FIGURE 4.

Imaging the distribution of β-actin mRNA in living fibroblasts. A mixture of three TMR-labeled β-actin mRNA-specific molecular beacons and a Texas red-labeled control molecular beacon, each complexed with streptavidin, was microinjected into each cell. After 1 h of incubation, a typical cell was imaged in quick succession with respect to (A) TMR and (B) Texas red. A ratio image (C) was obtained by dividing the fluorescence intensity of TMR by the fluorescence intensity of Texas red at every pixel in the image. The color of each pixel reflects the value of the ratio, with warmer colors representing higher ratios and cooler colors representing lower ratios. (D and E) Two ratio images of a typical cell that was grown in the absence of serum. Image D shows the steady state in the absence of serum, and image E shows the changes that occurred 2 min after the addition of fresh serum to the medium. (F) Table of colors used to represent the ratio at each pixel in images C, D, and E.