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Imaging isolated strands of DNA molecules by atomic force microscopy.

Authors
Type
Published Article
Journal
Ultramicroscopy
0304-3991
Publisher
Elsevier
Publication Date
Volume
42-44 ( Pt B)
Pages
1101–1106
Identifiers
PMID: 1413247
Source
Medline
License
Unknown

Abstract

We 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 micrograms/ml isolated strands of the plasmid DNA are usually seen, while for concentrations higher than 3 micrograms/ml a uniform coverage of interconnected DNA strands was observed. We found that the contrast and the width of DNA were dependent upon humidity. When the relative 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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