An investigation of structure-reactivity relationships of δ-alkenyl oximes; competitive thermal reactions leading to cyclic nitrones and/or N-unsubstituted bicyclic isoxazolidines

Thermal reactions of C-aryl δ-alkenyl oximes give N-unsubstituted bicylic lactone, lactam and pyrrolidine fused isoxazolidines by an intramolecular oxime olefin cycloaddition pathway (IOOC) and/or cyclic nitrones by an azaprotio cyclotransfer (APT) route; a number of factors, including the nature of the aryl group, the oxime geometry and the structure of the linker between the oxime and the terminal alkene, contribute to the competition.     

A New Nonconjugated Naphthalene Derivative of Meso-tetra-(3-hydroxy)-phenyl-porphyrin as a Potential Sensitizer for Photodynamic Therapy

A new 5,10,15,20-tetra-(phenoxy-3-carbonyl-1-amino-naphthyl)-porphyrin was prepared by an isocyanate condensation reaction and its photophysical properties fully evaluated, both in terms of photostability and singlet oxygen production. It shows considerably enhanced photostability when compared with the parent 5,10,15,20-tetra-(3-hydroxy-phenyl)-porphyrin, with the photodegradation quantum yields for T(NAF)PP and T(OH)PP being 4.65 × 10⁻⁴ and 5.19 × 10⁻³, respectively. Its photodynamic effect in human carcinoma HT-29 cells was evaluated. The new porphyrin showed good properties as a sensitizer in photodynamic therapy with an in vitro cytotoxicity IC₅₀ value of 6.80 μg mL⁻¹ for a 24 h incubation. In addition to the potential of this compound, the synthetic route used provides possibilities of extension to a wide range of new sensitizers.     

Coil-stretch Transition of DNA Molecules in Slit-like Confinement

We experimentally investigate the influence of slit-like confinement on the coil-stretch transition of single DNA molecules in a homogeneous planar elongational electric field. We observe a more gradual coil-stretch transition characterized by two distinct critical strain rates for DNA in confinement, different from the unconfined case where a single critical strain rate exists. We postulate that the change in the coil-stretch transition is due to a modified spring law in confinement. We develop a dumbbell model to extract an effective spring law by following the relaxation of an initially stretched DNA. We then use this spring law and kinetic theory modeling to predict the extension and fluctuations of DNA in planar elongational fields. The model predicts that a two-stage coil-stretch transition emerges in confinement, in accord with experimental observations.     

Differentiation between intra-axial metastatic tumor progression and radiation injury following fractionated radiation therapy or stereotactic radiosurgery using MR spectroscopy, perfusion MR imaging or volume progression modeling

Objective

To determine the accuracy of magnetic resonance spectroscopy (MRS), perfusion MR imaging (MRP), or volume modeling in distinguishing tumor progression from radiation injury following radiotherapy for brain metastasis.

Methods

Twenty-six patients with 33 intra-axial metastatic lesions who underwent MRS (n=41) with or without MRP (n=32) after cranial irradiation were retrospectively studied. The final diagnosis was based on histopathology (n=4) or magnetic resonance imaging (MRI) follow-up with clinical correlation (n=29). Cho/Cr (choline/creatinine), Cho/NAA (choline/N-acetylaspartate), Cho/nCho (choline/contralateral normal brain choline) ratios were retrospectively calculated for the multi-voxel MRS. Relative cerebral blood volume (rCBV), relative peak height (rPH) and percentage of signal-intensity recovery (PSR) were also retrospectively derived for the MRPs. Tumor volumes were determined using manual segmentation method and analyzed using different volume progression modeling. Different ratios or models were tested and plotted on the receiver operating characteristic curve (ROC), with their performances quantified as area under the ROC curve (AUC). MRI follow-up time was calculated from the date of initial radiotherapy until the last MRI or the last MRI before surgical diagnosis.

Results

Median MRI follow-up was 16 months (range: 2-33). Thirty percent of lesions (n=10) were determined to be radiation injury; 70% (n=23) were determined to be tumor progression. For the MRS, Cho/nCho had the best performance (AUC of 0.612), and Cho/nCho >1.2 had 33% sensitivity and 100% specificity in predicting tumor progression. For the MRP, rCBV had the best performance (AUC of 0.802), and rCBV >2 had 56% sensitivity and 100% specificity. The best volume model was percent increase (AUC of 0.891); 65% tumor volume increase had 100% sensitivity and 80% specificity.

Conclusion

Cho/nCho of MRS, rCBV of MRP, and percent increase of MRI volume modeling provide the best discrimination of intra-axial metastatic tumor progression from radiation injury for their respective modalities. Cho/nCho and rCBV appear to have high specificities but low sensitivities. In contrast, percent volume increase of 65% can be a highly sensitive and moderately specific predictor for tumor progression after radiotherapy. Future incorporation of 65% volume increase as a pretest selection criterion may compensate for the low sensitivities of MRS and MRP.     

Recent results on the spin structure of the nucleon

The process of polarised deep inelastic scattering and the information it has given on the spin structure of the nucleon are introduced. The experimental programmes in this field are described and the latest inclusive and semi-inclusive data and analyses are reviewed. Proposed future measurements are summarised.     

Methyl modified siloxane melting gels for hydrophobic films

Hybrid melting gels were prepared by a sol–gel process, starting with a mono-substituted siloxane and a di-substituted siloxane. Methyl-modified melting gels were prepared using (a) methyltriethoxysilane (MTES) with dimethyldiethoxysilane (DMDES) and (b) methyltrimethoxysilane (MTMS) together with dimethyldimethoxysilane (DMDMS). The gels with MTES–DMDES were prepared with concentrations between 50–50 and 75–25 mol%. The gels with MTMS–DMDMS were prepared with concentrations between 50–50 and 70–30 mol%. For both systems, the consolidation temperature, after which the melting gel no longer softens, increased with an increase in the amount of the mono-substituted siloxane, increasing from 135 to 160 °C for MTES–DMDES and increasing from 145 to 170 °C for MTMS–DMDMS. Coatings formed on mica substrates were about 1 mm thick, and showed no visible cracks. The surfaces of the coatings were profiled using micro-Raman spectroscopy, which revealed that methyl groups were concentrated at the surfaces of the films. All contact angles measured with water were greater than 90°.