Imaging isolated strands of DNA molecules by atomic force microscopy
1992; Elsevier BV; Volume: 42-44; Linguagem: Inglês
10.1016/0304-3991(92)90409-d
ISSN1879-2723
AutoresThomas Thundat, David P. Allison, R. J. Warmack, T. L. Ferrell,
Tópico(s)Surface and Thin Film Phenomena
ResumoWe have employed an atomic force microscope (AFM) to image in air isolated strands of pBS+ plasmid DNA adsorbed onto freshly cleaved mica. At a DNA concentration below 0.3 μg/ml isolated strands of the plasmid DNA are usually seen, while for concentrations higher than 3 μg/ml a uniform coverage of inteconnected DNA strands was observed. We found that the contrast and the width of DNA were dependent upon humidity. When the relatively humidity exceeds 60%, negative contrast images with strand widths 20 times the width of DNA are found, while positive contrast images with 7 to 10 times the width of DNA are found when the humidity is below 30%. By placing the AFM in an environment where the humidity could be controlled, we were able to switch between positive and negative contrasts.
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