Department of Radiology, University of Texas HSCSA, San Antonio, Texas, USA.
Med Phys. 2011 Jan;38(1):363-76. doi: 10.1118/1.3514123.
This article introduces a new method to study macromolecular hydration using micro-CT dilatometry. The complexity of hydration dependence on solvent temperature, pH, ionic charge, ionic activity, and ionic radii are barriers to comprehensive understanding of protein function. The crystalline character of collagen-tendon suggests that tendon dilatometry may give direct access to measures of molecular tropocollagen solvation response.
The molecular basis of the stoichiometric hydration model (SHM) provides tools to validate bovine tendon as a model to study protein-solvent shape response by micro-CT measures of tendon diameter, length, and mass during dehydration. The SHM relates macroscopic properties to molecular properties of water interacting with the surface of collagen molecules. There are marked changes at critical SHM hydration levels h = 0.0653, 0.262, and 0.724 g water/g dry weight.
Micro-CT analysis of the length, diameter, and volume combined with gravimetric measures of tendon mass as a function of hydration h (g water/g dry solid) shows asymmetric changes in length, diameter, and density as predicted by SHM. The collagen molecules perturb water properties of polar hydration N=11 waters per tripeptide unit or h approximately 0.724 g/g to confirm MDS prediction of elevated hydration density 20%-50% higher than bulk water.
Results validate the use of tendon dilatometry amplification factors of 10(6)-10(8) as an effective model to investigate protein molecule shape change response to solvent molecules. The tendon model for the first time allows direct study of protein hydration and functional response under physiological conditions.
本文介绍了一种使用微 CT 膨胀计研究大分子水合作用的新方法。溶剂温度、pH 值、离子电荷、离子活度和离子半径对水合作用的复杂性是全面理解蛋白质功能的障碍。胶原肌腱的结晶特性表明，肌腱膨胀计可能直接测量分子原胶原的溶胀响应。
化学计量水合模型（SHM）的分子基础为验证牛肌腱作为研究蛋白质-溶剂形状响应的模型提供了工具，通过微 CT 测量脱水过程中肌腱直径、长度和质量来测量分子 tropocollagen 溶胀的响应。SHM 将宏观性质与与胶原分子表面相互作用的水分子的分子性质联系起来。在临界 SHM 水合水平 h = 0.0653、0.262 和 0.724 g 水/g 干重时，会发生明显的变化。
微 CT 分析长度、直径和体积与肌腱质量随水合作用 h（g 水/g 干固体）变化的重量测量相结合，表明长度、直径和密度的变化不对称，与 SHM 预测一致。胶原分子扰乱极性水合作用的水分子性质，每个三肽单元有 11 个水分子或 h 约为 0.724 g/g，以确认 MDS 对水合密度升高的预测，比体相水高 20%-50%。
结果验证了肌腱膨胀计放大因子为 10（6）-10（8）作为研究蛋白质分子形状变化对溶剂分子响应的有效模型的使用。该肌腱模型首次允许在生理条件下直接研究蛋白质水合作用和功能响应。
