Abstract:
:We report on the application of two photon molecular excitation to fluorescence correlation spectroscopy. We demonstrate the first fluorescence correlation spectroscopy measurements of translational mobility in the cytoplasm of living cells. Two-photon excitation inherently excites small sample volumes in three dimensions, providing depth discrimination similar to confocal microscopy, without emission pinholes. We demonstrated accurate measurements of the diffusion constant, D, for particles of several different known sizes, in bulk solutions of different viscosity. We then showed measurements of translational diffusion for 7- and 15-nm radius latex beads in the cytoplasm of mouse fibroblast cells. We measured time-dependent diffusion coefficients. When first injected in the cells, the spheres moved from two to five times slower than in water, with average rates of 18 x 10(-8) cm2/s for the 7 nm and 5 x 10(-8) cm2/s for the 15 nm radius spheres. After a few hours, spheres stick to the cells, and the motion slows down 10 to 100 times.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Berland KM,So PT,Gratton Edoi
10.1016/S0006-3495(95)80230-4subject
Has Abstractpub_date
1995-02-01 00:00:00pages
694-701issue
2eissn
0006-3495issn
1542-0086pii
S0006-3495(95)80230-4journal_volume
68pub_type
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