduction in toxic PCDDs. When the same experiment was carried out using dead strain RW1 cells a 20.2% reduction in toxic PCDDs was observed, indicating that adsorption onto biomass was an important factor in dioxin elimination. Further analyses revealed that live strain RW1 cells removed 83.8% of the 2,3,7,8-substituted congeners from the fly ash, while dead cells removed 32.1% of the same congeners. To enhance the removal efficiency of toxic PCDDs, the effects of adding surfactant, repeated inoculation, and pre-adaptation of cultures were also studied. The removal of toxic PCDDs was enhanced by up to 10.3% upon repeated inoculation of the strain RW1, but was not much affected by the addition of surfactant. The present results suggest that S. wittichii strain RW1 is a potential candidate for the industrial removal of PCDDs from incinerator fly ash.

Biodegradation of dibenzo-p-dioxin, dibenzofuran, and chlorodibenzo-p-dioxins by Pseudomonas veronii PH-03.

The dioxin-degrading strain Pseudomonas veronii PH-03 was isolated from contaminated soil by selective enrichment techniques. Strain PH-03 grew on dibenzo-p-dioxin and dibenzofuran as a sole carbon source. Further, 1-chlorodibenzo-p-dioxin, 2-chlorodibenzo-p-dioxin and other dioxin metabolites, salicylic acid, and catechol were also metabolized well. Resting cells of strain PH-03 transformed dibenzo-p-dioxin, dibenzofuran, 2,2',3-trihydroxybiphenyl, and some chlorodioxins to their corresponding metabolic intermediates such as catechol, salicylic acid, 2-hydroxy-(2-hydroxyphenoxy)-6-oxo-2,4-hexadienoic acid, and chlorocatechols. The formation of these metabolites was confirmed by comparison of gas chromatography-mass spectrometry (GC-MS) data with those of authentic compounds. Although we did observe the production of 3,4,5,6-tetrachlorocatechol (3,4,5,6-TECC) from 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TCDD) with resting cell suspensions of PH-03, growth of strain PH-03 in the presence of 1,2,3,4-TCDD was poor. This result suggests that strain PH-03 is unable to utilize 3,4,5,6-TECC, even at very low concentration (0.01 mM) due to its toxicity. In cell-free extracts of DF-grown cells, 2,2',3-trihydroxybiphenyl dioxygenase, 2-hydroxy-6-oxo-6-phenyl-2,4-hexadienoic acid hydrolase, and catechol-2,3-dioxygense activities were detected. Moreover, the activities of meta-pyrocatechase and 2,2',3-trihydroxybiphenyl dioxygenase from the crude cell-free extracts were inhibited by 3-chlorocatechol. However, no inhibition was observed in intact cells when 3-chlorocatechol was formed as intermediate.

Adsorption of halogenated aromatic pollutants by a protein released from Bacillus pumilus.

Previous studies of the biosorption of halogenated aromatic pollutants (HAPs) have focused on the sorption of these compounds by cell bodies. However, in this study we investigated the adsorption of HAPs by biocompounds released from a bacterium, Bacillus pumilus. When B. pumilus was exposed to high temperature, it released a protein and carbohydrates, exclusively. After determining experimental conditions using 1,2,3,4-tetrachlorinated dibenzofuran (1,2,3,4-TCDF), the adsorption characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), chlorinated benzenes, and chlorinated naphthalenes were investigated. These HAPs were adsorbed considerably not only by cells but also by the released protein. In general, highly chlorinated congeners were adsorbed to a greater extent on the protein than lowly chlorinated ones, and the amount adsorbed differed between isomers. The present results are consistent with adsorption occurring via a passive physico-chemical mechanism. Finally, the importance of biocompounds released or excreted from microorganisms for the removal of HAPs is discussed.

Biotransformation of 2,7-dichloro- and 1,2,3,4-tetrachlorodibenzo-p-dioxin by Sphingomonas wittichii RW1.

Aerobic biotransformation of the diaryl ethers 2,7-dichlorodibenzo-p-dioxin and 1,2,3,4-tetrachlorodibenzo-p-dioxin by the dibenzo-p-dioxin-utilizing strain Sphingomonas wittichii RW1, producing corresponding metabolites, was demonstrated for the first time. Our strain transformed 2,7-dichlorodibenzo-p-dioxin, yielding 4-chlorocatechol, and 1,2,3,4-tetrachlorodibenzo-p-dioxin, producing 3,4,5,6-tetrachlorocatechol and 2-methoxy-3,4,5,6-tetrachlorophenol; all of these compounds were unequivocally identified by mass spectrometry both before and after N,O-bis(trimethylsilyl)-trifluoroacetamide derivatization by comparison with authentic standards. Additional experiments showed that strain RW1 formed a second metabolite, 2-methoxy-3,4,5,6-tetrachlorophenol, from the original degradation product, 3,4,5,6-tetrachlorocatechol, by methylation of one of the two hydroxy substituents.