Carlà M, Cuomo M, Arcangeli A, Olivotto M
Dipartimento di Fisica della Università di Firenze, Italy.
Biophys J. 1995 Jun;68(6):2615-21. doi: 10.1016/S0006-3495(95)80446-7.
The interfacial adsorption properties of polar/apolar inducers of cell differentiation (PAIs) were studied on a mercury electrode. This study, on a clean and reproducible charged surface, unraveled the purely physical interactions among these compounds and the surface, apart from the complexity of the biological membrane. The interfacial behavior of two classical inducers, hexamethylenebisacetamide (HMBA) and dimethylsulfoxide, was compared with that of a typical apolar aliphatic compound, 1-octanol, that has a similar hydrophobic moiety as HMBA but a much smaller dipolar moment. Both HMBA and Octanol adsorb flat in contact with the surface because of hydrophobic forces, with a very similar free energy of adsorption. However, the ratio of polar to apolar moieties in PAIs turned out to be crucial to drive the adsorption maximum toward physiological values of surface charge density, where octanol is desorbed. The electrostatic effects in the interfacial region reflected the adsorption properties: the changes in the potential drop across the interfacial region as a function of the surface charge density, in the physiological range, were opposite in PAIs as compared with apolar aliphatic compounds, as exemplified by octanol. This peculiar electrostatic effect of PAIs has far-reaching relevance for the design of inducers with an adequate therapeutic index to be used in clinical trials.
在汞电极上研究了细胞分化的极性/非极性诱导剂（PAIs）的界面吸附特性。这项在清洁且可重现的带电表面上进行的研究，揭示了这些化合物与表面之间纯粹的物理相互作用，而不涉及生物膜的复杂性。将两种经典诱导剂，即六亚甲基双乙酰胺（HMBA）和二甲基亚砜的界面行为，与一种典型的非极性脂肪族化合物1-辛醇进行了比较，1-辛醇具有与HMBA相似的疏水部分，但偶极矩要小得多。由于疏水作用，HMBA和辛醇均以与表面接触的方式平躺吸附，吸附自由能非常相似。然而，PAIs中极性与非极性部分的比例对于将最大吸附量驱动至表面电荷密度的生理值至关重要，此时辛醇会解吸。界面区域的静电效应反映了吸附特性：在生理范围内，与非极性脂肪族化合物（如辛醇）相比，PAIs中跨界面区域的电位降随表面电荷密度的变化情况相反。PAIs的这种特殊静电效应对于设计具有足够治疗指数以用于临床试验的诱导剂具有深远的意义。
