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Tip-radius-induced artifacts in AFM images of protamine-complexed DNA fibers.

Authors
  • Allen, M J
  • Hud, N V
  • Balooch, M
  • Tench, R J
  • Siekhaus, W J
  • Balhorn, R
Type
Published Article
Journal
Ultramicroscopy
Publisher
Elsevier
Publication Date
Jul 01, 1992
Volume
42-44 ( Pt B)
Pages
1095–1100
Identifiers
PMID: 1413246
Source
Medline
License
Unknown

Abstract

Isolated DNA fibers complexed with protamine (the chromosomal protein that packages DNA in mammalian sperm) have been produced by partially decondensing the highly compacted mouse sperm chromatin particle on a glass coverslip. These DNA fibers were then scanned with the atomic force microscope (AFM). While the smallest of the fibers appear in AFM images as ribbon-like structures 250-350 A wide and 10-25 A high, experiments indicate that these images are the result of a convolution of the imaging-tip's shape with the object's actual shape. In such convolutions the height of the object is affected only by the compressibility of the object, while the width is affected in addition by the sharpness of the tip. Images of polyamidoamine particles also appear to show this artifact. We have also deduced the tip's radius of curvature from images of sharp steps and attempt to demonstrate the artifacts associated with a relatively large imaging tip.

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