Franchi M, Bramanti E, Bonzi L M, Orioli P L, Vettori C, Gallori E
Department of Animal Biology and Genetics, University of Florence, Italy.
Orig Life Evol Biosph. 1999 May;29(3):297-315. doi: 10.1023/a:1006557832574.
The equilibrium adsorption of three nucleic acids: chromosomal DNA, supercoiled plasmid DNA, and 25S rRNA, on the clay minerals, montmorillonite (M) and kaolinite (K), were studied. Adsorption of the nucleic acid on the clays was rapid and maximal after 90 min of contact time. Chromosomal DNA was adsorbed to a greater extent than plasmid DNA and RNA, and the adsorption was also greater on M than on K. Adsorption isotherms were of the L type, and a plateau was reached with all the complexes, with the exception of chromosomal DNA adsorbed on M. To deterine where nucleic acids are adsorbed on clay minerals and the nature of the interaction, complexes were studied by X-ray diffraction (X-RD), electron microscopy, and Fourier transform infrared (FT-IR) spectroscopy. X-RD showed that nucleic acids did not penetrate the clay, indicating that the adsorption occurred primarily on the external surfaces of clay particles, as also suggested by electron microscopy observations. FT-IR spectra of clay-tightly bound nucleic acid complexes showed adsorption bands that indicate a variation of the nucleic acids status as a consequence of their adsorption on clay. Data obtained suggested that the formation of clay-nucleic acid complex could have an important role in the preservation of genetic material in primeval habitats.
研究了三种核酸（染色体DNA、超螺旋质粒DNA和25S rRNA）在粘土矿物蒙脱石（M）和高岭石（K）上的平衡吸附。核酸在粘土上的吸附迅速，接触90分钟后达到最大吸附量。染色体DNA的吸附程度大于质粒DNA和RNA，且在蒙脱石上的吸附量也大于高岭石。吸附等温线为L型，除吸附在蒙脱石上的染色体DNA外，所有复合物均达到平台期。为了确定核酸在粘土矿物上的吸附位置以及相互作用的性质，通过X射线衍射（X-RD）、电子显微镜和傅里叶变换红外（FT-IR）光谱对复合物进行了研究。X射线衍射表明核酸没有穿透粘土，这表明吸附主要发生在粘土颗粒的外表面，电子显微镜观察也证实了这一点。粘土紧密结合核酸复合物的傅里叶变换红外光谱显示出吸附带，表明核酸由于吸附在粘土上而导致其状态发生变化。所得数据表明，粘土-核酸复合物的形成可能在原始栖息地遗传物质的保存中发挥重要作用。
