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Strong regenerated gratings with a maximum grating strength exceeding (40-50) dB are fabricated inside an optical fibre by bulk macro thermal processing ∼ 900˚C using a UV-laser seeded Bragg grating. Further annealing between 1000˚C and 1100˚C leads to a stabilised grating ∼ 18 dB in strength. This suffers no further degradation at 1100˚C for the period monitored, over 4 hours. The potential resolution of this process is demonstrated by regenerating two complex profiles. Phase information is retained between seed and regenerated structures. This opens the way for nano-engineering of materials using thermal processing and seed templates.

Crystals were prepared from samples of noncovalent and covalently linked dimers previously isolated as intermediates and end products in the interconversion of conformational isomers of immunoglobulin light chains from the patient Mcg. In ammonium sulfate these dimers crystallized in the trigonal form characteristic of the native Bence-Jones protein and in an abnormal needle form associated with conformational changes in the vicinity of the interchain disulfide bond. Trigonal forms were compared with the native covalent dimer by difference Fourier analysis at 3.5-A resolution. Criteria were established for recognizing and cutting twinned trigonal crystals into fragments useful for diffraction experiments. The packing of molecules in the trigonal crystal lattice was examined in detail to determine the steric limitations governing chemical modifications, chemical modifications within crystals or in solutions slated for crystallization. When the modifications involved only the cleavage and alkylation of the interchain disulfide bond, the difference Fourier maps I n the interconversions of conformational isomers of the Mcg immunoglobulin light chains (see Firca et al., 1978), we initially considered crystallization of the products to be just a routine step in the correlation of chemical and diffraction results. Instead, the unexpected appearance of different crystal forms and variations in the properties of the expected crystal forms directed us into a more enlightened study of conformational changes in the constituent molecules. By using the crystal properties in conjunction with chemical modifications and CD spectroscopy (see Firca et al., 1978), we were able to identify regions involved in conformational changes during the interconversion experiments. The morphology and pertinent properties of these crystals will be described in the present indicated only local conformational changes mainly in the COOH-terminal pentapeptide segment of monomer 2 of the dimer. When light chains were dissociated from heavy chains and reassembled into a dimer, there were changes in segments which interact to stabilize the V domain dimer (i.e., in the lining of the deep binding pocket in the V interface). These changes, as well as the more extensive changes in the needle forms, could be reversed by dissolving the crystals. cleaving the interchain disulfide bond, and allowing it to reoxidize. The resulting proteins crystallized as trigonal forms indistinguishable from those of the native dimer. After the binding of two molecules of bis(dinitropheny1)lysine and subsequent removal of the ligands by dialysis, the dimer crystallized only as needles. The needles could be converted into trigonal forms as before. These results suggest that the binding of ligands by the V domains can lead to conformational changes in the most distal regions of the C domain dimer.article. In cases in which the crystal morphology was similar to that of the trigonal form of the native Bence-Jones dimer (Edmundson et al., 1971). subtle conformational changes were s...

The synthesis of a series of bifunctional Gd(III) complexes 1-3 covalently bound to arylphosphonium cations possessing a varying degree of delocalisation at the phosphonium centre is presented. The influence of the degree of delocalisation was investigated with regards to in vitro cytotoxicity, cellular uptake of Gd, tumor-cell selectivity and intracellular localisation of Gd within human glioblastoma (T98G) and human glial (SVG p12) cells. Cellular uptake and selectivity studies for the Gd(III) complexes indicate that a reduced delocalisation at the phosphonium centre can lead to an enhanced Gd uptake into SVG p12 cells which results in a decrease in the overall tumor cell selectivity. Synchrotron X-ray fluorescence (microbeam XRF) imaging has demonstrated for the first time that uniform uptake of Gd(III) complex 2 within a population of T98G cells increased as a function of increasing Gd incubation times. The Gd maps show dispersed spots of high intensity which are consistent with mitochondrial uptake.

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