Enter your DNA Concentration, Plasmid Length, DNA Type, Sample Volume, and Number of Cells into the Plasmid Copy Number Calculator to find how many plasmid copies exist per cell, plus total copies, copies per μL, and molecular weight.
Copies per Cell
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Total Copies
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Copies per μL
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Molecular Weight
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Double-stranded DNA (dsDNA) has approximately 660 g/mol per base pair, while single-stranded DNA (ssDNA) has about 330 g/mol per base. This difference affects the molecular weight calculation and thus the final copy number.
The estimation using 660 g/mol per bp for dsDNA is very accurate for most applications. For higher precision, you can measure the exact molecular weight of your specific plasmid if needed.
Use the total length of your plasmid in base pairs, including the insert and vector backbone. This information is usually available in the plasmid map or sequence file.
Copy number per cell helps determine transformation efficiency, gene expression levels, and is crucial for quantitative PCR standard curve preparation and cloning experiments.
Actual copy number depends on the plasmid origin of replication, cell type, growth conditions, and selective pressure. High-copy plasmids typically have 100-700 copies per cell.
Use spectrophotometry (A260/A280 ratio), fluorometry, or gel electrophoresis. Ensure your sample is free of contaminants that could affect the measurement.