DNA原子力显微镜成象条件的研究

Imaging condition of DNA with atomic force microscope

原子力显微镜 (AFM)在空气中对DNA进行观察时 ,针尖很容易对其造成损伤 ,从而影响图象质量 .为探索此问题的解决办法 ,本研究在空气、水和无水乙醇中对DNA进行成象 ,同时对针尖的结构进行了扫描电镜观察 .取 10 0 μg ml质粒pQE30水溶液 2 0 μl滴加在新鲜剥离的云母基底上 ,吸附 1min ,用滤纸吸去基底上的多余残液 ,氮气吹干后在空气中成像 ;pQE30分别溶于去离子水和无水乙醇 ,质量浓度为 10 0 μg ml ,各取10 0 μl加入液体池中成象 .成象时均采用MultiModeAFM (NanoscopeⅢa)的敲击模式 ,并记录力曲线 .结果发现 :在液体中DNA的图象分辨率优于在空气中 ,在无水乙醇中优于在水中 ;针尖与DNA样品间的相互作用力越大 ,成象的分辨率越低 ;多次使用后针尖磨损 ,分辨率降低 .这一结果为选择DNA的理想AFM成象环境 。

To investigate the ideal condition, DNA was imaged in air, water and ethanol, meanwhile, the tip's structure were studied with scanning electrical microscopy. 20 μl of the plasmid pQE30 water solution was added to the newly cleaved mica, adsorbed for 1min and dried with nitrogen. pQE30 was diluted in deionized water and ethanol with a concentration of 100 μg/ml and 100 μl of the solutions were applied to the fluid cell. The above three samples were observed with MultiMode AFM(Nanoscope Ⅲa) in tapping mode, and force calibration plots in different condition were noted. The results showed that there is a higher resolution in solution than that in air, images quality of DNA in ethanol is better than in water. The more the force between tip and sample, the lower the resolution acquired. Tips could be worn out after application for many times, thus the resolution decreased. This study is helpful to selection of DNA imaging condition with AFM, it provides experimental foundation for physiologically study of DNA structure and function.