Investigating water interactions with collagen using 2H multiple quantum filtered NMR spectroscopy to provide insights into the source of double quantum filtered signal in tissue.
In an effort to provide insight into the molecular origins of the (2)H double quantum filtered (DQF) NMR signal observed in connective tissue, specifically spinal disc tissue, (2)H multiple quantum filtered (MQF) NMR spectroscopy is used to study the structure and dynamics of D2O in collagen as a function of hydration. Residual quadrupolar coupling constants are measured and decrease from 3500 to 20 Hz while T2 relaxation times increase from 0.65 to 20 ms as hydration increases. Analysis of the data indicates that the quadrupolar coupling and T2 relaxation arises when water molecules spend time in restricted environments. The residual quadrupolar coupling is influenced almost exclusively by the most restricted water sites, the clefts of the triple helices not exposed on the surface of the fibrils, while the T2 relaxation has secondary contributions from less restricted water environments. The magnitudes of the measured values are consistent with results from DQF NMR studies of spinal disc tissue, supporting the assertion that water binding to collagen is a major contributor to the DQF NMR signal observed in spinal disc tissue.