Relationship between TU and pg of p24

• There are approximately 2000 molecules of p24 per physical particle (PP) of HIV, i.e.
• 2x10³ x 24x10³ Da of p24 per PP. i.e.
• 48x10⁶/Avogadro = 48x10⁶ / 6x10²³ = 8x10^-17 g of p24 per PP, i.e.
• approx. 1 PP per 10e^-16 g of p24, i.e.
• 10⁴ PP per pg of p24

A reasonably well packaged, VSVG pseudotyped lentiviral vector will have an infectivity index in the range of 1 transducing unit (TU) per 1000 physical particles (PP) to 1 TU per 100 PP (or less). Thus, the range is approximately 10 to 100 TU/pg of p24. Below these values, your vector has experienced problems during packaging.