Hansma H G, Bezanilla M, Zenhausern F, Adrian M, Sinsheimer R L
Department of Physics, University of California, Santa Barbara 93106.
Nucleic Acids Res. 1993 Feb 11;21(3):505-12. doi: 10.1093/nar/21.3.505.
DNA on mica can be imaged in the atomic force microscope (AFM) in water or in some buffers if the sample has first been dehydrated thoroughly with propanol or by baking in vacuum and if the sample is imaged with a tip that has been deposited in the scanning electron microscope (SEM). Without adequate dehydration or with an unmodified tip, the DNA is scraped off the substrate by AFM-imaging in aqueous solutions. The measured heights and widths of DNA are larger in aqueous solutions than in propanol. The measured lengths of DNA molecules are the same in propanol and in aqueous solutions and correspond to the base spacing for B-DNA, the hydrated form of DNA; when the DNA is again imaged in propanol after buffer, however, it shortens to the length expected for dehydrated A-DNA. Other results include the imaging of E. coli RNA polymerase bound to DNA in a propanol-water mixture and the observation that washing samples in the AFM is an effective way of disaggregating salt-DNA complexes. The ability to image DNA in aqueous solutions has potential applications for observing processes involving DNA in the AFM.
如果首先用丙醇将样品彻底脱水或通过真空烘烤进行脱水，并且使用在扫描电子显微镜（SEM）中沉积过的探针进行成像，云母上的DNA可以在水中或某些缓冲液中用原子力显微镜（AFM）成像。如果没有充分脱水或使用未修饰的探针，在水溶液中通过AFM成像时，DNA会从底物上被刮掉。在水溶液中测量的DNA高度和宽度比在丙醇中更大。在丙醇和水溶液中测量的DNA分子长度相同，且对应于B-DNA（DNA的水合形式）的碱基间距；然而，当在缓冲液后再次在丙醇中对DNA成像时，它会缩短到脱水A-DNA预期的长度。其他结果包括在丙醇-水混合物中对与DNA结合的大肠杆菌RNA聚合酶进行成像，以及观察到在AFM中洗涤样品是分解盐-DNA复合物的有效方法。在水溶液中对DNA进行成像的能力对于在AFM中观察涉及DNA的过程具有潜在应用。
