Fig. 2.

Tracking single BR mRNPs in the nucleus of a living salivary-gland cell. (A) Five subsequent frames of a movie obtained with the LSM 5 Live. BR2 mRNPs are marked by black arrows. Their pathways could be followed by time-lapse imaging with 20 Hz. C marks the location of a polytene chromosome. (Scale bar, 2 μm.) (B) LSM image of the nuclear envelope marked by Alexa488-labeled Imp β1. Selected trajectories were plotted on the image, which provided a rough structure reference. (C) Plot of all trajectories obtained from this nucleus. (D) Frequency distribution of BR2 mRNP jumps performed within 0.05 s. Eq. 3 was used to fit the data points (bold, solid line). Thin or broken lines indicate distributions for each of the mobility fractions I–III. (E) Mean-square displacements (MSDs) plotted against the time. The initial slope of the curve was fitted by Eq. 1.