Nezu Takashi, Nishiyama Norihiro, Nemoto Kimiya, Terada Yoshihiro
Section of Fixed Prosthodontics, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
Biomaterials. 2005 Jun;26(18):3801-8. doi: 10.1016/j.biomaterials.2004.10.010.
The adsorption effects of adhesive monomers on the structural stability of type I collagen were studied at an acid pH condition for two monomers: 2-hydroxyethyl methacrylate (HEMA), a neutral monomer and N-methacryloyl glycine (NMGly), an acidic monomer. Differential scanning calorimetry (DSC) measurements were done to assess the denaturation temperature (Td), which is a measure of the structural stability of the proteins, including the bovine tendon collagen (BTC). While HEMA lowered the Td of the BTC linearly with HEMA concentrations, NMGly exhibited a two-step decrease of the Td. The rate of decrease in the Td by the NMGly was by far greater than the rate of decrease with the HEMA. The first step had a larger slope than the second step in the Td vs. CNMGly plot. The degree of adsorption of these two monomers to the BTC was estimated from infrared absorption measurements on the monomer solutions of various concentrations, before and after the immersion of the BTC. Both the adsorption of HEMA to the BTC and the Td of the BTC were linearly dependent on HEMA concentrations. Conversely, NMGly was adsorbed to the BTC, again, in a two-step decrease similar to the Td vs. CNMGLy profile. An enhanced adsorption of NMGly, which might be attributed to a strong electrostatic interaction, was observed below 0.013 mol%. Circular dichroism measurements of the collagen of the same type as the BTC, in the absence and in the presence of the monomers, revealed that the native collagen helix structure was scarcely affected by the monomers. From these observations, it was concluded that (1) both of the monomers were adsorbed onto the BTC, which thus destabilized the triple helical collagen structure, and that (2) the effect was higher for NMGly in which the electrostatic attraction with the oppositely charged collagen might be effective at a pH of 3. If compared to HEMA, an acidic NMGly is a potential monomer that binds strongly to collagen and one that is hardly hydrolyzed.
在酸性pH条件下，研究了两种单体对I型胶原蛋白结构稳定性的吸附作用：中性单体甲基丙烯酸2-羟乙酯（HEMA）和酸性单体N-甲基丙烯酰甘氨酸（NMGly）。采用差示扫描量热法（DSC）测量变性温度（Td），以此评估蛋白质（包括牛肌腱胶原蛋白（BTC））的结构稳定性。虽然HEMA使BTC的Td随HEMA浓度呈线性降低，但NMGly使Td呈现两步降低。NMGly导致Td降低的速率远大于HEMA。在Td与CNMGly的关系图中，第一步的斜率大于第二步。通过对不同浓度单体溶液在BTC浸泡前后进行红外吸收测量，估算了这两种单体对BTC的吸附程度。HEMA对BTC的吸附以及BTC的Td均与HEMA浓度呈线性相关。相反，NMGly对BTC的吸附同样呈现类似于Td与CNMGLy关系曲线的两步降低。在0.013 mol%以下观察到NMGly的吸附增强，这可能归因于强烈的静电相互作用。在有无单体存在的情况下，对与BTC同类型的胶原蛋白进行圆二色性测量，结果表明天然胶原蛋白螺旋结构几乎不受单体影响。从这些观察结果得出以下结论：（1）两种单体均吸附到BTC上，从而使三螺旋胶原蛋白结构不稳定；（2）在pH为3时，带相反电荷的胶原蛋白与NMGly之间的静电吸引可能起作用，因此NMGly的这种作用更强。与HEMA相比，酸性的NMGly是一种可能与胶原蛋白强烈结合且几乎不水解的潜在单体。
