Moreno E C, Kresak M, Hay D I
J Biol Chem. 1982 Mar 25;257(6):2981-9.
The thermodynamics of adsorption of four acidic proline-rich salivary proteins from their aqueous solutions onto hydroxyapatite (HA) and fluorapatite (FA) have been analyzed. Enthalpies and entropies of adsorption were derived from isotherms at 37 degrees C and 4 degrees C and led to the unexpected conclusion that adsorption of the macromolecules studied is an endothermic process. Consequently, adsorption is driven by an increase in entropy. Most of this increase originates in the adsorbate molecules, probably through disruption of internal ion pairs, hydrogen bonds, and displacement of water molecules. Integral free energies of adsorption (delta G) and the partial contributions of adsorbent and adsorbate were both calculated as a function of the adsorption coverages. For equal coverages (of each adsorbate), delta G is lower with FA than with HA. Most of the contribution to delta G originates from the adsorbate, although the adsorbent contribution becomes significant as adsorption saturation is approached. The differences in the various thermodynamic quantities are qualitatively related to the known structural features of the four proteins. The results are important in understanding the role played by the proline-rich proteins in the oral environment.
对四种富含酸性脯氨酸的唾液蛋白从其水溶液吸附到羟基磷灰石（HA）和氟磷灰石（FA）上的热力学进行了分析。吸附焓和熵是从37℃和4℃下的等温线得出的，得出了一个意想不到的结论，即所研究的大分子吸附是一个吸热过程。因此，吸附是由熵的增加驱动的。这种增加大部分源于被吸附物分子，可能是通过内部离子对的破坏、氢键以及水分子的置换。吸附的积分自由能（ΔG）以及吸附剂和被吸附物的部分贡献都作为吸附覆盖率的函数进行了计算。对于相同的覆盖率（每种被吸附物），FA的ΔG低于HA。对ΔG的大部分贡献来自被吸附物，尽管随着吸附饱和度的接近，吸附剂的贡献变得显著。各种热力学量的差异与四种蛋白质已知的结构特征在定性上相关。这些结果对于理解富含脯氨酸的蛋白质在口腔环境中所起的作用很重要。
