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MINERAL CHARACTERIZION OF MOUSE BONE AFTER EXPOSURE TO MICRO-GRAVITY USING FOURIER TRANSFORM INFRARED (FTIR) SPECTROSCOPY.  R.E. Thacker, Y. Yuan, T.A. Bateman. Dept. of Bioengineering, Clemson University, Clemson, SC. 

   The purpose of this study was to investigate the effects of micro-gravity on murine skeletal mineralization.  Of interest when analyzing the mineral composition of the bone samples, is the ν₁, ν₃ phosphate absorption region (900-1200 cm^-1).  This was part of a larger study, in which female C57BL/6J mice, aged 64 days were divided into Animal Enclosure Module ground control (AEM) and Space Flight (SF).  SF animals were exposed to approximately 11 days and 17 hours of micro-gravity while flying aboard the Space Shuttle Endeavour (STS-108/UF-1).  Following the shuttle flight, both AEM control and SF animals were sacrificed, and the left femur was cleaned of all non-osseous tissue and air dried.  After mechanical testing, the femurs were then ashed at 800^oC for 24 hrs to remove all organic content.     
   Fourier Transform Infrared (FTIR) microscopy was used in this study to determine the mineral content of four specific sites of an individual bone (head, neck, proximal diaphysis, and distal metaphysis).  Due to the nature of ashed bones, the sections needed to be pelletized in order to be viable for FTIR analysis.  The medium used to aid the pellet formation was Potassium Bromide (KBr).  There was no discernable difference of mineral composition observed between the SF and AEM groups.  However, noticeable differences in the phosphate region (1020-1060 cm^-1) were detected between the head and the other three sites of the femur being examined.  These differences were observed in all groups.  In conclusion, though previous analyses observed spaceflight-induced changes in mineral density, it does not cause a compositional change in the mineral constituents of bone.  Additional analysis of these data will explore potential changes in the proportions of mineral constituents, in addition to directly measuring the material properties of bone via microhardness and nano-indentation. 

(Supported by NASA/SC EPSCoR)