Hi,

I am calculating the N/P ratio to encapsulate dsDNA into a LNP. I am using two different methods, but obtaining a worrying difference in the result. I believe it could be a mistake in one of my calculations but not sure which.

1st Calculation - Using atomic count of N to P ratio

My mixture has 0.0075M of Lipid x 0.001L x 6.022x1023 = 4.5x1018 Ns (considering one N per lipid molecule)

N/P ratio of 4/1 so I need 1.125x1018 Phosphates (4.5x1018/4). My DNA is 7000bp long and therefore has 14000 phosphates, so dividing the Nº of Phosphates needed by the Nº of phosphates I have per DNA molecule (1.125x1018/14000) equals 8.03x1013 of DNA molecules needed. I can then easily calculate the DNA mass (DNA molecules needed x MW of 7000bp DNA)/6.022x1023

This equals 618ug of DNA

2nd Calculation - Using a mol/mol N/P ratio.

Molecular Weight of my lipid is 620.09g/mol and I am adding 4.65ug so dividing 4.65x10-6 g ÷ 620.09g/mol) I get 7.5x10-9 mols of N used, since there is 1 mol of N per mol of lipid.

N/P ratio 4/1 so I need 1.88x10-9 moles of Phosphate. There are approx. 3x10-9 moles of phosphate per ug of DNA so dividing the moles of phosphate I want by what I have (1.88x10-9moles ÷ 3x10-9 moles/ug)

This equals 0.626ug of DNA

Surely there is a mistake I am not seeing, any help will be greatly appreciated.

Thanks!!!