Dynamics in Cytoplasm, Nucleus, and Lipid Droplet of a Live CHO Cell: Time-Resolved Confocal Microscopy

Different regions of a single live Chinese hamster ovary (CHO) cell are probed by time-resolved confocal microscopy. We used coumarin 153 (C153) as a probe. The dye localizes in the cytoplasm, nucleus, and lipid droplets, as is dearly revealed by the image. The fluorescence correlation spectroscopy (FCS) data shows that the micro-viscosity of lipid droplets is similar to 34 +/- 3 cP. The microviscosities of nucleus and cytoplasm are found to be 13 +/- 1 and 14.5 +/- 1 cP, respectively. The average solvation time () in the lipid droplets (3600 +/- 50 ps) is slower than that in the nucleus ( = 750 +/- 50 ps) and cytoplams ( = 1100 +/- 50 ps). From the position of emission maxima of C153, the polarity of the nucleus is estimated to be similar to that of a mixture containing 26% DMSO in triacetin (eta similar to 11.2 cP, epsilon similar to 26.2). The cytoplasm resembles a mixture of 18% DMSO in triacetin (eta similar to 12.6 cP, epsilon similar to 21.9). The polarity of lipid droplets is less than that of pure triacetin (eta similar to 21.7 cP, epsilon similar to 7.11).