Nonexchangeable markers, lipid transfer

In equations (3) and (4), the fraction of the labeled lipid in the donor particle after the exchange reaction is subtracted to correct for contamination. In these equations, it is assumed that the acceptor particles are recovered quantitatively. If this is not the case, both the labeled lipid appearing in the acceptor and contaminating donor particles, and the fraction of donor particles contaminating the acceptor particles must be corrected for incomplete recovery of the acceptor particles. To use Equation (4), it is necessary to have a nonexchangeable marker in the donor particles to quantitate contamination of the acceptor. The errors introduced by contamination may be reduced without a correction formula when the apparent background transfer in the absence of transfer protein is subtracted from the total apparent transfer in the presence of protein. 

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