Magnetic Bead Purification of Labeled DNA Fragments for High-Throughput Capillary Electrophoresis Sequencing

Sep 12, 2026

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Automated purification of terminator sequencing products is presented using a magnetic bead workflow for 384-well plates. The method yields labeled DNA fragments essentially free of contaminants at very low cost per reaction and streamlines sample handling by avoiding laborious precipitation steps. Compared with ethanol precipitation, it increases phred20 read length by about forty bases across PCR fragments, plasmids, cosmids, and RCA products. It is compatible with MegaBACE 1000 and ABI Prism 3700 instruments and has produced large-scale sequencing output.

LanguageEnglish

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Pages5

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Abstract

Introduction

Material and Methods

Results and Discussion

Table 1. Sequencing Fragment Purification Protocol

Reagent/Stock Preparation

Common Issues

Reagent and Binding-Buffer Design Considerations

Magnetic Bead Purification of Labeled DNA Fragments for High-Throughput Capillary Electrophoresis Sequencing ABSTRACT We have developed an automated purification method for terminator sequencing products based on a magnetic bead technology. This 384-well protocol generates labeled DNA fragments that are essentially free of contaminates for less than $0.005 per reaction. In comparison to laborious ethanol precipitation protocols, this method increases the phred20 read length by forty bases with various DNA templates such as PCR fragments, Plasmids, Cosmids and RCA products. Our method eliminatescentrifugation and is compatible with both the MegaBACE 1000 and ABI Prism 3700 capillary instruments. As of September 2001, this method has produced over 1.6 million samples with 93% averaging 620 phred20 bases as part of Joint Genome Institutes Production Process. INTRODUCTION In the late 1990’s, high-throughput capillary electrophoresis instruments were introduced to meet the demands of large scale sequencing labs working on the Human Genome Project. While these instruments provided faster turnaround times, they also created a need for large numbers of high purity DNA samples. The typical approach was to scale up and automate molecular biology methods designed for small-scale bench work. Since these methods often contained laborious and irreproducible steps like centrifugation, we decided to design a high-throughput method tailored for robotic platforms and capillary electrophoresis instruments. MATERIAL AND METHODS See Table 1 for purification protocol. RESULTS AND DISCUSSION In developing a high-throughput method to purify DNA sequencing fragments, we began with a magnetic bead technology previously used at our facility to purify template DNA for sequencing(1) . This method bound crude DNA to carboxylated Table 1. Sequencing Fragment Purification Protocol 1. Sequence RCA generated template with Amersham Pharmacia ET Terminator Kit (part\# US81095) according to instructions except; reduce final volume to 5ul and process in a 384 well PCR plate. 2. Add 10uL of BET solution to each well with 384-well Multidrop. 3. Verify solution is mixed thoroughly. Mix by pipetting or vortex as needed. 4. Incubate at room temperature for 15 minutes. 5. Place 384 well plate on a plate magnet for 1 minute. 6. Place 384 well plate/magnet assembly on 384 Hydra and aspirate solution. 7. Add 15ul of 70% ethanol solution to each well with 384 well Multidrop 8. Place 384 well plate/magnet assembly on 384 Hydra and aspirate solution. 9. Air-dry samples for 10 minutes or continue to step 10. 10. Dispense 15uL of deionized water to each plate. 11. Mix by pipetting or vortex until beads are resuspended 12. Incubate 10 minutes at room temperature. 13. Place 384 well plate on plate magnet for 2 minutes. 14. Transfer 10ul of water solution to suitable plate for electrokinetic injection 15. Cover and store at-20°C or load onto MegaBACE 1000 or ABI 3700 16. MegaBACE 1000 (Inject-1.6KV/36 seconds, Run-7KV/170 minutes) Reagent/Stock Preparation BET Solution (processes twenty 384-well plates) Ethanol(100%) 64.0 mls Deionized Water 7.0 mls Tetra Ethylene Glycol 6.4 mls Carboxylated Beads (5% solids.0.8um dia.) 2.0 mls Common Issues Trapped Air Bubbles Can Prevent Mixing Evaporation During Thermal Cycling Causes Low Read-Length Improper Mixing Causes Dropouts and Loss ofTrace Resolution magnetic particles with a solution of polyethylene glycol and sodium chloride. The beads were washed multiple times with 70% ethanol and pure DNA was eluted with water. While this method met the requirements listed above, we needed a technique that worked in 384-well PCR plates and produced extremely pure DNA. Our first design consideration focused on replacing the polyethylene glycol and sodium chloride binding buffer. Sodium chloride inhibits electrokinetic injection and is significant source of variability in capi

FAQs

What sequencing purification approach is described in the document?

An automated magnetic bead purification workflow is used to clean terminator sequencing products in a 384-well format.

How does the magnetic bead method compare with ethanol precipitation?

Compared with laborious ethanol precipitation, it increases phred20 read length by about forty bases while producing highly pure labeled DNA fragments.

Which capillary electrophoresis instruments are compatible with the method?

The protocol is compatible with both the MegaBACE 1000 and ABI Prism 3700 capillary instruments.

Sep 12, 2026

Upload by Aladdin