Kinetics of the gas-phase reactions of NO3 radicals with a series of aromatics at 296 ± 2 K

Rate constants have been determined at 296 ± 2 K for the gas phase reaction of NO₃ radicals with a series of aromatics using a relative rate technique. The rate constants obtained (in cm³ molecule^?1 s^?1 units) were: benzene, <2.3 × 10^?17; toluene, (1.8 ± 1.0) × 10^?17; o? xylene, (1.1 ± 0.5) × 10^?16; m? xylene, (7.1 ± 3.4) × 10^?17; p? xylene, (1.4 ± 0.6) × 10^?16; 1,2,3-trimethylbenzene, (5,6 ± 2.6) × 10^?16; 1,2,4-trimethylbenzene (5.4 - 2.5) × 10^?16; 1,3,5-trimethylbenzene, (2.4 ± 1.1) × 10^?16; phenol, (2.1 ± 0.5) × 10^?12; methoxybenzene, (5.0 ± 2.8) × 10^?17; o-cresol, (1.20 ± 0.34) × 10^?11; m-cresol, (9.2 ± 2.4) × 10^?12; p-cresol, (1.27 ± 0.36) × 10^?11; and benzaldehyde, (1.13 ± 0.25) × 10^?15. These kinetic data, together with, in the case of phenol, product data, suggest that these reactions proceed via H-atom abstraction from the substituent groups. The magnitude of the rate constants for the hydroxy-substituted aromatics indicates that the nighttime reaction of NO₃ radicals with these aromatics can be an important loss process for both NO₃ radicals and these organics, as well as being a possible source of nitric acid, a key component of acid deposition.     

Cross relaxation between the spin levels of phosphorescent 1,2,4,5-tetrachlorobenzene and photochemical products of the durene host

At certain magnetic fields, intensity changes have been observed in the phosphorescence of 1,2,4,5-tetrachlorobenzene (TCB) doped in a single crystal oFollowing the application of a magnetic field of the proper magnitude and direction to induce CR, the phosphorescence intensity of TCB displays an obse     

X-ray Crystallographic Structure of the Potent Antiplasmodial Compound 2,7-Dibromocryptolepine Acetic Acid Solvate

Abstract  The structure of 2,7-dibromocryptolepine acetic acid solvate, C₁₆H₁₁N₂Br₂ [1.5(C₂H₄O₂)][C₂H₃O₂⁻][0.5H₂O], M_r = 460.17, has been determined from X-ray diffraction data. The crystals are monoclinic, space group P2₁/c with Z = 4 molecules per unit cell and a = 7.3243(3), b = 18.7804(6), c = 15.8306(7) ?, β = 94.279(1)°, V_c = 2171.5(2) ?, crystal density D_c = 1.667 g/cm³. The structure was determined using direct methods and refined by full-matrix least-squares to a conventional R-index of 0.0496 for 4,908 reflections and 258 parameters. The cryptolepine nucleus of the 2,7-dibromocryptolepine molecule is highly planar and the two Br atoms are in this plane within 0.06 and 0.01 ?, respectively. The crystal structure is maintained via hydrogen bonding between N(10) in the cryptolepine nucleus and the oxygen of one of the three solvated acetic acid molecules. The acetic acid molecules also form hydrogen bonded chains. Acetic acid B is deprotonated and its two C–O bond lengths are equivalent, unlike those in A and C. Acetic acid C lies very close to a crystallographic centre of symmetry. To avoid overlap the two repeats cannot exist together and are subject to 50% statistical disorder. O(1C) of this methanol is furthest from the two-fold axis and its occupancy refines to a value of 1.0 and is assumed to exist alternately as a water oxygen hydrogen bonding to methanol O(1C) across the two-fold axis at a distance of 2.775 ?. Index Abstract  The antiplasmodial activity of the analogue 2,7-dibromocryptolepine is nine times greater than that of cryptolepine itself against chloroquine-resistant Plasmodium falciparum (multi-drug resistant strain K1) with IC₅₀ values = 0.44 and 0.049 μM, respectively. This analogue also showed promising in vivo activity against P. berghei in mice. Parasitaemia was suppressed by 91.4% compared to untreated infected control animals at a dose of 25 mg/kg given daily by i.p. injection with no apparent toxicity to the mice, in contrast to cryptolepine which was toxic to mice when given i.p. at 20 mg/kg. Further experiments showed a dose-dependent relationship with ED₅₀ and ED₉₀ values of 6.92 and 21.46 mg/kg/day, respectively. Although 2,7-dibromocryptolepine was not toxic to the mice its cytotoxic activity is similar to that of cryptolepine, but unlike cryptolepine it does not appear to intercalate into DNA as assessed using thermodenaturation techniques (ΔTm values = 3 and 9 °C, respectively). Like cryptolepine, 2,7-dibromocryptolepine inhibits the formation of haemozoin, but its increased antiplasmodial potency does not appear to be due to more potent inhibition of haemozoin formation, nor to increased accumulation into the acidic parasite food vacuole suggesting that 2,7-dibromocryptolepine has additional modes of action compared to cryptolepine. The X-ray structure of this compound will help to determine whether or not 2,7-dibromocryptolepine is able to intercalate into DNA and facilitate the design of new cryptolepine analogues with DNA binding properties appropriate for antimalarial (with no DNA intercalation) or anticancer (sequence-specific binding) applications.      

Making the SF5 Group More Accessible: A Gas‐Reagent‐Free Approach to Aryl Tetrafluoro‐λ6‐sulfanyl Chlorides

Modern pentafluorosulfanyl (SF₅) chemistry has an Achilles heel: synthetic accessibility. Herein, we present the first approach to aryl‐SF₄Cl compounds (key intermediates in state‐of‐the‐art aryl‐SF₅ synthesis) that overcomes the reliance on hazardous fluorinating reagents and/or gas reagents (e.g. Cl₂) by employing easy‐to‐handle trichloroisocyanuric acid, potassium fluoride, and catalytic amounts of acid. These simple, mild conditions allow direct access to aryl‐SF₄Cl intermediates that either have not been or cannot be demonstrated using previous methods. Furthermore, the same approach provides access to aryl‐SF₃ and aryl‐SeF₃ compounds, which extend the applications of this chemistry beyond arene SF₅‐functionalization, and demonstrate its ability to address a more general oxidative fluorination problem.     

Association of the T allele of an intronic single nucleotide polymorphism in the colony stimulating factor 1 receptor with Crohn's disease: a case-control study

BACKGROUND: Polymorphisms in several genes (NOD2, MDR1, SLC22A4) have been associated with susceptibility to Crohn's disease. Identification of the remaining Crohn's susceptibility genes is essential for the development of disease-specific targets for immunotherapy. Using gene expression analysis, we identified a differentially expressed gene on 5q33, the colony stimulating factor 1 receptor (CSF1R) gene, and hypothesized that it is a Crohn's susceptibility gene. The CSF1R gene is involved in monocyte to macrophage differentiation and in innate immunity. METHODS: Patients provided informed consent prior to entry into the study as approved by the Institutional Review Board at LSU Health Sciences Center. We performed forward and reverse sequencing of genomic DNA from 111 unrelated patients with Crohn's disease and 108 controls. We also stained paraffin-embedded, ileal and colonic tissue sections from patients with Crohn's disease and controls with a polyclonal antibody raised against the human CSF1R protein. RESULTS: A single nucleotide polymorphism (A2033T) near a Runx1 binding site in the eleventh intron of the colony stimulating factor 1 receptor was identified. The T allele of this single nucleotide polymorphism occurred in 27% of patients with Crohn's disease but in only 13% of controls (X2 = 6.74, p < 0.01, odds ratio (O.R.) = 2.49, 1.23 < O.R. < 5.01). Using immunohistochemistry, positive staining with a polyclonal antibody to CSF1R was observed in the superficial epithelium of ileal and colonic tissue sections. CONCLUSIONS: We conclude that the colony stimulating factor receptor 1 gene may be a susceptibility gene for Crohn's disease.     

Overview of edge electrostatic turbulence experiments on TCV

Experiments on edge turbulence in the TCV tokamak have been performed for the first time at the beginning of 2003. This paper presents an overview of some of the results obtained, concentrating in particular on two areas: universality of density fluctuations and the dynamical coupling between radial turbulent-driven fluxes and parallel flows.Plasma fluctuations in the edge of the TCV tokamak have been found to exhibit statistical properties which are universal across a broad range of discharge conditions. Analysis of the time series of density fluctuations in the entire scrape-off layer (SOL) region from just inside the magnetic separatrix to the plasma-wall interface, yields a probability distribution function (PDF) of density which conforms closely to a Gamma distribution. In the wall vicinity, the density fluctuations exhibit clear evidence of self-similarity and are characterised by a PDF with universal shape and with a standard deviation proportional to the mean density. It is also found that radial particle-flux fluctuations scale solely with the mean density. Such findings indicate that it may be possible to improve the prediction of transport in the critical plasma-wall interaction region of future large-scale tokamaks.Recent experiments on JET [C. Hidalgo et al.: Phys. Rev. Lett. 91 (2003) 065001] have investigated a possible link between turbulent transport and the parallel flows. Similar experiments have been performed on TCV for a variety of plasma conditions and flow magnitudes. Although correlations have been found as seen on JET, especially in the wall vicinity, it appears that the magnitude of the coupling is insufficient to drive any significant flow.Presented at the Workshop Electric Fields Structures and Relaxation in Edge Plasmas, Nice, France, October 26–27, 2004.     

New photoactivators for multiphoton excited three-dimensional submicron cross-linking of proteins: bovine serum albumin and type 1 collagen

We report the synthesis and optical characterization of two new photoactivators and demonstrate their use for multiphoton excited three-dimensional free-form fabrication with proteins. These reagents were developed with the goal of cross-linking Type 1 collagen. This cross-linking process produces structures on the micron and submicron size scales. A rose bengal diisopropyl amine derivative combines the classic photoactivator and co-initiator system into one molecule, reducing the reaction kinetics and increasing cross-linking efficiency. This derivative was successful at producing stable structures from collagen, whereas rose bengal alone was not effective. A benzophenone dimer connected by a flexible diamine tether was also synthesized. This activator has two photochemically reactive groups and is highly efficient in cross-linking bovine serum albumin and Type 1 collagen to form stable, robust structures. This approach is more flexible in terms of cross-linking a variety of proteins than by traditional benzophenone photochemistry. The photophysical properties vary greatly from that of benzophenone, with the appearance of a new, lower energy absorption band (lambda max approximately 370 nm in water) and broad, visible emission band (approximately 500 nm maximum). This absorption band is highly solvatochromic, suggesting it arises, at least in part, from a charge transfer interaction. Collagens are typically difficult to cross-link photochemically, and the results here suggest that these two new activators will be suitable for cross-linking other forms of collagen and additional proteins for biomedical applications such as the de novo assembly of biomimetic tissue scaffolds.