FT-IR microscopy of endochondral ossification at 20 mu spatial resolution.

A Fourier transform infrared spectrometer has been coupled with an optical microscope to study the distribution and characteristics of the mineral phase in calcifying tissues at 20 mu spatial resolution. This represents the first biophysical application of this technique. High quality spectra were obtained in a relatively short scan time (1-2 minutes) from thin longitudinal sections of normal and rachitic rat femurs. Substantial spatial variations in the extent and structure of the mineral phase were observed as a function of spatial position both within and beyond the growth plates, as judged by the phosphate vibrations in the 900-1200 cm-1 spectral region. The current experiments reveal the utility of FT-IR microscopy in identification of sites where mineralization has occurred. In addition to vibrations from the inorganic components, the Amide I and Amide II motions of the protein constituents are readily observed and may be useful as a probe of protein/mineral interactions.