Aryl substituent effects upon the thermal isomerization of n-alkyl oxaziridines to nitrones

The results of a kinetic study of the thermal isomerization of oxaziridines derived from $\text{para}$-substituted C-arylaldimines and C-diarylketimines to the isomeric nitrones is reported.     

Shape Memory Particles Capable of Controlled Geometric and Chemical Asymmetry made from Aliphatic Polyesters

A novel method for producing monodisperse micro‐ and nanosized shape memory particles from various shape memory polymers (SMPs) is reported. This method uses a polydimethylsiloxane mold to uniformly deform particles from complex shapes to other well‐defined shapes, harvest them without aggressive solvents or heat, and then return them to their original shapes upon heating above a preselected trigger temperature. By manipulating the material properties of both the mold and SMP, monodisperse asymmetric particles are easily achieved. This method is demonstrated with traditional SMPs and polymers with varying degrees of reactive functionality, crystallinity, and transition temperature. This additional reactivity and the robustness of this system allow easy tailoring of the surface with click chemistry to achieve chemical asymmetry.

     

Acoustic scattering by a spherical obstacle: modification to the analytical long-wavelength solution for the zero-order coefficient

Classical long wavelength approximate solutions to the scattering of acoustic waves by a spherical liquid particle suspended in a liquid (an emulsion) show small but significant differences from full solutions at very low k(c)a (typically k(c)a < 0.01) and above at k(c)a > 0.1, where k(c) is the compressional wavenumber and a the particle radius. These differences may be significant in the context of dispersed particle size estimates based on compression wave attenuation measurements. This paper gives an explanation of how these differences arise from approximations based on the significance of terms in the modulus of the complex zero-order partial wave coefficient, A(0). It is proposed that a more accurate approximation results from considering the terms in the real and imaginary parts of the coefficient, separately.     

Ground state 14N quadrupole couplings in the microwave spectra of N,N'-dimethylaniline and 4,4'-dimethylaminobenzonitrile

Microwave spectra of N,N'-dimethylaniline and 4,4'-dimethylaminobenzonitrile have been recorded in a pulsed supersonic jet using chirped pulse techniques. Experimental substitution structures have been determined for both molecules by detection of the spectra of all (13)C and (15)N isotopomers in natural abundance using a broadband spectrometer. Additionally, a narrowband spectrometer has been used to reveal the (14)N quadrupole splittings at high resolution, from which the orbital occupancy numbers of the amino- and cyano-nitrogen atoms have been determined. An apparent direct relationship between these values and the barriers to inversion of the amino groups is discussed.     

Monte Carlo Simulation of Ion Trajectories of Reacting Chemical Systems: Mobility of Small Water Clusters in Ion Mobility Spectrometry

For the comprehensive simulation of ion trajectories including reactive collisions at elevated pressure conditions, a chemical reaction simulation (RS) extension to the popular SIMION software package was developed, which is based on the Monte Carlo statistical approach. The RS extension is of particular interest to SIMION users who wish to simulate ion trajectories in collision dominated environments such as atmospheric pressure ion sources, ion guides (e.g., funnels, transfer multi poles), chemical reaction chambers (e.g., proton transfer tubes), and/or ion mobility analyzers. It is well known that ion molecule reaction rate constants frequently reach or exceed the collision limit obtained from kinetic gas theory. Thus with a typical dwell time of ions within the above mentioned devices in the ms range, chemical transformation reactions are likely to occur. In other words, individual ions change critical parameters such as mass, mobility, and chemical reactivity en passage to the analyzer, which naturally strongly affects their trajectories. The RS method simulates elementary reaction events of individual ions reflecting the behavior of a large ensemble by a representative set of simulated reacting particles. The simulation of the proton bound water cluster reactant ion peak (RIP) in ion mobility spectrometry (IMS) was chosen as a benchmark problem. For this purpose, the RIP was experimentally determined as a function of the background water concentration present in the IMS drift tube. It is shown that simulation and experimental data are in very good agreement, demonstrating the validity of the method.      

The Global Response of Nostoc punctiforme ATCC 29133 to UVA Stress,Assessed in a Temporal DNA Microarray Study

Cyanobacteria in nature are exposed not only to the visible spectrum of sunlight but also to its harmful ultraviolet components (UVA and UVB). We used Nostoc punctiforme ATCC 29133 as a model to study the UVA response by analyzing global gene expression patterns using genomic microarrays. UVA exposure resulted in the statistically detectable differential expression of 573 genes of the 6903 that were probed, compared with that of the control cultures. Of those genes, 473 were up‐regulated, while only 100 were down‐regulated. Many of the down‐regulated genes were involved in photosynthetic pigment biosynthesis, indicating a significant shift in this metabolism. As expected, we detected the up‐regulation of genes encoding antioxidant enzymes and the sunscreen, scytonemin. However, a majority of the up‐regulated genes, 47%, were unassignable bioinformatically to known functional categories, suggesting that the UVA stress response is not well understood. Interestingly, the most dramatic up‐regulation involved several contiguous genes of unassigned metabolism on plasmid A. This is the first global UVA stress response analysis of any phototrophic microorganism and the differential expression of 8% of the genes of the Nostoc genome indicates that adaptation to UVA in Nostoc has been an evolutionary force of significance.     

Anti-Inflammatory Effects of the Iron Chelator,DIBI, in Experimental Acute Lung Injury

Iron plays a critical role in the immune response to inflammation and infection due to its role in the catalysis of reactive oxygen species (ROS) through the Haber-Weiss and Fenton reactions. However, ROS overproduction can be harmful and damage healthy cells. Therefore, iron chelation represents an innovative pharmacological approach to limit excess ROS formation and the related pro-inflammatory mediator cascades. The present study was designed to investigate the impact of the iron chelator, DIBI, in an experimental model of LPS-induced acute lung injury (ALI). DIBI was administered intraperitoneally in the early and later stages of lung inflammation as determined by histopathological evaluation. We found that lung tissues showed significant injury, as well as increased NF-κB p65 activation and significantly elevated levels of various inflammatory mediators (LIX, CXCL2, CCL5, CXCL10, IL-1𝛽, IL-6) 4 h post ALI induction by LPS. Mice treated with DIBI (80 mg/kg) in the early stages (0 to 2 h) after LPS administration demonstrated a significant reduction of the histopathological damage score, reduced levels of NF-κB p65 activation, and reduced levels of inflammatory mediators. Intravital microscopy of the pulmonary microcirculation also showed a reduced number of adhering leukocytes and improved capillary perfusion with DIBI administration. Our findings support the conclusion that the iron chelator, DIBI, has beneficial anti-inflammatory effects in experimental ALI.     

Dual-Color Photoconvertible Fluorescent Probes Based on Directed Photooxidation Induced Conversion for Bioimaging

We herein present a new concept to produce dual-color photoconvertible probes based on a mechanism called Directed Photooxidation Induced Conversion (DPIC). As a support of this mechanism, styryl-coumarins ( SCs ) bearing Aromatic Singlet Oxygen Reactive Moieties (ASORMs) like furan and pyrrole have been synthesized. SCs are bright fluorophores, which undergo a hypsochromic conversion upon visible light irradiation due to directed photooxidation of the ASORM that leads to the disruption of conjugation. SC-P , a yellow emitting probe bearing a pyrrole moiety, converts to a stable blue emitting coumarin with a 68 nm shift allowing the photoconversion and tracking of lipid droplet in live cells. This new approach might pave the way to a new generation of photoconvertible dyes for advanced bioimaging applications.