Theoretical investigation into the potential of halogenated methanes to undergo reductive metabolism

The density-functional theory (DFT)-based computational chemistry software package DMol was used to provide insight into the reductive potentials of a series of halomethanes. It is known that certain members of this series are readily reduced in vivo via catalysis by cytochrome P450. DMol was used to calculate the electron affinities of these molecules to be used as measures of their reduction potentials. Our results are consistent with experimental electrochemical reduction potentials and indicate that electron affinity is dependent upon the number and type of halogens present in the molecule. Calculated bond lengths and angles also compared favorably with experimental results and estimates derived from other ab initio methods of calculation. Concurrent with this study was the observation of a linear empirical relationship between electron affinity and the lowest unoccupied molecular orbital energy. It is possible that these values could be used as indicators of reductive potentials and ultimately of metabolic rates for use in PB–PK models designed to predict the dose associated with the toxicity of molecules of this and other classes. © John Wiley & Sons, Inc.     

Magnetic field effects on surgical ligation clips

Magnetic forces exerted on surgical clips and the magnetic resonance imaging distortion they create in phantoms and rabbits at magnetic field strengths of 1.5 Tesla were investigated. Results are reported for both ligation and aneurysm clips manufactured from three types of stainless steel as well as titanium, tantalum and niobium metals. Paramagnetism and eddy currents were measured in a customized moving Gouy balance. Direct measurements of other magnetic forces were carried out in a 1.5T MRI system. The titanium and tantalum clips showed the least interaction with the magnetic field, both in terms of forces exerted and the observed image distortion with the larger clips generating the larger interactions. The strongest field distortions and attractive forces occurred with 17-7PH stainless steel clips. These interactions were ferromagnetic in origin and of sufficient strength to present significant risk to patients having this type of clip present during an MRI scan.     

Microfluidic platform for real-time signaling analysis of multiple single T cells in parallel

Deciphering the signaling pathways that govern stimulation of na?ve CD4+ T helper cells by antigen-presenting cells via formation of the immunological synapse is key to a fundamental understanding of the progression of successful adaptive immune response. The study of T cell-APC interactions in vitro is challenging, however, due to the difficulty of tracking individual, non-adherent cell pairs over time. Studying single cell dynamics over time reveals rare, but critical, signaling events that might be averaged out in bulk experiments, but these less common events are undoubtedly important for an integrated understanding of a cellular response to its microenvironment. We describe a novel application of microfluidic technology that overcomes many limitations of conventional cell culture and enables the study of hundreds of passively sequestered hematopoietic cells for extended periods of time. This microfluidic cell trap device consists of 440 18 micromx18 micromx10 microm PDMS, bucket-like structures opposing the direction of flow which serve as corrals for cells as they pass through the cell trap region. Cell viability analysis revealed that more than 70% of na?ve CD4+ T cells (TN), held in place using only hydrodynamic forces, subsequently remain viable for 24 hours. Cytosolic calcium transients were successfully induced in TN cells following introduction of chemical, antibody, or cellular forms of stimulation. Statistical analysis of TN cells from a single stimulation experiment reveals the power of this platform to distinguish different calcium response patterns, an ability that might be utilized to characterize T cell signaling states in a given population. Finally, we investigate in real time contact- and non-contact-based interactions between primary T cells and dendritic cells, two main participants in the formation of the immunological synapse. Utilizing the microfluidic traps in a daisy-chain configuration allowed us to observe calcium transients in TN cells exposed only to media conditioned by secretions of lipopolysaccharide-matured dendritic cells, an event which is easily missed in conventional cell culture where large media-to-cell ratios dilute cellular products. Further investigation into this intercellular signaling event indicated that LPS-matured dendritic cells, in the absence of antigenic stimulation, secrete chemical signals that induce calcium transients in T(N) cells. While the stimulating factor(s) produced by the mature dendritic cells remains to be identified, this report illustrates the utility of these microfluidic cell traps for analyzing arrays of individual suspension cells over time and probing both contact-based and intercellular signaling events between one or more cell populations.     

Trinuclear silver(I) complexes of fluorinated pyrazolates

Silver pyrazolates [[3-(CF3)Pz]Ag]3, [[3-(CF3),5-(CH3)Pz]Ag]3, [[3-(CF3),5-(Ph)Pz]Ag]3, [[3-(CF3),5-(But)Pz]Ag]3, and [[3-(C3F7),5-(But)Pz]Ag]3 have been synthesized by treatment of the corresponding pyrazole with a slight molar excess of silver(I) oxide. This economical and convenient route gives silver pyrazolates in high (>80%) yields. X-ray crystal structures of [[3-(CF3),5-(CH3)Pz]Ag]3, [[3-(CF3),5-(But)Pz]Ag]3, and [[3-(C3F7),5-(But)Pz]Ag]3 show that these molecules have trinuclear structures with essentially planar to highly distorted Ag3N6 metallacycles. [[3-(CF3),5-(CH3)Pz]Ag]3 forms extended columns via intertrimer argentophilic contacts (the closest Ag...Ag separation between the neighboring trimers are 3.355 and 3.426 A). The trinuclear [[3-(CF3),5-(But)Pz]Ag]3 units crystallize in pairs, basically forming "dimers of trimers", with the six silver atom core of the adjacent trimers adopting a chair conformation. However, in these dimers of trimers, even the shortest intertrimer Ag...Ag distance (3.480 A) is slightly longer than the van der Waals contact of silver (3.44 A). [[3-(C3F7),5-(But)Pz]Ag]3, which has two bulky groups on each pyrazolyl ring, shows no close intertrimer Ag...Ag contacts (closest intertrimer Ag...Ag distance = 5.376 A). The Ag-N bond distances and the intratrimer Ag...Ag separations of the silver pyrazolates do not show much variation. However, their N-Ag-N angles are sensitive to the nature (especially, the size) of substituents on the pyrazolyl rings. The pi-acidic [[3,5-(CF3)2Pz]Ag]3 and [[3-(C3F7),5-(But)Pz]Ag]3 form adducts with the pi-base toluene. X-ray data show that they adopt extended columnar structures of the type [[Ag3]2.[toluene]]infinity and [[Ag3]'.[toluene]]infinity ([[3,5-(CF3)2Pz]Ag]3 = [Ag3],[[3-(C3F7),5-(But)Pz]Ag]3 = [Ag3]'), in which toluene interleaves and makes face-to-face contacts with [[3-(C3F7),5-(But)Pz]Ag]3 or dimers of [[3,5-(CF3)2Pz]Ag]3.     

Stereospecific effects determine the structure of a four-way DNA junction

Conversion of a centrally located phosphate group to an electrically neutral methyl phosphonate in a four-way DNA junction can exert a major influence on its conformation. However, the effect is strongly dependent on stereochemistry. Substitution of the proR oxygen atom by methyl leads to conformational transition to the stacking conformer that places this phosphate at the point of strand exchange. By contrast, corresponding modification of the proS oxygen destabilizes this conformation of the junction. Single-molecule analysis shows that both molecules are in a dynamic equilibrium between alternative stacking conformers, but the configuration of the methyl phosphonate determines the bias of the conformational equilibrium. It is likely that the stereochemical environment of the methyl group affects the interaction with metal ions in the center of the junction.     

Radial oscillations of neutron stars in strong magnetic fields

The eigen frequencies of radial pulsations of neutron stars are calculated in a strong magnetic field. At low densities we use the magnetic BPS equation of state (EOS) similar to that obtained by Lai and Shapiro while at high densities the EOS obtained from the relativistic nuclear mean field theory is taken and extended to include strong magnetic field. It is found that magnetized neutron stars support higher maximum mass whereas the effect of magnetic field on radial stability for observed neutron star masses is minimal.     

The metabolism of norethandrolone in the horse: characterization of 16-, 20- and 21-oxygenated metabolites by gas chromatography/mass spectrometry

After oral administration to a thoroughbred gelding, the anabolic steroid norethandrolone was converted into a complex mixture of oxygenated metabolites. These metabolites were extracted from the urine, deconjugated by methanolysis and converted to their O-methyloxime trimethylsilyl derivatives. Gas chromatographic/mass spectrometric analysis indicated the major metabolites to be 19-norpregnane-3,16,17-triols, 19-norpregnane-3,17,20-triols and 3,17-dihydroxy-19-norpregnan-21-oic acids. Some minor metabolites were also detected.     

A rapid and efficient method for the reduction of quinoxalines

Mono and di‐substituted alkyl and aryl quinoxalines are rapidly reduced in high yield to their respective 1,2,3,4‐tetrahydro‐derivatives by borane in THF solution. In the case of the 2,3‐di‐substituted compounds, reduction is stereoselective yielding exclusively the cis‐isomers. Sodium borohydride in acetic acid also reduces alkyl and aryl quinoxalines, but proceeds with lower yields and often produces side products. Sodium borohydride in ethanol reduces quinoxaline and 2‐methylquinoxaline in high yield; however, the reaction is very slow, whereas 2,3‐dialkyl and 2‐aryl quinoxalines are not efficiently reduced by sodium borohydride in ethanol.