ADRF-CP SURFACE-COIL SPECTROSCOPY OF SYNTHETIC CALCIUM PHOSPHATES ANDBONE-MINERAL

Proton to phosphorus-31 cross polarization via adiabatic demagnetizati on in the rotating frame (ADRF-CP) has been used, in conjunction with a surface coil, to detect monohydrogen phosphate (acid phosphate) ions in the presence of a large background of nonprotonated phosphate (ort hophosphate) ions in porcine bone and synthetic calcium phosphates, Tr ansient oscillations were observed in the transfer of polarization bet ween the proton dipolar and phosphorus Zeeman nuclear-spin reservoirs at short times after the initiation of thermal contact, The oscillatio ns were observed in all samples, including bone, Orthophosphate suppre ssion was achieved by detecting the signal when the orthophosphate osc illation was passing through zero, and by adjusting the phosphorus RF field to achieve optimal cross polarization with the proton local fiel ds of the acid phosphate ions, ADRF-CP techniques deposit less RF powe r than traditional spin-lock CP techniques, and are hence compatible w ith in vivo application. As the ratio of the protonated to nonprotonat ed phosphate can be used as a marker for bone-mineral maturity, ADRF-C P spectroscopy creates the possibility of characterizing bone-mineral dynamics in vivo by solid-state NMR. (C) 1996 Academic Press, Inc.