An NMR method to characterize multiple water compartments on mammalian collagen

Abstract

A molecular model is proposed to explain water 1H NMR spin-lattice relaxation at different levels of hydration (NMR titration method) on collagen. A fast proton exchange model is used to identify and characterize protein hydration compartments at three distinct Gibbs free energy levels. The NMR titration method reveals a spectrum of water motions with three well-separated peaks in addition to bulk water that can be uniquely characterized by sequential dehydration. Categorical changes in water motion occur at critical hydration levels h (g water/g collagen) defined by integral multiples N = 1, 4 and 24 times the fundamental hydration value of one water bridge per every three amino acid residues as originally proposed by Ramachandran in 1968. Changes occur at (1) the Ramachandran single water bridge between a positive amide and negative carbonyl group at h1 = 0.0658 g/g, (2) the Berendsen single water chain per cleft at h2 = 0.264 g/g, and (3) full monolayer coverage with six water chains per cleft level at h3 = 1.584 g/g. The NMR titration method is verified by comparison of measured NMR relaxation compartments with molecular hydration compartments predicted from models of collagen structure. NMR titration studies of globular proteins using the hydration model may provide unique insight into the critical contributions of hydration to protein folding.

Clinical ultrashort echo time imaging of bone and other connective tissues

“…In tendons these different relaxation components provide additional information about the structure of the collagen, suggesting that the protons in the cleft of the collagen have short T 1 and are in rapid exchange with the other protons and hence act as a relaxation sink for the collagen. A similar situation is found in bone (52), where rapid exchange of magnetization is found between the solid pool of protons (associated with the backbone of the collagen) and the hydrogen-bonded protons of collagen.…”

“…Collagen may display strong magic angle behaviour owing to the uniform orientation of the collagen fibers and the restricted motion of the protons associated with these fibers (46)(47)(48)(49)(50). This magic angle phenomenon has been used to examine the structure of the collagen itself (51,52). Collagen has multiple relaxation components that depend on the hydration of the collagen.…”

Estudo do comportamento higroscópico do pericárdio bovino liofilizado

“…O cálculo do valor monomolecular através da equação de BET torna-se progressivamente impreciso à medida que o valor de C se aproxima da unidade. [10] [5,6], trabalhando com colágeno de tendão bovino, por cristalografia, encontraram valores semelhantes aos nossos para o teor de umidade na camada monomolecular.…”

Translational and Rotational Dynamics of Water Molecules in Aligned Collagenous Tissues: Implications for Assessing Collagen Organisation with Magnetic Resonance Imaging

“…Fullerton Again, it is noted that studies which seemingly agree with the notion of ice-like bonds [146,147,175,177] are carried out on fibres or fibrils, while those which disagree were concerned with a sole collagen molecule [64,65,148,181]. The key difference is the possible inclusion of intra-fibrillar water in the former.…”

“…A summary of the research into collagen hydration, by Fullerton, can be found in [53]. Based on the hydrations calculated from NMR titration experiments [146] of tendon, Cameron and Fullerton [145] developed the Stoichiometric Hydration Model (SHM), which predicts one single and one double water bridge for every tripeptide unit in the tropocollagen molecule.…”