Unreliability of rate constants derived from a linear transformation of kinetic data, with special reference to cholesterol equilibration between phospholipid vesicles.
In the time-dependent transfer of a lipid from a donor to an acceptor vesicle population a(t) is the amount transferred to the acceptor vesicles at time t, a infinity is the equilibrium transfer value and a0 is the value at zero time. In order to plot kinetic data (a(t) as ln[(a infinity - a(t))/(a infinity - a(t))] against time and to fit these with a linear regression, it is necessary to know the equilibrium value, a infinity, or to choose one. Here it is shown that even if a very larger error is made in the choice of a infinity, the resulting plot can still be acceptably linear and the correlation coefficient of the regression acceptably high. When a infinity is overestimated the rate constant derived from the slope of such a plot is underestimated. In extreme cases a 10-fold error can occur.
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Pharma Division, Preclinical Research, F. Hoffmann-LaRoche Ltd., Basel, Switzerland.
D002784:Cholesterol / Q000378:metabolism*; D007700:Kinetics; D008081:Liposomes; D008433:Mathematics; D008563:Membrane Lipids / Q000378:metabolism*; D008954:Models, Biological; D010743:Phospholipids / Q000378:metabolism*
D008081:Liposomes; D008563:Membrane Lipids; D010743:Phospholipids; D002784:Cholesterol