A quantitative comparison of single-dye tracking analysis tools using Monte Carlo simulations
Weimann L, Ganzinger KA, McColl J, Irvine KL, Davis SJ, Gay NJ, Bryant CE, Klenerman D. (2013), PLoS One. 8, e64287
Single-particle tracking (SPT) is widely used to study processes from membrane receptor organization to the dynamics of RNAs in living cells. While single-dye labeling strategies have the benefit of being minimally invasive, this comes at the expense of data quality; typically a data set of short trajectories is obtained and analyzed by means of the mean square displacements (MSD) or the distribution of the particles’ displacements in a set time interval (jump distance, JD). To evaluate the applicability of both approaches, a quantitative comparison of both methods under typically encountered experimental conditions is necessary. Here we use Monte Carlo simulations to systematically compare the accuracy of diffusion coefficients (D-values) obtained for three cases: one population of diffusing species, two populations with different D-values, and a population switching between two D-values. For the first case we find that the MSD gives more or equally accurate results than the JD analysis (relative errors of D-values <6%). If two diffusing species are present or a particle undergoes a motion change, the JD analysis successfully distinguishes both species (relative error <5%). Finally we apply the JD analysis to investigate the motion of endogenous LPS receptors in live macrophages before and after treatment with methyl-β-cyclodextrin and latrunculin B.
Key figure: Illustration of the parameter β
Depending on the SNR, a particle can be localized within a certain localization precision σ (red circle). After a certain time interval the particle has traveled a distance d. If σ is a substantial fraction of the distance d (i.e. β is small), the measurement of d is imprecise, leading to errors in the determination of the diffusion coefficient. Increasing the time interval Δt and thus β allows a more precise measurement of d.