Tamura Hiroki, Chiba Jun, Ito Masahiro, Takeda Takashi, Kikkawa Shinichi, Mawatari Yasuteru, Tabata Masayoshi
Division of Materials Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan.
J Colloid Interface Sci. 2006 Aug 15;300(2):648-54. doi: 10.1016/j.jcis.2006.04.007. Epub 2006 May 4.
The formation reaction and the intercalation of adenosine triphosphate (ATP) were studied for hydrotalcite (HT), a layered double hydroxide (LDH) of magnesium and aluminum. Hydrotalcite with nitrate ions in the interlayer (HT-NO(3)) was formed (A) by dropwise addition of a solution of magnesium and aluminum nitrates (pH ca. 3) to a sodium hydroxide solution (pH ca. 14) until the pH decreased from 14 to 10 and (B) by dropwise addition of the NaOH solution to the solution of magnesium and aluminum nitrates with pH increasing from 3 to 10. The precipitate obtained with method B was contaminated with aluminum hydroxide and the crystallinity of the product was low, possibly because aluminum hydroxide precipitates at pH 4 or 5 and remains even after HT-NO(3) forms at pH above 8. With method A, however, the precipitate was pure HT-NO(3) with increased crystallinity, since the solubility of aluminum hydroxide at pH above and around 10 is high as dissolved aluminate anions are stable in this high pH region, and there was no aluminum hydroxide contamination. The formed HT-NO(3) had a composition of Mg(0.71)Al(0.29)(OH)(2)(0.29).0.58H(2)O. To intercalate ATP anions into the HT-NO(3), HT-NO(3) was dispersed in an ATP solution at pH 7. It was found that the interlayer nitrate ions were completely exchanged with ATP anions by ion exchange, and the interlayer distance expanded almost twice with a free space distance of 1.2 nm. The composition of HT-ATP was established as Mg(0.68)Al(0.32)(OH)(2)(0.080)0.88H(2)O. The increased distance could be explained with a calculated molecular configuration of the ATP as follows: An ATP molecule is bound to an interlayer surface with the triphosphate group, the adenosine group bends owing to its bond angles and projects into the interlayer to a height of 1 nm, and the adenosine groups aligned in the interlayer support the interlayer distance.
对镁铝层状双氢氧化物水滑石（HT）的生成反应及三磷酸腺苷（ATP）的插层进行了研究。层间含有硝酸根离子的水滑石（HT-NO(3)）通过以下两种方法制备：（A）将硝酸镁和硝酸铝溶液（pH约为3）逐滴加入到氢氧化钠溶液（pH约为14）中，直至pH从14降至10；（B）将氢氧化钠溶液逐滴加入到硝酸镁和硝酸铝溶液中，使pH从3升至10。采用方法B得到的沉淀被氢氧化铝污染，产物结晶度低，这可能是因为氢氧化铝在pH为4或5时沉淀，即使在pH高于8形成HT-NO(3)后仍残留。然而，采用方法A时，沉淀为纯HT-NO(3)且结晶度提高，因为在pH高于及约为10时氢氧化铝的溶解度较高，这是由于溶解的铝酸根阴离子在该高pH区域稳定，且不存在氢氧化铝污染。所形成的HT-NO(3)的组成为Mg(0.71)Al(0.29)(OH)(2)(0.29).0.58H(2)O。为了将ATP阴离子插入HT-NO(3)中，将HT-NO(3)分散在pH为7的ATP溶液中。发现层间硝酸根离子通过离子交换完全被ATP阴离子取代，层间距几乎扩大了两倍，自由空间距离为1.2 nm。HT-ATP的组成确定为Mg(0.68)Al(0.32)(OH)(2)(0.080)0.88H(2)O。层间距增加可以用ATP的计算分子构型解释如下：一个ATP分子通过三磷酸基团与层间表面结合，腺苷基团由于其键角而弯曲并伸入层间至1 nm的高度，层间排列的腺苷基团支撑着层间距。
