Structural studies of polytene chromosomes and bone implant coatings: Raman microspectroscopy and atomic force microscopy

Raman microscopy and atomic force microscopy (AFM) are used for the investigation of the composition and structure of the banding patterns of polytene chromosomes and of hydroxyapatite bone-implant coatings. For Raman microspectroscopy two new measuring methods are introduced: line-scan Raman and Low-wavenumber Raman microspectroscopy. A transparent and easy to use model to predict the depth resolution of a confocal microscope is described. A Chevron-type of filter set was developed for simultaneous measurements of Stokes and anti-Stokes Raman scattering close to the exciting laser frequency. Bands of polytene chromosomes appeared to contain a higher concentration of DNA and proteins compared to interbands. AFM measurements revealed that bands consist of a densely packed chromatin structure and are hardly affected by stretching of the chromosome. Interbands have a more open chromatin structure and are more accessible to solvent molecules. For the study of bone implant coatings Raman micro spectroscopy appeared to provide an easy, non- destructive, way to obtain information about the apatite structure and the degree of crystallinity. It was shown that the degree of crystallinity was constant over coatings produced by plasma spraying while the material density did vary.