Weakly and strongly associated nonfreezable water bound in bones.
ABSTRACT Water bound in bone of rat tail vertebrae was investigated by 1H NMR spectroscopy at 210-300 K and by the thermally stimulated depolarization current (TSDC) method at 190-265 K. The 1H NMR spectra of water clusters were calculated by the GIAO method with the B3LYP/6-31G(d,p) basis set, and the solvent effects were analyzed by the HF/SM5.45/6-31G(d) method. The 1H NMR spectra of water in bone tissue include two signals that can be assigned to typical water (chemical shift of proton resonance deltaH=4-5 ppm) and unusual water (deltaH=1.2-1.7 ppm). According to the quantum chemical calculations, the latter can be attributed to water molecules without the hydrogen bonds through the hydrogen atoms, e.g., interacting with hydrophobic environment. An increase in the amount of water in bone leads to an increase in the amount of typical water, which is characterized by higher associativity (i.e., a larger average number of hydrogen bonds per molecule) and fills larger pores, cavities and pockets in bone tissue.
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ABSTRACT: Nuclear Magnetic Resonance (NMR) cryoporometry is a technique for non-destructively determining pore size distributions in porous media through the observation of the depressed melting point of a confined liquid. It is suitable for measuring pore diameters in the range 2 nm–1 μm, depending on the absorbate. Whilst NMR cryoporometry is a perturbative measurement, the results are independent of spin interactions at the pore surface and so can offer direct measurements of pore volume as a function of pore diameter. Pore size distributions obtained with NMR cryoporometry have been shown to compare favourably with those from other methods such as gas adsorption, DSC thermoporosimetry, and SANS. The applications of NMR cryoporometry include studies of silica gels, bones, cements, rocks and many other porous materials. It is also possible to adapt the basic experiment to provide structural resolution in spatially-dependent pore size distributions, or behavioural information about the confined liquid.Physics Reports 01/2008; · 22.93 Impact Factor
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ABSTRACT: With an ability to quantify matrix-bound and pore water in bone, (1)H nuclear magnetic resonance (NMR) relaxometry can potentially be implemented in clinical imaging to assess the fracture resistance of bone in a way that is independent of current X-ray techniques, which assess bone mineral density as a correlate of bone strength. Working towards that goal, we quantified the effect of partial dehydration in air on the mechanical and NMR properties of human cortical bone in order to understand whether NMR is sensitive to water-bone interactions at low energy and whether such interactions contribute to the age-related difference in the toughness of bone. Cadaveric femurs were collected from male and female donors falling into two age groups: 21-60 years of age (young) and 74-99 years of age (old). After extracting two samples from the medial cortex of the mid-shaft, tensile tests were conducted on Wet specimens and paired, Partially Dry (PtlD) specimens (prepared by low-energy drying in air to remove ∼3% of original mass before testing). Prior analysis by micro-computed tomography found that there were no differences in intra-cortical porosity between the Wet and PtlD specimens nor did an age-related difference in porosity exist. PtlD specimens from young and old donors had significantly less toughness than Wet specimens, primarily due to a dehydration-related decrease in post-yield strain. The low-energy drying protocol did not affect the modulus and yield strength of bone. Subsequent dehydration of the PtlD specimens in a vacuum oven at 62°C and then 103°C, with quantification of water loss at each temperature, revealed an age-related shift from more loosely bound water to more tightly bound water. NMR detected a change in both bound and pore water pools with low-energy air-drying, and both pools were effectively removed when bone was oven-dried at 62°C, irrespective of donor age. Although not strictly significant due to variability in the drying and testing conditions, the absolute difference in toughness between Wet and PtlD tended to be greater for the younger donors that had higher bone toughness and more bound water for the wet condition than did the older donors. With sensitivity to low-energy bone-water interactions, NMR, which underpins magnetic resonance imaging, has potential to assess fracture resistance of bone as it relates to bone toughness.Journal of the mechanical behavior of biomedical materials. 10/2012;
Conference Paper: Molecular Spectroscopic Identification of Water Compartments in Bone[Show abstract] [Hide abstract]
ABSTRACT: Bone has a significant amount of water, up to 20% bone’s wet weight. Water molecules exist in unbound state in the microscopic pores or they are bound to collagen and mineral with affinities ranging from tightly to loosely. While Raman spectroscopy is one of few nondestructive modalities to assess the hydration status in bone, it has not been used to study the OH-band in bone. Methods: A sequential sample treatment protocol was developed so as replace unbound (heat drying below 100 ºC) and bound (ethanol or deuterium replacement of hear dried samples) water. Raman spectra were collected in the range of 2700-4000 cm-1 after each treatment step to track the OH-band during dehydration. Band assignments were further supported by computational simulation of molecular vibrations of Gly-Pro-Hyp tripeptide. The library of experimentally and theoretically obtained spectra was interpreted cumulatively for band-assignments. Water loss was measured gravimetrically and correlated to Raman intensities. Results: The results indicated that there are four peaks which were sensitive to dehydration. The first peak is at 3220 cm-1 and belongs to only water, the second peak at 3325 cm-1 belongs to NH and water, the third one at 3453 cm-1 belongs to OH of Hyp and water, and the last one at 3584 cm-1 belongs to OH of mineral and water. These peaks had differential sensitivity to deuterium treatment such that some were replaced faster than the rest, indicating that peaks at 3325 and 3584 cm-1 are more tightly bound to the matrix. In addition, the results indicate that the OH-range of bone is mostly dominated by collagen and the water bound to collagen.7th World Congress of Biomechanics, Boston, MA; 07/2014