Sheared DNA fragment sizing: comparison of techniques.

Area of Science:

• Molecular Biology
• Biochemistry
• Genomics

Background:

• Conventional French press shearing is a common method for DNA fragmentation.
• Previous studies reported an average DNA fragment size of 450 base pairs for this method.
• Accurate DNA fragment size determination is crucial for molecular biology applications.

Purpose of the Study:

• To accurately determine the number-average fragment size of DNA processed by French press shearing.
• To compare the reliability of different DNA sizing techniques.
• To evaluate the impact of fragment size assessment on downstream applications.

Main Methods:

• DNA fragmentation using a French press (30,000 lbs/in2).
• Sizing of DNA fragments using five different techniques: velocity sedimentation, Kleinschmidt Electron Microscopy, adsorption grid electron microscopy, and gel electrophoresis.
• Analysis of fragment size distribution.

Main Results:

• French press shearing resulted in a number-average fragment size of 230 base pairs, significantly smaller than previously reported values.
• Velocity sedimentation and Kleinschmidt Electron Microscopy tend to overestimate DNA fragment size.
• Adsorption grid electron microscopy and gel electrophoresis provide the most reliable estimates for small DNA fragment populations.
• Fragment size distribution analysis, not possible with sedimentation, offers critical insights.

Conclusions:

• The actual DNA fragment size from French press shearing is smaller than commonly assumed.
• Adsorption grid electron microscopy and gel electrophoresis are recommended for accurate DNA fragment sizing.
• Accurate assessment of DNA fragment size and distribution enhances the evaluation of DNA hybridization and reassociation kinetics.