The basic properties of magnetism depend strongly on the spin and orbital components of magnetization. Information about the magnetic moments can be gained using new techniques, like X-ray magnetic circular dichroism or Compton scattering, developed at third-generation synchrotron sources. After a brief introduction to the basic principles of these new magnetic tools, examples of experiments on 5f-electron based systems are presented.
Magnetic optical rotatory dispersion (MORD) of thin selected biological tissues and thin film of composite made from akaganeite mineral and PVA as well as ferritin and their mimetics aqueous suspensions were performed in spectral range 250-650 nm at room temperature. Good correlation between MORD spectra for akaganeite composite film, ferritin and their mimetics aqueous suspensions with spectra of thin slices of human tissue obtained from white matter of the brain and spleen were observed. Comparison suggest a contribution from Fe(III) to MORD spectra of tissues. This preliminary results show that application of MORD spectroscopy to clinical analysis may be useful.
The technology and applications of fluorescence spectroscopy are rapidly advancing. In this overview presentation we summarize some recent developments from this laboratory. Two and three-photon excitation have been observed for a wide variety of intrinsic and extrinsic fluorophores, including tryptophan, tyrosine, DNA stains, membrane probes, and even alkanes. It has been possible to observe multi-photon excitation of biopolymers without obvious photochemical or photo-thermal effects. Although not described in our lecture, another area of increasing interest is the use of engineered proteins for chemical and clinical sensing. We show results for the glucose-galactose binding protein from E. coli. The labeled protein shows spectral changes in response to micromolar concentrations of glucose. This protein was used with a novel sensing method based on the modulated emission of the labeled proteins and a long lifetime reference fluorophore. And finally, we describe a recently developed rhenium complex which displays a lifetime near 3ľs in oxygenated aqueous solution. Such long lifetime probes allow detection of microsecond dynamic processes, bypassing the usual nanosecond timescale limit of fluorescence. The result of these developments in protein engineering, sensing methods, and metal-ligand probe chemistry will be the increased use of fluorescence in clinical chemistry and point-of-care analyses.
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