Two plasmids that can be used to make inexpensive 100 bp or 1 kb DNA molecular weight ladders were recently deposited with Addgene. A team of undergraduate students led by Dr. Song Tan at Penn State developed the plasmids, pPSU1 and pPSU2. When restriction digested with PstI or EcoRV, these plasmids generate 100 bp or 1 kb DNA ladders, respectively. Unlike many commercially available ladders, the 100 bp ladder works well for both agarose and native polyacrylamide gels.
Table 1: Comparing Typical Comericial Ladders with the PSU Ladders
|DNA Lader||Commercial DNA Ladder||Penn State Ladder: Homemade Plasmid Prep||Penn State Ladder: Commercial Plasmid Prep Kit|
|Amount||1000 Lanes||1000 Lanes||1000 Lanes|
Cost Comparison: While convenient, commercial ladders cost between $200-$500 for 1000 lanes worth of ladder. The Penn State ladders are significantly cheaper. When using a homemade plasmid prep protocol, it cost less than $10 to make 1000 lanes worth of the 100 bp or the 1 kb ladder. Using a commercial plasmid prep kit increases the costs to $20-30 per ladder: still significantly cheaper than commercial ladders.
1. Henrici, R. C., Pecen, T. J., Johnston, J. L., & Tan, S. (2017). The pPSU Plasmids for Generating DNA Molecular Weight Markers. Scientific Reports,7(1). doi:10.1038/s41598-017-02693-1. PubMed PMID: 28550309. PubMed Central PMCID: 5446395.
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Resources on Addgene.org
- Use the Kit-Free Alkaline Lysis Plasmid Miniprep Protocol
- Learn How to Analyze Your Restriction Digests
- Make Your Agarose Gel
- Read about Gel Stains on the BitesizeBio Blog
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