Titration of eYFP labelled VLPs. Mixed particles were purified from the tissue culture supernatant of 293T cells transfected with an equimolar mixture of pCHIV and pCHIVeYFP by centrifugation through a sucrose cushion and their concentration determined by p24 ELISA. The relative eYFP fluorescence intensity of serial dilutions in DMEM/10% FCS was determined using a TECAN Saphire multi-well reader. Background fluorescence from the medium was subtracted and fluorescence intensities of the samples were plotted as a function of p24 CA concentration. The plot shows mean values and standard deviation from triplicate dilutions; the line represents a linear regression. The inset shows an expansion of the lower part of the same data set. The line represents a linear regression to the data points shown.