Evidence that collagen and tendon have monolayer water coverage in the native state

Abstract

This paper investigates an alternative explanation for widely reported paradoxical intracellular water properties. The most frequent biological explanation assumes water structure extending multiple layers from surfaces of compactly folded macromolecules to explain large amounts of perturbed water. Long range water structuring, however, contradicts molecular models widely accepted by the scientific majority. This study questions whether the paradoxical cell water could result from larger than expected amounts of first layer interfacial water on internal protein surfaces rather than structured multilayers. Native mammalian tendon is selected for the study because (1) the organ consists of highly compact structures of a single macromolecular protein--collagen, (2) molecular structure and geometry of collagen is well characterized by X-ray diffraction, (3) molecular structure extends to the macroscopic tendon level and (4) perturbed water behavior similar to cellular water is reported on tendon. Native tendon holds 1.6 g water/g dry mass. The 62% native water content simulates the water content of many cell types. MicroCT studies of tendon dilatometry as a function of hydration are measured and correlated to X-ray diffraction measurements of interaxial separation. Correlations show that native tendon has sufficient water for only a single monolayer of interfacial water. Thus the paradoxical properties of water in native tendon are first-layer interfacial water properties. Similar water behavior on globular proteins suggests that paradoxical cell water behavior could be caused by larger than expected amounts of first layer interfacial water on internal and external macromolecular surfaces of cell components.

The Size Exclusion Characteristics of Type I Collagen

“…Micro-CT measurements have shown convincingly that the progressive hydration of a collagen fiber increases the diameter of the fiber but not its length. This observation shows that hydration affects the lateral structure of the fiber but not the axial structure (22). X-ray structural analyses support this conclusion.…”

“…In contrast, hydration progressively increases the Bragg spacing between adjacent collagen molecules in the lateral plane, from 1.1 nm in the dry fibril to 1.8 nm when the fibril is fully hydrated (24). In the lateral plane, each collagen molecule is therefore separated from its neighbors by a water layer 6 -7 Å thick (22).…”

“…22 and references therein). Micro-CT measurements have shown convincingly that the progressive hydration of a collagen fiber increases the diameter of the fiber but not its length.…”

What is the required energy deficit per unit weight loss?

“…I propose that h ¼ 1.6 g H 2 O per gram protein is a reasonable estimate for the protein hydration coefficient because this value is in the middle of the range 1.1-2.2 g H 2 O per gram measured as the osmotically unresponsive water compartment in a variety of cells 15 and corresponds to the monolayer hydration of a typical protein. 16 This results in a calculated energy density for lean body mass changes of…”

Delayed luminescence: a novel technique to obtain new insights into water structure

“…DL has been successfully used to investigate the role of water in collagen [10,11] where water appears to be structured in regular chains along the collagen fibrils [12], which would indeed facilitate the proton jump-conduction that could be used by molecules, cells, and tissues to intercommunicate. Such collagen water chains are reminiscent of those seen in carbon nanotubes [13], which are thought to represent an entirely new phase of water.…”