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Tin (Sn4+) and zinc (Zn") derivatives of horse heart cytochrome c have been prepared and their optical spectra have been characterized. Zinc cytochrome c has visible absorption maxima at 549 and 585 nm and Soret absorption at 423 nm. Tin cytochrome c shows visible absorption maxima at 536 and 574 nm and Soret absorption at 410 nm. Unlike iron cytochrome c in which the emission spectrum of the porphyrin is almost completely quenched by the central metal, the zinc and tin derivatives of cytochrome c are both fluorescent and phosphorescent. The fluorescence maxima of zinc cytochrome c are at 590 and 640 nm and the fluorescence lifetime is 3.2 ns. The fluorescence maxima of Sn cytochrome are at 580 and 636 nm and the fluorescence lifetime is under 1 ns. The quantum yield of fluorescence is Zn > Sn while the quantum yield of phosphorescence is Sn > Zn.At 77 K the fluorescence and phosphorescence emission spectra of Sn and Zn cytochrome c show evidence of resolution into vibrational bands. The best resolved bands occur at frequency differences 750 cm-' and 1540-1550 cm-' from the 0-0 transition. These frequencies correspond with those obtained by resonance Raman spectroscopy for in-plane deformations of the porphyrin macrocycle.

Composition of microstructural compartments in compact bone of aging male subjects was assessed using Raman microscopy. Secondary mineralization of unremodeled fragments persisted for two decades. Replacement of these tissue fragments with secondary osteons kept mean composition constant over age, but at a fully mineralized limit. Slowing of remodeling may increase fracture susceptibility through an increase in proportion of highly mineralized tissue.In this study, the aging process in the microstructural compartments of human femoral cortical bone was investigated and related to changes in the overall tissue composition within the age range of 17-73 years. Raman microprobe analysis was used to assess the mineral content, mineral crystallinity, and carbonate substitution in fragments of primary lamellar bone that survived remodeling for decades. Tissue composition of the secondary osteonal population was investigated to determine the composition of turned over tissue volume.

During fracture of ceramics containing tetragonal zirconia particles, a volume of zirconia material on either side of the crack irreversibly transforms to the monoclinic crystal structure. Transformation zone sizes, measured using Raman microprobe spectroscopy, are presented for three sintered ceramics. In a single-phase ZrO2-3.5 mol% Y203 material, an upper bound measurement of 5 p m is obtained for the zone size. In the A1203/Zr02 composites studied, the zone size is deduced to correspond to ==l grain in diameter. On the basis of the monoclinic concentrations derived from the Raman spectra it is further concluded that only a fraction of the ZrOz grains within the transformation zone transform, providing indirect evidence for the effect of particle size on the propensity for transformation.

Spherical aberration is probably the most important factor limiting the practical performance of a confocal Raman microscope. This paper suggests some simple samples that can be readily fabricated in any laboratory to test the performance of a confocal Raman microscope under realistic operating conditions (i.e., a deeply buried interface, rather than the often-selected alternative of a bare silicon wafer or a thin film in air). The samples chosen were silicon wafers buried beneath transparent polymeric or glass overlayers, and a polymer laminate buried beneath a cover glass. These samples were used to compare the performance of three types of objectives (metallurgical, oil immersion, and dry corrected) in terms of depth resolution and signal throughput. The oil immersion objective gave the best depth resolution and intensity, followed by a dry corrected (60x, 0.9 numerical aperture) objective. The 100x metallurgical objective was the worst choice, with degradations of approximately 5x and 8x in the depth resolution and signal from a silicon wafer, comparing a bare wafer with one buried under a 150 microm cover glass. In particular, the high signal level obtained makes the immersion objective an attractive choice. Results from the buried laminate were even more impressive; a 30x improvement in spectral contrast was obtained using the oil immersion objective to analyze a thin (19 microm) coating on a PET substrate, buried beneath a 150 microm cover glass, compared with the metallurgical objective.