Calculate Multiplicity of Infection for viral transductions. Determine virus volume for target MOI or effective MOI from a given volume. Includes Poisson-based infection probability estimates.
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Multiplicity of Infection (MOI) is the ratio of infectious agents (viruses, bacteria, phages) to target cells. It represents the average number of virus particles that each cell is exposed to during infection. MOI is a critical parameter in virology, gene therapy, and molecular biology experiments.
MOI = Total Virus Particles / Total CellsVolume = (MOI × Cell Count) / (Titer per mL) × 1000P(0) = e-MOIP(≥1) = 1 - e-MOIViral infection follows a Poisson distribution because virus particles randomly encounter cells. This means not every cell receives the same number of particles even at a given MOI:
| MOI | % Uninfected | % Infected (≥1) | Typical Use |
|---|---|---|---|
| 0.1 | 90.5% | 9.5% | Clonal selection |
| 0.5 | 60.7% | 39.3% | Low infection |
| 1 | 36.8% | 63.2% | Standard transduction |
| 3 | 5.0% | 95.0% | High efficiency |
| 5 | 0.7% | 99.3% | Near-complete infection |
| 10 | 0.0045% | 99.9955% | Multiple integrations |
Different virus types use different units to express titer:
Note: Physical particle counts (vg, genome copies) may be 10-1000× higher than infectious titers (TU, pfu) depending on the virus and preparation quality.
MOI provides a theoretical estimate, but actual infection efficiency depends on:
Calculate cells needed and volumes for well plates, flasks, and dishes before transduction.
Plan serial dilutions for virus titration and plaque assays.
Calculate volumes for polybrene, media supplements, and transduction reagents.
Convert between mass, molarity, and copy number for viral DNA/RNA quantification.
Build essential skills in virology, gene delivery, and infection modeling for your research
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