Proton to phosphorus-31 cross polarization via adiabatic demagand minimizes the application of RF power. Cross polarizanetization in the rotating frame (ADRF-CP) has been used, in tion by means of adiabatic demagnetization in the rotating conjunction with a surface coil, to detect monohydrogen phosphate frame (ADRF-CP) satisfies these requirements. (acid phosphate) ions in the presence of a large background of nonprotonated phosphate (orthophosphate) ions in porcine bone Bone-Mineral Chemistry and synthetic calcium phosphates. Transient oscillations were ob-Bone-mineral research has grown in recent years, spurred served in the transfer of polarization between the proton dipolar by public health concerns over osteoporosis (1). While the and phosphorus Zeeman nuclear-spin reservoirs at short times
mineral is often considered to be the inert, inorganic compoafter the initiation of thermal contact. The oscillations were observed in all samples, including bone. Orthophosphate suppression nent of bone whose sole function is to provide mechanical was achieved by detecting the signal when the orthophosphate support, it has long been known that there is continual reoscillation was passing through zero, and by adjusting the phosmodeling of bone throughout life, with resorption of older phorus RF field to achieve optimal cross polarization with the bone and synthesis of new bone. This process allows the proton local fields of the acid phosphate ions. ADRF-CP techbone to grow, to play its role as a reservoir of calcium and niques deposit less RF power than traditional spin-lock CP techphosphorus, and to maintain its structural integrity by repair niques, and are hence compatible with in vivo application. As the of small defects and trauma. Many aspects of this remodeling ratio of the protonated to nonprotonated phosphate can be used process are poorly understood, and additional knowledge of as a marker for bone-mineral maturity, ADRF-CP spectroscopy bone-mineral dynamics will be central to our understanding creates the possibility of characterizing bone-mineral dynamics in of fracture healing, the determinants of bone strength, and vivo by solid-state NMR.